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MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 1
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
CONTENTS
CHAPTER -1.............................................................................................................................. 5
1 INTRODUCTION.................................................................................................................... 6
1.1 DEFINATION:.................................................................................................................. 6
1.2 BACKGROUND:.............................................................................................................. 6
1.3 WORKING OF GEOPOLYMER CONCRETE:............................................................... 7
1.4 TYPES OF GEOPOLYMER CONCRETE:...................................................................... 7
1.4.1 SLAG BASED GEOPOLYMER:................................................................................ 7
1.4.2 ROCK BASED GEOPOLYMER:............................................................................... 8
1.4.3 FLY ASH BASED GEOPOLYMER:.......................................................................... 8
CHAPTER -2............................................................................................................................ 10
2 LITERATURE REVIEW ...................................................................................................... 11
2.1 Introduction.................................................................................................................... 11
2.2 Geopolymer..................................................................................................................... 11
2.2.1 Terminology and Chemistry...................................................................................... 11
2.3 Constituents of Geopolymer............................................................................................ 12
2.3.1 Source Materials ....................................................................................................... 12
2.3.2 Alkaline Liquids........................................................................................................ 13
2.3.3 Factors Affecting the Properties of Geopolymers ...................................................... 13
2.3.4 Fields of Applications ................................................................................................ 14
2.3.5 Properties of Geopolymers ........................................................................................ 16
2.3.6 Studies on Geopolymer Mortar................................................................................. 17
2.3.7 Studies on Geopolymer Concrete .............................................................................. 18
CHAPTER -3............................................................................................................................ 19
3 METHODOLOGY................................................................................................................. 20
3.1 Experimental Investigation.............................................................................................. 20
3.2 Materials ......................................................................................................................... 20
3.2.1 Fly Ash...................................................................................................................... 20
3.2.2 TESTING FOR FLY ASH ........................................................................................ 22
3.2.2 Chemical Composition of Fly Ash............................................................................. 24
3.3 GGBS (Ground Granulated Blast Furnace Slag) ......................................................... 24
3.3.1 GENERAL................................................................................................................ 24
3.3.2 USES OF GGBS........................................................................................................ 24
3.4 Alkaline Liquid................................................................................................................ 26
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 2
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
3.5 Sodium silicate................................................................................................................. 27
3.6 Super Plasticizer.............................................................................................................. 28
3.6.1 Properties of Superplasticizers .................................................................................. 30
3.6.2 Effects of Super Plasticizers on Concrete Properties ................................................. 30
3.7 Aggregates....................................................................................................................... 31
3.7.1 Coarse Aggregate ...................................................................................................... 31
3.7.2 FINE AGGREGATE................................................................................................. 32
3.8 FIBRES AND ITS PROPERTIES................................................................................... 35
3.8.1 GLASS FIBRE.......................................................................................................... 35
3.8.2 CRIMPED STEEL FIBRE........................................................................................ 37
3.9 MIXDESIGN REQUIREMENT..................................................................................... 38
3.9.1 MIXDESIGN PROCESS FOR GEOPOLYMER CONCRETE................................ 39
3.9.1 TYPES OF MIXES................................................................................................... 42
3.10 FACTORS AFFECTING THE CHOICE OF MIX PROPORTIONS............................ 43
CHAPTER -4............................................................................................................................ 46
4. GEOPOLYMER MORTAR ................................................................................................. 47
4.1 Material Preparation....................................................................................................... 47
4.2 Mixing........................................................................................................................ 48
4.3 SIZE OF TEST SPECIMEN...................................................................................... 49
4.4 Compaction..................................................................................................................... 50
4.5 Curing........................................................................................................................ 51
4.6 Testing ....................................................................................................................... 51
4.6.1 Compression Strength Test ....................................................................................... 51
4.6.2 Split Tensile Strength Test ........................................................................................ 52
4.6.3 Flexural Strength Test............................................................................................... 53
CHAPTER – 5.......................................................................................................................... 54
5 RESULTS AND DISCUSSION.............................................................................................. 55
5.1 General............................................................................................................................ 55
5.2 Concentration of alkaline solution, fly ash, GGBS, and fibres ......................................... 55
5.3 Tests onM50 cubes, cylinders and prisms using steel fibres ............................................ 55
5.3B Split tensile strength test on M50 cylinders using steel fibres ........................................ 57
5.3C Flexural strength test on M50 prisms using steel fibres................................................. 59
5.4 Test on M50 cubes, cylinders, prisms using glass fibre .................................................... 61
5.4B Split tensile strength test for M50 cylinders using glass fibres....................................... 63
5.5 Analysis on combination of fibres based on maximum strength....................................... 67
5.5A Maximum compressive strength obtained for cubes...................................................... 67
5.5B Maximum split tensile strength obtained for cylinders.................................................. 68
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
5.5C Maximum flexural strength obtained for prisms........................................................... 69
6. CONCLUSIONS................................................................................................................... 72
LIST OF FIGURES
Figure no: 1.4.3 Fly ash............................................................................................................... 9
Figure no: 2.2.1 Chemical Structure of Polysialates.................................................................. 11
Figure no: 3.2.1Sem Image Figure no: 3.2.2 Fly Ash.................. 22
Figure no: 3.3 GGBS................................................................................................................. 25
Figure no: 3.5 Sodium Silicate Pellets ....................................................................................... 28
Figure no: 3.6 Super Plasticizer................................................................................................ 30
Figure no: 3.7.1 Coarse Aggregate............................................................................................ 31
Figure no: 3.8.2 Crimped Steel Fibre ........................................................................................ 38
Figure no: 4.1.A Material Preparation...................................................................................... 48
Figure no: 4.2A Hand Mixing ................................................................................................... 49
Figure no: 4.3A Mould Preparation.......................................................................................... 49
Figure no: 4.3A Mould Preparation Figure no: 4.4B Vibrating Machine............. 50
Figure no: 4.5A Curing............................................................................................................. 51
Figure no: 4.6.1Compression strength test................................................................................ 52
Figure no. 4.6.2 Split tensile strength test.................................................................................. 53
Figure no: 4.6.3 Flexural strength test...................................................................................... 53
Figure no: 5.3A Compressive strength of standard mix (Cubes)............................................... 56
Figure no: 5.3A1 Compressive strength ofM50 cubes using Steel fibres................................... 57
Figure no: 5.3B Split tensile strength ofstandard mix (Cylinders)............................................ 58
Figure no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres...................................... 59
Figure no: 5.3C Flexural strength ofstandard mix (Prism) ...................................................... 60
Figure no: 5.3C1 Split tensile strength ofM50 Prism using Steel fibres .................................... 61
Figure no: 5.4A Compressive strength of standard mix (Cubes)............................................... 62
Figure no: 5.4A1 Compressive strength ofM50 cubes using glass fibres................................... 63
Figure no: 5.4B Split tensile strength ofstandard mix (Cylinders)............................................ 64
Figure no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres ............................... 65
Figure no: 5.4C Flexural strength ofstandard mix (Prism) ...................................................... 66
Figure no: 5.4C1 Flexural strength ofM50 prisms using glass fibres........................................ 67
Figure no: 5.5A Maximum compressive strength for cubes....................................................... 68
Figure no: 5.5B Maximum split tensile strength for cylinder.................................................... 69
Figure no: 5.5C Maximum flexural strength for prisms............................................................ 70
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
LIST OF TABLES
Table no: 2.3.4Application of Geopolymeric Material Based on Si: Al Atomic ratio................. 15
Table no: 3.3B Chemical Properties of GGBS........................................................................... 26
Table no: 3.3C Physical Properties of GGBS............................................................................ 26
Table no: 3.4 Specification and Impurity limits of NaOH ......................................................... 27
Table no: 3.5 Property Specification of Sodium Silicates .......................................................... 28
Table no: 3.7.2 Sieve Analysis ................................................................................................... 33
Table no: 3.8.1 Properties of Glass Fibre of Glass Fibre ........................................................... 36
Table no: 3.8.2 Properties of Crimped Steel Fibre .................................................................... 38
Table no: 3.9.1 Nominal mix..................................................................................................... 43
Table no: 5.3A Compressive strength for standard mix (Cubes)............................................... 55
Table no: 5.3A1 Compressive strength ofM50 cubes using Steel fibres .................................... 56
Table no: 5.3B Split tensile strength for standard mix (Cylinders)............................................ 57
Table no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres....................................... 58
Table no: 5.3C Flexural strength for standard mix (Prism) ...................................................... 59
Table no: 5.2C1 Flexural strength of M50 Prisms using Steel fibres ......................................... 60
Table no: 5.4A compressive strength test for M50 cubes using glass fibre................................. 61
Table no: 5.4A1 Compressive strength ofM50 cubes using glass fibres .................................... 62
Table no: 5.4B1 Split tensile strength ofM50 cylinders using glass fibres................................. 64
Table no: 5.4C Flexural strength test for M50 prism using glass fibres..................................... 65
Table no: 5.4C1 Flexural strength of M50 prism using glass fibres........................................... 66
Table no: 5.5AMaximum compressive strength obtained for cubes ......................................... 68
Table no: 5.5B Maximum split tensile strength obtained for cylinders...................................... 68
Table no: 5.5CMaximum flexural strength for prisms% of glass and steel fibers .................... 70
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 5
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
CHAPTER -1
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
1 INTRODUCTION
1.1 DEFINATION:
There is often confusion between the meanings of the terms 'geopolymer cement' and
'geopolymer concrete'. A cement is a binder, whereas concrete is the composite material
resulting from the mixing and hardening of cement with water (or an alkaline solution in the
case of geopolymer cement), and stone aggregates. Materials of both types (geopolymer
cements and geopolymer concretes) are commercially available in various markets.
Davidovits proposed that an alkaline liquid could be used to react with the silicon (Si) and the
aluminium (Al) in a source material of geological origin or in by product materials such as fly
ash, blast furnace slag, and rice husk ash to produce binders. Because the chemical reaction
that takes place in this case is a polymerization process occurs, he coined the term
‘Geopolymer’ to represent these binders.ionally. Geopolymer cement is a new kind of cement
which uses a different chemistry to that found in traditional Ordinary Portland Cement (OPC).
A geopolymer is made by activating amorphous alumino-silicate materials, such as fly ash and
slag, with alkali-based chemicals such as sodium hydroxide and sodium silicate. Geopolymer
cement does not need to contain OPC to work. Geopolymers have been known to be useful
binders in concrete for over 60 years, but have recently developed rapidly in Australia due to
the fact they have a CO2 footprint which is approximately 80% lower than OPC cement.
There are two main constituents of geopolymers, namely the source materials and the alkaline
liquids. The source materials for geopolymers based on alumina-silicate should be rich in
silicon (Si) and aluminium (Al). These could be natural minerals such as kaolinite, clays, etc.
Alternatively, by-product materials such as fly ash, silica fume, slag, rice-husk ash, red mud,
etc. could be used as source materials. The choice of the source materials for making
geopolymers depends on factors such as availability, cost, type of application, and specific
demand of the end users.
1.2 BACKGROUND:
The first geopolymer cement developed in the 1980s was of the type (K,Na,Ca)-
poly(sialate) (or slag-based geopolymer cement) and resulted from the research developments
carried out by Joseph Davidovits and J.L. Sawyer at Lone Star Industries, USA and yielded the
invention of Pyrament® cement. Geopolymers have been known to be useful binders in
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 7
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concrete for over 60 years, but have recently developed rapidly in Australia due to the fact they
have a CO2 footprint which is approximately 80% lower than OPC cement.
1.3 WORKING OF GEOPOLYMER CONCRETE:
Water, expelled from the geopolymer matrix during the curing and further drying periods,
leaves behind nano-pores in the matrix, which provide benefits to the performance of
geopolymers. The water in a low-calcium fly ash-based geopolymer mixture, therefore, plays
no direct role in the chemical reaction that takes place; it merely provides the workability to
the mixture during handling. This is in contrast to the chemical reaction of water in a Portland
cement concrete mixture during the hydration process. However, a small proportion of
calcium-rich source materials such as slag may be included in the source material in order to
accelerate the setting time and to alter the curing regime adopted for the geopolymer mixture.
In that situation, the water released during the geopolymerisation reacts with the calcium
present to produce hydration products.
1.4 TYPES OF GEOPOLYMER CONCRETE:
There are currently four different types of geopolymer concrete used in construction
 Slag based geopolymer
 Rock based geopolymer
 Fly ash based geopolymer
 Ferro-sialate based geopolymer
1.4.1 SLAG BASED GEOPOLYMER:
The first geopolymer developed was a slag based geopolymer in the 1980s. The reason for
using this type of cement is due to it’s the rapid strength gain as it can reach strengths of up to
20 MPa after just 4 hours. Slag is a partially transparent material and a by-product in the process
of melting iron ore. It usually consists of a mixture of metal oxides and silicon dioxide. It is
also used in the cement and concrete industry. The substitution of OPC with slag is one of the
many benefits that it provides to OPC concrete, reducing life cycle costs and improving the
workability of the fresh concrete, Easier finishability, higher compressive and flexural strength
and also the improved resistance to acid materials. The reactions of slag in alkali activating
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
systems and in cement blends are dominated by the small particles. The particles that are above
20 µm usually react slowly, while particles under 2 µm react completely within 24 hours. Thus,
when slag is used in geopolymerisation, careful control of the particle size distribution must be
ensured to control the strength of the binder.
Examples of slag used are; Iron blast-furnace slag, Corex slag& Steel slag.
1.4.2 ROCK BASED GEOPOLYMER:
To compose this type of geopolymer, a fraction of the MK-750(“MK” is an abbreviation for
metakaolin and the “750” represents the temperature at which it was produced) in the slag
based geopolymer is replaced by natural rock forming materials such as feldspar and quarts.
This mixture yields a geopolymer with better properties and less CO2 emissions than that of
the ordinary slag based geopolymer. The components of rock based geopolymer cement is
metakaolin MK-750, blast-furnace slag, natural rock forming materials (calcined or non-
calcined) and a user friendly alkali silicate.
1.4.3 FLY ASH BASED GEOPOLYMER:
Fly ash is the waste material produced in blast furnace. Components of fly ash are amorphous
composition (60%), quartz (20%), mullite (17%), maghemite (1.7%) and hematite (.9%).
Fly ash is commonly used as a substitute for OPC in concrete and the addition of it
provides; Fly ash consists of spherical particles which improve the workability of the fresh
OPC concrete. This enables one to reduce the amount of water in the mix which reduces the
amount of bleeding of OPC concrete.
Improves mechanical properties such as compressive strength, due to the water reduction and
ensures a higher reactiveness and better “packing” of particles.
Reduce the cost of the OPC concrete. Reduces the CO2 emissions and drying shrinkage and
Smoother surface.
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Figure no: 1.4.3 Fly ash
1.4.3.1 Graded Fly Ash
Fly ash can be divided in to two, type F fly ash and type C fly ash. The type F fly ash can be
again classified into two Alkali-activated fly ash geopolymer and Fly ash/slag based
geopolymer. Most of the globally available fly ash material is a low calcium by product
obtained from the burning of anthracite and bituminous coal.
1.4.3.2 Alkali-Activated Fly Ash Geopolymer
This kind of geopolymer usually requires heat curing at 60 ºC to 80 ºC. It is also known as the
alkali activation method. A high concentration of sodium hydroxide solution is required to
ensure an adequate geopolymerisation process. The mixture consists of fly ash and a user-
hostile sodium hydroxide solution. The fly ash particles are embedded into an aluminosilicate
gel with a Si: Al ratio of 1 to 2.
This kind of geopolymer is more user-friendly and it hardens at room temperature. The mixture
consists of a user-friendly silicate, blast furnace slag and fly ash. The fly ash particles are
embedded into a geopolymer matrix with and Si: Al ratio of 2.
1.4.4 FERRO SIALATE BASED GEOPOLYMER:
This type of geopolymer has the same properties as rock based geopolymers but contains
geological elements with high iron oxide content, giving the geopolymer a red colour. Some
of the aluminium atoms in the matrix are substituted with iron ions to yield a poly (Ferro-
sialate) type geopolymer with the following formation: (Ca,K)- (-Fe-O)-(-Si-O-Al-O-).
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
CHAPTER -2
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2 LITERATURE REVIEW
2.1 Introduction
This Chapter presents a brief review of the terminology and chemistry of geopolymers, and
past studies on geopolymers.
2.2 Geopolymer
2.2.1 Terminology and Chemistry
The term ‘geopolymer’ was first introduced by Davidovits in 1978 to describe a family of
mineral binders with chemical composition similar to zeolites but with amorphous
microstructure. He also suggested the use of the term ‘poly (sialate)’ for the chemical
designation of geopolymers based on silico-aluminate (Davidovits, 1988a, 1988b, 1991; van
Jaarsveld et. al., 2002a); Sialate is an abbreviation forsilicon-oxo-aluminate. Poly(sialates) are
chain and ring polymers with Si4+ and AL3+ in IV-fold coordination with oxygen and range
from amorphous to semi-crystalline with the empirical formula:
Mn (-(SiO2) z – AlO2) n. wH2O ---------------- (2-1)
Where “z” is 1, 2 or 3 or higher up to 32; M is a monovalent cation such as potassium or
sodium, and “n” is a degree of poly condensation has also distinguished 3 types of polysialates,
namely the Poly(sialate) type (-Si-O-Al-O), the Poly(sialate-siloxo) type(-Si-O-Al-O-Si-O)
and the Poly(sialate-disiloxo) type (-Si-O-Al-O-Si-O). The structures of these polysialates can
be schematised as in Figure 2.2.1.
Figure no: 2.2.1 Chemical Structure of Polysialates
Geo polymerization involves the chemical reaction of alumino-silicate oxides (Si2O5, Al2O2)
with alkali polysilicates yielding polymeric Si – O – Al bonds.
Poly silicates are generally sodium or potassium silicate supplied by chemical industry or
manufactured fine silica powder as a by-product of Ferro-silicon metallurgy. Equation 2-2
shows an example of polycondensation by alkali into poly (sialatesiloxo).
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
(Si2O5, Al2O2) n + 2nSiO2 +4nH2O+ NaOH, KOH Na+, K++ n (OH) 3 -Si-O-Al--O-Si-(OH) 3
(Si-Al material) |
(OH) 2 (2-2)
(Geopolymer precursor)
| | |
n(OH)3 -Si-O-Al--O-Si-(OH)3+ NaOH or KOH (Na,K)(+) –(-Si-O-Al-O-Si-O-) + 4nH2O
| | | |
(OH) 2 O O O (2-3)
| | |
(Geopolymer backbone)
Unlike ordinary Portland/pozzolanic cements, geopolymers do not form calcium silicate
hydrates (CSHs) for matrix formation and strength, but utilise the Poly condensation of silica
and alumina precursors and a high alkali content to attain structural strength.
Therefore, geopolymers are sometimes referred to as alkali activated alumino silicate binders.
The last term of Equation 2-2 indicates that water is released during the chemical reaction that
occurs in the formation of geopolymers.
This water is expelled from the mixture during the curing process.
2.3 Constituents of Geopolymer
2.3.1 Source Materials
Any material that contains mostly Silicon (Si) and Aluminium (Al) in amorphous form is a
possible source material for the manufacture of geopolymer. Several minerals and industrial
by-product materials have been investigated in the past.
Metakaolin or calcined kaolin, low-calcium ASTM Class F fly ash, natural Al-Si minerals,
combination of calcined mineral and non-calcined materials.
Combination of fly ash and Metakaolin and combination of granulated blast furnace slag and
Metakaolin (Cheng and Chiu 2003) have been studied as source materials.
Metakaolin is preferred by the niche geopolymer product developers due to its high rate of
dissolution in the reactant solution, easier control on the Si/Al ratio and the white colour.
However, for making concrete in a mass production state, Metakaolin is expensive.
Low-calcium (ASTM Class F) fly ash is preferred as a source material than high calcium
(ASTM Class C) fly ash.
The presence of calcium in high amount may interfere with the polymerization process and
alter the microstructure.
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Davidovits calcined kaolin clay for 6 hours at 750oC.He termed this Metakaolin as KANDOXI
(Kaolinite, Nacrite, Dickite Oxide), and used it to make geopolymers.
For the purpose of making geopolymer concrete, he suggested that the molar ratio of Si-to-Al
of the material should be about 2.0.
On the nature of the source material, it was stated that the calcined source materials, such as
fly ash, slag, calcined kaolin, demonstrated a higher final compressive strength when compared
to those made using non-calcined materials, for instance kaolin clay, mine tailings, and
naturally occurring minerals.
However, Xu and van Deventer (2002) found that using a combination of calcined (e.g. fly ash)
and non-calcined material (e.g. kaolinite or kaolin clay and albite) resulted in significant
improvement in compressive strength and reduction in reaction time.
2.3.2 Alkaline Liquids
The most common alkaline liquid used in geopolymerisation is a combination of sodium
hydroxide (NaOH) or potassium hydroxide (KOH) and sodium silicate or potassium silicate.
The use of a single alkaline activator has been reported (Palomo et al. 1999; Teixeira- Pinto et
al. 2002), Palomo et al (1999) concluded that the type of alkaline liquid plays an important role
in the polymerization process.
Reactions occur at a high rate when the alkaline liquid contains soluble silicate, either sodium
or potassium silicate, compared to the use of 14 only alkaline hydroxides. Xu and van Deventer
(2000) confirmed that the addition of sodium silicate solution to the sodium hydroxide solution
as the alkaline liquid enhanced the reaction between the source material and the solution.
Furthermore, after a study of the geopolymerisation of sixteen natural Al-Si minerals, they
found that generally the NaOH solution caused a higher extent of dissolution of minerals than
the KOH solution.
2.3.3 Factors Affecting the Properties of Geopolymers
Several factors have been identified as important parameters affecting the properties of
geopolymers.
Palomo et al (1999) concluded that the curing temperature was a reaction accelerator in fly
ash-based geopolymers, and significantly affected the mechanical strength, together with the
curing time and the type of alkaline liquid.
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Higher curing temperature and longer curing time were proved to result in higher compressive
strength.
Alkaline liquid that contained soluble silicates was proved to increase the rate of reaction
compared to alkaline solutions that contained only hydroxide Van Jaarsveld et al (2002)
concluded that the water content, and the curing and calcining condition of kaolin clay affected
the properties of geopolymers. However, they also stated that curing at too high temperature
caused cracking and a negative effect on the properties of the material.
Finally, they suggested the use of mild curing to improve the physical properties of the material.
In another study, van Jaarsveld et al (2003) stated that the source materials determine the
properties of geopolymers, especially the CaO content, and the water-to-fly ash ratio.
Based on a statistical study of the effect of parameters on the polymerization process of Meta
kaolin-based geopolymers, Barbosa et al (1999; 2000) reported the importance of the molar
composition of the oxides present in the mixture and the water content.
They also confirmed that the cured geopolymers showed an amorphous microstructure and
exhibited low bulk densities between 1.3 and 1.9. Based on the study of geopolymerisation of
sixteen natural Si-Al minerals, Xu and van Deventer (2000) reported that factors such as the
percentage of CaO, K2O, and the molar Si-to-Al ratio in the source material, the type of alkali
liquid, the extent of dissolution of Si, and the molar Si-to-Al ratio in solution significantly
influenced the compressive strength of geopolymers.
2.3.4 Fields of Applications
According to Davidovits (1988b), geopolymeric materials have a wide range of applications in
the field of industries such as in the automobile and aerospace, nonferrous foundries and
metallurgy, civil engineering and plastic industries.
The type of application of geopolymeric materials is determined by the chemical structure in
terms of the atomic ratio Si:Al in the polysialate. Davidovits (1999) classified the type of
application according to the Si:Al ratio as presented in Table 2.1. A low ratio of Si: Al of 1, 2,
or 3 initiates a 3D-Network that is very rigid, while Si: Al ratio higher than 15 provides a
polymeric character to the geopolymeric material. It can be seen from Table 2.3.4 that for many
applications in the civil engineering field a low Si: Al ratio is suitable.
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One of the potential fields of application of geopolymeric materials is in toxic waste
management because geopolymers behave similar to zeolites materials that have been known
for their ability to absorb the toxic chemical wastes (Davidovits, 1988b).
Comrie (1988) also provided an overview and relevant test results of the potential of the use of
geopolymer technology in toxic waste management. Based on tests using GEOPOLYMITE 50,
they recommend that geopolymeric materials could be used in waste containment.
GEOPOLYMITE 50 is a registered trademark of Cordi-Geopolymere SA, a type of
geopolymeric binder prepared by mixing various alumina-silicates precondensates with alkali
hardeners.
Table no: 2.3.4Application of Geopolymeric Material Basedon Si: Al Atomic ratio
Si:Al ratio Applications
1
- Bricks
- Ceramics
- Fire protection
2
- Low CO2 cements and concretes
- Radioactive and toxic waste encapsulation
3
- Fire protection fiber glass composite
- Foundry equipments
- Heat resistant composites, 200oC to 1000oC
- Tooling for aeronautics titanium process
>3 - Sealants for industry, 200oC to 600oC
- Tooling for aeronautics SPF aluminum
20-35 - Fire resistant and heat resistant fiber composites
Another application of geopolymer is in the strengthening of concrete structural elements.
Bal guru (1997) reported the results of the investigation on using geopolymers, instead of
organics polymers, for fastening carbon fabrics to surfaces of reinforced concrete beams. It was
found that geopolymer provided excellent adhesion to both concrete surface and in the inter
laminar of fabrics.
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In addition, the researchers observed that geopolymer was fire resistant, did not degrade under
UV light, and was chemically compatible with concrete. In Australia, the geopolymer
technology has been used to develop sewer pipeline products, railway sleepers, building
products including fire and chemically resistant wall panels, masonry units, protective coatings
and repairs materials, shotcrete and high performance fiber reinforced laminates (Gurley, 2003;
Gurley & Johnson, 2005).
2.3.5 Properties of Geopolymers
Previous studies have reported that geopolymers possess high early strength, low shrinkage,
freeze-thaw resistance, sulfate resistance, corrosion resistance, acid resistance, fire resistance,
and no dangerous alkali-aggregate reaction.
Based on laboratory tests, Davidovits (1988b) reported that geopolymer cement can harden
rapidly at room temperature and gain the compressive strength in the range of 20 MPa after
only 4 hours at 20o
C and about 70-100 MPa after 28 days. Comrie et. al., (1988) conducted
tests on geopolymer mortars and reported that most of the 28- day strength was gained during
the first 2 days of curing.
Geopolymeric cement was superior to Portland cement in terms of heat and fire resistance, as
the Portland cement experienced a rapid deterioration in compressive strength at 300o
C,
whereas the geopolymeric cements were stable up to 600o
C (Davidovits, 1988b; 1994b). It has
also been shown that compared to Portland cement, geopolymeric cement has extremely low
shrinkage.
The presence of alkalis in the normal Portland cement or concrete could generate dangerous
Alkali-Aggregate-Reaction.
However the geopolymeric system is safe from that phenomenon even with higher alkali
content. As demonstrated by Davidovits (1994a; 1994b), based on ASTM C227 bar expansion
test, geopolymer cements with much higher alkali content compared to Portland cement did
not generate any dangerous alkali-aggregate reaction where the Portland cement did.
Geopolymer cement is also acid-resistant, because unlike the Portland cement, geopolymer
cements do not rely on lime and are not dissolved by acidic solutions.
As shown by the tests of exposing the specimens in 5% of sulfuric acid and hydrochloric acid,
geopolymer cements were relatively stable with the weight loss in the range of 5-8% while the
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Portland based cements were destroyed and the calcium alumina cement lost weight about 30-
60% (Davidovits, 1994b). Some recently published papers (Bakharev, 2005c; Gurley &
Johnson, 2005; Song et. al., 2005a) also reported the results of the tests on acid resistance of
geopolymers and geopolymer concrete.
By observing the weight loss after acid exposure, these researchers concluded that geopolymers
or geopolymer concrete is superior to Portland cement concrete in terms of acid resistance as
the weight loss is much lower. However, Bakharev and Song et. Al has also observed that there
is degradation in the compressive strength of test specimens after acid exposure and the rate of
degradation depended on the period of exposure.
Tests conducted by U.S. Army Corps of Engineers also revealed that geopolymers have
superior resistance to chemical attack and freeze/thaw, and very low shrinkage coefficients
(Comrie et. al., 1988; Malone et. al., 1985).
2.3.6 Studies on Geopolymer Mortar
Swanepoel, J.C and Strydom, C.A have prepared the geopolymers was made by mixing fly
ash, kaolinite, Na2Sio3, NaOH, and water. The samples were cured at 40o,50o,60o,& 70o C for
different time intervals (6,24,48,72 hours ) the compressive strength testing was performed at
the age of 7 & 28 days using 3 members 50mm cubic samples the authors reported that the
optimum curing condition for geopolymerisation was 60oC for a period of 48 hours .
Compressive strength measurements show a maximum strength of almost 80 MPa after 28
days.
Fernandez- Jimenez and Palomo have carried out the physical, chemical, mineralogical and
micro structural characterization of type F fly ash was carried out.
The reactivity of fly ash was determined using compressive strength testing data of mortar
specimen of size 4x4x16. The specimens were prepared by alkaline activation of various fly
ashes with 8molar NaOH solution. The sand to fly ash ratio was 1:2 all the specimens were
thermally cured in oven at 85oc for 20 hours. From results of experimental study, it was
concluded that the main characteristics of a fly ash for getting geopolymer material with
optimal binding properties should be within following limits. Percentage of unburned materials
lower than 5%: fe2o3 content not higher than 10% low content of Cao; content of reactive silica
between 40%-50% of particles with size lower than 45mm between 80 & 90% and also high
content of vitreous phase.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Kamhangrittirong and Suanvitaya were investigated the effect of fly ash content and NaoH
molarity on the compressive strength and setting time geopolymer paste .The fly ash (content
ranging from 45.0,52.5.60.0,67.5,&75% of the weight of the mix )was mixed with NaOH
solution. The NaOH concentration in the solution was varied as 8, 10 and 12 molar. The
specimen with dimensions of 3.81cmx3.81cmx3.81cm was cured in oven at 60oC for 6, 12, 18,
24, 48 and 72 hours.
The compressive strength was obtained at the age of 7 days. The setting time of the mix was
determined using Vicat’s apparatus by following procedure as per ASTM 191-192.It was
found that increasing the morality of NaOH significantly affected the setting time of the
geopolymer paste. Increasing NaOH morality from 8M to 12M decreased setting time from 68-
95 minutes to 31-66 minutes with increasing fly ash content from 45% to 75%.
It was also reported that the compressive strength of specimen increased rapidly within the
first 24 hours, there after the rate dropped sharply .The authors concluded that compressive
strength of geopolymer depends on NaOH Molarity and fly ash content of the mix.
2.3.7 Studies on Geopolymer Concrete
Hardijto, D.Wallah S.E.,Sumajouw D.M.J., and Rangan, B.V were investigated the effect of
various synthesizing parameters on fly ash based geopolymer concrete. Numerous bathes of
geopolymer concrete were prepared by activated class-F fly ash with sodium silicate and
sodium hydroxide solutions.
Four types of locally available aggregates of size20, 14, and 7 mm and fine sand, in saturated
surface dry condition, were used in making geopolymer concrete specimens. In this influence
of various geopolymer synthesizing parameters such as
 Concentration of sodium hydroxide.
 Sodium silicate to sodium hydroxide liquid ratio.
 Curing temperature and curing time.
 Addition of high range of water reducing admixtures.
 Handling time.
 Water content in admixtures.
 Age of concrete.
The drying shrinkage, creep and sulfate resistance of the geopolymer concrete was also
studied.
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CHAPTER -3
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
3 METHODOLOGY
3.1 Experimental Investigation
In order to develop the fiber-based geopolymer concrete, therefore, rigorous trail-and-error
process was used. The aim of the study was to identify the salient parameters that enhances the
mixture proportions and the properties of low calcium fly ash-based geopolymer concrete.
As far as possible, the current practice used in the manufacture and testing of ordinary Portland
cement (OPC) concrete was followed. The aim of this action was to ease the promotion of this
‘new’ material to the concrete construction industry.
In order to simplify the development process, the compressive strength was selected as the
benchmark parameter. This is not unusual because compressive strength has an intrinsic
importance in the structural design of concrete structures (Neville 2000).
Although geopolymer composites can be made using various source materials, the present
study used only low-calcium (ASTM Class F) dry fly ash.
Also, as in the case of OPC, the aggregates occupied 75-80 % of the total mass of concrete. In
order to minimize the effect of the properties of the aggregates on the properties of fly ash
based geopolymer, the study used aggregates from only one.
3.2Materials
3.2.1 Fly Ash
Fly ash is defined as ‘the finely divided residue that results from the combustion of ground or
powdered coal and that is transported by flue gasses from the combustion zone to the particle
removal system’ (ACI Committee 232 2004).
Fly ash is removed from the combustion gases by the dust collection system, either
mechanically or by using electrostatic precipitators, before they are discharged to the
atmosphere. Fly ash particles are typically spherical, finer than Portland cement and lime,
ranging in diameter from less than 1 μm to no more than 150 μm.
The types and relative amounts of incombustible matter in the coal determine the chemical
composition of fly ash. The chemical composition is mainly composed of the oxides of silicon
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
(SiO2), aluminium (Al2O3), iron (Fe2O3), and calcium (CaO), whereas magnesium, potassium,
sodium, titanium, and sulphur are also present in a lesser amount.
The major influence on the fly ash chemical composition comes from the type of coal. The
combustion of sub-bituminous coal contains more calcium and less iron than fly ash from
bituminous coal. The physical and chemical characteristics depend on the combustion methods,
coal source and particle shape.
CLASS F:
Class F fly ash is that type which moderates heat gain during curing of concrete.
Class F provides solution to summer concreting problems.
Recommended for use where concrete exposed to sulphate ion in soil and ground water.
Advantages:
 Hydration.
 Decreased water demand. Increased late compressive strength (after 28 days).
 Increased resistance to alkali silica reaction (ASR).
 Increased resistance to sulphate attack.
 Less heat generation during.
Cautions:
The time is slightly delayed and early compressive strength may be decreased slightly. If the
fly ash has high calcium content, it should not be used in hydraulic applications.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 3.2.1Sem Image Figure no: 3.2.2 Fly Ash
3.2.2 TESTING FOR FLY ASH
3.2.2.1 SPECIFIC GRAVITY
Objective: To determine the specific gravity of fly ash by using Le chatelier flask or specific
gravity bottle.
Apparatus:
a. Le chatelier flask or sp. Gravity bottle – 100 ml capacity.
b. Balance capable of weighing accurately up to 0.1 gm.
Producer:
Weigh a clean and dry Le chatelier flask or sp. gravity bottle with its stopper as (W1). Place a
sample of fly ash upto half of the flask (about 50 gm) and weight with its stopper (W2). Add
kerosene to fly ash in flask till it is about half filled. Mix thoroughly with a glass rod to remove
entrapped air. Continue stirring and add more kerosene till it is flush with the graduated mark.
Dry the outside and weigh it as (W3). Entrapped air may be removed by vacuum pump, if
available empty the flask, clean it and refill with kerosene flush with graduated mark wipe dry
the outside and weigh (W4).
Calculations:
Where, W1 = weight of empty bottle. = 0.55gms
W2 = weight of flask + fly ash. = 0.32gms
W3= weight of flask + fly ash + kerosene. = 0.98
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
W4= weight of flask + kerosene. = 0.70
0.79 is the specific gravity of kerosene.
Limits: specific gravity of fly ash ranges from 2.1 to 3.0
3.2.2.2 FINENESS TEST FOR FLY ASH
The fineness of fly ash is a measure of the size of particles of the fly ash. Hence it is necessary
to check the proper grading of fly ash as it has a influence on the behaviour of flyash. For a
given weight of fly ash the surface area is more for finer fly ash than for coarse flyash. The
finer fly ash has quicker chemical reaction with alkaline solutions and gain early strength.
Fine fly ash covers more surface area of aggregates. Fineness gives more cohesiveness and
bleeding. Too much fineness is undesirable because finer fly ash deteriorates more quickly
when exposed to air due to pre hydration and likely to cause more shrinkage. The fineness of
fly ash can be expressed either as surface area of particles in cm 2 per gram weight or
percentage weight of fly ash particle finer than 90 microns IS sieve.
Procedure:
Break down any air set lumps in the fly ash sample with fingers and mix it uniformly.
Weigh 100 grams of fly ash to the nearest 0.01 gram and place on a clean and dry 90 microns
IS sieve with pan attachment. Continuously sieve the sample by looking the sieve in both hands
for 15 minutes with a gentle wrist motion.
While sieving it ensures that there is no spillage of the fly ash and the fly ash shall be kept well
spread over on the sieve.
Do not use washers, bolts, and slugs on the sieve.
Slightly brush underside of the sieve after every 5 minutes of sieving.
Find the weight of residue on the sieve and report the value as a percentage of original samples
taken.
Observations:
Average of values = 2.55.
Results: The fineness of fly ash is 2.55 %.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
3.2.2 Chemical Composition of Fly Ash
3.3 GGBS (Ground Granulated BlastFurnace Slag)
3.3.1 GENERAL
Ground granulated blast furnace slag is also sometimes referred to as GGBS. It is obtained by
quenching molten iron slag from blast furnace in water or steam, dried and ground into a fine
powder. Its use results in the in lower heat of hydration and lower temperature rises, further it
reduces the risk of damages caused by alkali – silica reaction. Provides higher resistance to
chloride ingress reducing the risk of reinforcement corrosion and provides higher resistance to
attacks by Portland cement sulphate and other chemicals. Use of GGBS increases the life of
the structure by up to 50% had only been used and precludes the need of stainless
reinforcement. It is also routinely used to limit the temperature rise in large concrete pours,
which prevents the occurrence of micro cracking.
3.3.2 USES OF GGBS
In the production of ready mix concrete, GGBS replaces a substantial portion of normal
Portland cement content, generally about 50% but sometimes up to70%. The higher the
proportion the better is the durability. The disadvantage of the higher replacement level is the
early age strength development is somewhat slower.
SI.NO Composition percent by mass
Result
1. SiO2+Al2O3+Fe2O3 94.66
2 SiO2 60.78
3. MgO 0.94
4. Total sulphur as SO3 0.12
5 Loss on ignition 0.88
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
GGBS is also used in ready mixed concrete and it is utilized a third of all UK ready mix
deliveries. Specifiers are well aware of all the technical benefits which GGBS imparts to
concrete, including:
 Better workability, making placing and compaction easier.
 Lower early age temperature rise, reducing the thermal cracking in in large pours.
 Elimination of the risk of damaging internal reaction such as ASR.
 High resistance chloride ingress, reducing the risk of reinforcement corrosion.
 Considerable sustainability benefits.
Figure no: 3.3 GGBS
Table no: 3.3.A Strength Achievement As % of 28 - Day strength
AGE 0% GGBS 50% GGBS 70%GGBS
7 DAYS
28 DAYS
75%
100%
45-55%
100%
40-50%
100%
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Table no: 3.3B Chemical Properties of GGBS
Cao 30-50%
siO2 28-38%
Al2O3 8-24%
MgO 1-18%
MnO 0.68%
TiO2 0.58%
K2O 0.37%
Table no: 3.3C Physical Properties of GGBS
Particle size 0.1 – 40 microns
Specific surface area 400 – 600 m2/kg
Bulk density 1.0 – 1.1 tones/m3
Relative density 2.85 – 2.95
pH ( T = 20 0C in water ) 9 - 11
3.4 Alkaline Liquid
A combination of sodium silicate solution and sodium hydroxide solution was chosen as the
alkaline liquid. Sodium-based solutions were chosen because they were cheaper than
Potassium-based solutions.
The sodium hydroxide solids were pellets form (3 mm), with a specific gravity of 1.51, 98%
purity.
The sodium hydroxide (NaOH) solution was prepared by dissolving either the flakes or the
pellets in water. The mass of NaOH solids in a solution varied depending on the concentration
of the solution expressed in terms of molar, M.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
For instance, NaOH solution with a concentration of 8M consisted of 8x40 = 320 grams of
NaOH solids (in flake or pellet form) per litre of the solution, where 40 is the molecular weight
of NaOH. .
Note that the mass of NaOH solids was only a fraction of the mass of the NaOH solution, and
water is the major component. Sodium hydroxide has a high heating capacity that can ignite
substances. To overcome this heat the sodium hydroxide pellets are dissolved in water 24hours
before the mix preparation.
Table no: 3.4 Specification and Impurity limits of NaOH
Acidimetric 97.0%
Carbonate 2.0%
Chloride 0.01%
Sulphate 0.01%
Phosphate 0.001%
Iron 0.005%
Heavy metal 0.001%
Molecular weight 40.00
3.5 Sodium silicate
Sodium silicate are used in alkaline solution along with sodium hydroxide. The pure form of
sodium silicate solution is of colourless or white in colour. Sodium silicate reacts with lime
that is present in our concrete.
Sodium hydroxide has a high heating capacity that can ignite substances. To overcome this
heat the sodium hydroxide pellets are dissolved in water 24hours before the mix preparation.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 3.5 Sodium Silicate
Table no: 3.5 Property Specification of Sodium Silicates
Description Clear viscous liquid
pH 8.2
SiO2 28.00%
Na2O 7.5%
Wt. per ml,200C 1.366g/ml
Figure no: 3.5 Sodium Silicate Pellets
3.6 Super Plasticizer
Super plasticizer that we use is water reducer it decrease the water cement ratio without
effecting the workability of our fiber based Geo-polymer concrete. The superplasticizer we are
using is SP-430.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Type F and Type G, High Range Water Reducer (HRWR) and retarding admixtures are used
to reduce the amount of water by 12% to 30% while maintaining a certain level of consistency
and workability (typically from 75 mm to 200 mm) and to increase workability for reduction
in w/cm ratio. The use of superplasticizers may produce high strength concrete (compressive
strength up to 22,000 psi). Superplasticizers can also be utilized in producing flowing concrete
used in a heavy reinforced structure with inaccessible areas.
Another benefit of superplasticizers is concrete early strength enhancement (50 to 75%). The
initial setting time may be accelerated up to an hour earlier or retarded to be an hour later
according to its chemical reaction.
Retardation is sometimes associated with range of cement particle between 4 – 30  m. The
use of superplasticizers does not significantly affect surface tension of water and does not
entrain a significant amount of air. The main disadvantage of superplasticizer usage is loss of
workability as a result of rapid slump loss and incompatibility of cement and superplasticizers.
Typical dosage of superplasticizers used for increasing the workability of concrete ranges from
1 to 3 liters per cubic meter of concrete where liquid superplasticizers contained about 40 % of
active material. In reducing the water cement ratio, higher dosage is used, that is from 5 to 20
liters per cubic meter of concrete. Dosage needed for a concrete mixture is unique and
determined by the Marsh Cone Test.
There are four types of superplasticizers:
1. Sulfonated melamine
2. Sulfonated naphthalene
3. Modified lignosulfonates and a combination of high dosages of water reducing and
accelerating admixtures.
Commonly used are melamine based and naphthalene based superplasticizers. The use of
naphthalene based has the advantage of retardation and affecst slump retention. This is due to
the modified hydration process by the sulfonates
To improve the workability of the fresh geopolymer concrete, a naphthalene sulphonate super
plasticizer rebuild used for improving the workability.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Superplasticizers are linear polymers containing sulphonic acid group attached to polymer
backbone and are new improved version of plasticizers called high range water reducers. Super
plasticizers are more powerful as dispersing agents. Super plasticizer is one of a class of
admixer called water reducer that are used to lower the mix water requirement of concrete.
Figure No: 3.6 Super Plasticizer
3.6.1 Properties of Superplasticizers
 Excellent flow ability at low water cement ratio.
 High reduction of water.
 Lower slump loss with time.
 Shorter retardation time and early strength.
 It works at low density.
3.6.2 Effects of Super Plasticizers on Concrete Properties
Purpose of using super plasticizers is to produce flowing concrete with very high slump range
of 7-9 inches (175-225mm) to be used in heavily reinforced structures and in placements
adequate.
 Major application is the production of high strength concrete
 To increase the workability of concrete.
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 Ability of super plasticizer to increase the slump of concrete depending on such
factors:
 Type
 Dosage
 Time of addition of super plasticizer
 Water cement ratio
 Nature or amount of cement
3.7 Aggregates
3.7.1 Coarse Aggregate
Majority of the particles of the coarse aggregates were of granite type.
Machine crushed angular granite metal of 12.5mm size from the local source is used as coarse
aggregate. It should be free from impurities such as dust, clay particle, and organic matter etc.
Figure No: 3.7.1 Coarse Aggregate
IMPACT TEST:
Objective: To determine the impact value of given coarse aggregate.
Apparatus:
Impact testing machine.
Tampering rod.
Balance.
Oven.
IS sieve of 12.5mm, 10mm, and 2.36mm for sieving aggregates.
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Procedure:
The test sample consists of aggregates passing 12.5mm sieve and retained on 10 mm sieve and
dried in an oven for four hours at a temperature 100°C to ll0 o C and cooled.
Test aggregates are filled up to about one-third full in the mould and tamped 25times.The
surplus aggregates are struck off using the tamping rod as straight edge .
The entire sample is filled in this way I three layers. The mould is fixed firmly in position on
the base of the machine and compacted by tamping with 25 strokes.
The hammer is raised until its lower face is 38cm above the upper surface of the aggregates in
the cup, and allowed to fall freely on the aggregates. The test sample is subjected to a total of
25 such blows, each being delivered at an interval of not less than one second. The crushed
aggregate is then removed from the cup and the whole of it sieved on the
2.36 mm sieve until no further significant amount passes.
Calculations:
The aggregate impact value is expressed as the percentage of the fines formed in terms of the
total weight of the sample.
Let the original weight of the oven dry sample be W 1 g and the weight of fraction passing 2.36
mm IS sieve be W 2 g.
Aggregate impact value =
Results: Therefore, the aggregate is exceptionally strong.
3.7.2 FINE AGGREGATE
The river sand obtained from local source was used as fine aggregate used for preparation. It
should be free from silt, clay, organic impurities, etc. The sand is tested for various properties
such as specific gravity, bulk density, etc., in accordance with IS: 2386-1963. The grading or
particle size distribution is close to zone – II or IS: 383 – 1970 fineness modulus of sand
aggregate is 3.42.The surface dry sand was used in geopolymer mix to avoid the water
absorption.
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Figure No: 3.7.2 Fine Aggregate
Table No: 3.7.2 Sieve Analysis
SNO Particle
size(mm)
Weight
retained(gm)
% Weight
retained
%cumulative
Weight
retained
% finer
1 4.75 2.99 0.299 0.299 99.701
2 2.36 1.16 0.116 0.415 99.585
3 1.18 16 1.6 2.015 97.985
4 0.60 82 8.2 10.215 89.785
5 0.30 686 68.6 78.815 21.185
6 0.15 168 16.8 95.615 4.385
7 0.075 34 3.4 99.015 0.985
8 Pan(<0.075) 1.39 0.139 99.154 0.846
SPECIFIC GRAVITY:
Objective: To determine the specific gravity of given sample of coarse aggregates.
Apparatus: pycnometer, sieve, vacuum pump, weighing balance, glass rod.
Procedure:
Tightly screw its cap. Take its mass (M1) to the nearest of 0.1g. Mark the cap and cylinder with
a vertical line parallel to the axis of the cylinder to ensure that the cap is screwed to the same
mark each time. Unscrew the cap and place about 200g of oven dried coarse aggregate in the
cylinder. Screw the cap. Determined the mass (M2).Unscrew the cap and add sufficient amount
of de-aired water to the cylinder so as to cover the soil. Screw on the cap. Shake the contents
well. Connect the cylinder to a vacuum pump to remove the entrapped air.
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For about 10 minutes for coarse-aggregates .Disconnect the vacuum pump. Fill the cylinder
with water, about three -fourth full. Reapply the vacuum for about 5min till air bubbles stop
appearing on the surface of the water. Fill the cylinder with water completely up to the mark.
Dry it from outside. Take its mass (M3). Record the temperature of contents. Empty the
cylinder.
Clean tit and wipe it dry. Fill the cylinder with water only. Screw on the cap up to the mark.
Wipe it dry. Take it mass (M4).
Result: Avg. of both readings specific gravity is taken as 2.68.
FLAKINESS INDEX:
Object: To determine flakiness index of a given aggregates sample.
Apparatus: The apparatus consists of a standard thickness gauge shown in fig 5.1, IS sieves
of the sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm and a balance to weight the
samples.
Procedure:
The flakiness index is the percentage by weight of Particles in it whose least dimension.
Thickness is less than three-fifths of their mean dimensions. The test is not applicable to sizes
smaller than 6.3mm.This test is conducted by using a metal thickness gauge, of the description.
A sufficient quantity of aggregate is taken such that a minimum number of 200 pieces of any
fraction can be tested. Each fraction is gauged in turn for the thickness on the metal gauge. The
total amount passing in the gauge is weighed to an accuracy of 0.1 percent of the weight of the
samples taken. The flakiness index is taken as the total weight of the material passing the
various thickness gauges expressed as a percentage of the total weight of the sample taken.
Results: The flakiness index is 70%.
ELONGATION INDEX:
Objective: To determine elongation index of a given aggregates sample.
Apparatus: The apparatus length gauge consists of the Standard length gauge. IS sieve of size
50, 40, 25, 20, 16, 12.5, 10 and 6.3 mm,a balance to weigh the samples.
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Procedure:
The elongation index on an aggregate is the percentage by weight of particles whose greatest
dimension is greater than 1.8 times their mean dimension. The elongation index is not
applicable to sizes smaller than 6.3mm.This test is conducted by using metal length gauge of
the description shown in fig. A sufficient quantity of aggregate is taken to provide a minimum
number of 200 pieces of any fraction to be tested. Each fraction shall be gauged individually
for length on the metal gauge. The total amount retained by the gauge length shall be weighed
to an accuracy of 0.1percent of the weight of the test samples taken. The elongation index is
the total weight on material retained on the various length gauges expressed as a percentage of
the total weight of the sample gauged. The presence of elongated particles in excess of 10 to
15 percent is generally considered undesirable, but no recognized limits are laid down.
Results: The elongation index is taken as 14%.
3.8 FIBRES AND ITS PROPERTIES
3.8.1 GLASS FIBRE
Glass fibre (or glass fibre) is a material consisting of numerous extremely fine fibres of glass.
Glass wool, which is one product called "fiberglass" today, was invented in 1932–1933 by
Russell Games Slayter of Owens-Corning, as a material to be used as thermal building
insulation.
It is marketed under the trade name Fiberglas, which has become a genericized trademark.
Glass fiber when used as a thermal insulating material, is specially manufactured with a
bonding agent to trap many small air cells, resulting in the characteristically air-filled low-
density "glass wool" family of products.
Glass fiber has roughly comparable mechanical properties to other fibers such as polymers and
carbon fiber. Although not as strong or as rigid as carbon fiber, it is much cheaper and
significantly less brittle when used in composites. Glass fibers are therefore used as a
reinforcing agent for many polymer products; to form a very strong and relatively lightweight
fiber-reinforced polymer (FRP) composite material called glass-reinforced plastic (GRP), also
popularly known as "fiberglass". This material contains little or no air or gas, is denser, and is
a much poorer thermal insulator than is glass wool.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Glass fibers are useful thermal insulators because of their high ratio of surface area to weight.
However, the increased surface area makes them much more susceptible to chemical attack.
By trapping air within them, blocks of glass fiber make good thermal insulation, with a thermal
conductivity of the order of 0.05 W/(m·K).
Tensile strength of glass is usually tested and reported for "virgin" or pristine fibers those that
have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner
fibers are more ductile. The more the surface is scratched, the less the resulting tenacity.
Because glass has an amorphous structure, its properties are the same along the fiber and across
the fiber. Humidity is an important factor in the tensile strength.
Moisture is easily adsorbed and can worsen microscopic cracks and surface defects, and
Lessen tenacity.
In contrast to carbon fiber, glass can undergo more elongation before it breaks. Thinner
filaments can bend further before they break. The viscosity of the molten glass is very important
for manufacturing success. During drawing, the process where the hot glass is pulled to reduce
the diameter of the fiber, the viscosity must be relatively low. If it is too high, the fiber will
break during drawing. However, if it is too low, the glass will form droplets instead of being
drawn out into a fiber.
Table No: 3.8.1 Properties of Glass Fibre of Glass Fibre
Density 2.5
Young’s modulus (Gpa) 70
Tensile strength (Mpa) 2000 -3500
Elongation at break (%) 2.5
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure No: 3.8 Glass Fibre
3.8.2 CRIMPED STEEL FIBRE
For the geopolymer mix we have used crimped stainless steel fibres. The use of fibres in
concrete has the property to resistance against cracking and crack propagation. The fibre
composite pronounced post cracking ductility which is unheard of in ordinary concrete. The
transformation from a brittle to a ductile type of material would increase substantially the
energy absorption characteristics of the fibre composite and its ability to withstand repeatedly
applied shock or impact loading. These fibres are short, discrete lengths having an aspect ratio
in the range of 20-100, with any cross section that are sufficiently small to be randomly
dispersed in an unhardened concrete.
Further they are low carbon, cold drawn steel wire fibres designed to provide concrete with
temperature and shrinkage crack control, enhanced flexural reinforcement, improved shear
strength and increase the crack resistance of concrete. These steel macro-fibres will also
improve impact, shatter, and fatigue and abrasion resistance while increasing toughness of
concrete. Dosage rates will vary depending upon the reinforcing requirements and can range
from 15 to 60 kg/m³.
3.8.2.1 FEATURES AND BENEFITS
 Increases impact, shatter and abrasion resistance of concrete
 Reduces segregation, plastic settlement, and shrinkage cracking of concrete
 Provides three-dimensional reinforcement against macro-cracking
 Increases overall durability, fatigue resistance and flexural toughness
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 Reduction of in-place cost versus wire mesh for temperature / shrinkage crack control
 Easily added to concrete mixture at any time prior to placement
3.8.2.1 APPLICATION
 Commercial and industrial slabs on ground
 Bridge decks, overlays and pavements
 Precast concrete applications
 Shotcrete, tunnel linings and slope stabilization
 Mass concrete and composite deck construction
Table No: 3.8.2 Properties of Crimped Steel Fibre
Length 3cm
Thickness 1mm
Tensile strength (mpa) 421-800
Elongation of break 1.62
Diameter (mm) 0.8-1.2mm
Density (g/cm3) 1.47
Young’s modulus (Gpa) 21-72
Figure 3.8.2 Crimped Steel Fibre
3.9 MIX DESIGN REQUIREMENT
The requirement which form the basis of selection and proportioning of mmix ingredients are:
The minimum compressive strength required from the structural consideration.
The adequate workability necessary for full compaction wuth compacting equipment available.
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3.9.1 MIX DESIGN PROCESS FOR GEOPOLYMER CONCRETE
Step1: By using Codebook IS10262:2009 we need to find the target strength for mix
proportions is given as
Fck = fck + 1.65S
Where, “S” is standard deviation
Fck = 50+1.65*5
= 58.25 Mpa.
Step2: Binder is assumed as 420kg/m3 and alkaline binder is taken as 0.50. By following the
codebook at A-8 mix calculations. Calculate volumes of materials as shown below
Volume of fly ash = mass of binder content /sp.gravity of solution * 1/1000
Where, Specific gravity of solution from codebook is taken as 2.2
= (420/2.2)*(1/1000)
= 0.19 m 3
Volume of alkaline solution = 0.5*binder/ sp. gravity of solution * 1/1000
Where, Specific gravity of solution is taken as 1.34
= (0.5*420/1.34)*1/1000
=0.156 m 3
Volume of super plasticizers= % of super plasticizer*binder/sp. gravity of solution
*1/1000 (sp. gravity is taken 1.2).
The quantity of super plasticizers is taken as 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%
for the mixture.
For super plasticizer 1.5% = ((1.5/100)*420/1.34)*1/1000
= 0.0047
For super plasticizer 2.0% = ((2.0/100)*420/1.34)*1/1000
=0.0062
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For super plasticizer 2.5% = ((2.5/100)*420/1.34)*1/1000
= 0.0078
For super plasticizer 3.0% = ((3.0/100)*420/1.34)*1/1000
= 0.0094
For super plasticizer 3.5% = ((3.5/100)*420/1.34)*1/1000
= 0.010
For super plasticizer 4.0% = ((4.0/100)*420/1.34)*1/1000
=0.012
Volume of aggregate = 1-(volume of fly ash + volume of alkaline solution + volume of super
plasticizers.
= 1- (0.193+0.156+0.012)
= 0.639m 3
Step3: Taking or by assuming the specific gravity of coarse and fine aggregate from
Codebook the ratio of coarse and fine aggregate is taken is calculated as given below.
Aggregate/binder = 4.23
Total aggregate = 4.23*420
=1776Kg/m3
Coarse /total aggregate = 0.543
Which is taken as
= 0.543*1776.6
= 965 kg/m 3
Mass of fine aggregate = Total aggregate – Coarse aggregate
=1776.6-965
= 811 kg/m3
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Alkaline solution = binder * 0.5 (0.5 is the water content).
= 420*0.5
= 210
By doing that we get a ratio as
Binders: fine aggregate: coarse aggregate: alkaline solution
420: 811: 965: 210
Divide the above ratios with 420
The ratio is taken as
1: 1.93: 2.29: 0.5
Step4: By taking the ratios from step3, we should find out how much quantity of material is
required for that particular mix .The steps are below,
Binder (fly ash &amp; GGBS) = ratio of binder/total ratio * total weight of cubes.
Binding varying GGBS 50% = 1/5.72*80 = 13.98(GGBS)
For 50% GGBS = 13.98*0.5 = 6.99
Fly ash = 13.98 – 6.99 = 6.99
Fine aggregate= ratio of fine aggregate/total ratio * total weight of cubes.
= 1.93/5.72*28
= 9.45 kg/m3
Coarse aggregate= ratio of coarse aggregate/total ratio * total weight of cubes.
= 2.29/5.72*28
= 11.2 kg/m3
Alkaline solution= water content (i.e., 0.5)/total ratio * total weight of cubes.
= 0.5/5.72*28
= 2.45 kg/m3
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Super plasticizer = volume of super plasticizer *total weight of cubes*0.5.
The quantity of super plasticizers is taken as 1.5%, 2.0%, 2.5%, 3.0%, 3.5%,
4.0%.for the mixture.
For super plasticizer 1.5% = 0.005*80*0.5 = 225ml.
For super plasticizer 2.0% = 0.0066*80*0.5 = 300ml.
For super plasticizer 2.5% = 0.0083*80*0.5 = 375ml.
For super plasticizer 3.0% = 0.01 *80*0.5 = 450 ml.
For super plasticizer 3.5% = 0.0116*80*0.5 =525 ml.
For super plasticizer 4.0% = 0.0133 *80*0.5 = 600ml
Combination of steel and glass fibre were taken in the range of 0.1% to 0.6%.
3.9.1 TYPES OF MIXES
A mix design can be designed in two ways as explained below
a) Nominal Mix
b) Design Mix
c) Standard Mix
3.9.1.1 Nominal Mix
It is used for relatively unimportant and simpler concrete works. In this type of mix, all the
ingredients are prescribed and their proportions are specified. Therefore there is no scope for
any deviation by the designer. Nominal mix concrete may be used for concrete of M-20 or
lower. The various ingredients are taken as given in the table below
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Table no: 3.9.1 Nominal mix
Grade
Max. quantity of dry
Aggregates per 50 kg
of cement
Fine Aggregate to
Coarse Aggregate
Ratio, by mass
Max. Quantity of water
in litres
M-5 800
Generally 1:2 but may
varies from 1:1.5 to
1:2.5
60
M-7.5 625 45
M-10 480 34
M-15 330 32
M-20 250 30
3.9.1.2 DesignMix
It is a performance based mix where choice of ingredients and proportioning are left to the
designer to be decided. The user has to specify only the requirements of concrete in fresh as
well as hardened state. The requirements in fresh concrete are workability and finishing
characteristics, whereas in hardened concrete these are mainly the compressive strength and
durability.
3.9.1.3 Standard Mixes
The nominal mixes of fixed cement-aggregate ratio (by volume) vary widely in strength and
may result in under- or over-rich mixes. For this reason, the minimum compressive strength
has been included in many specifications. These mixes are termed standard mixes.IS 456-2000
has designated the concrete mixes into a number of grades as M10, M15, M20, M25, M30,
M35 and M40. In this designation the letter M refers to the mix and the number to the specified
28 day cube strength of mix in N/mm2. The mixes of grades M10, M15, M20 and M25
correspond approximately to the mix proportions (1:3:6), (1:2:4), (1:1.5:3) and (1:1:2)
respectively.
3.10 FACTORS AFFECTINGTHE CHOICE OF MIX PROPORTIONS
The various factors affecting the mix design are:
1. Compressive strength: It is one of the most important properties of concrete and
influences many other describable properties of the hardened concrete. The mean
compressive strength required at a specific age, usually 28 days, determines the nominal
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water-cement ratio of the mix. The other factor affecting the strength of concrete at a
given age and cured at a prescribed temperature is the degree of compaction. According
to Abraham’s law the strength of fully compacted concrete is inversely proportional to
the water-cement ratio.
2. Workability: The degree of workability required depends on three factors. These are
the size of the section to be concreted, the amount of reinforcement, and the method of
compaction to be used. For the narrow and complicated section with numerous corners
or inaccessible parts, the concrete must have a high workability so that full compaction
can be achieved with a reasonable amount of effort. This also applies to the embedded
steel sections. The desired workability depends on the compacting equipment available
at the site.
3. Durability: The durability of concrete is its resistance to the aggressive environmental
conditions. High strength concrete is generally more durable than low strength concrete.
In the situations when the high strength is not necessary but the conditions of exposure
are such that high durability is vital, the durability requirement will determine the
water-cement ratio to be used.
4. Maximum nominal size of aggregate: In general, larger the maximum size of
aggregate, smaller is the cement requirement for a particular water-cement ratio,
because the workability of concrete increases with increase in maximum size of the
aggregate. However, the compressive strength tends to increase with the decrease in
size of aggregate. IS 456:2000 and IS 1343:1980 recommend that the nominal size of
the aggregate should be as large as possible.
5. Grading and type of aggregate: The grading of aggregate influences the mix
proportions for a specified workability and water-cement ratio. Coarser the grading
leaner will be mix which can be used. Very lean mix is not desirable since it does not
contain enough finer material to make the concrete cohesive.The type of aggregate
influences strongly the aggregate-cement ratio for the desired workability and
stipulated water cement ratio. An important feature of a satisfactory aggregate is the
uniformity of the grading which can be achieved by mixing different size fractions.
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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
6. Quality Control: The degree of control can be estimated statistically by the variations
in test results. The variation in strength results from the variations in the properties of
the mix ingredients and lack of control of accuracy in batching, mixing, placing, curing
and testing. The lower the difference between the mean and minimum strengths of the
mix lower will be the cement-content required. The factor controlling this difference is
termed as quality control.
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CHAPTER -4
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4. GEOPOLYMER MORTAR
Geopolymers prepared by mixing of ggbs and fly ash with alkali activator solution is called
geopolymer paste. The mixer is usually homogeneous slurry. In manufacturing geopolymer
mixes, following range of synthesizing parameters are selected and studied their effect on
compressive strength of geopolymer mortar.
 NaOH molarity : 8M
 Curing type : Ambient curing
 Curing time : 3days,7days, 28days
4.1 MaterialPreparation
Initially collect the material and weigh to require proportion i.e. fly ash, sand, coarse
aggregates, ggbs, NaOH and sodium silicate solution. A combination of sodium hydroxide
solution and sodium silicate solution was used as the alkaline activator. Sodium hydroxide
solution prepared by taking specified weight of sodium hydroxide pellets into a beaker and add
required amount of water according to its molarity. Sodium hydroxide solution was used as
alkaline activator because it is widely available and is less expensive than potassium hydroxide
solution. The alkaline activator was prepared in the laboratory. In order to avoid the effect of
unknown contaminants, distilled water was used to dissolve the sodium hydroxide pellets.
The alkaline activator was prepared by mixing the sodium hydroxide solution with sodium
silicate solution together just before the mixing of mortar to ensure the reactivity of solution.
The aim of adding sodium silicate is to enhance the formation of Geopolymer precursors or the
polymerization process.
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Figure no: 4.1.A Material Preparation
4.2 Mixing
The fly ash and the fine aggregate were first dry mixed together in pan for 2 minutes to ensure
homogeneity of the mixture. The mixture was activated by adding activator solution containing
sodium hydroxide and sodium silicate according to the required concentration range of 8 to
16M and mixed for a further 10 minutes. The concrete shall be mixed by hand or preferably in
a laboratory mixer, in such a manner as to avoid loss of other materials. Each batch of concrete
shall be of such as to leave about 10 percent excess after moulding the desired number of test
specimen.
a. Hand mixing
Concrete is mixed by any two methods, based on requirement as per quality and quantity of
concrete required. Normally for mass concrete, where good quality of concrete is required,
mechanical mixer is used.
Mixing by hand is employed only to specific cases where quality control is not of much
importance and quantity of concrete required is less. Stone aggregate is washed with water to
remove dirt, dust or any other foreign material before mixing.
The main purpose of mixing the concrete is to finally obtain a uniform mixture that shows
uniformity in terms of color and consistency.
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Figure no: 4.2A Hand Mixing
4.3 SIZE OF TEST SPECIMEN
Test specimens cubical in shape shall be 15x15x15cm.Cylindrical test specimens shall have a
length equal to twice the diameter they shall be 15 cm in diameter and 30 cm in height. Beam
moulds shall have the dimensions 10x15x10 cm
Cylinder Cube Beam
Figure no: 4.3A Mould Preparation
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4.4 Compaction
The test specimens shall be made as soon as practicable after mixing, and in such a way as to
produce full compaction of the concrete with no segregation. The concrete shall be filled into
the mould in the layers approximately 5 cm deep, in placing each scoopful of concrete, the
scoop shall be moved around the top edge of the mould as the concrete slides from it, in order
to ensure symmetrical distribution of concrete with in mould. Each mould shall be compacted
either by hand or by vibration as described below. After the top layer has been compacted
either, the surface of the concrete shall be finished level with the top of the mould, using a
trowel. All the cast specimens were vibrated on a vibrating table for 2 minutes to remove air
voids. The tamping bar shall be a steel bar 16mm in diameter, 0.6m long and bullet pointed at
the lower end.
Figure no: 4.3A Mould Preparation Figure no: 4.4B Vibrating Machine
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4.5 Curing
All the specimens were kept at a room temperature for setting in the moulds and were moved
under open air for ambient curing. The moulds were kept under ambient curing for the specified
number of days i.e., 3days, 7 days, 28days before testing.
Figure no: 4.5A Curing
4.6 Testing
After the ambient curing, all the specimens were removed and cured undisturbed at room
temperature until they are tested. The Geopolymer mortar specimens were tested for 3 and7
day’s compressive strength using the Compression Testing Machine and tensile strength using
tensile strength machine. The specimens were subjected to a compressive force at the rate of
1700 N/sec and tensile strength until the specimen failed. The reported strengths were the
average results of the three tests.
4.6.1 Compression Strength Test
Out of many test applied to the concrete, this is the utmost important which gives an idea about
all the characteristics of concrete. By this single test one judge that whether Concreting has
been done properly or not. Compressive strength of concrete depends on many factors such as
water-cement ratio, fly ash strength, quality of concrete material, and quality control during
production of concrete. For most of the works cubical moulds of size 15 cm x 15cm x 15 cm
are commonly used. This concrete is poured in the mould and tempered properly so as not to
have any voids. After 24 hours these moulds are removed and test specimens are put for
ambient curing. The top surface of these specimens should be made even and smooth. This is
done by putting paste and spreading smoothly on whole area of specimen. These specimens
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are tested by compression testing machine after 3, 7 and 28 days of curing. Load should be
applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the
failure divided by area of specimen gives the compressive strength of concrete.
Figure no: 4.6.1Compression strength test
4.6.2 Split Tensile Strength Test
Tensile strength is one of the basic and important properties of concrete. A knowledge of its
value is required for the design of the concrete elements. Direct tensile strength is difficult to
determine; recourse is often taken to the determination of flexural strength or the splitting
tensile strength, further it is a method of determining the tensile strength of concrete using a
cylinder which splits across a vertical diameter. In direct tensile strength test it is impossible to
apply true axial load. The mould and base plate shall be coated with a thin film of mould oil
before use, in order to prevent adhesion of the concrete prepare three cylindrical concrete
cylindrical. After moulding and curing the specimens for the specified number of days under
ambient curing, they can be tested. The cylindrical specimen is placed in the manner that the
longitudinal axis is perpendicular to the load. The load shall be applied without shock and
increased continuously at a nominal rate within the range 1.2 N/mm2 to 2.4 N/mm2. Record the
maximum applied load indicated by the testing machine at failure.
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Figure no. 4.6.2 Split tensile strength test
4.6.3 Flexural Strength Test
It is also known as modulus of rupture, bend strength or fracture strength, a mechanical
parameter for brittle material, is defined as a materials ability to resist deformation under load.
The test specimens prepared after curing under ambient curing for the specified number of
day’s i.e. (7 days, 14 days, and 28 days). The specimens shall be placed in the machine in such
a manner that the load shall be applied to the upper most surface as cast in the mould. The axis
of the specimen shall be carefully aligned with axis of the loading device. The load was
increased until the specimen failed and the maximum applied load to the specimen during the
test is recorded.
Figure no: 4.6.3 Flexural strength test
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CHAPTER – 5
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5 RESULTS AND DISCUSSION
5.1 General
In this chapter the strength parameters of the fibre based geopolymer concrete are discussed.
The parameters such as compressive strength and tensile strength of the geopolymer concrete
using fibres (crimped steel fibre and glass fibre) are discussed.
5.2 Concentration of alkaline solution, fly ash, GGBS, and fibres
Mix was prepared for M50 to study the effect of Molarity (or) concentration of Sodium
Hydroxide solution, fly ash, GGBS and fibers (i.e. crimped steel and glass fibers) on the
compressive strength of geopolymer concrete. The concentration of NaOH of 8M was used.
For M50 mix for the beams the fly ash content was kept zero and GGBS was kept 100% further
sand and Na2SiO3 weights were kept constant.
5.3 Tests on M50 cubes, cylinders and prisms using steelfibres
Table no: 5.3A Compressive strength for standard mix (Cubes)
Mix
3 Days 7 Days 28 Days
Compressive
Strength in
N/mm2
Average
strength
in
N/mm2
Compressive
Strength in
N/mm2
Average
strength
in
N/mm2
Compressive
Strength in
N/mm2
Average
strength
in
N/mm2
Standard
mix
23.4
23.32
23.48
23.4
46.8
46.64
46.96
46.8
58.5
58.3
58.7
58.5
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Figure no: 5.3A Compressive strength of standard mix (Cubes)
The mix design ratio for Cubes of M-50 grade (1:1.93:2.29:0.5) using steel fibres
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=4.9 kgs.
Fine aggregate=9.45 kgs.
Coarse aggregate=11.2 kgs.
Alkaline=2.45 kgs.
Table no: 5.3A1 Compressive strength of M50 cubes using Steel fibres
% of Steel fibers 3 Days 7 Days 28 Days
0.1% 24.08 48.16 60.2
0.2% 24.6 49.2 61.5
0.3% 24.9 49.8 62.3
0.4% 24.72 49.4 61.8
0.5% 24.56 49.1 61.4
0.6% 24.1 48.2 60.3
0
10
20
30
40
50
60
3 Days 7Days 28Days
23.4
46.8
58.5
CUBES
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Figure no: 5.3A1 Compressive strength of M50 cubes using Steel fibres
5.3B Split tensile strength test on M50 cylinders using steel fibres
Table no: 5.3B Split tensile strength for standard mix (Cylinders)
Mix
3 Days 7 Days 28 Days
Tensile
Strength
in
N/mm2
Average
Tensile
Strength
in
N/mm2
Tensile
Strength
in
N/mm2
Average
Tensile
Strength
N/mm2
Tensile
Strength
in
N/mm2
Average
Tensile
Strength
N/mm2
Standard
mix
1.92
1.92
1.94
1.92
3.84
3.82
3.88
3.85
4.80
4.82
4.85
4.82
24.08 24.6 24.92 24.72 24.56 24.12
48.16 49.2 49.8 49.4 49.12 48.2
60.2 61.5 62.3 61.8 61.4 60.3
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
10
20
30
40
50
60
70
1 2 3 4 5 6
CUBES
3 Days 7 Days 28 Days % of fibers
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Figure no: 5.3B Split tensile strength of standard mix (Cylinders)
The mix design ratio for Cylinders of M-50 grade is 1:1.93:2.29:0.5 using Steel fibres
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alakaline=3.5 kgs
Table no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres
% of steel fibers 3 Days 7 Days 28 Days
0.1% 2.1 4.2 5.25
0.2% 2.16 4.32 5.40
0.3% 2.19 4.38 5.48
0.4% 2.16 4.36 5.42
0.5% 2.12 4.2 5.3
0.6% 2.06 4.08 5.2
0
1
2
3
4
5
3 Days 7Days 28Days
1.92
3.85
4.82
CYLINDERS
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 59
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres
5.3C Flexural strength test on M50 prisms using steel fibres
Table no: 5.3C Flexural strength for standard mix (Prism)
Mix
3 Days 7 Days 28 Days
Flexural
strength
in
N/mm2
Average
strength
in
N/mm2
Flexural
strength
in
N/mm2
Average
strength
in
N/mm2
Flexural
strength
in
N/mm2
Average
strength
in
N/mm2
Standard
Mix
1.8
1.81
1.82
1.81
3.60
3.63
3.65
3.62
4.50
4.54
4.56
4.53
2.1 2.16 2.19 2.16 2.12 2.06
4.2 4.32 4.38 4.36
4.2 4.08
5.24
5.4 5.48 5.42 5.3 5.2
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
1
2
3
4
5
6
1 2 3 4 5 6
CYLINDERS
3 Days 7 Days 28 Days % of fibers
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 60
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.3C Flexural strength of standard mix (Prism)
The mix design of prism ratio for M-50 grade is 1:1.93:2.29:0.5
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
Table no: 5.2C1 Flexural strength of M50 Prisms using Steel fibres
% of steel fibers 3 Days 7 Days 28 Days
0.1% 1.89 3.78 4.73
0.2% 1.92 3.84 4.81
0.3% 1.96 3.92 4.90
0.4% 1.93 3.86 4.83
0.5% 1.88 3.76 4.70
0.6% 1.84 3.69 4.62
0
1
2
3
4
5
3 Days 7Days 28Days
1.81
3.62
4.53
PRISM
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 61
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.3C1 Split tensile strength of M50 Prism using Steel fibres
5.4 Teston M50 cubes, cylinders, prisms using glass fibre
Table no: 5.4A compressive strength test for M50 cubes using glass fibre
Mix
3 Days 7 Days 28 Days
Compressive
Strength in
N/mm2
Average
Strength
in
N/mm2
Compressive
Strength in
N/mm2
Average
Strength
in
N/mm2
Compressive
Strength in
N/mm2
Average
Strength
in
N/mm2
Standard
Mix
23.12
22.8
22.5
22.08
46.2
45.5
45.0
45.6
57.8
56.9
57.2
57.3
1.89 1.92 1.96 1.93 1.88 1.84
3.78 3.84 3.92 3.86 3.76 3.69
4.73 4.81 4.9 4.83 4.7 4.62
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
1
2
3
4
5
6
1 2 3 4 5 6
PRISMS
3 Days 7 Days 28 Days % of fibers
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 62
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4A Compressive strength of standard mix (Cubes)
The mix design of cubes ratio for M-50 grade is 1:1.93:2.29:0.5
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
Table no: 5.4A1 Compressive strength of M50 cubes using glass fibres
% of glass fibers 3 Days 7 Days 28 Days
0.1% 23.2 46.56 58.2
0.2% 23.5 47.04 58.8
0.3% 23.7 47.62 59.4
0.4% 23.8 47.68 59.6
0.5% 23.4 46.8 58.5
0.6% 22.8 45.7 57.2
0
10
20
30
40
50
60
3 Days 7Days 28Days
22.8
45.6
57.3
CUBES
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 63
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4A1 Compressive strength of M50 cubes using glass fibres
5.4B Split tensile strength test for M50 cylinders using glass fibres
Mix
3 Days 7 Days 28 Days
Compressive
Strength in
N/mm2
Average
Strength in
N/mm2
Compressive
Strength in
N/mm2
Average
Strength
in
N/mm2
Compressive
Strength in
N/mm2
Average
Strength
in
N/mm2
Standard
Mix
1.84
1.80
1.78
1.80
3.68
3.65
3.39
3.64
4.6
4.4
4.2
4.4
23.2 23.5 23.7 23.8 23.4 22.8
46.56 47.04 47.62 47.68 46.8 45.7
58.2 58.8 59.4 59.6 58.5 57.2
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
10
20
30
40
50
60
70
1 2 3 4 5 6
CUBES
3 Days 7 Days 28 Days % of fibers
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 64
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4B Split tensile strength of standard mix (Cylinders)
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
Table no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres
% of glass fibers 3 Days 7 Days 28 Days
0.1% 1.96 3.92 4.9
0.2% 2.04 4.08 5.1
0.3% 2.12 4.24 5.3
0.4% 2.13 4.27 5.34
0.5% 2.09 4.18 5.23
0.6% 2.08 4.16 5.21
0
1
2
3
4
5
3 Days 7Days 28Days
1.8
3.64
4.4
CYLINDERS
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 65
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres
Table no: 5.4C Flexural strength test for M50 prism using glass fibres
Mix
3 Days 7 Days 28 Days
Flexural
Strength in
N/mm2
Average
Strength in
N/mm2
Flexural
Strength in
N/mm2
Average
Strength
in
N/mm2
Flexural
Strength
in
N/mm2
Average
Strength
in
N/mm2
Standard
Mix
1.8
1.72
1.6
1.74
3.6
3.44
3.2
3.41
4.5
4.3
4.0
4.26
1.96 2.04 2.12 2.13 2.09 2.08
3.92 4.08 4.24 4.27 4.18 4.16
4.9
5.1
5.3 5.34 5.23 5.21
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
1
2
3
4
5
6
1 2 3 4 5 6
CYLINDERS
3 Days 7 Days 28 Days % of fibers
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 66
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4C Flexural strength of standard mix (Prism)
The mix design of prism ratio for M-50 grade is 1:1.93:2.29:0.5
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
Table no: 5.4C1 Flexural strength of M50 prism using glass fibres
% of glass fibers 3 Days 7 Days 28 Days
0.1% 1.92 3.84 4.81
0.2% 1.97 3.94 4.93
0.3% 2.08 4.16 5.21
0.4% 2.17 4.34 5.43
0.5% 2.09 4.18 5.23
0.6% 2.04 4.04 5.1
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
3 Days 7Days 28Days
1.74
3.41
4.26
PRISMS
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 67
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Figure no: 5.4C1 Flexural strength of M50 prisms using glass fibres
5.5Analysis on combination of fibres based on maximum strength
5.5A Maximum compressive strength obtained for cubes
The mix design ratio of cubes for M-50 grade is 1:1.93:2.29:0.5
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
Steel fibres= 50grms
Glass fibres= 100grms
The maximum compressive strength for cubes using M50 grade was obtained at 0.3% for steel
and 0.4% for glass fibres separately.
1.92 1.97 2.08 2.17 2.09 2.04
3.84 3.94
4.16
4.34
4.18 4.08
4.81 4.93
5.21
5.43
5.23 5.1
0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0
1
2
3
4
5
6
1 2 3 4 5 6
PRISMS
3 Days 7 Days 28 Days % of fibers
% of Glass Fibres
MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 68
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
Table no: 5.5A Maximum compressive strength obtained for cubes
Combination of
glass and steel
fibers
3 Days 7 Days 28 Days
steel+glass fibers 24.17 48.34 60.43
Figure no: 5.5A Maximum compressive strength for cubes
5.5B Maximum split tensile strength obtained for cylinders
The mix design ratio of cylinders for M-50 grade is 1:1.93:2.29:0.5
Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution.
Binder=7 kgs
Fine aggregate=13.5 kgs
Coarse aggregate=16 kgs
Alkaline=3.5 kgs
0
10
20
30
40
50
60
70
3 Days 7Days 28Days
24.17
48.34
60.43
CUBES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES
MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES

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MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES

  • 1. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 1 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CONTENTS CHAPTER -1.............................................................................................................................. 5 1 INTRODUCTION.................................................................................................................... 6 1.1 DEFINATION:.................................................................................................................. 6 1.2 BACKGROUND:.............................................................................................................. 6 1.3 WORKING OF GEOPOLYMER CONCRETE:............................................................... 7 1.4 TYPES OF GEOPOLYMER CONCRETE:...................................................................... 7 1.4.1 SLAG BASED GEOPOLYMER:................................................................................ 7 1.4.2 ROCK BASED GEOPOLYMER:............................................................................... 8 1.4.3 FLY ASH BASED GEOPOLYMER:.......................................................................... 8 CHAPTER -2............................................................................................................................ 10 2 LITERATURE REVIEW ...................................................................................................... 11 2.1 Introduction.................................................................................................................... 11 2.2 Geopolymer..................................................................................................................... 11 2.2.1 Terminology and Chemistry...................................................................................... 11 2.3 Constituents of Geopolymer............................................................................................ 12 2.3.1 Source Materials ....................................................................................................... 12 2.3.2 Alkaline Liquids........................................................................................................ 13 2.3.3 Factors Affecting the Properties of Geopolymers ...................................................... 13 2.3.4 Fields of Applications ................................................................................................ 14 2.3.5 Properties of Geopolymers ........................................................................................ 16 2.3.6 Studies on Geopolymer Mortar................................................................................. 17 2.3.7 Studies on Geopolymer Concrete .............................................................................. 18 CHAPTER -3............................................................................................................................ 19 3 METHODOLOGY................................................................................................................. 20 3.1 Experimental Investigation.............................................................................................. 20 3.2 Materials ......................................................................................................................... 20 3.2.1 Fly Ash...................................................................................................................... 20 3.2.2 TESTING FOR FLY ASH ........................................................................................ 22 3.2.2 Chemical Composition of Fly Ash............................................................................. 24 3.3 GGBS (Ground Granulated Blast Furnace Slag) ......................................................... 24 3.3.1 GENERAL................................................................................................................ 24 3.3.2 USES OF GGBS........................................................................................................ 24 3.4 Alkaline Liquid................................................................................................................ 26
  • 2. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 2 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 3.5 Sodium silicate................................................................................................................. 27 3.6 Super Plasticizer.............................................................................................................. 28 3.6.1 Properties of Superplasticizers .................................................................................. 30 3.6.2 Effects of Super Plasticizers on Concrete Properties ................................................. 30 3.7 Aggregates....................................................................................................................... 31 3.7.1 Coarse Aggregate ...................................................................................................... 31 3.7.2 FINE AGGREGATE................................................................................................. 32 3.8 FIBRES AND ITS PROPERTIES................................................................................... 35 3.8.1 GLASS FIBRE.......................................................................................................... 35 3.8.2 CRIMPED STEEL FIBRE........................................................................................ 37 3.9 MIXDESIGN REQUIREMENT..................................................................................... 38 3.9.1 MIXDESIGN PROCESS FOR GEOPOLYMER CONCRETE................................ 39 3.9.1 TYPES OF MIXES................................................................................................... 42 3.10 FACTORS AFFECTING THE CHOICE OF MIX PROPORTIONS............................ 43 CHAPTER -4............................................................................................................................ 46 4. GEOPOLYMER MORTAR ................................................................................................. 47 4.1 Material Preparation....................................................................................................... 47 4.2 Mixing........................................................................................................................ 48 4.3 SIZE OF TEST SPECIMEN...................................................................................... 49 4.4 Compaction..................................................................................................................... 50 4.5 Curing........................................................................................................................ 51 4.6 Testing ....................................................................................................................... 51 4.6.1 Compression Strength Test ....................................................................................... 51 4.6.2 Split Tensile Strength Test ........................................................................................ 52 4.6.3 Flexural Strength Test............................................................................................... 53 CHAPTER – 5.......................................................................................................................... 54 5 RESULTS AND DISCUSSION.............................................................................................. 55 5.1 General............................................................................................................................ 55 5.2 Concentration of alkaline solution, fly ash, GGBS, and fibres ......................................... 55 5.3 Tests onM50 cubes, cylinders and prisms using steel fibres ............................................ 55 5.3B Split tensile strength test on M50 cylinders using steel fibres ........................................ 57 5.3C Flexural strength test on M50 prisms using steel fibres................................................. 59 5.4 Test on M50 cubes, cylinders, prisms using glass fibre .................................................... 61 5.4B Split tensile strength test for M50 cylinders using glass fibres....................................... 63 5.5 Analysis on combination of fibres based on maximum strength....................................... 67 5.5A Maximum compressive strength obtained for cubes...................................................... 67 5.5B Maximum split tensile strength obtained for cylinders.................................................. 68
  • 3. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 3 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 5.5C Maximum flexural strength obtained for prisms........................................................... 69 6. CONCLUSIONS................................................................................................................... 72 LIST OF FIGURES Figure no: 1.4.3 Fly ash............................................................................................................... 9 Figure no: 2.2.1 Chemical Structure of Polysialates.................................................................. 11 Figure no: 3.2.1Sem Image Figure no: 3.2.2 Fly Ash.................. 22 Figure no: 3.3 GGBS................................................................................................................. 25 Figure no: 3.5 Sodium Silicate Pellets ....................................................................................... 28 Figure no: 3.6 Super Plasticizer................................................................................................ 30 Figure no: 3.7.1 Coarse Aggregate............................................................................................ 31 Figure no: 3.8.2 Crimped Steel Fibre ........................................................................................ 38 Figure no: 4.1.A Material Preparation...................................................................................... 48 Figure no: 4.2A Hand Mixing ................................................................................................... 49 Figure no: 4.3A Mould Preparation.......................................................................................... 49 Figure no: 4.3A Mould Preparation Figure no: 4.4B Vibrating Machine............. 50 Figure no: 4.5A Curing............................................................................................................. 51 Figure no: 4.6.1Compression strength test................................................................................ 52 Figure no. 4.6.2 Split tensile strength test.................................................................................. 53 Figure no: 4.6.3 Flexural strength test...................................................................................... 53 Figure no: 5.3A Compressive strength of standard mix (Cubes)............................................... 56 Figure no: 5.3A1 Compressive strength ofM50 cubes using Steel fibres................................... 57 Figure no: 5.3B Split tensile strength ofstandard mix (Cylinders)............................................ 58 Figure no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres...................................... 59 Figure no: 5.3C Flexural strength ofstandard mix (Prism) ...................................................... 60 Figure no: 5.3C1 Split tensile strength ofM50 Prism using Steel fibres .................................... 61 Figure no: 5.4A Compressive strength of standard mix (Cubes)............................................... 62 Figure no: 5.4A1 Compressive strength ofM50 cubes using glass fibres................................... 63 Figure no: 5.4B Split tensile strength ofstandard mix (Cylinders)............................................ 64 Figure no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres ............................... 65 Figure no: 5.4C Flexural strength ofstandard mix (Prism) ...................................................... 66 Figure no: 5.4C1 Flexural strength ofM50 prisms using glass fibres........................................ 67 Figure no: 5.5A Maximum compressive strength for cubes....................................................... 68 Figure no: 5.5B Maximum split tensile strength for cylinder.................................................... 69 Figure no: 5.5C Maximum flexural strength for prisms............................................................ 70
  • 4. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 4 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES LIST OF TABLES Table no: 2.3.4Application of Geopolymeric Material Based on Si: Al Atomic ratio................. 15 Table no: 3.3B Chemical Properties of GGBS........................................................................... 26 Table no: 3.3C Physical Properties of GGBS............................................................................ 26 Table no: 3.4 Specification and Impurity limits of NaOH ......................................................... 27 Table no: 3.5 Property Specification of Sodium Silicates .......................................................... 28 Table no: 3.7.2 Sieve Analysis ................................................................................................... 33 Table no: 3.8.1 Properties of Glass Fibre of Glass Fibre ........................................................... 36 Table no: 3.8.2 Properties of Crimped Steel Fibre .................................................................... 38 Table no: 3.9.1 Nominal mix..................................................................................................... 43 Table no: 5.3A Compressive strength for standard mix (Cubes)............................................... 55 Table no: 5.3A1 Compressive strength ofM50 cubes using Steel fibres .................................... 56 Table no: 5.3B Split tensile strength for standard mix (Cylinders)............................................ 57 Table no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres....................................... 58 Table no: 5.3C Flexural strength for standard mix (Prism) ...................................................... 59 Table no: 5.2C1 Flexural strength of M50 Prisms using Steel fibres ......................................... 60 Table no: 5.4A compressive strength test for M50 cubes using glass fibre................................. 61 Table no: 5.4A1 Compressive strength ofM50 cubes using glass fibres .................................... 62 Table no: 5.4B1 Split tensile strength ofM50 cylinders using glass fibres................................. 64 Table no: 5.4C Flexural strength test for M50 prism using glass fibres..................................... 65 Table no: 5.4C1 Flexural strength of M50 prism using glass fibres........................................... 66 Table no: 5.5AMaximum compressive strength obtained for cubes ......................................... 68 Table no: 5.5B Maximum split tensile strength obtained for cylinders...................................... 68 Table no: 5.5CMaximum flexural strength for prisms% of glass and steel fibers .................... 70
  • 5. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 5 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CHAPTER -1
  • 6. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 6 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 1 INTRODUCTION 1.1 DEFINATION: There is often confusion between the meanings of the terms 'geopolymer cement' and 'geopolymer concrete'. A cement is a binder, whereas concrete is the composite material resulting from the mixing and hardening of cement with water (or an alkaline solution in the case of geopolymer cement), and stone aggregates. Materials of both types (geopolymer cements and geopolymer concretes) are commercially available in various markets. Davidovits proposed that an alkaline liquid could be used to react with the silicon (Si) and the aluminium (Al) in a source material of geological origin or in by product materials such as fly ash, blast furnace slag, and rice husk ash to produce binders. Because the chemical reaction that takes place in this case is a polymerization process occurs, he coined the term ‘Geopolymer’ to represent these binders.ionally. Geopolymer cement is a new kind of cement which uses a different chemistry to that found in traditional Ordinary Portland Cement (OPC). A geopolymer is made by activating amorphous alumino-silicate materials, such as fly ash and slag, with alkali-based chemicals such as sodium hydroxide and sodium silicate. Geopolymer cement does not need to contain OPC to work. Geopolymers have been known to be useful binders in concrete for over 60 years, but have recently developed rapidly in Australia due to the fact they have a CO2 footprint which is approximately 80% lower than OPC cement. There are two main constituents of geopolymers, namely the source materials and the alkaline liquids. The source materials for geopolymers based on alumina-silicate should be rich in silicon (Si) and aluminium (Al). These could be natural minerals such as kaolinite, clays, etc. Alternatively, by-product materials such as fly ash, silica fume, slag, rice-husk ash, red mud, etc. could be used as source materials. The choice of the source materials for making geopolymers depends on factors such as availability, cost, type of application, and specific demand of the end users. 1.2 BACKGROUND: The first geopolymer cement developed in the 1980s was of the type (K,Na,Ca)- poly(sialate) (or slag-based geopolymer cement) and resulted from the research developments carried out by Joseph Davidovits and J.L. Sawyer at Lone Star Industries, USA and yielded the invention of Pyrament® cement. Geopolymers have been known to be useful binders in
  • 7. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 7 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES concrete for over 60 years, but have recently developed rapidly in Australia due to the fact they have a CO2 footprint which is approximately 80% lower than OPC cement. 1.3 WORKING OF GEOPOLYMER CONCRETE: Water, expelled from the geopolymer matrix during the curing and further drying periods, leaves behind nano-pores in the matrix, which provide benefits to the performance of geopolymers. The water in a low-calcium fly ash-based geopolymer mixture, therefore, plays no direct role in the chemical reaction that takes place; it merely provides the workability to the mixture during handling. This is in contrast to the chemical reaction of water in a Portland cement concrete mixture during the hydration process. However, a small proportion of calcium-rich source materials such as slag may be included in the source material in order to accelerate the setting time and to alter the curing regime adopted for the geopolymer mixture. In that situation, the water released during the geopolymerisation reacts with the calcium present to produce hydration products. 1.4 TYPES OF GEOPOLYMER CONCRETE: There are currently four different types of geopolymer concrete used in construction  Slag based geopolymer  Rock based geopolymer  Fly ash based geopolymer  Ferro-sialate based geopolymer 1.4.1 SLAG BASED GEOPOLYMER: The first geopolymer developed was a slag based geopolymer in the 1980s. The reason for using this type of cement is due to it’s the rapid strength gain as it can reach strengths of up to 20 MPa after just 4 hours. Slag is a partially transparent material and a by-product in the process of melting iron ore. It usually consists of a mixture of metal oxides and silicon dioxide. It is also used in the cement and concrete industry. The substitution of OPC with slag is one of the many benefits that it provides to OPC concrete, reducing life cycle costs and improving the workability of the fresh concrete, Easier finishability, higher compressive and flexural strength and also the improved resistance to acid materials. The reactions of slag in alkali activating
  • 8. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 8 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES systems and in cement blends are dominated by the small particles. The particles that are above 20 µm usually react slowly, while particles under 2 µm react completely within 24 hours. Thus, when slag is used in geopolymerisation, careful control of the particle size distribution must be ensured to control the strength of the binder. Examples of slag used are; Iron blast-furnace slag, Corex slag& Steel slag. 1.4.2 ROCK BASED GEOPOLYMER: To compose this type of geopolymer, a fraction of the MK-750(“MK” is an abbreviation for metakaolin and the “750” represents the temperature at which it was produced) in the slag based geopolymer is replaced by natural rock forming materials such as feldspar and quarts. This mixture yields a geopolymer with better properties and less CO2 emissions than that of the ordinary slag based geopolymer. The components of rock based geopolymer cement is metakaolin MK-750, blast-furnace slag, natural rock forming materials (calcined or non- calcined) and a user friendly alkali silicate. 1.4.3 FLY ASH BASED GEOPOLYMER: Fly ash is the waste material produced in blast furnace. Components of fly ash are amorphous composition (60%), quartz (20%), mullite (17%), maghemite (1.7%) and hematite (.9%). Fly ash is commonly used as a substitute for OPC in concrete and the addition of it provides; Fly ash consists of spherical particles which improve the workability of the fresh OPC concrete. This enables one to reduce the amount of water in the mix which reduces the amount of bleeding of OPC concrete. Improves mechanical properties such as compressive strength, due to the water reduction and ensures a higher reactiveness and better “packing” of particles. Reduce the cost of the OPC concrete. Reduces the CO2 emissions and drying shrinkage and Smoother surface.
  • 9. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 9 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 1.4.3 Fly ash 1.4.3.1 Graded Fly Ash Fly ash can be divided in to two, type F fly ash and type C fly ash. The type F fly ash can be again classified into two Alkali-activated fly ash geopolymer and Fly ash/slag based geopolymer. Most of the globally available fly ash material is a low calcium by product obtained from the burning of anthracite and bituminous coal. 1.4.3.2 Alkali-Activated Fly Ash Geopolymer This kind of geopolymer usually requires heat curing at 60 ºC to 80 ºC. It is also known as the alkali activation method. A high concentration of sodium hydroxide solution is required to ensure an adequate geopolymerisation process. The mixture consists of fly ash and a user- hostile sodium hydroxide solution. The fly ash particles are embedded into an aluminosilicate gel with a Si: Al ratio of 1 to 2. This kind of geopolymer is more user-friendly and it hardens at room temperature. The mixture consists of a user-friendly silicate, blast furnace slag and fly ash. The fly ash particles are embedded into a geopolymer matrix with and Si: Al ratio of 2. 1.4.4 FERRO SIALATE BASED GEOPOLYMER: This type of geopolymer has the same properties as rock based geopolymers but contains geological elements with high iron oxide content, giving the geopolymer a red colour. Some of the aluminium atoms in the matrix are substituted with iron ions to yield a poly (Ferro- sialate) type geopolymer with the following formation: (Ca,K)- (-Fe-O)-(-Si-O-Al-O-).
  • 10. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 10 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CHAPTER -2
  • 11. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 11 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 2 LITERATURE REVIEW 2.1 Introduction This Chapter presents a brief review of the terminology and chemistry of geopolymers, and past studies on geopolymers. 2.2 Geopolymer 2.2.1 Terminology and Chemistry The term ‘geopolymer’ was first introduced by Davidovits in 1978 to describe a family of mineral binders with chemical composition similar to zeolites but with amorphous microstructure. He also suggested the use of the term ‘poly (sialate)’ for the chemical designation of geopolymers based on silico-aluminate (Davidovits, 1988a, 1988b, 1991; van Jaarsveld et. al., 2002a); Sialate is an abbreviation forsilicon-oxo-aluminate. Poly(sialates) are chain and ring polymers with Si4+ and AL3+ in IV-fold coordination with oxygen and range from amorphous to semi-crystalline with the empirical formula: Mn (-(SiO2) z – AlO2) n. wH2O ---------------- (2-1) Where “z” is 1, 2 or 3 or higher up to 32; M is a monovalent cation such as potassium or sodium, and “n” is a degree of poly condensation has also distinguished 3 types of polysialates, namely the Poly(sialate) type (-Si-O-Al-O), the Poly(sialate-siloxo) type(-Si-O-Al-O-Si-O) and the Poly(sialate-disiloxo) type (-Si-O-Al-O-Si-O). The structures of these polysialates can be schematised as in Figure 2.2.1. Figure no: 2.2.1 Chemical Structure of Polysialates Geo polymerization involves the chemical reaction of alumino-silicate oxides (Si2O5, Al2O2) with alkali polysilicates yielding polymeric Si – O – Al bonds. Poly silicates are generally sodium or potassium silicate supplied by chemical industry or manufactured fine silica powder as a by-product of Ferro-silicon metallurgy. Equation 2-2 shows an example of polycondensation by alkali into poly (sialatesiloxo).
  • 12. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 12 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES (Si2O5, Al2O2) n + 2nSiO2 +4nH2O+ NaOH, KOH Na+, K++ n (OH) 3 -Si-O-Al--O-Si-(OH) 3 (Si-Al material) | (OH) 2 (2-2) (Geopolymer precursor) | | | n(OH)3 -Si-O-Al--O-Si-(OH)3+ NaOH or KOH (Na,K)(+) –(-Si-O-Al-O-Si-O-) + 4nH2O | | | | (OH) 2 O O O (2-3) | | | (Geopolymer backbone) Unlike ordinary Portland/pozzolanic cements, geopolymers do not form calcium silicate hydrates (CSHs) for matrix formation and strength, but utilise the Poly condensation of silica and alumina precursors and a high alkali content to attain structural strength. Therefore, geopolymers are sometimes referred to as alkali activated alumino silicate binders. The last term of Equation 2-2 indicates that water is released during the chemical reaction that occurs in the formation of geopolymers. This water is expelled from the mixture during the curing process. 2.3 Constituents of Geopolymer 2.3.1 Source Materials Any material that contains mostly Silicon (Si) and Aluminium (Al) in amorphous form is a possible source material for the manufacture of geopolymer. Several minerals and industrial by-product materials have been investigated in the past. Metakaolin or calcined kaolin, low-calcium ASTM Class F fly ash, natural Al-Si minerals, combination of calcined mineral and non-calcined materials. Combination of fly ash and Metakaolin and combination of granulated blast furnace slag and Metakaolin (Cheng and Chiu 2003) have been studied as source materials. Metakaolin is preferred by the niche geopolymer product developers due to its high rate of dissolution in the reactant solution, easier control on the Si/Al ratio and the white colour. However, for making concrete in a mass production state, Metakaolin is expensive. Low-calcium (ASTM Class F) fly ash is preferred as a source material than high calcium (ASTM Class C) fly ash. The presence of calcium in high amount may interfere with the polymerization process and alter the microstructure.
  • 13. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 13 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Davidovits calcined kaolin clay for 6 hours at 750oC.He termed this Metakaolin as KANDOXI (Kaolinite, Nacrite, Dickite Oxide), and used it to make geopolymers. For the purpose of making geopolymer concrete, he suggested that the molar ratio of Si-to-Al of the material should be about 2.0. On the nature of the source material, it was stated that the calcined source materials, such as fly ash, slag, calcined kaolin, demonstrated a higher final compressive strength when compared to those made using non-calcined materials, for instance kaolin clay, mine tailings, and naturally occurring minerals. However, Xu and van Deventer (2002) found that using a combination of calcined (e.g. fly ash) and non-calcined material (e.g. kaolinite or kaolin clay and albite) resulted in significant improvement in compressive strength and reduction in reaction time. 2.3.2 Alkaline Liquids The most common alkaline liquid used in geopolymerisation is a combination of sodium hydroxide (NaOH) or potassium hydroxide (KOH) and sodium silicate or potassium silicate. The use of a single alkaline activator has been reported (Palomo et al. 1999; Teixeira- Pinto et al. 2002), Palomo et al (1999) concluded that the type of alkaline liquid plays an important role in the polymerization process. Reactions occur at a high rate when the alkaline liquid contains soluble silicate, either sodium or potassium silicate, compared to the use of 14 only alkaline hydroxides. Xu and van Deventer (2000) confirmed that the addition of sodium silicate solution to the sodium hydroxide solution as the alkaline liquid enhanced the reaction between the source material and the solution. Furthermore, after a study of the geopolymerisation of sixteen natural Al-Si minerals, they found that generally the NaOH solution caused a higher extent of dissolution of minerals than the KOH solution. 2.3.3 Factors Affecting the Properties of Geopolymers Several factors have been identified as important parameters affecting the properties of geopolymers. Palomo et al (1999) concluded that the curing temperature was a reaction accelerator in fly ash-based geopolymers, and significantly affected the mechanical strength, together with the curing time and the type of alkaline liquid.
  • 14. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 14 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Higher curing temperature and longer curing time were proved to result in higher compressive strength. Alkaline liquid that contained soluble silicates was proved to increase the rate of reaction compared to alkaline solutions that contained only hydroxide Van Jaarsveld et al (2002) concluded that the water content, and the curing and calcining condition of kaolin clay affected the properties of geopolymers. However, they also stated that curing at too high temperature caused cracking and a negative effect on the properties of the material. Finally, they suggested the use of mild curing to improve the physical properties of the material. In another study, van Jaarsveld et al (2003) stated that the source materials determine the properties of geopolymers, especially the CaO content, and the water-to-fly ash ratio. Based on a statistical study of the effect of parameters on the polymerization process of Meta kaolin-based geopolymers, Barbosa et al (1999; 2000) reported the importance of the molar composition of the oxides present in the mixture and the water content. They also confirmed that the cured geopolymers showed an amorphous microstructure and exhibited low bulk densities between 1.3 and 1.9. Based on the study of geopolymerisation of sixteen natural Si-Al minerals, Xu and van Deventer (2000) reported that factors such as the percentage of CaO, K2O, and the molar Si-to-Al ratio in the source material, the type of alkali liquid, the extent of dissolution of Si, and the molar Si-to-Al ratio in solution significantly influenced the compressive strength of geopolymers. 2.3.4 Fields of Applications According to Davidovits (1988b), geopolymeric materials have a wide range of applications in the field of industries such as in the automobile and aerospace, nonferrous foundries and metallurgy, civil engineering and plastic industries. The type of application of geopolymeric materials is determined by the chemical structure in terms of the atomic ratio Si:Al in the polysialate. Davidovits (1999) classified the type of application according to the Si:Al ratio as presented in Table 2.1. A low ratio of Si: Al of 1, 2, or 3 initiates a 3D-Network that is very rigid, while Si: Al ratio higher than 15 provides a polymeric character to the geopolymeric material. It can be seen from Table 2.3.4 that for many applications in the civil engineering field a low Si: Al ratio is suitable.
  • 15. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 15 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES One of the potential fields of application of geopolymeric materials is in toxic waste management because geopolymers behave similar to zeolites materials that have been known for their ability to absorb the toxic chemical wastes (Davidovits, 1988b). Comrie (1988) also provided an overview and relevant test results of the potential of the use of geopolymer technology in toxic waste management. Based on tests using GEOPOLYMITE 50, they recommend that geopolymeric materials could be used in waste containment. GEOPOLYMITE 50 is a registered trademark of Cordi-Geopolymere SA, a type of geopolymeric binder prepared by mixing various alumina-silicates precondensates with alkali hardeners. Table no: 2.3.4Application of Geopolymeric Material Basedon Si: Al Atomic ratio Si:Al ratio Applications 1 - Bricks - Ceramics - Fire protection 2 - Low CO2 cements and concretes - Radioactive and toxic waste encapsulation 3 - Fire protection fiber glass composite - Foundry equipments - Heat resistant composites, 200oC to 1000oC - Tooling for aeronautics titanium process >3 - Sealants for industry, 200oC to 600oC - Tooling for aeronautics SPF aluminum 20-35 - Fire resistant and heat resistant fiber composites Another application of geopolymer is in the strengthening of concrete structural elements. Bal guru (1997) reported the results of the investigation on using geopolymers, instead of organics polymers, for fastening carbon fabrics to surfaces of reinforced concrete beams. It was found that geopolymer provided excellent adhesion to both concrete surface and in the inter laminar of fabrics.
  • 16. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 16 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES In addition, the researchers observed that geopolymer was fire resistant, did not degrade under UV light, and was chemically compatible with concrete. In Australia, the geopolymer technology has been used to develop sewer pipeline products, railway sleepers, building products including fire and chemically resistant wall panels, masonry units, protective coatings and repairs materials, shotcrete and high performance fiber reinforced laminates (Gurley, 2003; Gurley & Johnson, 2005). 2.3.5 Properties of Geopolymers Previous studies have reported that geopolymers possess high early strength, low shrinkage, freeze-thaw resistance, sulfate resistance, corrosion resistance, acid resistance, fire resistance, and no dangerous alkali-aggregate reaction. Based on laboratory tests, Davidovits (1988b) reported that geopolymer cement can harden rapidly at room temperature and gain the compressive strength in the range of 20 MPa after only 4 hours at 20o C and about 70-100 MPa after 28 days. Comrie et. al., (1988) conducted tests on geopolymer mortars and reported that most of the 28- day strength was gained during the first 2 days of curing. Geopolymeric cement was superior to Portland cement in terms of heat and fire resistance, as the Portland cement experienced a rapid deterioration in compressive strength at 300o C, whereas the geopolymeric cements were stable up to 600o C (Davidovits, 1988b; 1994b). It has also been shown that compared to Portland cement, geopolymeric cement has extremely low shrinkage. The presence of alkalis in the normal Portland cement or concrete could generate dangerous Alkali-Aggregate-Reaction. However the geopolymeric system is safe from that phenomenon even with higher alkali content. As demonstrated by Davidovits (1994a; 1994b), based on ASTM C227 bar expansion test, geopolymer cements with much higher alkali content compared to Portland cement did not generate any dangerous alkali-aggregate reaction where the Portland cement did. Geopolymer cement is also acid-resistant, because unlike the Portland cement, geopolymer cements do not rely on lime and are not dissolved by acidic solutions. As shown by the tests of exposing the specimens in 5% of sulfuric acid and hydrochloric acid, geopolymer cements were relatively stable with the weight loss in the range of 5-8% while the
  • 17. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 17 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Portland based cements were destroyed and the calcium alumina cement lost weight about 30- 60% (Davidovits, 1994b). Some recently published papers (Bakharev, 2005c; Gurley & Johnson, 2005; Song et. al., 2005a) also reported the results of the tests on acid resistance of geopolymers and geopolymer concrete. By observing the weight loss after acid exposure, these researchers concluded that geopolymers or geopolymer concrete is superior to Portland cement concrete in terms of acid resistance as the weight loss is much lower. However, Bakharev and Song et. Al has also observed that there is degradation in the compressive strength of test specimens after acid exposure and the rate of degradation depended on the period of exposure. Tests conducted by U.S. Army Corps of Engineers also revealed that geopolymers have superior resistance to chemical attack and freeze/thaw, and very low shrinkage coefficients (Comrie et. al., 1988; Malone et. al., 1985). 2.3.6 Studies on Geopolymer Mortar Swanepoel, J.C and Strydom, C.A have prepared the geopolymers was made by mixing fly ash, kaolinite, Na2Sio3, NaOH, and water. The samples were cured at 40o,50o,60o,& 70o C for different time intervals (6,24,48,72 hours ) the compressive strength testing was performed at the age of 7 & 28 days using 3 members 50mm cubic samples the authors reported that the optimum curing condition for geopolymerisation was 60oC for a period of 48 hours . Compressive strength measurements show a maximum strength of almost 80 MPa after 28 days. Fernandez- Jimenez and Palomo have carried out the physical, chemical, mineralogical and micro structural characterization of type F fly ash was carried out. The reactivity of fly ash was determined using compressive strength testing data of mortar specimen of size 4x4x16. The specimens were prepared by alkaline activation of various fly ashes with 8molar NaOH solution. The sand to fly ash ratio was 1:2 all the specimens were thermally cured in oven at 85oc for 20 hours. From results of experimental study, it was concluded that the main characteristics of a fly ash for getting geopolymer material with optimal binding properties should be within following limits. Percentage of unburned materials lower than 5%: fe2o3 content not higher than 10% low content of Cao; content of reactive silica between 40%-50% of particles with size lower than 45mm between 80 & 90% and also high content of vitreous phase.
  • 18. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 18 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Kamhangrittirong and Suanvitaya were investigated the effect of fly ash content and NaoH molarity on the compressive strength and setting time geopolymer paste .The fly ash (content ranging from 45.0,52.5.60.0,67.5,&75% of the weight of the mix )was mixed with NaOH solution. The NaOH concentration in the solution was varied as 8, 10 and 12 molar. The specimen with dimensions of 3.81cmx3.81cmx3.81cm was cured in oven at 60oC for 6, 12, 18, 24, 48 and 72 hours. The compressive strength was obtained at the age of 7 days. The setting time of the mix was determined using Vicat’s apparatus by following procedure as per ASTM 191-192.It was found that increasing the morality of NaOH significantly affected the setting time of the geopolymer paste. Increasing NaOH morality from 8M to 12M decreased setting time from 68- 95 minutes to 31-66 minutes with increasing fly ash content from 45% to 75%. It was also reported that the compressive strength of specimen increased rapidly within the first 24 hours, there after the rate dropped sharply .The authors concluded that compressive strength of geopolymer depends on NaOH Molarity and fly ash content of the mix. 2.3.7 Studies on Geopolymer Concrete Hardijto, D.Wallah S.E.,Sumajouw D.M.J., and Rangan, B.V were investigated the effect of various synthesizing parameters on fly ash based geopolymer concrete. Numerous bathes of geopolymer concrete were prepared by activated class-F fly ash with sodium silicate and sodium hydroxide solutions. Four types of locally available aggregates of size20, 14, and 7 mm and fine sand, in saturated surface dry condition, were used in making geopolymer concrete specimens. In this influence of various geopolymer synthesizing parameters such as  Concentration of sodium hydroxide.  Sodium silicate to sodium hydroxide liquid ratio.  Curing temperature and curing time.  Addition of high range of water reducing admixtures.  Handling time.  Water content in admixtures.  Age of concrete. The drying shrinkage, creep and sulfate resistance of the geopolymer concrete was also studied.
  • 19. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 19 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CHAPTER -3
  • 20. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 20 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 3 METHODOLOGY 3.1 Experimental Investigation In order to develop the fiber-based geopolymer concrete, therefore, rigorous trail-and-error process was used. The aim of the study was to identify the salient parameters that enhances the mixture proportions and the properties of low calcium fly ash-based geopolymer concrete. As far as possible, the current practice used in the manufacture and testing of ordinary Portland cement (OPC) concrete was followed. The aim of this action was to ease the promotion of this ‘new’ material to the concrete construction industry. In order to simplify the development process, the compressive strength was selected as the benchmark parameter. This is not unusual because compressive strength has an intrinsic importance in the structural design of concrete structures (Neville 2000). Although geopolymer composites can be made using various source materials, the present study used only low-calcium (ASTM Class F) dry fly ash. Also, as in the case of OPC, the aggregates occupied 75-80 % of the total mass of concrete. In order to minimize the effect of the properties of the aggregates on the properties of fly ash based geopolymer, the study used aggregates from only one. 3.2Materials 3.2.1 Fly Ash Fly ash is defined as ‘the finely divided residue that results from the combustion of ground or powdered coal and that is transported by flue gasses from the combustion zone to the particle removal system’ (ACI Committee 232 2004). Fly ash is removed from the combustion gases by the dust collection system, either mechanically or by using electrostatic precipitators, before they are discharged to the atmosphere. Fly ash particles are typically spherical, finer than Portland cement and lime, ranging in diameter from less than 1 μm to no more than 150 μm. The types and relative amounts of incombustible matter in the coal determine the chemical composition of fly ash. The chemical composition is mainly composed of the oxides of silicon
  • 21. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 21 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES (SiO2), aluminium (Al2O3), iron (Fe2O3), and calcium (CaO), whereas magnesium, potassium, sodium, titanium, and sulphur are also present in a lesser amount. The major influence on the fly ash chemical composition comes from the type of coal. The combustion of sub-bituminous coal contains more calcium and less iron than fly ash from bituminous coal. The physical and chemical characteristics depend on the combustion methods, coal source and particle shape. CLASS F: Class F fly ash is that type which moderates heat gain during curing of concrete. Class F provides solution to summer concreting problems. Recommended for use where concrete exposed to sulphate ion in soil and ground water. Advantages:  Hydration.  Decreased water demand. Increased late compressive strength (after 28 days).  Increased resistance to alkali silica reaction (ASR).  Increased resistance to sulphate attack.  Less heat generation during. Cautions: The time is slightly delayed and early compressive strength may be decreased slightly. If the fly ash has high calcium content, it should not be used in hydraulic applications.
  • 22. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 22 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 3.2.1Sem Image Figure no: 3.2.2 Fly Ash 3.2.2 TESTING FOR FLY ASH 3.2.2.1 SPECIFIC GRAVITY Objective: To determine the specific gravity of fly ash by using Le chatelier flask or specific gravity bottle. Apparatus: a. Le chatelier flask or sp. Gravity bottle – 100 ml capacity. b. Balance capable of weighing accurately up to 0.1 gm. Producer: Weigh a clean and dry Le chatelier flask or sp. gravity bottle with its stopper as (W1). Place a sample of fly ash upto half of the flask (about 50 gm) and weight with its stopper (W2). Add kerosene to fly ash in flask till it is about half filled. Mix thoroughly with a glass rod to remove entrapped air. Continue stirring and add more kerosene till it is flush with the graduated mark. Dry the outside and weigh it as (W3). Entrapped air may be removed by vacuum pump, if available empty the flask, clean it and refill with kerosene flush with graduated mark wipe dry the outside and weigh (W4). Calculations: Where, W1 = weight of empty bottle. = 0.55gms W2 = weight of flask + fly ash. = 0.32gms W3= weight of flask + fly ash + kerosene. = 0.98
  • 23. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 23 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES W4= weight of flask + kerosene. = 0.70 0.79 is the specific gravity of kerosene. Limits: specific gravity of fly ash ranges from 2.1 to 3.0 3.2.2.2 FINENESS TEST FOR FLY ASH The fineness of fly ash is a measure of the size of particles of the fly ash. Hence it is necessary to check the proper grading of fly ash as it has a influence on the behaviour of flyash. For a given weight of fly ash the surface area is more for finer fly ash than for coarse flyash. The finer fly ash has quicker chemical reaction with alkaline solutions and gain early strength. Fine fly ash covers more surface area of aggregates. Fineness gives more cohesiveness and bleeding. Too much fineness is undesirable because finer fly ash deteriorates more quickly when exposed to air due to pre hydration and likely to cause more shrinkage. The fineness of fly ash can be expressed either as surface area of particles in cm 2 per gram weight or percentage weight of fly ash particle finer than 90 microns IS sieve. Procedure: Break down any air set lumps in the fly ash sample with fingers and mix it uniformly. Weigh 100 grams of fly ash to the nearest 0.01 gram and place on a clean and dry 90 microns IS sieve with pan attachment. Continuously sieve the sample by looking the sieve in both hands for 15 minutes with a gentle wrist motion. While sieving it ensures that there is no spillage of the fly ash and the fly ash shall be kept well spread over on the sieve. Do not use washers, bolts, and slugs on the sieve. Slightly brush underside of the sieve after every 5 minutes of sieving. Find the weight of residue on the sieve and report the value as a percentage of original samples taken. Observations: Average of values = 2.55. Results: The fineness of fly ash is 2.55 %.
  • 24. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 24 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 3.2.2 Chemical Composition of Fly Ash 3.3 GGBS (Ground Granulated BlastFurnace Slag) 3.3.1 GENERAL Ground granulated blast furnace slag is also sometimes referred to as GGBS. It is obtained by quenching molten iron slag from blast furnace in water or steam, dried and ground into a fine powder. Its use results in the in lower heat of hydration and lower temperature rises, further it reduces the risk of damages caused by alkali – silica reaction. Provides higher resistance to chloride ingress reducing the risk of reinforcement corrosion and provides higher resistance to attacks by Portland cement sulphate and other chemicals. Use of GGBS increases the life of the structure by up to 50% had only been used and precludes the need of stainless reinforcement. It is also routinely used to limit the temperature rise in large concrete pours, which prevents the occurrence of micro cracking. 3.3.2 USES OF GGBS In the production of ready mix concrete, GGBS replaces a substantial portion of normal Portland cement content, generally about 50% but sometimes up to70%. The higher the proportion the better is the durability. The disadvantage of the higher replacement level is the early age strength development is somewhat slower. SI.NO Composition percent by mass Result 1. SiO2+Al2O3+Fe2O3 94.66 2 SiO2 60.78 3. MgO 0.94 4. Total sulphur as SO3 0.12 5 Loss on ignition 0.88
  • 25. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 25 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES GGBS is also used in ready mixed concrete and it is utilized a third of all UK ready mix deliveries. Specifiers are well aware of all the technical benefits which GGBS imparts to concrete, including:  Better workability, making placing and compaction easier.  Lower early age temperature rise, reducing the thermal cracking in in large pours.  Elimination of the risk of damaging internal reaction such as ASR.  High resistance chloride ingress, reducing the risk of reinforcement corrosion.  Considerable sustainability benefits. Figure no: 3.3 GGBS Table no: 3.3.A Strength Achievement As % of 28 - Day strength AGE 0% GGBS 50% GGBS 70%GGBS 7 DAYS 28 DAYS 75% 100% 45-55% 100% 40-50% 100%
  • 26. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 26 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Table no: 3.3B Chemical Properties of GGBS Cao 30-50% siO2 28-38% Al2O3 8-24% MgO 1-18% MnO 0.68% TiO2 0.58% K2O 0.37% Table no: 3.3C Physical Properties of GGBS Particle size 0.1 – 40 microns Specific surface area 400 – 600 m2/kg Bulk density 1.0 – 1.1 tones/m3 Relative density 2.85 – 2.95 pH ( T = 20 0C in water ) 9 - 11 3.4 Alkaline Liquid A combination of sodium silicate solution and sodium hydroxide solution was chosen as the alkaline liquid. Sodium-based solutions were chosen because they were cheaper than Potassium-based solutions. The sodium hydroxide solids were pellets form (3 mm), with a specific gravity of 1.51, 98% purity. The sodium hydroxide (NaOH) solution was prepared by dissolving either the flakes or the pellets in water. The mass of NaOH solids in a solution varied depending on the concentration of the solution expressed in terms of molar, M.
  • 27. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 27 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES For instance, NaOH solution with a concentration of 8M consisted of 8x40 = 320 grams of NaOH solids (in flake or pellet form) per litre of the solution, where 40 is the molecular weight of NaOH. . Note that the mass of NaOH solids was only a fraction of the mass of the NaOH solution, and water is the major component. Sodium hydroxide has a high heating capacity that can ignite substances. To overcome this heat the sodium hydroxide pellets are dissolved in water 24hours before the mix preparation. Table no: 3.4 Specification and Impurity limits of NaOH Acidimetric 97.0% Carbonate 2.0% Chloride 0.01% Sulphate 0.01% Phosphate 0.001% Iron 0.005% Heavy metal 0.001% Molecular weight 40.00 3.5 Sodium silicate Sodium silicate are used in alkaline solution along with sodium hydroxide. The pure form of sodium silicate solution is of colourless or white in colour. Sodium silicate reacts with lime that is present in our concrete. Sodium hydroxide has a high heating capacity that can ignite substances. To overcome this heat the sodium hydroxide pellets are dissolved in water 24hours before the mix preparation.
  • 28. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 28 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 3.5 Sodium Silicate Table no: 3.5 Property Specification of Sodium Silicates Description Clear viscous liquid pH 8.2 SiO2 28.00% Na2O 7.5% Wt. per ml,200C 1.366g/ml Figure no: 3.5 Sodium Silicate Pellets 3.6 Super Plasticizer Super plasticizer that we use is water reducer it decrease the water cement ratio without effecting the workability of our fiber based Geo-polymer concrete. The superplasticizer we are using is SP-430.
  • 29. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 29 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Type F and Type G, High Range Water Reducer (HRWR) and retarding admixtures are used to reduce the amount of water by 12% to 30% while maintaining a certain level of consistency and workability (typically from 75 mm to 200 mm) and to increase workability for reduction in w/cm ratio. The use of superplasticizers may produce high strength concrete (compressive strength up to 22,000 psi). Superplasticizers can also be utilized in producing flowing concrete used in a heavy reinforced structure with inaccessible areas. Another benefit of superplasticizers is concrete early strength enhancement (50 to 75%). The initial setting time may be accelerated up to an hour earlier or retarded to be an hour later according to its chemical reaction. Retardation is sometimes associated with range of cement particle between 4 – 30  m. The use of superplasticizers does not significantly affect surface tension of water and does not entrain a significant amount of air. The main disadvantage of superplasticizer usage is loss of workability as a result of rapid slump loss and incompatibility of cement and superplasticizers. Typical dosage of superplasticizers used for increasing the workability of concrete ranges from 1 to 3 liters per cubic meter of concrete where liquid superplasticizers contained about 40 % of active material. In reducing the water cement ratio, higher dosage is used, that is from 5 to 20 liters per cubic meter of concrete. Dosage needed for a concrete mixture is unique and determined by the Marsh Cone Test. There are four types of superplasticizers: 1. Sulfonated melamine 2. Sulfonated naphthalene 3. Modified lignosulfonates and a combination of high dosages of water reducing and accelerating admixtures. Commonly used are melamine based and naphthalene based superplasticizers. The use of naphthalene based has the advantage of retardation and affecst slump retention. This is due to the modified hydration process by the sulfonates To improve the workability of the fresh geopolymer concrete, a naphthalene sulphonate super plasticizer rebuild used for improving the workability.
  • 30. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 30 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Superplasticizers are linear polymers containing sulphonic acid group attached to polymer backbone and are new improved version of plasticizers called high range water reducers. Super plasticizers are more powerful as dispersing agents. Super plasticizer is one of a class of admixer called water reducer that are used to lower the mix water requirement of concrete. Figure No: 3.6 Super Plasticizer 3.6.1 Properties of Superplasticizers  Excellent flow ability at low water cement ratio.  High reduction of water.  Lower slump loss with time.  Shorter retardation time and early strength.  It works at low density. 3.6.2 Effects of Super Plasticizers on Concrete Properties Purpose of using super plasticizers is to produce flowing concrete with very high slump range of 7-9 inches (175-225mm) to be used in heavily reinforced structures and in placements adequate.  Major application is the production of high strength concrete  To increase the workability of concrete.
  • 31. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 31 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES  Ability of super plasticizer to increase the slump of concrete depending on such factors:  Type  Dosage  Time of addition of super plasticizer  Water cement ratio  Nature or amount of cement 3.7 Aggregates 3.7.1 Coarse Aggregate Majority of the particles of the coarse aggregates were of granite type. Machine crushed angular granite metal of 12.5mm size from the local source is used as coarse aggregate. It should be free from impurities such as dust, clay particle, and organic matter etc. Figure No: 3.7.1 Coarse Aggregate IMPACT TEST: Objective: To determine the impact value of given coarse aggregate. Apparatus: Impact testing machine. Tampering rod. Balance. Oven. IS sieve of 12.5mm, 10mm, and 2.36mm for sieving aggregates.
  • 32. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 32 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Procedure: The test sample consists of aggregates passing 12.5mm sieve and retained on 10 mm sieve and dried in an oven for four hours at a temperature 100°C to ll0 o C and cooled. Test aggregates are filled up to about one-third full in the mould and tamped 25times.The surplus aggregates are struck off using the tamping rod as straight edge . The entire sample is filled in this way I three layers. The mould is fixed firmly in position on the base of the machine and compacted by tamping with 25 strokes. The hammer is raised until its lower face is 38cm above the upper surface of the aggregates in the cup, and allowed to fall freely on the aggregates. The test sample is subjected to a total of 25 such blows, each being delivered at an interval of not less than one second. The crushed aggregate is then removed from the cup and the whole of it sieved on the 2.36 mm sieve until no further significant amount passes. Calculations: The aggregate impact value is expressed as the percentage of the fines formed in terms of the total weight of the sample. Let the original weight of the oven dry sample be W 1 g and the weight of fraction passing 2.36 mm IS sieve be W 2 g. Aggregate impact value = Results: Therefore, the aggregate is exceptionally strong. 3.7.2 FINE AGGREGATE The river sand obtained from local source was used as fine aggregate used for preparation. It should be free from silt, clay, organic impurities, etc. The sand is tested for various properties such as specific gravity, bulk density, etc., in accordance with IS: 2386-1963. The grading or particle size distribution is close to zone – II or IS: 383 – 1970 fineness modulus of sand aggregate is 3.42.The surface dry sand was used in geopolymer mix to avoid the water absorption.
  • 33. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 33 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure No: 3.7.2 Fine Aggregate Table No: 3.7.2 Sieve Analysis SNO Particle size(mm) Weight retained(gm) % Weight retained %cumulative Weight retained % finer 1 4.75 2.99 0.299 0.299 99.701 2 2.36 1.16 0.116 0.415 99.585 3 1.18 16 1.6 2.015 97.985 4 0.60 82 8.2 10.215 89.785 5 0.30 686 68.6 78.815 21.185 6 0.15 168 16.8 95.615 4.385 7 0.075 34 3.4 99.015 0.985 8 Pan(<0.075) 1.39 0.139 99.154 0.846 SPECIFIC GRAVITY: Objective: To determine the specific gravity of given sample of coarse aggregates. Apparatus: pycnometer, sieve, vacuum pump, weighing balance, glass rod. Procedure: Tightly screw its cap. Take its mass (M1) to the nearest of 0.1g. Mark the cap and cylinder with a vertical line parallel to the axis of the cylinder to ensure that the cap is screwed to the same mark each time. Unscrew the cap and place about 200g of oven dried coarse aggregate in the cylinder. Screw the cap. Determined the mass (M2).Unscrew the cap and add sufficient amount of de-aired water to the cylinder so as to cover the soil. Screw on the cap. Shake the contents well. Connect the cylinder to a vacuum pump to remove the entrapped air.
  • 34. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 34 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES For about 10 minutes for coarse-aggregates .Disconnect the vacuum pump. Fill the cylinder with water, about three -fourth full. Reapply the vacuum for about 5min till air bubbles stop appearing on the surface of the water. Fill the cylinder with water completely up to the mark. Dry it from outside. Take its mass (M3). Record the temperature of contents. Empty the cylinder. Clean tit and wipe it dry. Fill the cylinder with water only. Screw on the cap up to the mark. Wipe it dry. Take it mass (M4). Result: Avg. of both readings specific gravity is taken as 2.68. FLAKINESS INDEX: Object: To determine flakiness index of a given aggregates sample. Apparatus: The apparatus consists of a standard thickness gauge shown in fig 5.1, IS sieves of the sizes 63, 50, 40, 31.5, 25, 20, 16, 12.5, 10 and 6.3 mm and a balance to weight the samples. Procedure: The flakiness index is the percentage by weight of Particles in it whose least dimension. Thickness is less than three-fifths of their mean dimensions. The test is not applicable to sizes smaller than 6.3mm.This test is conducted by using a metal thickness gauge, of the description. A sufficient quantity of aggregate is taken such that a minimum number of 200 pieces of any fraction can be tested. Each fraction is gauged in turn for the thickness on the metal gauge. The total amount passing in the gauge is weighed to an accuracy of 0.1 percent of the weight of the samples taken. The flakiness index is taken as the total weight of the material passing the various thickness gauges expressed as a percentage of the total weight of the sample taken. Results: The flakiness index is 70%. ELONGATION INDEX: Objective: To determine elongation index of a given aggregates sample. Apparatus: The apparatus length gauge consists of the Standard length gauge. IS sieve of size 50, 40, 25, 20, 16, 12.5, 10 and 6.3 mm,a balance to weigh the samples.
  • 35. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 35 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Procedure: The elongation index on an aggregate is the percentage by weight of particles whose greatest dimension is greater than 1.8 times their mean dimension. The elongation index is not applicable to sizes smaller than 6.3mm.This test is conducted by using metal length gauge of the description shown in fig. A sufficient quantity of aggregate is taken to provide a minimum number of 200 pieces of any fraction to be tested. Each fraction shall be gauged individually for length on the metal gauge. The total amount retained by the gauge length shall be weighed to an accuracy of 0.1percent of the weight of the test samples taken. The elongation index is the total weight on material retained on the various length gauges expressed as a percentage of the total weight of the sample gauged. The presence of elongated particles in excess of 10 to 15 percent is generally considered undesirable, but no recognized limits are laid down. Results: The elongation index is taken as 14%. 3.8 FIBRES AND ITS PROPERTIES 3.8.1 GLASS FIBRE Glass fibre (or glass fibre) is a material consisting of numerous extremely fine fibres of glass. Glass wool, which is one product called "fiberglass" today, was invented in 1932–1933 by Russell Games Slayter of Owens-Corning, as a material to be used as thermal building insulation. It is marketed under the trade name Fiberglas, which has become a genericized trademark. Glass fiber when used as a thermal insulating material, is specially manufactured with a bonding agent to trap many small air cells, resulting in the characteristically air-filled low- density "glass wool" family of products. Glass fiber has roughly comparable mechanical properties to other fibers such as polymers and carbon fiber. Although not as strong or as rigid as carbon fiber, it is much cheaper and significantly less brittle when used in composites. Glass fibers are therefore used as a reinforcing agent for many polymer products; to form a very strong and relatively lightweight fiber-reinforced polymer (FRP) composite material called glass-reinforced plastic (GRP), also popularly known as "fiberglass". This material contains little or no air or gas, is denser, and is a much poorer thermal insulator than is glass wool.
  • 36. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 36 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Glass fibers are useful thermal insulators because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fiber make good thermal insulation, with a thermal conductivity of the order of 0.05 W/(m·K). Tensile strength of glass is usually tested and reported for "virgin" or pristine fibers those that have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily adsorbed and can worsen microscopic cracks and surface defects, and Lessen tenacity. In contrast to carbon fiber, glass can undergo more elongation before it breaks. Thinner filaments can bend further before they break. The viscosity of the molten glass is very important for manufacturing success. During drawing, the process where the hot glass is pulled to reduce the diameter of the fiber, the viscosity must be relatively low. If it is too high, the fiber will break during drawing. However, if it is too low, the glass will form droplets instead of being drawn out into a fiber. Table No: 3.8.1 Properties of Glass Fibre of Glass Fibre Density 2.5 Young’s modulus (Gpa) 70 Tensile strength (Mpa) 2000 -3500 Elongation at break (%) 2.5
  • 37. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 37 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure No: 3.8 Glass Fibre 3.8.2 CRIMPED STEEL FIBRE For the geopolymer mix we have used crimped stainless steel fibres. The use of fibres in concrete has the property to resistance against cracking and crack propagation. The fibre composite pronounced post cracking ductility which is unheard of in ordinary concrete. The transformation from a brittle to a ductile type of material would increase substantially the energy absorption characteristics of the fibre composite and its ability to withstand repeatedly applied shock or impact loading. These fibres are short, discrete lengths having an aspect ratio in the range of 20-100, with any cross section that are sufficiently small to be randomly dispersed in an unhardened concrete. Further they are low carbon, cold drawn steel wire fibres designed to provide concrete with temperature and shrinkage crack control, enhanced flexural reinforcement, improved shear strength and increase the crack resistance of concrete. These steel macro-fibres will also improve impact, shatter, and fatigue and abrasion resistance while increasing toughness of concrete. Dosage rates will vary depending upon the reinforcing requirements and can range from 15 to 60 kg/m³. 3.8.2.1 FEATURES AND BENEFITS  Increases impact, shatter and abrasion resistance of concrete  Reduces segregation, plastic settlement, and shrinkage cracking of concrete  Provides three-dimensional reinforcement against macro-cracking  Increases overall durability, fatigue resistance and flexural toughness
  • 38. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 38 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES  Reduction of in-place cost versus wire mesh for temperature / shrinkage crack control  Easily added to concrete mixture at any time prior to placement 3.8.2.1 APPLICATION  Commercial and industrial slabs on ground  Bridge decks, overlays and pavements  Precast concrete applications  Shotcrete, tunnel linings and slope stabilization  Mass concrete and composite deck construction Table No: 3.8.2 Properties of Crimped Steel Fibre Length 3cm Thickness 1mm Tensile strength (mpa) 421-800 Elongation of break 1.62 Diameter (mm) 0.8-1.2mm Density (g/cm3) 1.47 Young’s modulus (Gpa) 21-72 Figure 3.8.2 Crimped Steel Fibre 3.9 MIX DESIGN REQUIREMENT The requirement which form the basis of selection and proportioning of mmix ingredients are: The minimum compressive strength required from the structural consideration. The adequate workability necessary for full compaction wuth compacting equipment available.
  • 39. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 39 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 3.9.1 MIX DESIGN PROCESS FOR GEOPOLYMER CONCRETE Step1: By using Codebook IS10262:2009 we need to find the target strength for mix proportions is given as Fck = fck + 1.65S Where, “S” is standard deviation Fck = 50+1.65*5 = 58.25 Mpa. Step2: Binder is assumed as 420kg/m3 and alkaline binder is taken as 0.50. By following the codebook at A-8 mix calculations. Calculate volumes of materials as shown below Volume of fly ash = mass of binder content /sp.gravity of solution * 1/1000 Where, Specific gravity of solution from codebook is taken as 2.2 = (420/2.2)*(1/1000) = 0.19 m 3 Volume of alkaline solution = 0.5*binder/ sp. gravity of solution * 1/1000 Where, Specific gravity of solution is taken as 1.34 = (0.5*420/1.34)*1/1000 =0.156 m 3 Volume of super plasticizers= % of super plasticizer*binder/sp. gravity of solution *1/1000 (sp. gravity is taken 1.2). The quantity of super plasticizers is taken as 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0% for the mixture. For super plasticizer 1.5% = ((1.5/100)*420/1.34)*1/1000 = 0.0047 For super plasticizer 2.0% = ((2.0/100)*420/1.34)*1/1000 =0.0062
  • 40. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 40 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES For super plasticizer 2.5% = ((2.5/100)*420/1.34)*1/1000 = 0.0078 For super plasticizer 3.0% = ((3.0/100)*420/1.34)*1/1000 = 0.0094 For super plasticizer 3.5% = ((3.5/100)*420/1.34)*1/1000 = 0.010 For super plasticizer 4.0% = ((4.0/100)*420/1.34)*1/1000 =0.012 Volume of aggregate = 1-(volume of fly ash + volume of alkaline solution + volume of super plasticizers. = 1- (0.193+0.156+0.012) = 0.639m 3 Step3: Taking or by assuming the specific gravity of coarse and fine aggregate from Codebook the ratio of coarse and fine aggregate is taken is calculated as given below. Aggregate/binder = 4.23 Total aggregate = 4.23*420 =1776Kg/m3 Coarse /total aggregate = 0.543 Which is taken as = 0.543*1776.6 = 965 kg/m 3 Mass of fine aggregate = Total aggregate – Coarse aggregate =1776.6-965 = 811 kg/m3
  • 41. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 41 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Alkaline solution = binder * 0.5 (0.5 is the water content). = 420*0.5 = 210 By doing that we get a ratio as Binders: fine aggregate: coarse aggregate: alkaline solution 420: 811: 965: 210 Divide the above ratios with 420 The ratio is taken as 1: 1.93: 2.29: 0.5 Step4: By taking the ratios from step3, we should find out how much quantity of material is required for that particular mix .The steps are below, Binder (fly ash &amp; GGBS) = ratio of binder/total ratio * total weight of cubes. Binding varying GGBS 50% = 1/5.72*80 = 13.98(GGBS) For 50% GGBS = 13.98*0.5 = 6.99 Fly ash = 13.98 – 6.99 = 6.99 Fine aggregate= ratio of fine aggregate/total ratio * total weight of cubes. = 1.93/5.72*28 = 9.45 kg/m3 Coarse aggregate= ratio of coarse aggregate/total ratio * total weight of cubes. = 2.29/5.72*28 = 11.2 kg/m3 Alkaline solution= water content (i.e., 0.5)/total ratio * total weight of cubes. = 0.5/5.72*28 = 2.45 kg/m3
  • 42. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 42 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Super plasticizer = volume of super plasticizer *total weight of cubes*0.5. The quantity of super plasticizers is taken as 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%.for the mixture. For super plasticizer 1.5% = 0.005*80*0.5 = 225ml. For super plasticizer 2.0% = 0.0066*80*0.5 = 300ml. For super plasticizer 2.5% = 0.0083*80*0.5 = 375ml. For super plasticizer 3.0% = 0.01 *80*0.5 = 450 ml. For super plasticizer 3.5% = 0.0116*80*0.5 =525 ml. For super plasticizer 4.0% = 0.0133 *80*0.5 = 600ml Combination of steel and glass fibre were taken in the range of 0.1% to 0.6%. 3.9.1 TYPES OF MIXES A mix design can be designed in two ways as explained below a) Nominal Mix b) Design Mix c) Standard Mix 3.9.1.1 Nominal Mix It is used for relatively unimportant and simpler concrete works. In this type of mix, all the ingredients are prescribed and their proportions are specified. Therefore there is no scope for any deviation by the designer. Nominal mix concrete may be used for concrete of M-20 or lower. The various ingredients are taken as given in the table below
  • 43. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 43 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Table no: 3.9.1 Nominal mix Grade Max. quantity of dry Aggregates per 50 kg of cement Fine Aggregate to Coarse Aggregate Ratio, by mass Max. Quantity of water in litres M-5 800 Generally 1:2 but may varies from 1:1.5 to 1:2.5 60 M-7.5 625 45 M-10 480 34 M-15 330 32 M-20 250 30 3.9.1.2 DesignMix It is a performance based mix where choice of ingredients and proportioning are left to the designer to be decided. The user has to specify only the requirements of concrete in fresh as well as hardened state. The requirements in fresh concrete are workability and finishing characteristics, whereas in hardened concrete these are mainly the compressive strength and durability. 3.9.1.3 Standard Mixes The nominal mixes of fixed cement-aggregate ratio (by volume) vary widely in strength and may result in under- or over-rich mixes. For this reason, the minimum compressive strength has been included in many specifications. These mixes are termed standard mixes.IS 456-2000 has designated the concrete mixes into a number of grades as M10, M15, M20, M25, M30, M35 and M40. In this designation the letter M refers to the mix and the number to the specified 28 day cube strength of mix in N/mm2. The mixes of grades M10, M15, M20 and M25 correspond approximately to the mix proportions (1:3:6), (1:2:4), (1:1.5:3) and (1:1:2) respectively. 3.10 FACTORS AFFECTINGTHE CHOICE OF MIX PROPORTIONS The various factors affecting the mix design are: 1. Compressive strength: It is one of the most important properties of concrete and influences many other describable properties of the hardened concrete. The mean compressive strength required at a specific age, usually 28 days, determines the nominal
  • 44. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 44 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES water-cement ratio of the mix. The other factor affecting the strength of concrete at a given age and cured at a prescribed temperature is the degree of compaction. According to Abraham’s law the strength of fully compacted concrete is inversely proportional to the water-cement ratio. 2. Workability: The degree of workability required depends on three factors. These are the size of the section to be concreted, the amount of reinforcement, and the method of compaction to be used. For the narrow and complicated section with numerous corners or inaccessible parts, the concrete must have a high workability so that full compaction can be achieved with a reasonable amount of effort. This also applies to the embedded steel sections. The desired workability depends on the compacting equipment available at the site. 3. Durability: The durability of concrete is its resistance to the aggressive environmental conditions. High strength concrete is generally more durable than low strength concrete. In the situations when the high strength is not necessary but the conditions of exposure are such that high durability is vital, the durability requirement will determine the water-cement ratio to be used. 4. Maximum nominal size of aggregate: In general, larger the maximum size of aggregate, smaller is the cement requirement for a particular water-cement ratio, because the workability of concrete increases with increase in maximum size of the aggregate. However, the compressive strength tends to increase with the decrease in size of aggregate. IS 456:2000 and IS 1343:1980 recommend that the nominal size of the aggregate should be as large as possible. 5. Grading and type of aggregate: The grading of aggregate influences the mix proportions for a specified workability and water-cement ratio. Coarser the grading leaner will be mix which can be used. Very lean mix is not desirable since it does not contain enough finer material to make the concrete cohesive.The type of aggregate influences strongly the aggregate-cement ratio for the desired workability and stipulated water cement ratio. An important feature of a satisfactory aggregate is the uniformity of the grading which can be achieved by mixing different size fractions.
  • 45. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 45 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 6. Quality Control: The degree of control can be estimated statistically by the variations in test results. The variation in strength results from the variations in the properties of the mix ingredients and lack of control of accuracy in batching, mixing, placing, curing and testing. The lower the difference between the mean and minimum strengths of the mix lower will be the cement-content required. The factor controlling this difference is termed as quality control.
  • 46. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 46 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CHAPTER -4
  • 47. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 47 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 4. GEOPOLYMER MORTAR Geopolymers prepared by mixing of ggbs and fly ash with alkali activator solution is called geopolymer paste. The mixer is usually homogeneous slurry. In manufacturing geopolymer mixes, following range of synthesizing parameters are selected and studied their effect on compressive strength of geopolymer mortar.  NaOH molarity : 8M  Curing type : Ambient curing  Curing time : 3days,7days, 28days 4.1 MaterialPreparation Initially collect the material and weigh to require proportion i.e. fly ash, sand, coarse aggregates, ggbs, NaOH and sodium silicate solution. A combination of sodium hydroxide solution and sodium silicate solution was used as the alkaline activator. Sodium hydroxide solution prepared by taking specified weight of sodium hydroxide pellets into a beaker and add required amount of water according to its molarity. Sodium hydroxide solution was used as alkaline activator because it is widely available and is less expensive than potassium hydroxide solution. The alkaline activator was prepared in the laboratory. In order to avoid the effect of unknown contaminants, distilled water was used to dissolve the sodium hydroxide pellets. The alkaline activator was prepared by mixing the sodium hydroxide solution with sodium silicate solution together just before the mixing of mortar to ensure the reactivity of solution. The aim of adding sodium silicate is to enhance the formation of Geopolymer precursors or the polymerization process.
  • 48. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 48 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 4.1.A Material Preparation 4.2 Mixing The fly ash and the fine aggregate were first dry mixed together in pan for 2 minutes to ensure homogeneity of the mixture. The mixture was activated by adding activator solution containing sodium hydroxide and sodium silicate according to the required concentration range of 8 to 16M and mixed for a further 10 minutes. The concrete shall be mixed by hand or preferably in a laboratory mixer, in such a manner as to avoid loss of other materials. Each batch of concrete shall be of such as to leave about 10 percent excess after moulding the desired number of test specimen. a. Hand mixing Concrete is mixed by any two methods, based on requirement as per quality and quantity of concrete required. Normally for mass concrete, where good quality of concrete is required, mechanical mixer is used. Mixing by hand is employed only to specific cases where quality control is not of much importance and quantity of concrete required is less. Stone aggregate is washed with water to remove dirt, dust or any other foreign material before mixing. The main purpose of mixing the concrete is to finally obtain a uniform mixture that shows uniformity in terms of color and consistency.
  • 49. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 49 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 4.2A Hand Mixing 4.3 SIZE OF TEST SPECIMEN Test specimens cubical in shape shall be 15x15x15cm.Cylindrical test specimens shall have a length equal to twice the diameter they shall be 15 cm in diameter and 30 cm in height. Beam moulds shall have the dimensions 10x15x10 cm Cylinder Cube Beam Figure no: 4.3A Mould Preparation
  • 50. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 50 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 4.4 Compaction The test specimens shall be made as soon as practicable after mixing, and in such a way as to produce full compaction of the concrete with no segregation. The concrete shall be filled into the mould in the layers approximately 5 cm deep, in placing each scoopful of concrete, the scoop shall be moved around the top edge of the mould as the concrete slides from it, in order to ensure symmetrical distribution of concrete with in mould. Each mould shall be compacted either by hand or by vibration as described below. After the top layer has been compacted either, the surface of the concrete shall be finished level with the top of the mould, using a trowel. All the cast specimens were vibrated on a vibrating table for 2 minutes to remove air voids. The tamping bar shall be a steel bar 16mm in diameter, 0.6m long and bullet pointed at the lower end. Figure no: 4.3A Mould Preparation Figure no: 4.4B Vibrating Machine
  • 51. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 51 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 4.5 Curing All the specimens were kept at a room temperature for setting in the moulds and were moved under open air for ambient curing. The moulds were kept under ambient curing for the specified number of days i.e., 3days, 7 days, 28days before testing. Figure no: 4.5A Curing 4.6 Testing After the ambient curing, all the specimens were removed and cured undisturbed at room temperature until they are tested. The Geopolymer mortar specimens were tested for 3 and7 day’s compressive strength using the Compression Testing Machine and tensile strength using tensile strength machine. The specimens were subjected to a compressive force at the rate of 1700 N/sec and tensile strength until the specimen failed. The reported strengths were the average results of the three tests. 4.6.1 Compression Strength Test Out of many test applied to the concrete, this is the utmost important which gives an idea about all the characteristics of concrete. By this single test one judge that whether Concreting has been done properly or not. Compressive strength of concrete depends on many factors such as water-cement ratio, fly ash strength, quality of concrete material, and quality control during production of concrete. For most of the works cubical moulds of size 15 cm x 15cm x 15 cm are commonly used. This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put for ambient curing. The top surface of these specimens should be made even and smooth. This is done by putting paste and spreading smoothly on whole area of specimen. These specimens
  • 52. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 52 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES are tested by compression testing machine after 3, 7 and 28 days of curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete. Figure no: 4.6.1Compression strength test 4.6.2 Split Tensile Strength Test Tensile strength is one of the basic and important properties of concrete. A knowledge of its value is required for the design of the concrete elements. Direct tensile strength is difficult to determine; recourse is often taken to the determination of flexural strength or the splitting tensile strength, further it is a method of determining the tensile strength of concrete using a cylinder which splits across a vertical diameter. In direct tensile strength test it is impossible to apply true axial load. The mould and base plate shall be coated with a thin film of mould oil before use, in order to prevent adhesion of the concrete prepare three cylindrical concrete cylindrical. After moulding and curing the specimens for the specified number of days under ambient curing, they can be tested. The cylindrical specimen is placed in the manner that the longitudinal axis is perpendicular to the load. The load shall be applied without shock and increased continuously at a nominal rate within the range 1.2 N/mm2 to 2.4 N/mm2. Record the maximum applied load indicated by the testing machine at failure.
  • 53. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 53 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no. 4.6.2 Split tensile strength test 4.6.3 Flexural Strength Test It is also known as modulus of rupture, bend strength or fracture strength, a mechanical parameter for brittle material, is defined as a materials ability to resist deformation under load. The test specimens prepared after curing under ambient curing for the specified number of day’s i.e. (7 days, 14 days, and 28 days). The specimens shall be placed in the machine in such a manner that the load shall be applied to the upper most surface as cast in the mould. The axis of the specimen shall be carefully aligned with axis of the loading device. The load was increased until the specimen failed and the maximum applied load to the specimen during the test is recorded. Figure no: 4.6.3 Flexural strength test
  • 54. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 54 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES CHAPTER – 5
  • 55. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 55 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES 5 RESULTS AND DISCUSSION 5.1 General In this chapter the strength parameters of the fibre based geopolymer concrete are discussed. The parameters such as compressive strength and tensile strength of the geopolymer concrete using fibres (crimped steel fibre and glass fibre) are discussed. 5.2 Concentration of alkaline solution, fly ash, GGBS, and fibres Mix was prepared for M50 to study the effect of Molarity (or) concentration of Sodium Hydroxide solution, fly ash, GGBS and fibers (i.e. crimped steel and glass fibers) on the compressive strength of geopolymer concrete. The concentration of NaOH of 8M was used. For M50 mix for the beams the fly ash content was kept zero and GGBS was kept 100% further sand and Na2SiO3 weights were kept constant. 5.3 Tests on M50 cubes, cylinders and prisms using steelfibres Table no: 5.3A Compressive strength for standard mix (Cubes) Mix 3 Days 7 Days 28 Days Compressive Strength in N/mm2 Average strength in N/mm2 Compressive Strength in N/mm2 Average strength in N/mm2 Compressive Strength in N/mm2 Average strength in N/mm2 Standard mix 23.4 23.32 23.48 23.4 46.8 46.64 46.96 46.8 58.5 58.3 58.7 58.5
  • 56. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 56 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3A Compressive strength of standard mix (Cubes) The mix design ratio for Cubes of M-50 grade (1:1.93:2.29:0.5) using steel fibres Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=4.9 kgs. Fine aggregate=9.45 kgs. Coarse aggregate=11.2 kgs. Alkaline=2.45 kgs. Table no: 5.3A1 Compressive strength of M50 cubes using Steel fibres % of Steel fibers 3 Days 7 Days 28 Days 0.1% 24.08 48.16 60.2 0.2% 24.6 49.2 61.5 0.3% 24.9 49.8 62.3 0.4% 24.72 49.4 61.8 0.5% 24.56 49.1 61.4 0.6% 24.1 48.2 60.3 0 10 20 30 40 50 60 3 Days 7Days 28Days 23.4 46.8 58.5 CUBES
  • 57. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 57 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3A1 Compressive strength of M50 cubes using Steel fibres 5.3B Split tensile strength test on M50 cylinders using steel fibres Table no: 5.3B Split tensile strength for standard mix (Cylinders) Mix 3 Days 7 Days 28 Days Tensile Strength in N/mm2 Average Tensile Strength in N/mm2 Tensile Strength in N/mm2 Average Tensile Strength N/mm2 Tensile Strength in N/mm2 Average Tensile Strength N/mm2 Standard mix 1.92 1.92 1.94 1.92 3.84 3.82 3.88 3.85 4.80 4.82 4.85 4.82 24.08 24.6 24.92 24.72 24.56 24.12 48.16 49.2 49.8 49.4 49.12 48.2 60.2 61.5 62.3 61.8 61.4 60.3 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 10 20 30 40 50 60 70 1 2 3 4 5 6 CUBES 3 Days 7 Days 28 Days % of fibers
  • 58. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 58 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3B Split tensile strength of standard mix (Cylinders) The mix design ratio for Cylinders of M-50 grade is 1:1.93:2.29:0.5 using Steel fibres Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alakaline=3.5 kgs Table no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres % of steel fibers 3 Days 7 Days 28 Days 0.1% 2.1 4.2 5.25 0.2% 2.16 4.32 5.40 0.3% 2.19 4.38 5.48 0.4% 2.16 4.36 5.42 0.5% 2.12 4.2 5.3 0.6% 2.06 4.08 5.2 0 1 2 3 4 5 3 Days 7Days 28Days 1.92 3.85 4.82 CYLINDERS
  • 59. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 59 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3B1 Tensile strength of M50 Cylinders using Steel fibres 5.3C Flexural strength test on M50 prisms using steel fibres Table no: 5.3C Flexural strength for standard mix (Prism) Mix 3 Days 7 Days 28 Days Flexural strength in N/mm2 Average strength in N/mm2 Flexural strength in N/mm2 Average strength in N/mm2 Flexural strength in N/mm2 Average strength in N/mm2 Standard Mix 1.8 1.81 1.82 1.81 3.60 3.63 3.65 3.62 4.50 4.54 4.56 4.53 2.1 2.16 2.19 2.16 2.12 2.06 4.2 4.32 4.38 4.36 4.2 4.08 5.24 5.4 5.48 5.42 5.3 5.2 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 1 2 3 4 5 6 1 2 3 4 5 6 CYLINDERS 3 Days 7 Days 28 Days % of fibers
  • 60. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 60 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3C Flexural strength of standard mix (Prism) The mix design of prism ratio for M-50 grade is 1:1.93:2.29:0.5 Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs Table no: 5.2C1 Flexural strength of M50 Prisms using Steel fibres % of steel fibers 3 Days 7 Days 28 Days 0.1% 1.89 3.78 4.73 0.2% 1.92 3.84 4.81 0.3% 1.96 3.92 4.90 0.4% 1.93 3.86 4.83 0.5% 1.88 3.76 4.70 0.6% 1.84 3.69 4.62 0 1 2 3 4 5 3 Days 7Days 28Days 1.81 3.62 4.53 PRISM
  • 61. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 61 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.3C1 Split tensile strength of M50 Prism using Steel fibres 5.4 Teston M50 cubes, cylinders, prisms using glass fibre Table no: 5.4A compressive strength test for M50 cubes using glass fibre Mix 3 Days 7 Days 28 Days Compressive Strength in N/mm2 Average Strength in N/mm2 Compressive Strength in N/mm2 Average Strength in N/mm2 Compressive Strength in N/mm2 Average Strength in N/mm2 Standard Mix 23.12 22.8 22.5 22.08 46.2 45.5 45.0 45.6 57.8 56.9 57.2 57.3 1.89 1.92 1.96 1.93 1.88 1.84 3.78 3.84 3.92 3.86 3.76 3.69 4.73 4.81 4.9 4.83 4.7 4.62 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 1 2 3 4 5 6 1 2 3 4 5 6 PRISMS 3 Days 7 Days 28 Days % of fibers
  • 62. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 62 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4A Compressive strength of standard mix (Cubes) The mix design of cubes ratio for M-50 grade is 1:1.93:2.29:0.5 Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs Table no: 5.4A1 Compressive strength of M50 cubes using glass fibres % of glass fibers 3 Days 7 Days 28 Days 0.1% 23.2 46.56 58.2 0.2% 23.5 47.04 58.8 0.3% 23.7 47.62 59.4 0.4% 23.8 47.68 59.6 0.5% 23.4 46.8 58.5 0.6% 22.8 45.7 57.2 0 10 20 30 40 50 60 3 Days 7Days 28Days 22.8 45.6 57.3 CUBES
  • 63. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 63 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4A1 Compressive strength of M50 cubes using glass fibres 5.4B Split tensile strength test for M50 cylinders using glass fibres Mix 3 Days 7 Days 28 Days Compressive Strength in N/mm2 Average Strength in N/mm2 Compressive Strength in N/mm2 Average Strength in N/mm2 Compressive Strength in N/mm2 Average Strength in N/mm2 Standard Mix 1.84 1.80 1.78 1.80 3.68 3.65 3.39 3.64 4.6 4.4 4.2 4.4 23.2 23.5 23.7 23.8 23.4 22.8 46.56 47.04 47.62 47.68 46.8 45.7 58.2 58.8 59.4 59.6 58.5 57.2 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 10 20 30 40 50 60 70 1 2 3 4 5 6 CUBES 3 Days 7 Days 28 Days % of fibers
  • 64. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 64 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4B Split tensile strength of standard mix (Cylinders) Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs Table no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres % of glass fibers 3 Days 7 Days 28 Days 0.1% 1.96 3.92 4.9 0.2% 2.04 4.08 5.1 0.3% 2.12 4.24 5.3 0.4% 2.13 4.27 5.34 0.5% 2.09 4.18 5.23 0.6% 2.08 4.16 5.21 0 1 2 3 4 5 3 Days 7Days 28Days 1.8 3.64 4.4 CYLINDERS
  • 65. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 65 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4B1 Split tensile strength of M50 cylinders using glass fibres Table no: 5.4C Flexural strength test for M50 prism using glass fibres Mix 3 Days 7 Days 28 Days Flexural Strength in N/mm2 Average Strength in N/mm2 Flexural Strength in N/mm2 Average Strength in N/mm2 Flexural Strength in N/mm2 Average Strength in N/mm2 Standard Mix 1.8 1.72 1.6 1.74 3.6 3.44 3.2 3.41 4.5 4.3 4.0 4.26 1.96 2.04 2.12 2.13 2.09 2.08 3.92 4.08 4.24 4.27 4.18 4.16 4.9 5.1 5.3 5.34 5.23 5.21 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 1 2 3 4 5 6 1 2 3 4 5 6 CYLINDERS 3 Days 7 Days 28 Days % of fibers
  • 66. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 66 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4C Flexural strength of standard mix (Prism) The mix design of prism ratio for M-50 grade is 1:1.93:2.29:0.5 Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs Table no: 5.4C1 Flexural strength of M50 prism using glass fibres % of glass fibers 3 Days 7 Days 28 Days 0.1% 1.92 3.84 4.81 0.2% 1.97 3.94 4.93 0.3% 2.08 4.16 5.21 0.4% 2.17 4.34 5.43 0.5% 2.09 4.18 5.23 0.6% 2.04 4.04 5.1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 3 Days 7Days 28Days 1.74 3.41 4.26 PRISMS
  • 67. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 67 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Figure no: 5.4C1 Flexural strength of M50 prisms using glass fibres 5.5Analysis on combination of fibres based on maximum strength 5.5A Maximum compressive strength obtained for cubes The mix design ratio of cubes for M-50 grade is 1:1.93:2.29:0.5 Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs Steel fibres= 50grms Glass fibres= 100grms The maximum compressive strength for cubes using M50 grade was obtained at 0.3% for steel and 0.4% for glass fibres separately. 1.92 1.97 2.08 2.17 2.09 2.04 3.84 3.94 4.16 4.34 4.18 4.08 4.81 4.93 5.21 5.43 5.23 5.1 0.10% 0.20% 0.30% 0.40% 0.50% 0.60%0 1 2 3 4 5 6 1 2 3 4 5 6 PRISMS 3 Days 7 Days 28 Days % of fibers % of Glass Fibres
  • 68. MARRI LAXMAN REDDY INSTITUTE OFTECHNOLOGY ANDMANAGEMENT 68 MECHANICAL PROPERTIES OF GEOPOLYMER CONCRETE USING HYBRID FIBRES Table no: 5.5A Maximum compressive strength obtained for cubes Combination of glass and steel fibers 3 Days 7 Days 28 Days steel+glass fibers 24.17 48.34 60.43 Figure no: 5.5A Maximum compressive strength for cubes 5.5B Maximum split tensile strength obtained for cylinders The mix design ratio of cylinders for M-50 grade is 1:1.93:2.29:0.5 Where the values denote the ratio of binder: fine aggregate: course aggregate: alkaline solution. Binder=7 kgs Fine aggregate=13.5 kgs Coarse aggregate=16 kgs Alkaline=3.5 kgs 0 10 20 30 40 50 60 70 3 Days 7Days 28Days 24.17 48.34 60.43 CUBES