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CHAPTER 1 INTRODUCTION 1.1 General Now a days usage of concrete occupies second place around the world other than the water. ordinary Portland concrete primarily consists of cement, aggregates (coarse & fine) and water. Due to increasing of developments in infrastructure, the usage of conventional concrete (CC) will be more and as well as the demand of cement would be increased in the future. Approximately it is estimated that the consumption of cement is more than 2.2 billion tons per year (Malhotra, 1999). It is widely known that concrete is the most widely used constructing material and Portland cement is one of the ingredient used in the concrete. Mainly the production of Portland cement takes considerable energy, due to that it releases large volume of carbon dioxide (Co2) into the atmosphere. The climate change is mainly concerned with the global warming. Generally the various greenhouse gases, such as carbon dioxide (Co2), methane, nitrous oxide are releasing into the atmosphere due to various human activities. These gases are mainly responsible for global warming. Many industries are releasing Co2 into the atmosphere, in those cement industry also playing one of the role. Generally the one ton of Co2 is approximately releasing due to the production of one ton of Portland cement.

However in concrete

construction, Portland cement is one of the main binder. So, we have to search for more environmental friendly materials. There are many attempts are under research for the replacement of Portland cement with other cementitious materials such as fly ash, ground granulated blast furnace slag (GGBS), ricehusk, in order to reduce global warming issues. Fly ash is the by-product of burning coal that is accessible at worldwide. It is being used for replacement of Portland cement in concrete. High calcium fly ash or ASTM class C ash possess the self binding properties. Low calcium fly ash or class F fly ash possesses pozzolanic properties. Davidovits (1978), had developed alternative binder “geopolymer” that contains cementing properties. So, it can be used as replacement of cement. A geopolymer will be created JNTUCEA

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by the combining of aluminosilicate material with high alkalic liquids. Usually geopolymer will be made up of the materials that contain Al (Al) and oxide (Si) content. Fly ash and ground granulated blast furnace slag (GGBS) are rich in Al and oxide content. So, these can be used for replacing the cement in concrete. 1.2 Geo-polymers There are two major constituents present in the geopolymers, namely the alkaline liquids and source materials. The alkaline liquid used in geopolymerisation process is a mixture of Sodium hydroxide (NaoH) and Sodium silicate (Na2SiO3) or potassium hydroxide (KOH) and potassium silicate (K2SiO3). The source materials used for geopolymers are based on percentage of silica (Si) and aluminium (Al) present in the material. Fly ash, silica fume, ground granulated blast furnace slag (GGBS), rise husk ash etc., could be used as source materials. The selection of source materials is mainly based on requirement, cost, users demand etc. The schematic structure of geopolymer material can be shown in Equations (1) and (2) (Davidovits, 1994; van Jaarsveld et al., 1997) [3]: n(Si2o5,Al2o2)+2nSiO2+4nH2o+KOH or KOH → Na+, K+ + n(oH)3-Si-o-Al--o-Si-(oH)3 │

(Si-Al materials)

(oH)2

(1)

(Geopolymer precursor) n(oH)3-Si-o-Al--o-Si-(oH)3 + KOH or KOH → (Na+, K+)-(-Si-o-Al--o-Si-o-) + 4nH2o │

│

│

(oH)2

o

o

│

o

(2)

(Geopolymer backbone)

The above chemical reaction may consist of the following steps (Davidovits 1999; Xu and van Deventer 2000): 

Dissolution of Si and Al atoms from the source material through the action of hydroxide ions.



Transportation or condensation or orientation of precursor ions into monomers.



Polymerisation of monomers into polymeric structures.

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However, the above three steps can overlap with each other and occur almost simultaneously, thus making it difficult to isolate and examine each of them separately (Palomo et al. 1999). A geopolymer can take one of the three basic forms (Davidovits 1999): 

Poly (sialate), which has [-Si-o-Al-o-] as the repeating unit.



Poly (sialate-siloxo), which has [-Si-o-Al-o-Si-o-] as the repeating unit.



Poly (sialate-disiloxo), which has [-Si-o-Al-o-Si-o-Si-o-] as the repeating unit.

Sialate is an abbreviation of silicon-oxo-aluminate.

From equation (2), it reveals that the last term i.e., water (H2o) is released during the chemical reaction that occurs in the formation of geopolymers. This water, removed from the geopolymer matrix during the curing and further drying periods, leaves behind discontinuous nano-pores in the matrix, which provide benefits to the performance of geopolymers.

1.2.1 Constituents of Geopolymer 1.2.1.1 Source materials In the present investigation the following materials are used as source materials. a) Fly ash b) Ground Granulated Blast furnace Slag

a) Fly ash Fly ash (ASTM Class F) is used in the manufacturing of geopolymer concrete and which is obtained from the by-product of coal-burning power stations. The production of fly ash will be increased day by day in our country, so it is best opportunity to employ this by-product in the geopolymer concrete. Approximately it is estimated that the production of fly ash is more than 780 million tons per year especially in the countries like China and India (Malhotra, 2002). So, JNTUCEA

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the abundant availability of fly ash may create the good opportunity to employ in the manufacturing of geopolymer concrete (GPC).

b) Ground Granulated Blast furnace Slag (GGBS) Ground granulated blast furnace slag is also one of the source materials used in the manufacturing of geopolymer concrete and which is obtained by the blast furnace used to make iron. GGBS is used in the ordinary Portland concrete either in the form of mineral admixture or in the form of constituent of blended cement. ordinary Portland cement is typically replaced by 35 to 65% of the GGBS. It improves strength and durability properties of the concrete and also increases the service life of concrete structures. on the other hand, the usage of ground granulated blast furnace slag may create some environmental benefits such as it produces less quantity of carbon dioxide as compare to the ordinary Portland cement. It also gives better workability (i.e., easy to mixing, transporting, placing and compacting etc).

c) SLAG As by-products of the metallurgical industry, the chemical composition, structure and properties of slag vary depending on the source, i.e. iron blast-furnace slag ar hydraulic while nickel and copper slag have only pozzolanic properties due to the lack of lime and therefore they need to react with lime before become hydraulic (Regourd, 1986) . The most common cementitious materials for AAS binder is iron blast-furnace slag and it is the only material to be used worldwide for the production of AAS binder using local sources (Al-otaibi, 2008; Bakharev, et al., 1999a; Bougara,Lynsdale, & Ezziane, 2009: Douglas & Brandstetr, 1990; Fernandez-Jimenez,Palomo, & Puertas, 1999; Gjorv, 1989; Krizan & Zivanovic, 2002; Ling, Pei, &Yan, 2004; Shi & Day, 1996; Wang & Scrivener, 1995; Zivica, 2007). Althoughother types of slag such as phosphorus slag (Shi & Li, 1989), red mud slag (Gong& Yang, 2000; Pan, et al., 2002) can also be activated, however as theirhydraulic activity is not as high as iron blast-furnace slag, their activation is not aseffective as iron blast-furnace slag.

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1.2.1.2 Alkaline Liquids The combination of Potassium hydroxide (KOH) and Potassium silicate solution (K2SiO3) are used as alkaline liquids. The Potassium silicate solution (K2o= 13.7%, SiO2=29.4%, and water (H2o) =55.9% by mass) was prepared by the manufacturer of required quantities. The Potassium hydroxide (KOH) in flakes or pellets from with 97%-98% purity was used in the investigation. The Potassium hydroxide (KOH) solution was prepared by dissolving either the flakes or the pellets in required quantity of water. The mass of Potassium hydroxide solids in a solution varied depending on the concentration of the solution expressed in terms of molarity (M). For instance, KOH solution with a concentration of 10M consisted of 10x40 = 400 grams of KOH solids (in flake or pellet form) per litre of the solution, where, 40 is the molecular weight of Potassium hydroxide (KOH) pellets or flakes.

1.2.2 Applications of Geopolymers 

Used in industrial floor repairs.



Airfield repairs (in war zones).



Fireproof composite panels.



External repair and structural retrofit for aging infrastructure.



For storage of toxic and radioactive wastes.



Potential utilizations in Art and Decoration.



LTGS Brick, railways sleepers, electric power poles, marine structures, waste containments etc..

Depending on the molar ratio of Si to Al, the possible applications of geopolymers were proposed by Davidovits (1999) as given in Table 1.1.

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Table 1.1. Applications of Geopolymers Si:Al

Application - Bricks

1

- Ceramics - Fire protection

2

- Low Co2 cements and concretes - Radioactive and toxic waste encapsulation - Fire protection fibre glass composite

3

- Foundry equipments - Heat resistant composites, 2000C to 100ooC - TOoling for aeronautics titanium process

>3

20-35

- Sealants for industry, 2000C to 600oC - TOoling for aeronautics SPF aluminium - Fire resistant and heat resistant fibre composites

1.2.3 Advantages of Geopolymers Geopolymer concrete is more resistant to corroSiOn and fire, has compressive and tensile strengths, gains its full strength quickly (cures fully faster), low creep, no shrinkage, good acid resistance, low permeability, resistant to sulphate attack and durable finishes. 1.3 Aim of the Project The main objective of this project is to reduce the carbon dioxide (Co2) emisSiOns into the atmosphere and also to develop and study the strength characteristics of fly ash and GGBS based geopolymer concrete at ambient room temperature curing. Based on the background of this project, the aims of this project are as follows: JNTUCEA

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1. TO develop the strength parameters of geopolymer concrete made with fly ash and GGBS with various proportions. 2. TO study the engineering properties of low calcium fly ash and GGBS based geopolymer concrete. 1.4 Scope of work The research utilized fly ash (ASTM Class F) and ground granulated blast furnace slag (GGBS) in the development of GPC. Potassium hydroxide and Potassium silicate solution are used as alkaline activators. The geopolymer concrete properties studied in this study are the compressive strength, split tensile strength, flexural strength at different curing periods. 1.5 Thesis arrangement The remainder of the thesis is arranged as follow: Chapter-1 describes the brief introduction about geopolymer, constituents of geopolymer, applications and advantages of geopolymer concrete, aim of the project and finally discuss about scope of work. Chapter-2 describes a brief literature review. This chapter describes in detail the various types of works carried out by the researchers to understand the behavior of geopolymer concrete. Chapter-3 describes the materials and methods of tests which are conducting the geopolymer concrete. The tests performed to study the mechanical properties of the hardened geopolymer concrete are described. Chapter-4 describes the results and discusSiOn of the experiments conducted on the geopolymer concrete. Chapter-5 describes the overall concluSiOns made in the project and suggestions of future work. The thesis ends with a Reference List and two Appendices.

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CHAPTER 2 LITERATURE REVIEW This Chapter presents the historical background of the geopolymer concrete, Terminology and Chemistry of the geopolymers. The study of literature survey corresponding to the geopolymer concrete technology has done in this chapter.

2.1 Historical Background The phenomenal durability of ancient concretes and mortars compared to those being used in modern time prompted research into the nature of these ancient compounds. Results from various studies, summarized by Davidovits, [6] proved that there is in fact a very distinct difference between ancient mortars and the Portland cement-based building materials in use today. The ancient products seem to be not only physically more durable, but also more resistant to acid attack and freeze-thaw-cycles. Initially it was thought that this difference is the consequence of calcium silicate hydrates (of the C-S-H-gel type) which constitute the main part of Portland cement. Later, however, it was discovered that these ancient concretes also contain amounts of C-S-H gel and consequently researchers turned their attention to the large amounts of zeolitic phases also found in the ancient products [6]. It was later concluded that the long term durability of ancient mortars is the result of high levels of zeolitic and amorphous compounds in their compositional make-up. The use of pozzolanic materials in the manufacture of concrete has a long, successful history. In fact, their use pre-dates the invention of modern day Portland cement by almost 200 years. Today, most concrete producers worldwide recognize the value of pozzolanic enhancements to their products and, where they are available; they are becoming a basic concrete ingredient. Mineral admixtures such as ground granulated blast furnace slag (GGBS), fly ash and silica fume are commonly used in concrete because they improve durability reduce porosity and improve the interface with the aggregate. Economics (lower cement requirement), energy, and environmental considerations have had a role in the mineral admixture usage as well as better engineering and performance properties. The lower cement requirement also leads to a reduction for Co2 generated by the production of cement. The engineering benefits from the use of mineral JNTUCEA

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admixtures in concrete result partly from their particle size distribution characteristics, and partly from the pozzolanic and cementations reactivity. Experimental programs conducted with the purpose of proving this theory partly resulted in the rediscovery of a new family of mineral binders named "Geopolymers" because of similarities with organic condensation polymers as far as their hydrothermal synthesis conditions were concerned.

2.1.1 Concrete and environment The emisSiOn of carbon dioxide (Co2) in to the atmosphere is the main cause of green house effect. Many industries including cement industries release lots of carbon dioxide in to the atmosphere, as the greenhouse effect created by these emisSiOns it results into increase in the global temperature that may result in climate changes. As cement is widely used as a binder material in the construction field all over the world, its production is increasing by 3% annually (McCaffrey 2002). The production of one ton of cement liberates about one ton of Co2 to the atmosphere which causes global warming. Among all the green house gas emisSiOns, into the atmosphere, emisSiOns from cement production only is estimated about 7%. The Cement manufacturing plants of all over world release about 1.35 billion tons of carbon-dioxide in to atmosphere annually (Malhotra 2002). After aluminium and steel, cement is one of the energyintensive construction materials. Furthermore, it has been noticed that the durability characteristics of ordinary Portland cement (OPC) concrete is under testing, as many concrete structures, these built in corrosive environments, start to deteriorate after 2o to 30 years, even though they have been designed for more than 50 years of service life (Mehta, 2002). In order to produce environmentally friendly concrete, Mehta (2002) proposed the advantages of some natural resources, lower energy and minimise carbon dioxide emisSiOns. Many attempts are in process to continue the use of Portland cement in concrete to notice the global warming problems.In order to develope the similar binding materials to ordinary portland cement, we will use the rice-husk, fly ash, metakaolin and ground granulated blast furnace slag. In this respect, the geopolymer concepts presents some of applications in cement factories as an similar binder to the ordinary Portland cement (Duxson et al, 2007). Inorder to control the global warming effects, the geopolymer studies should minimize the releasing of Co2

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into the atmosphere due to the cement industries as shown by the detailed analyses of Gartner (2004).

2.2 Terminology Davidovits, created and applied the term Geopolymer. For the chemical designation of geopolymers based on silico-aluminates, "Poly (sialate)" was suggested. Sialate is an abbreviation for silicon-oxo-aluminate. Although the mechanism of polymerization is yet to be fully understood, a critical feature is that water is present only to facilitate workability and does not become a part of the resulting geopolymer structure. In other words, water is not involved in the chemical reaction and instead is expelled during curing and subsequent drying. This is in contrast to the hydration reactions that occur when Portland cement is mixed with water, which produce the primary hydration products calcium silicate hydrate and calcium hydroxide. This difference has a significant impact on the mechanical and chemical properties of the resulting geopolymer concrete, and also renders it more resistant to heat, water ingress, alkali-aggregate reactivity, and other types of chemical attack (Davidovits 2008; Lloyd and Rangan 2009), [9&1o]. The chemical composition of the geopolymer material is similar to natural zeolitic materials, but the microstructure is amorphous instead of crystalline (Palomo et al. 1999; Xu and van Deventer 2000, [11]. The polymerisation process involves a substantially fast chemical reaction under alkaline condition on Si-Al minerals, which results in a three dimenSiOnal polymeric chain and ring structure consisting of Si-o-Al-o bonds, as follows (Davidovits 1999), [12]: Mn [-(SiO2) z-A102] n. wH2o (2-1) Where: M = the alkaline element or cation such as potassium, Potassium or calcium; the symbol indicates the presence of a bond, n is the degree of polycondensation or polymerisation; z is l, 2, 3, or higher, up to 32.

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2.3 Literature review on Geopolymer Concrete Rangan (2008) has reported on the fly ash-based geopolymer concrete. He study the effects of salient factors that influence the short and long term properties of the geopolymer concrete in the fresh and hardened states. He describes the applications and economic merits of geopolymer concrete in the construction industry. He finally concluded that the low-calcium fly ash-based geopolymer concrete has excellent compressive strength and is suitable for structural applications. The salient factors that influence the short and long term properties of the fresh concrete and the hardened concrete have been identified. Sumajouw and Rangan (2006) have reported on the low-calcium fly ash-based geopolymer concrete: reinforced beams and columns. This Research Report describes the behaviour and strength of reinforced low-calcium fly ash-based geopolymer concrete structural beams and columns, the development, the mixture proportions, the short-term properties, and the long-term properties of lowcalcium fly ash-based geopolymer concrete. Heat-cured low-calcium fly ash-based geopolymer concrete has excellent compressive strength, suffers very little drying shrinkage and low creep, excellent resistance to sulfate attack, and good acid resistance

Hardjito and Rangan (2005) made an investigation on the development and properties of low-calcium fly ash-based geopolymer concrete. The report describes the short, long term properties of fly ash based geopolymer concrete and strength behavior of structural beams and columns. They studied the strength properties by using fly ash as the cementanious material in the concrete. They concludes that increase in the concentration levels of Sodium hydroxide and ratio of sodium silicate to sodium hydroxide results the higher compressive strength of geopolymer concrete and also recommended the usage of super plasticizer (naphthalene sulphonate) is optimum up to 2% of fly ash by mass. Supraja and Kanta Rao (2011) have investigated the geopolymer concrete is fully replaced with Ground Granulated Blast furnace Slag (GGBS) and alkaline liquids are used for the binding of materials. Different molarities of the Potassium hydroxide solution i.e. 3M, 5M, and 7M and 9M are taken to prepare different mixes and studied the mechanical properties of geopolymer concrete. Two different curing are carried i.e. oven curing at 50o-degree centigrade JNTUCEA

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and curing directly by placing the specimens to direct sunlight. He observed that the compressive strength is increased with the increase in the molarities of Potassium hydroxide. The oven cured specimens gave best results as compared to specimens cured by direct sunlight, oven cured specimens gives the higher compressive strength. He recommended that sunlight curing is convenient for practical conditions. Ganapati Naidu et al. (2012) have studied the strength properties of geopolymer concrete using low calcium fly ash (ASTM Class F) replacing with slag in 5 different percentages of o, 9, 16.66, 23.07 and 28.57. He observed that the compressive strength of geopolymer concrete increases with replacement of fly ash with GGBS. Fly ash was replaced by ground granulated blast furnace slag up to 28.57%, beyond that fast setting was observed. He observed 90% of compressive strength was achieved within 14 days. Khadar et al. (2014) have study the strength properties of class F fly ash (FA) based geopolymer concrete (GPC) using slag as sand replacement at different levels (o%, 50% and 100%). Sodium silicate (Na2SiO3) and sodium hydroxide (NaoH) solution has been used as an alkaline activator. In the present investigation, it is proposed to study the mechanical properties viz. compressive strength after 7, 14 and 28 days and split tensile strength after 28 days of ambient room temperature curing. From the results, it is concluded that the increased replacement level of slag increased the mechanical properties of FA based GPC mixes. Results recommended using fly ash based GPC mixes using slag as a sand replacement. Priyanka et al. (2014) reported that the effect of molarity (8M, 10M and 12M) on strength properties of fly ash (class F) and ground granulated blast furnace slag (GGBS) blended geopolymer concrete (GPC) at the 50% replacement level (FA50-GGBS50). Sosdum silicate (Na2SiO3) and Sodium hydroxide (NaoH) solution has been used as an alkaline activator. In the present investigation, it is proposed to study the mechanical properties viz. compressive strength after 7, 14 and 28 days and split tensile strength after 28 days of ambient room temperature curing.

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From the results, it is concluded that the increased molarity of NaoH solution increased the compressive strength of GPC at all curing periods and split tensile strength after 28 days of curing. Results revealed that fly ash and GGBS blended GPC mixes have attained enhanced mechanical properties at all curing periods. Wallah and Rangan (2006) conducted work on the long term properties of low-calcium fly ash based geopolymer concrete. They reported that, there was no substantial gain in the compressive strength of heat-cured fly ash based geopolymer concrete with age, heat-cured fly ash based geopolymer concrete undergoes low creep and little drying shrinkage after one year and had excellent resistance against sulphate attack, even after one year of exposure. They also reported that, exposure of geopolymer concrete to the sulphuric acid solution, resulted in degradation of compressive strength as well as damaged the surface of the heat-cured geopolymer concrete. Mass loss of about 3% was observed, after one year of exposure. However, the sulphuric acid resistance of heat-cured geopolymer concrete was significantly better than of cement concrete. Venkatesh babu and Divya mohan (2005) studied the strength properties of fly ash based geopolymer concrete-concrete without cement. They investigated the performance characteristics of source materials, strength and microstructural properties of geopolymer concrete. The variables considered in their study were the molarity of chemical activators and the ratio of sodium silicate to sodium hydroxide. The result shows that as the molarity and the ratio of sodium silicate to sodium hydroxide increase the compressive strength of GPC also increases. The maximum compressive strength of 25.50 Mpa was obtained, within 24 hours by oven curing at 90°C temperature Kedarswamy (2007) has studied the performance of geopolymer concrete at elevated temperature. He had exposed the specimens to a temperature of 250°C, 400°C, 600°C and 800°C for a sustained duration of 2 hours and 4 hours. His study showed that there is considerable reduction in strength to an extent of 65% at 250°C and 400°C at much higher rate beyond the rate of reduction in strength reduces with the increase in temperature, 74% Up to 600°C and 77% up to 800°C. The tests indicated that up to 250°C the reduction in strength is linear.

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Satia et al. (2008) the objective of the present work is to study the fly ash based geopolymer prepared with sodium silicate and sodium hydroxide as alkaline activators. The concrete was prepared with varying fly ash content 350,450 and 550 kg/m3 and activator solution to fly ash ratio of 0.40 and 0.50. The compressive strength in the range of 10-60 Mpa was obtained. The performance of these concrete in aggressive environment was also studied, using tests on absorption, acid resistance and potential. Results indicated that water absorption decreased with increase in strength of concrete and fly ash content. All Geopolymer concrete showed excellent resistance to acid attack compared to conventional concrete. Rajamane et al. (2011) a compressive literature survey on various aspects of Geopolymer concrete has been provided in this paper to understand the nature of GPC from engineering applications point of view so that a rational technical plan for development for GPC with aluminosilicate sources (Fly ash, Ground Granulated Blast furnace slag) can be formulated. The literature survey indicates that Geopolymer is the only one of many names used for describing the binder formed aluminosilicate gel structure. Comparatively, more paper published on a science of geo polymerisation where often paste is utilised. Concrete and mortar based Geopolymer are also reported, but lesser in numbers. The science of geopolymer has not reached the stage where geopolymer concrete mix can be made by the user just adding the water as it happens in the case of Portland cement technology. This requires actual Engineers onsite to be aware of the chemical nature of geopolymer binding action involved. However, enough qualitative information is on mechanical strength so that geopolymer concrete mixes can be developed to achieve the desired level of strength for use in the structure. The second part of the paper would concentrate on typical research plan to develop the engineering properties of GPC based information available in the literature. Sanjay Kumar et al. (2005) worked on high strength Geopolymeric materials through mechanical activation of fly ash. They prepared fly ash based geopolymers using raw and mechanically activated fly ash. A remarkably higher strength was observed in mechanically activated fly ash based geopolymers, the compressive strength also increases with an increase in alkaline activator. Depending upon the mechanical activation device used, geopolymers having compressive strength in the range of 45-120 Mpa could be prepared. TGA/DTA studies indicated

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the greater formation of geopolymerisation product in case of mechanically activated fly ash and this was supported by a compact microstructure during SEM examination of the samples.

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CHAPTER 3 EXPERIMENTAL PROGRAM 3.1 General This Chapter presents the details of development of the process of making low calcium (ASTM Class F) fly as based geopolymer concrete using slag as sand replacement. First, the materials, mixture proportions, manufacturing and curing of the test specimens are explained. This is then followed by the test procedures. 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. The parameter compressive strength is the important factor in any concrete structures. Based on the compressive strength, the development process is improved. The physico chemical properties of fly ash, ground granulated blast furnace slag, aggregate and water used in the investigation were analyzed based on standard experimental procedures laid down in IS, ASTM and BS codes. The experiments conducted on coarse aggregate (Hard Broken Granite, HBG) are specific gravity and water absorption, Bulk density & Sieve analysis. The experiments conducted on fine aggregate (sand and granite fines) are specific gravity, moisture content, sieve analysis and bulking of fine aggregate using volume method. The tests conducted on geopolymer concrete are Compressive strength, Split Tensile strength5 and Flexural strength as per the respective IS, BS and ASTM codes.

3.2 Materials 3.2.1 Fly ash According to ASTM C 618 (2003) the fly ash can be divided into two types based on amount of calcium present in the Fly ash. The classified Fly ashes are Class F (low-calcium) and Class C (high-calcium). In the Present investigation Class F fly ash produced from Rayalaseema Thermal Power Plant (RTPP), Muddanur, and A.P was used. The chemical and physical properties are presented in the Table 3.1

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3.2.2 Slag In the present investigation, slag produced from the Lanco Industries was used as sand replacement at different levels (o%,50% and 100%) in the manufacturing of GPC. The chemical and physical properties are presented in the Table 3.1 Table 3.1 Chemical and Physical Properties of Class F Fly Ash and GGBS Particulars

Class

ASTM C 618

“F” fly ash

Class “F” fly ash

GGBS

Chemical composition % Silica(SiO2)

65.6

30.61

% Alumina(Al2O3)

28.0

16.24

% Iron oxide(Fe2O3)

3.0

% Lime(CaO)

1.0

34.48

% Magnesia(MgO)

1.0

6.79

% Titanium oxide

0.5

-

(Tio2) % Sulphur Trioxide

0.2

Max. 5.0

1.85

(So3) Loss on Ignition

0.29

Max. 6.0

2.1

SiO2+ Al2o3+ Fe2o3>70

0.584

Physical properties Specific gravity

2.24

Fineness (m2/Kg)

360

2.86 Min.225 m2/kg

400

3.2.3 Coarse aggregate Crushed granite stones of size 20 mm and 10 mm of coarse aggregate are used. The bulk specific gravity in oven dry condition and water absorption of the coarse aggregate 20 mm and 10mm as per IS code were 2.60 and 0.3% respectively.

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The gradation of the coarse aggregate was determined by sieve analysis as per IS code and presented in the Tables 3.2 and 3.3. The grading curves of the coarse aggregates as per IS code are shown in Fig 3.1 and 3.2. (Quantity taken=5 Kg) Table 3.2 Sieve analysis of 20 mm Coarse aggregate Sieve S.No

Cumulative percent passing

size

IS 383 (1970)

(mm)

20 mm

1

2o

91.88

85-100

2

16

45.22

N/A

3

12.5

18.6

N/A

4

1o

6.86

o-2o

5

4.75

0.18

o-5

Limits

Table 3.3 Sieve analysis of 10 mm Coarse aggregate Sieve S.No

size (mm)

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Cumulative percent passing 10

IS 383

mm

(1970) limits

1

1o

99.56

85-100

2

4.75

9.67

o-2o

3

2.36

2.2

o-5

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120

Lower Limit (IS 393:1970) Coarse Aggregate

Percentage Passing

100 80 60 40 20 0 0.1

1

10

100

IS Seive Size (mm) Fig. 3.1 Grading curve of 20 mm Coarse aggregate

120 Lower Limit (IS 393:1970)

Percentage Passing

100 80 60 40 20 0 0.1

1

10

100

IS Seive Size (mm) Fig. 3.2 Grading curve of 10 mm Coarse aggregate

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3.2.4 Fine aggregate The sand used throughout the experimental work was obtained locally in Anantapuramu district. The bulk specific gravity in oven dry condition and water absorption of the sand as per IS code were 2.60 and 1% respectively. The gradation of the sand was determined by sieve analysis as per IS code and presented in the Table 3.4. The grading curve of the fine aggregate as per IS code is shown in Fig. 3.3. Fineness modulus of sand was 2.56. (Quantity taken=1 Kg)

Table 3.4 Sieve analysis of Fine Aggregate (Sand) Cumulative percent passing S.No

Sieve No/ size Fine aggregate

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IS 383 (1970) – Zone II requirement

1

3/8” (10mm)

100

100

2

N0.4 (4.75mm)

98.6

90-100

3

N0.8 (2.36mm)

95.83

75-100

4

N0.16 (1.18mm)

80.7

55-90

5

N0.30 (600μm)

44.2

35-59

6

N0.50 (300μm)

18.2

8-30

7

N0.100 (150μm)

2.9

0-10

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110

Lower Limit (IS 383:1970) Fine Aggregate

100

Percentage Passing

90 80

70 60 50 40 30 20 10 0 0.01

0.1

1

10

100

IS Seive Size (mm) Fig. 3.3 Grading curve of fine aggregate 3.2.5 Alkaline Liquid The alkaline liquid used was a combination of Potassium silicate solution and Potassium hydroxide solution. The Potassium silicate solution (K2o= 13.7%, SiO2=29.4%, and water=55.9% by mass) was purchased from a local supplier. The Potassium hydroxide (KOH) in flakes or pellets from with 97%-98% purity was also purchased from a local supplier. The Potassium hydroxide (KOH) solution was prepared by dissolving either the flakes or the pellets in required quantity of water. The mass of KOH solids in a solution varied depending on the concentration of the solution expressed in terms of molarity, M. For instance, KOH solution with a concentration of 10M consisted of 10x40 = 400 grams of KOH solids (in flake or pellet form) per litre of the solution, where, 40 is the molecular weight of Potassium hydroxide (KOH) pellets or flakes. 3.3 Mixture Proportions Based on the limited past research on GPC (Hardjito & Rangan, 2005), the following proportions were selected for the constituents of the mixtures [1-5]. 

The combined mass of coarse and fine aggregates has taken as 77% of the mass of concrete.



Alkaline liquid as given in Section 3.2.5.

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

Ratio of activator solution-to-fly ash and GGBS, by mass, in the range of 0.3 and 0.4. This ratio was fixed at 0.35.



Class F fly ash and SLAG replacement levels (FA100o-SLAG0; FA100-SLAG50& FA100o-SLAG100).



Ratio of Potassium silicate solution-to-Potassium hydroxide solution, by mass, of 0.4 to 2.5. This ratio was fixed at 2.5 for most of the mixtures, because the Potassium silicate solution is considerably cheaper than the Potassium hydroxide solution.



Molarity of Potassium hydroxide (KOH) solution was kept at 10M.



Calculate water-to-geopolymer solids.



Extra water, when added, in mass.

The following scenario describes the GPC mix design of the present study: Assume that normal-density aggregates in SSD (Saturated surface Dry) condition are to be used and the unit-weight of concrete is 2400 kg/m3. In this study, take the mass of combined aggregates as 77% of the total mass of concrete, i.e. 0.77x2400=1848 kg/m3. The coarse and fine (combined) aggregates may be selected to match the standard grading curves used in the design of Portland cement concrete mixtures. For instance, the coarse aggregates (70%) may comprise 776 kg/m3 (60%) of 20 mm aggregates, 518 kg/m3 (40%) of 10 mm aggregates, and 554 kg/m3 (30%) of fine aggregate to meet the requirements of standard grading curves. The adjusted values of coarse and fine aggregates are 774 kg/m3 of 20 mm aggregates, 516 kg/m3 of 10 mm aggregates and 549 kg/m3 (30%) of fine aggregate, after considering the water absorption values of coarse and fine aggregates. The mass of geopolymer binders (fly ash )and the alkaline liquid = 2400 – 1848 = 552 kg/m3. Take the alkaline liquid-to-fly ash ratio by mass as 0.35; the mass of fly ash = 552/ (1+0.35) = 409 kg/m3 and the mass of alkaline liquid = 552 – 409 = 143 kg/m3. Take the ratio of Potassium silicate (K2SiO3) solution-to-Potassium hydroxide (KOH) solution by mass as 2.5; the mass of Potassium hydroxide (KOH) solution = 144/ (1+2.5) = 41 kg/m3; the mass of Potassium silicate solution = 143 – 41 =102 kg/m3. JNTUCEA

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The Potassium hydroxide solids (KOH) is mixed with water to make a solution with a concentration of 10 Molar. This solution comprises 40% of KOH solids and 60% water, by mass. For the trial mixture, water-to-geopolymer solids ratio by mass is calculated as follows: In Potassium silicate solution, water = 0.559x102 = 57 kg, and solids = 102 – 57 = 45 kg. In Potassium hydroxide solution, solids = 0.40x41 = 16 kg, and water = 41 – 16 = 25 kg. Therefore, total mass of water = 57+25 = 82 kg, and the mass of geopolymer solids = 409 (i.e. mass of fly ash and GGBS) + 45 + 16 = 470 kg. Hence, the water-to-geopolymer solids ratio by mass = 82/470 = 0.17. Extra water of 90 litres is calculated on trial basis to get adequate workability. Superplasticizer was added to maintain adequate workability. The geopolymer concrete mixture proportions are given as follows:

Table 3.6 GPC Mix Proportions Mass (kg/m3) Materials

FA100-

FA100-

FA100-

SLAG0

SLAG50

SLAG100

20 mm

776

776

776

10 mm

517

517

517

Sand

554

277

o

Fly ash (Class F)

409

409

409

SLAG

o

277

554

Potassium silicate solution

102

102

102

Potassium hydroxide solution

41 (10M)

41 (10M)

41 (10M)

Extra water

90

90

90

Superplasticizer

2.86

2.86

2.86

Coarse aggregate Fine aggregate

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3.4 Manufacture of Test Specimens 3.4.1 Preparation of Alkaline Liquid In this study, KOH solids of 10x40=400 grams have been dissolved in 600 ml of water to prepare one litre of KOH solution with a concentration of 10 M. Where, 40 is the molecular weight of KOH pellets. The Potassium silicate solution and the Potassium hydroxide solution were mixed together one day before prior to use.

3.4.2 Manufacture of Fresh concrete The aggregates were prepared in saturated-surface-dry (SSD) condition. Fly ash, SLAG and aggregates were mixed for about 3 minutes. 70% of extra water was added to the mix and mixed for one minute. Then, the alkaline liquid was added with remaining 30% of extra water and the mix was thoroughly mixed for about 2 minutes. The fresh concrete was cast and compacted by the usual methods used in the case of Portland cement concrete (Hardjito and Rangan, 2005). Fresh fly ash and GGBS-based geopolymer concrete was usually cohesive. The workability of the fresh fly ash and GGBS-based geopolymer concrete was measured by means of the conventional slump test.

3.4.3 Curing of Test Specimens After casting and demoulding, the test specimens were kept for curing at ambient room temperature till the execution of the testing on the specimens.

3.5 Test methods 3.5.1 General In the course of investigation, Portland cement has been replaced fly ash and SLAG with different proportions as FA100-SLAG0; FA100-SLAG50& FA100-SLAG100. The physico chemical properties of fly ash, ground granulated blast furnace slag, sand and water used in the investigation were analyzed based on standard experimental procedures laid down in IS ASTM and BS codes. The tests conducted on Geo polymer concrete are

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Compressive strength, Split Tensile strength, Flexural strength and Modulus of Elasticity as per the respective IS, BS and ASTM codes. 3.5.2 Compressive Strength test Compression test is one of the most common test conducted on hardened concrete, partly because it is most important and it is easy to perform further most of the desirable characteristic properties of concrete are qualitatively related to its strength. The compression test is carried out on specimens like cubical or cylindrical in shape sometimes prisms are also used. The end parts of beam are left intact after failure in flexure and because of the square cross section of the beam this part of the beam could be advantageously used to find out the compressive strength.

Fig.3.4 Testing of cubes for compressive strength The compressive strength of concrete is the most important and useful property of Concrete. The compression test was carried out using 2000 KN compression testing machine. The compressive strength of the GPC was conducted on the cubical specimens for all the mixes after 7, 14, 28, 56 and 112 days of curing as per code. 9 No’s of 150 mm cube specimen were made for each mix and 3 samples in each were cast and tested for 7, 14, 28, 56 and 112 days respectively. The average value of these 3 specimens was taken for study.

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The compressive strength (f’c) of the specimen was calculated by dividing the maximum load applied to the specimen by the cross-sectional area of the specimen as given below. f ’c = P/A

Where, f ’c = Compressive strength of the concrete (in N/mm2) P = Maximum load applied to the specimen (in Newton) A = Cross-sectional area of the specimen (in mm2)

3.5.3 Split Tensile Strength test

Fig.3.5 Testing of cylinders for Split tensile strength

Splitting Tensile Strength (STS) test was conducted on the specimens for all the mixes after 28 days of curing as per code. Three cylindrical specimens of size 150 mm x 300 mm were cast and tested for each age and each mix. The load was applied gradually till the failure of the specimen occurs. The maximum load applied was then noted. Length and cross-section of the specimen was measured. The splitting tensile strength (fct) was calculated as follows:

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fct =2P / 𝝅𝒍𝒅

Where, fct = Splitting tensile strength of concrete (in N/mm2) P = Maximum load applied to the specimen (in Newton) l = Length of the specimen (in mm) d = cross-sectional diameter of the specimen (in mm) The experimental results were compared to the predicted STS values of all mixes as given by Table 4.4.

3.5.4 Flexure Strength test

Fig.3.6 Testing of prisms for Flexure strength

Flexural strength test was conducted on the specimens for all the mixes at different curing periods as per code. Three concrete beam specimens of size 100 mm x 100 mm x 50o mm were cast and tested for each age and each mix. The load was applied gradually till the failure of the specimen occurs. The maximum load applied was then noted. The distance between the line of fracture and the near support ‘a’ was measured. The flexural strength (fcr) was calculated as follows: JNTUCEA

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When ‘a’ is greater than 13.3 cm for 1o cm specimen, fcr is fcr = (P x l) / (b x d2) When ‘a’ is less than 13.3 cm but greater than 11.0 cm for 1o cm specimen, fcris fcr = (3 x P x a) / (b x d2) Where, fcr = Flexural strength of concrete (in N/mm2) P = Maximum load applied to the specimen (in Newton) b = measured width of the specimen (in mm) d = measured depth of the specimen at the point of failure (in mm) l = Length of the specimen on which the specimen was supported (in mm)

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CHAPTER-4 RESULTS AND DISCUSSiONS 4.1 Introduction This chapter describes the Compressive strength, Split tensile strength and flexural strength of GPC at ambient room temperature curing. The compressive strength values of GPC mixes were measured after 7, 14, 28, 56and 112 days of curing. The split tensile strength values of GPC mixes were measured after 28, 56 and 112 days of curing. The flexural strength values of GPC mixes were measured at 28, 56 and 112 days of curing. 4.2 Compressive Strength Table 4.1 shows the compressive strength of GPC mixes with different proportions of fly ash and GGBS (FA100-SLAG0; FA100-SLAG50 & FA100-SLAG100 ) at different curing periods. Table 4.1 Compressive strength of GPC

Mechanical property

Compressive strength, f’c (MPa)

Mix type

Age FA100-

FA100-

FA100-

SLAG0

SLAG50

SLAG100

7

13.24

30.1

42.0

14

21.42

34.6

48.2

28

27.21

41.8

53.4

56

31.6

45.5

57.3

112

34.5

49.8

61.6

(days)

It was observed that there was a significant increase in compressive strength with the increase in percentage of SLAG from o% to 100% in all curing periods as shown in Fig. 4.1. It can be concluded that the increase in SAND replacement level enhances strength improvement in geopolymers. The GPC with 100% SLAG sample exhibited compressive strength values of

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42 MPa, 48.2 MPa, 53.4 MPa, 57.3 MPa and 61.6 MPa after 7, 14, 28, 56 and 112 days of curing respectively at ambient room temperature. 70

Compressive strength (MPa)

60

50 40 FA100-SLAG0 30

FA100-SLAG50 FA100-SLAG100

20

10 0 7

14

28

56

112

Age (Days)

Fig. 4.1 Compressive strength versus Age

4.3 Split Tensile Strength Table 4.2 shows the split tensile strength of GPC mixes with different proportions of Fly ash and GGBS (FA100-SLAG0; FA100-SLAG50& FA100-SLAG100 ) at different curing periods. Table 4.2 Split tensile strength of GPC

Mechanical property

Split tensile strength, fct (MPa)

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Mix type

Age FA100-

FA100-

FA100-

SLAG0

SLAG50

SLAG100

28

1.92

2.62

3.42

56

2.24

2.83

3.74

112

2.48

2.92

3.92

(days)

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4.5

Split Tensile strength(MPa)

4 3.5 3 2.5 FA100-SLAG0 2

FA100-SLAG50

1.5

FA100-SLAG100

1 0.5 0 28

56

112

Age (Days)

Fig. 4.2 Split tensile strength of mixes

It was observed that there was a significant increase in splitting tensile strength with the increase in percentage of SLAG from o% to 100% in all curing periods as shown in Fig. 4.2. It can be concluded that the increase in SAND replacement level improves the microstructure of GPC thus leads to enhancement of splitting tensile strength of GPC. The GPC with 100% SLAG sample exhibited splitting tensile strength values of 3.42 MPa, 3.74 MPa and 3.92 MPa after 28, 56 and 112 days of curing respectively at ambient room temperature.

4.4 Flexural strength Table 4.3 shows the flexural strength of GPC mixes with different proportions of fly ash and GGBS ( FA100-SLAG0; FA100-SLAG50& FA100-SLAG100 ) at different curing periods.

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Table 4.3 Flexural strength of GPC

Mechanical property

Mix type

Age FA100-

FA100-

FA100-

SLAG0

SLAG50

SLAG100

28

3.96

5.09

5.39

56

4.11

5.32

5.95

112

4.46

5.46

6.28

(days)

Flexural strength, fcr (MPa)

7

Flexural strength(MPa)

6 5 4 FA100-SLAG0 3

FA100-SLAG50 FA100-SLAG100

2 1 0 28

56

112 Age(Days)

Fig. 4.3 Flexural strength of mixes

It was observed that there was a significant increase in flexural strength with the increase in percentage of SLAG from o% to 100% in all curing periods as shown in Fig. 4.2. It can be concluded that the increase in SAND replacement level refines the pore structure of GPC thus improves the flexural strength of GPC. The GPC with 100% SLAG sample exhibited splitting tensile strength values of 5.39 MPa, 5.95 MPa and 6.28 MPa after 28, 56 and 112 days of curing respectively at ambient room temperature.

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From the results it is revealed that the FA based GPC mixes have attained higher values of strength properties at all curing period, when slag is used as complete replacement(100%)of sand. For the 50% replacement of slag, the GPC mixes have attained medium properties at all curing periods. Hence from the figs 4.1, 4.2 and 4.3, it is concluded that the increased replacement level of slag increased the mechanical properties of FA based GPC mixes at ambient room temperature curing. Keeping in view of sustainability, slag can be used as complete replacement of sand in FA based GPC mixes Siddique (2007).

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5.0 CONCLUSIONS This chapter summarizes the overall conclusions drawn from the investigation of FA

based

GPC mixes using slag as sand replacement. The GPC mixture proporti ons used in this study were developed based on the previous study on GPC (Hardjito and Rangan, 2005). In this study, short-term mechanical properties of FA based GPC mixes were studied at different replacement level of slag and curing period. 5.1. CONCLUSIONS

Based on the test results, the following conclusions are drawn: 1. The increased level of slag replacement increased the mechanical properties of FA based GPC mixes at ambient room temperature curing itself without the need of heat curing as in the case of only FA based GPC mixes. 2. For 50% and 100% slag replacement, FA and GPC mixes attained enhanced mechanical properties at ambient room temperature curing at all ages. 3. Keeping in view of savings in natural resources, sustainability, environment, production cost, maintenance cost and all other GPC properties, it can be recommended slag as an alternative to sand for the use of constructions. 5.2. Future work Based on the investigation of this project, the future work includes: ●

Study on the effect of molarity of KOH on mechanical properties of FA and GGBS based GPC mixes.

●

Study on durability properties of FA and GGBS based GPC mixes.

●

Keeping in view of the availability of natural resources and environmental aspects, it is recommended to replace some percentage of sand with quarry dust in FA and GGBS based GPC mixes and study all GPC hardened and durability properties.

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