AN EXPERIMENTAL STUDY ON GEOPOLYMER CONCRETEA PROJECT REPORT Submitted by Reg. No. 30609103014 30609103035 30609103051 Student’s Name JOE FATIMA SHAMILI.S PARAMESWARI.M VISHNUPRIYA.D in partial fulfillment for the award of the degree of BACHELOR OF ENGINEERING IN CIVIL ENGINEERING JEPPIAAR ENGINEERING COLLEGE, CHENNAI ANNA UNIVERSITY: CHENNAI-600 025 APRIL 2013 ANNA UNIVERSITY CHENNAI-600 025 JEPPIAAR ENGINEERING COLLEGE DEPARTMENT OF CIVIL ENGINEERING JEPPIAAR NAGAR, RAJIV GANDHI SALAI, CHENNAI-600 119 BONAFIDE CERIFICATE Certified that this project report “AN EXPERIMENTAL STUDY ON GEOPOLYMER CONCRETE ” is a bonafide work of JOE FATIMA SHAMILI.S, PARAMESWARI.M, VISHNUPRIYA.D who carried out project under my supervision. PROJECT GUIDE HEAD OF THE DEPARTMENT Submitted for the examination held on ____________________ INTERNAL EXAMINER EXTERNAL EXAMINER CERTIFICATE OF EVALUATION S. No. 1. Name of the student/s who have done the project S. JOE FATIMA SHAMILI M. PARAMESWARI D. VISHNUPRIYA Title of the project Name of the Supervisor with Designation Mrs. C.Swarnalatha Assistant professor 2. AN EXPERIMENTAL STUDY ON GEOPOLYMER CONCRETE 3. The Reports of the project work submitted by the above students in partial fulfillment for the award of Bachelor of Engineering of Anna University, Chennai were evaluated and confirmed to be reports of the work by the above students and then evaluated. INTERNAL EXAMINER EXTERNAL EXAMINER I also thank the teaching and non teaching staff members of the Department of Civil Engineering for their constant support.K.Sc (Engg). Hon’ble. for his encouragement provided throughout the completion of our project work.E.. JEPPIAAR. Ph.SWARNALATHA... Nungambakkam for giving us the opportunity to do this project under their esteemed guidance. Ph.E.L.ACKNOWLEDGEMENT We are very much indebted to our Chairman. Our sincere thanks to our Head of the Department Dr.RAJAN. Dr.D.. for their indispensible help. our Principal.D. Ph.. We would also like to express our deep sense of gratitude to our guide Mrs.D.. Sushil Lal Das.P. M. M. Project Manager. C. VGN Creating Access. M. for giving valuable suggestions for making this project a grand success.. M. We take this opportunity to express our sincere gratitude to our external guide Mr.A. amenities provided to carry out our project work.GOKULNARESH M. Colonel Dr.Tech. . B. N. TABLE OF CONTENTS Page .1 GENERAL 1.5 CHAPTER 2 2.2 Applications of geopolymer concrete 2.3 Alkaline liquids 9 10 10 11 12 .1 Source materials 2.3 1.2.No ABSTRACT LIST OF TABLES LIST OF FIGURES CHAPTER 1 INTRODUCTION 1.3.2.2 Fly ash 2.1 Chemical reaction of geopolymer concrete 8 2.1 2.3.4 1.3 CONSTITUENTS OF GEOPOLYMER 2.3.2 MOTIVATION OBJECTIVE OF THE PROJECT SCOPE OF THE PROJECT ORGANISATION OF THE REPORT REVIEW OF LITERATURE GENERAL GEOPOLYMER i iii iv 1 1 4 5 5 6 7 7 7 2.2 1. 4 Alkaline solution 3.3 Fine aggregates 3.6 Water Content of Mixture 3.2.1 3.4 Curing of Test Specimens 3.5.2.2 Manufacture of Fresh Concrete and Casting 3.3 Curing of geopolymer concrete 3.4.1 Workability Test 35 36 37 38 40 40 .4.5 CHAPTER 3 GEOPOLYMER CONCRETE AN OVERVIEW 13 SUMMARY OF LITERATURE 25 EXPERIMENTATION AND METHODOLOGY 27 3.2.2 GENERAL MATERIALS AND THEIR PROPERTIES 3.5 EXPERIMENTAL CONDUCTED 3.2.1 Preparation of Liquids 3.2 Coarse aggregates 3.2.2.1 Fly ash 27 27 27 28 30 32 32 32 33 35 3.2.5 Super Plasticizer 3.3 MIXTURE PROPORTIONS 3.4.4 MANUFACTURE OF GEOPOLYMER CONCRETE 3.4 2.4. 5.1 4.3.2 Compressive Strength Test CHAPTER 4 4.3.2 4.2 Curing conditions CHAPTER 5 CONCLUSIONS 44 47 51 APPENDIX – A MIX DESIGN PROCEDURE FOR GEOPOLYMER CONCRETE REFERENCES 55 57 .3.3 RESULTS AND DISCUSSION INTRODUCTION COMPRESSIVE STRENGTH EFFECT OF SALIENT PARAMETERS 40 42 42 42 44 4.1 Ratio of Alkaline solution-to-Fly ash 4. The combination of sodium silicate solution and sodium hydroxide solution was used as alkaline solution for fly ash activation. such as CO2. Alkaline solution to fly ash ratio was varied as 0. The global cement industry contributes about 7% of greenhouse gas emission to the earth’s atmosphere. low-calcium (Class F) fly ash-based geopolymer from Ennore Thermal power plant has been used for the production of geopolymer concrete.35. 14 and 28 days. synthesized from materials of geological origin or by-product materials such as fly ash that are rich in silicon and aluminum. Cement manufacturing industry is one of the carbon dioxide emitting sources besides deforestation and burning of fossil fuels. there is a need to develop alternative binders to make concrete. In this project work. In order to address environmental effects associated with Portland cement.40 & 0. The global warming is caused by the emission of greenhouse gases. CO2 contributes about 65% of global warming. One of the efforts to produce more environmentally friendly concrete is the development of inorganic alumino-silicate polymer. to the atmosphere. called geopolymer.I ABSTRACT Ordinary Portland cement is a major construction material worldwide. . Among the greenhouse gases.45.The curing condition of geopolymer concrete was varied as ambient curing and oven curing at 60°C and 100°C. The compressive strength of the geopolymer concrete was tested at various ages such as 7. 0.The concentration of sodium hydroxide solution was maintained as 8M (Molars). the compressive strength of geopolymer concrete also increases. (c) Compressive strength of concrete increases as the curing temperature increased from 60°C to 100°C. (b) Compressive strength of oven cured concrete was more than that of ambient cured concrete. .II From the test results it was found that (a) as the alkaline solution to fly ash ratio increases. 45 Effect of alkaline solutions on Compressive Strength 10 28 28 29 29 30 31 34 35 Table 3. No Title Page.2 43 Table 4.1 Table 3.6 Table 3.35 Compressive Strength of geopolymer concrete for alkaline solution to fly ash ratio of 0.III LIST OF TABLES Figure.3 Table 3. No Table 2.4 .40 Compressive Strength of geopolymer concrete for alkaline solution to fly ash ratio of 0.1 43 Table 4.1 Table 3.4 Table 3.8 Table 4.5 Table 3.2 Table 3.7 Applications of geopolymer concrete Chemical composition of Ennore fly ash Physical properties of fly ash Properties of coarse aggregate Sieve analysis of coarse aggregate Properties of fine aggregate Sieve analysis of fine aggregate Data for design of low–calcium fly Ash based Geopolymer Concrete Mixtures Mixture proportion per m3 of geopolymer concrete Compressive Strength of geopolymer concrete for alkaline solution to fly ash ratio of 0.3 44 45 Table 4. No Title Page .1 Figure 2.4 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.1 Effect of alkaline solution to fly ash ratio on compressive strength of oven cured concrete at 60°C Effect of alkaline solution to fly ash ratio on compressive Strength of oven cured concrete at 100°C 46 Figure 4.2 Figure 3.No Figure 2.3 Figure 3.3 Effect of alkaline solution to fly ash ratio on compressive strength of ambient cured concrete 47 Figure 4.2 Figure 2.IV LIST OF FIGURES Figure.1 Figure 3.6 Basic forms of geopolymer as a repeating unit SEM analysis of fresh transition zone SEM analysis after hydration Gradation curve for coarse Aggregate Gradation curve for Fine Aggregate Fresh Geopolymer concrete Oven cured specimens Specimens under ambient curing Compressive Strength of cube specimen 13 17 18 30 31 37 39 39 41 Figure 4.2 46 Figure 4.5 Figure 3.35 48 .4 Figure 3.3 Figure 3. 40 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.V Figure 4.5 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.6 49 50 Figure 4.45 Effect of curing temperature on Compressive strength 49 Figure 4.7 . In order to meet the . fences and poles.35 billion tons annually or approximately 7% of the total green house gas emissions to the earth‟s atmosphere.1 CHAPTER 1 INTRODUCTION 1. infrastructure and corporate capital expenditures. After thermal power plants and the iron and steel sector. CO2 contributes about 65% of global warming. Among the green house gases. Considering an expected production and consumption growth of 9 to 10 percent.1 GENERAL Concrete is the widely used construction material that makes best foundations. The cement demand in India is expected to grow at 10% annually in the medium term buoyed by housing. the manufacturing of Portland cement is the most energy intensive process as it consumes 4GJ of energy per ton. bridges. The production of one ton of Portland cement emits approximately one ton of CO2 into the atmosphere. architectural structures.2006 2005) . the cement industry is extremely energy intensive. Coal-based thermal power installations in India contribute about 65% of the total installed capacity for electricity generation. The industry‟s capacity at the beginning of the year 2008-09 was about 198 million tones. The contribution of ordinary Portland cement (OPC) production worldwide to greenhouse gas emissions is estimated to be approximately 1. After aluminium and steel. However. the Indian cement industry is the third largest user of coal in the country. block walls. roads. the demand-supply position of the cement industry is expected to improve from 2008-09 onwards (Ragan & Hardjito. GGBS. density. granular. GGBS is a glassy. a huge amount of fly ash (FA) is generated in thermal power plants. non metallic material consisting essentially of silicates and aluminates of calcium. India produces 130 million ton of FA annually which is expected to reach 175 million ton by 2012 and may exceed 225 million tons by 2017. However. As a consequence.2 growing energy demand of the country. There is effective utilization of FA in making cement concretes as it extends technical advantages as well as controls the environmental pollution (Vijai 2006). several non-governmental organizations and research and development organizations. the remainder being used for land filling. coal with an ash content of around 40% is predominantly used in India for thermal power generation. . GGBS has almost the same particle size as cement. FA has been successfully used as a mineral admixture component of Portland cement for nearly 60 years. less than 25% of the total annual FA produced in the world is utilized. the total utilization of FA is only about 50%. durability and resistance to alkali-silica reaction. Globally. causing several disposal-related problems In spite of initiatives taken by the government. often blended with Portland cement as low cost filler. The ash content of coal used by thermal power plants in India varies between 25 and 45%. Disposal of FA is a growing problem as only 15% of FA is currently used for high value addition applications like concrete and building blocks. since coal reserves in India are expected to last for more than 100 years. enhances concrete workability. coal-based thermal power generation is expected to play a dominant role in the future as well. Ground granulated blast furnace slag (GGBS) is a by-product from the blast-furnaces used to make iron. 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 an amorphous microstructure. therefore there is a great potential for reducing stockpiles of these waste materials. slag. Unlike ordinary Portland cements. „Geopolymer concrete (GPC) are inorganic polymer composites. These are commonly formed by alkali activation of industrial alumino-silicate waste materials such as FA and GGBS. rice-husk ash.g.. glasses. GPC have high strength. which by appropriate process technology utilize all classes and grades of FA and GGBS. Two main constituents of geopolymers are source materials and alkaline liquids. They could be by-product materials such as fly ash.3 Alternative utility of FA and GGBS in construction industry that has emerged in recent years is in the form of Geopolymer concrete (GPC). 2010). The source materials on alumino-silicate should be rich in silicon (Si) and aluminium (Al). and zeolites) (Davidovits 1978). . silica fume.silicate-hydrates for matrix formation and strength. alumino-silicate gels. and have a very small Greenhouse footprint when compared to traditional concretes (Ravikumar et al. etc. which are prospective concretes with the potential to form a substantial element of an environmentally sustainable construction by replacing or supplementing the conventional concretes. geopolymers do not form calcium. but utilize the polycondensation of silica and alumina precursors to attain structural strength. acid attack. red mud. with good resistance to chloride penetration. Geopolymers are also unique in comparison to other alumino-silicate materials (e. etc. good mechanical and durability properties and can serve as eco-friendly and sustainable alternative to ordinary Portland cement concretes (Thokchom et al. Since fly ash is a waste material and can be reused. It has high cementicious property. geopolymer concrete came into usage since CO2 emitted is very low. A geopolymer concrete cement is replaced by fly ash in which the concrete gives more compressive strength comparing to normal concrete and also it has many more advantages.4 The geopolymer technology may reduce the total energy demand for producing concrete. elimination of water curing.fly ash constitutes of high amount of Si-Al materials. an alternate innovative material used is fly ash.2 MOTIVATION A normal cement contains high amount of (silica and alumina). . lower the CO2 emission to the atmosphere caused by cement and aggregates industries by about 80%. Hence. 1. may 2006). Comparatively geopolymer concrete has more merits than the other types of concrete this motivated us to do this project. The main advantage of geopolymer concrete is that normal concrete produces more CO2 increasing the global warming in order to avoid this emission of CO2 gas. Fly ash is also less expansive when compare to cement.. fly ash is by product of coal that is available in thermal power plant. the usage of cement is increasing day to day worldwide. They possess the advantages of rapid strength gain. thereby reducing the global warming. Chapter 2 presents the information about the constituents of geopolymer concrete and its applications. manufacturing process and salient characteristics of geopolymer concrete.45. 14 days and 28 days. 1.5 1. Ambient curing and oven curing (60oC & 100oC) was adopted.35. Ratio of alkaline solution to binder by mass varies as 0.40 & 0. curing condition on compressive strength of fly ash based geopolymer concrete at various ages.3 OBJECTIVE OF THE PROJECT The aim of the project is to study the influence of parameters such as alkaline solution to binder ratio. 1. To determine the compressive strength of fly ash based geopolymer concrete at various ages such as 7days.5 ORGANISATION OF THE REPORT Chapter 1 gives introduction about the evolution of geopolymer concrete. concentration of sodium hydroxide solution and curing conditions on fly ash based geopolymer concrete. . 0. This chapter also provides a detailed literature review of geopolymer technology.4 SCOPE OF THE PROJECT To study the effect of alkaline solution to binder ratio. Chapter 5 states the salient conclusions of this study. The tests performed to study the properties of fresh and hardened concrete is also described. curing conditions of geopolymer concrete.6 Chapter 3 describes the experimental program carried out to develop the mixture proportions. . Chapter 4 presents and discusses the test results of various parameters such as alkaline solution to fly ash ratio. and the curing conditions of geopolymer concrete. the mixing process. The available published literature on geopolymer technology is also reviewed. Davidovits proposed that binders could be produced by a polymeric reaction of alkaline liquids with the silicon and the aluminum in source materials of geological origin or by-product materials such as fly ash and rice husk ash.7 CHAPTER 2 REVIEW OF LITERATURE 2. The chemical composition of the geopolymer material is similar to natural zeolitic materials.2 GEOPOLYMER In 1978. These binders were termed as geopolymers. The polymerization process involves a substantially fast chemical reaction under alkaline condition on Si-Al minerals.1 GENERAL This chapter presents the information about the constituents of geopolymer concrete and its applications. The schematic formation of geopolymer material can be described by the following equations (Ragan & Hardjito 2006). . that results in a three dimensional polymeric chain and ring structure consisting of Si-O-Al-O bonds are formed. geopolymers are members of the family of inorganic polymers. but the microstructure is amorphous instead of crystalline. 2. because the chemical reaction that takes place in this case is a polymerization process. 2.8 2.1 CHEMICAL REACTION OF GEOPOLYMER Fly ash Alkaline activator Geopolymer precursor + + NaOH NaOH Na2SiO3 Back bone of geopolymer . 2. which has [-Si-O-Al-O-Si-O-] as the repeating unit. For many applications in the civil engineering field. • Poly (sialate). therefore. non ferrous foundries. • Poly (sialate-siloxo). which has [-Si-O-Al-O-Si-O-Si-O-] as the repeating unit. which has [-Si-O-Al-O-] as the repeating unit. civil engineering and plastic industries. A geopolymer can take one of the three basic forms. The type of application of geopolymeric material is determined by the chemical structure in terms of the atomic ratio Si: Al in the polysialate. Sialate is an abbreviation of silicon-oxo-aluminate.2 Applications of Geopolymers Geopolymeric materials have a wide range of applications in the automobile and aerospace industries. leaves behind discontinuous nano-pores in the matrix. The water in a geopolymer mixture. plays no role in the chemical reaction that takes place. • Poly (sialate-disiloxo). as a repeating unit as shown in Figure.9 The equation revealed that water is released during the chemical reaction that occurs in the formation of geopolymers. while Si :Al ratio higher than 15 provides a polymeric character to the geopolymeric material. This water. it merely provides the workability to the mixture during handling (ragan & hardjito et al 2010). 2. which provide benefits to the performance of geopolymers. 2 or 3 initiates a 3 D network that is very rigid. expelled from the geopolymer matrix during the curing and further drying periods. a low Si: Al ratio is suitable [Ragan & Hardjito . A low ratio of Si: Al of 1.2.1. rice husk ash.1: Applications of Geopolymers Si:Al ratio 1 2 Applications Bricks.3. Heat resistant composites >3 20 – 35 Sealants for industry. Table 2. clays. Based on various Si: Al atomic ratio. Ceramics.3 CONSTITUENTS OF GEOPOLYMER 2. silica fume. Radioactive and toxic waste encapsulation 3 Fire protection fiber glass composite. etc.1 Source Materials Any material that contains mostly Silicon (Si) and Aluminum (Al) in amorphous form is a possible source material for the manufacture of geopolymer.1. red mud. The choice of the source materials for making geopolymers depends on . or byproduct materials such as fly ash. These could be natural minerals such as kaolinite.10 2006]. slag. Fire protection Low CO2 cements and concretes.200⁰C-600⁰C Fire resistant and heat resistant fiber composites 2. the applications of geopolymer concrete are shown in Table 2. 11 factors such as availability, cost and type of application and specific demand of the end users (Ragan & Hardjito et al 2010). Fly ash According to the American Concrete Institute Committee(ACI) 116R, 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 gases from the combustion zone to the particle removal system‟. Fly ash particles are typically spherical, finer than Portland cement and lime, ranging in diameter from less than 1µm to no more than 150µm.The chemical composition is mainly composed of the oxides of silicon (SiO2), aluminum (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. Fly ash that results from burning sub-bituminous coals is referred as ASTM Class C fly ash or high-calcium fly ash, as it typically contains more than 20 percent of CaO. On the other hand, fly ash from the bituminous and anthracite coals is referred as ASTM Class F fly ash or low-calcium fly ash. It consists of mainly an alumino-silicate glass, and has less than 10 percent of CaO (Hardjito.d & Ragan.b.v 2007). 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 12 amount may interfere with the polymerization process and alter the microstructure. Low calcium fly ash has been successfully used to manufacture geopolymer concrete when the silicon and aluminum oxides constituted about 80% by mass, with Si to Al ratio of about 2. The content of iron oxide usually ranged from 10 to 20% by mass, whereas the calcium oxide content was less than 3% by mass and the loss on ignition by mass, was as low as less than 2% and 80% of the fly ash particles were smaller than 50µm (Vijaya Ragan , Hardjito 2005-2006). 2.3.2 Alkaline Liquids The alkaline liquids are from soluble alkali metals that are usually sodium or potassium based. 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 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 only alkaline hydroxides. Generally the NaOH solution caused a higher extent of dissolution of minerals than the KOH solution. The sodium hydroxide (NaOH) solution is 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. For instance, NaOH solution with a concentration of 8M consisted of 8x40 = 320 grams of NaOH solids (in flake or pellet form) per liter of the solution, where 40 is the molecular weight of NaOH. The mass of NaOH solids was measured as 262 grams per kg of NaOH solution of 8M. Similarly, the mass of NaOH 13 solids per kg of the solution for other concentrations were measured as 10M: 314 grams, 12M: 361 grams, 14M: 404 grams, and 16M: 444 grams (Vijaya Ragan et al., 2006-2010). Figure 2.1: Basic forms of geopolymer as repeating unit 2.4 GEOPOLYMER CONCRETE AN OVERVIEW Rangan [17] conducted studies on heat cured low calcium fly ash based geopolymer concrete. The influence of salient factors such as water to geopolymer solids ratio, mixing time, curing time and curing temperature on the properties of geopolymer concrete in the fresh and hardened states were identified. The short term and long term properties of geopolymer concrete, creep and drying shrinkage, sulfate and sulfuric acid resistance of geopolymer concrete were discussed. The economic benefits of the geopolymer concrete were also briefly discussed. This paper concluded that heat cured low - undergoes low creep and drying shrinkage. [18] described the effect of curing types such as ambient curing and hot curing on the compressive strength of fly ash based geopolymer concrete. handling time. the recommended values for test variables are the following (i) The concentration of sodium hydroxide solution was in the range between 8 M and 16 M. The experimental work has been done using low calcium fly ash as binder and sodium hydroxide and sodium silicate solution as activators. For hot curing. The compressive strength of hot cured concrete was higher than the ambient cured concrete. good acid resistance. Vijai et al. Based on the compressive strength of geopolymer concrete. The . The effect of salient parameters like concentration of sodium hydroxide solution. the temperature was maintained as 60oC for 24 hrs in hot air oven.14 calcium fly ash based geopolymer concrete possess excellent resistance to sulfate attack. addition of super plasticizer. (iii)The alkaline solution-to-fly ash ratio by mass was approximately 0. ratio of sodium silicate solution to sodium hydroxide solution.35 to 0.4 to 2. water content in the mixture and mixing time on the properties of fresh and hardened concrete were discussed. The compressive strength of hot cured fly ash based geopolymer concrete has not increased substantially after 7 days. (ii) The sodium silicate solution-to-sodium hydroxide solution ratio by mass was in the range of 0.5. curing temperature. curing time. Hardjito and Rangan [9] had investigated the use of fly ash as binder to make concrete with no cement.. the compressive strength increases about five times with age of concrete from 7days to 28 days.45. In ambient curing. with . Water to sodium oxide molar ratio and water to geopolymer solids ratio had influence on the compressive strength of geopolymer concrete. which is equivalent to that of conventional concrete. curing time on the compressive strength of geopolymer concrete.095 to 0. Mourougane et al.120 had no significant effect on the compressive strength. Hardjito et al. When these ratio increases.15 density of geopolymer concrete was around 2400 Kg/m3. In this experimentation 10% by mass of binder (fly ash) was replaced by granulated blast furnace slag.. The total mass of water is the sum of mass of water in sodium silicate solution. compressive strength of geopolymer decreases. [14] presented the engineering properties such as compressive strength.. One day compressive strength of heat cured fly ash based geopolymer concrete ranges from 60MPa to 80MPa. The effect of influencing parameters such as ratio of alkaline liquid to binder. split tensile strength and flexural strength of fly ash based geopolymer concrete and compared with normal concrete. while it decreases with increase in extra water. As the water to sodium oxide molar ratio increased. the compressive strength also increases. mass of water in sodium hydroxide solution and extra water if any added in concrete. Sodium oxide to silicon oxide molar ratio within the range of 0. The mass of geopolymer solids is the sum of the mass of fly ash. mass of sodium hydroxide flakes and mass of sodium silicate solids. the mixture contained more water and became more workable. When the alkaline liquid to binder ratio and molarity of sodium hydroxide increases. [10] presented the effect of mixture composition on the compressive strength of fly ash based geopolymer concrete. The flexural strength of geopolymer concrete and normal concrete was found to be similar. In addition.. but these voids were not found in the bulk matrix. However EDXA results showed that the contents of K/Al and Si/Al in the ITZ were higher than those in the bulk matrix. For experimentation metakaolin was used as a source material and potassium hydroxide was used as an activator. Environmental scanning electron microscopy (ESEM) was used to study the hydration process of the interfacial transition zone (ITZ) between coarse aggregate and potassium polysialate (K-PSDS) geopolymer under an 80% relative humidity environment. [21] reported the hydration process of interfacial transition in potassium polysialate geopolymer concrete. This indicates that K and Si accumulate in the ITZ. An energy dispersion X-ray analysis (EDXA) was also used to distinguish the chemical composition of the hydration products. At the beginning there were many large voids filled with water in the fresh ITZ as shown in Figure 2. which results in a difference in chemical composition between the ITZ and the matrix.3. Zhang et al. well- .3 & 0. the difference in the micrograph between the ITZ and the matrix was hardly distinguishable. As hydration proceeded. Eventually these voids were completely filled with hydration product as shown in Figure 2. The addition of 10% of granulated blast furnace slag increases the cube strength from 25 to 33%.35. At this stage.16 different alkaline liquid to binder ratio as 0. The ESEM micrographs and corresponding EDXA results showed that the development of the microstructure of ITZ is quite different from that of matrix. gel products gradually precipitated on the edges of these voids and extended outward.2. 17 developed crystals were not found in the ITZ at any stage and sponge-like amorphous gel was always observed. [10] described the development of geopolymer concrete. Figure 2. Hardjito et al. the geopolymer paste is formed by activating byproduct materials. higher the ratio of sodium silicate solution to sodium hydroxide solution.. Hardjito 2005) . Based on the experimental work. and higher curing temperature increases the compressive strength of geopolymer concrete. that are rich in silicon and aluminum. A combination of sodium silicate solution and sodium hydroxide solution was used as the activator. longer curing duration. The geopolymer paste binds the loose coarse and fine aggregates and any unreacted materials to form the geopolymer concrete. The binder. the paper concluded that higher the concentration of sodium hydroxide solution.2 SEM analysis of fresh transition zone (Development of geopolymer concrete. The low calcium fly ash based geopolymer concrete possess excellent resistance to sulfate attack. undergoes low creep and drying shrinkage. such as low-calcium (Class F) fly ash. Geopolymer mortar posses excellent fire resistance up to 800°C exposure for three hours. Hardjito 2005) Hardjito and Tsen. .8–1. [7] presented the engineering properties of geopolymer mortar manufactured from class F (low calcium) fly ash with potassium-based alkaline reactor. 600oC and 800oC. This indicates that the geopolymerisation process continues when geopolymer mortar is exposed to high temperature.3 SEM analysis after hydration (Development of geopolymer concrete. Above 800oC. Geopolymer mortar specimens were tested for thermal stability for three hours under 400oC. When exposed to temperature of 400oC for three hours.5 produced highest compressive strength geopolymer mortar.18 Figure 2. The ratio of potassium silicate-to-potassium hydroxide by mass in the range between 0. The results revealed that as the concentration of KOH increased. up to 400oC. the compressive strength of geopolymer mortar also increased. compressive strength of fly ash based geopolymer concrete decreases with increase in temperature. the compressive strength doubled than the one of control mixture. .64% in Sulfuric acid and from 0. Through Optical microscope.21% to 1. corroded surface could be seen which increased with duration of exposure. The weight loss in the range from 0. changes in weight and compressive strength at regular intervals..42% in Nitric acid was observed in 12weeks exposure. Wallah et al. the surfaces of specimens soaked in sulfuric acid solution started . Mortar with lesser Na2O lost its alkalinity faster than those with higher Na2O content in both Sulfuric acid and Nitric acid solutions.81% to 1. Geopolymer mortar samples did not show any change in colour and remained structurally intact though the exposed surface turned slightly softer. This paper concluded that fly ash based geopolymers were highly resistant to both Sulfuric and Nitric acid. Loss of alkalinity depended on alkali content in the geopolymer mortar.19 Thokchom et al. residual alkalinity. the compressive strength increased from 44% to 71% and 40% to 70% in Sulfuric acid and Nitric acid respectively. The specimens were immersed in solutions of 10% Sulfuric acid and 10% Nitric acid up to a period of 24 weeks. The specimens were soaked in sodium sulfate solution and sulfuric acid solution for various periods of exposure. At the end of 24 weeks of exposure. [16] an experimental study was conducted to assess the acid resistance of fly ash based geopolymer mortar specimens having percentage Na2O ranging from 5% to 8% of fly ash. There was no significant change in the external appearance of the surface of specimens soaked in sodium sulfate up to 12 weeks. However. [19] this paper presented the performance of fly ash based geopolymer concrete to sulfate attack. The performance of geopolymer concrete was studied by evaluating the effect on the compressive strength. The acid resistance was evaluated in terms of surface corrosion. change in length and change in mass. were used for the experimental work and cured at 60°C for 24h. sulfate resistance and acid resistance. In Mixture-2. the concentration of the sodium hydroxide solution was 14 Molars (M). Based on the compressive strength test . less than 0. Mixture-1 and Mixture-2. drying shrinkage. and there was no extra added water. The change in length of specimens soaked in sodium sulfate solution for various periods of exposure is very small. a significant change in compressive strength is observed in the case of specimens exposed to sulfuric acid solution. The average compressive strength of Mixture-1 was around 60 MPa and that of Mixture-2 was about 40 MPa. the reduction of compressive strength was about 30 %.20 to erode after one week of exposure. The two different mixtures. It appears that the penetration of sulfuric acid may have affected the microstructure and decreased the bond between geopolymer paste and the aggregates. For the 12 weeks soaking period. The mass did not change for specimens soaked in sodium sulfate solution. thus resulting in a decrease in compressive strength. and the mixture contained extra added water. The alkaline liquid used was a combination of sodium silicate solution and sodium hydroxide solution. Wallah and Rangan.01%. it was observed that exposure to sodium sulfate solution up to 12 weeks had very little effect on the compressive strength. The low-calcium fly ash from Collie Power Station. the concentration of the sodium hydroxide solution was 8 Molars (M). the mass decreased less than one percent after 12 weeks. The geopolymer specimens were tested for creep. In Mixture-1. In the case of specimens soaked in sulfuric acid. However. [20] studied the long term properties of low calcium fly ash based geopolymer concrete. From the test result. Western Australia was used as a source material. The specific creep after one year ranged from 15 to 29 x10-6 MPa for the corresponding compressive strength of 67 MPa to 40 MPa. these may be due to partial reaction of fly ash particles.21 results. No shrinkage due to hydration.. The ratio of the compressive strength to the tensile strength under bending varies in the range of 10. Skvara et al. .5. The heat cured fly ash based geopolymer concrete also had a better resistance to sulfate and acid attack. takes place in the geopolymer concrete. cured in ambient conditions gains compressive strength with age. The presence of Ca-containing additives (slag. This value is significantly smaller than the range of values of 500 to 800 micro strains for Portland cement concrete. The geopolymers strength was affected substantially by macro-pores (103 nm and more) formed in result of the air entrained into the geopolymers. SiQ4 (2-3Al).The transition phase was not found between the binder and the aggregates in geopolymer concrete. [8] had investigated the properties of the concretes on the basis of geopolymers.0: 5. Heat-cured fly ash-based geopolymer concrete undergoes low creep. gypsum) reduces considerably the porosity because of the co-existence of the geopolymer phase with the C-S-H phase. The heatcured fly ash-based geopolymer concrete undergoes very little drying shrinkage in the order of about 100 micro strains after one year. The porosity of the geopolymers was very similar in the region of nanopores regardless of the conditions of their preparation. The structure of the geopolymers prepared on the basis of fly ash was predominantly of the AlQ4 (4Si) type and SiQ4 (4Al). The geopolymer on the basis of fly ash was a porous material. there was no substantial gain in the compressive strength of heatcured fly ash based geopolymer concrete with age. Fly ash-based geopolymer concrete. there was also diffusion of Mg and Ca in the surface layer of . used to determine resistance of geopolymer materials were 5% solution of sodium sulfate and magnesium sulfate. a mixture of sodium and potassium hydroxide and sodium silicate solutions. In magnesium sulfate solution. providing 8-9%Na in the mixture and water binder ratio of 0. In magnesium sulfate solution. The tests.3. The migration of alkalis from the geopolymer samples into the solution was observed in sodium sulfate solution. In sodium sulfate solution. 5% of sodium sulfate+5% magnesium sulfate for a period of 5 months. while 4% increase of strength was measured in sodium hydroxide activated sample. after that the mixtures were ramped at 90°C and cured at this temperature for 24 h and cured at room temperature for 2 days prior to test.22 Bakharev. The most significant fluctuation of strength and micro structural changes took place in 5% solution of sodium sulfate and magnesium sulfate. in addition to migration of alkalies from geopolymer into the solution. significant fluctuations of strength occurred with strength reduction of 18% in the sodium silicate activated sample and 65% reduction in the sample prepared with sodium hydroxide and potassium hydroxide as activators. Fly ash was activated by sodium hydroxide. [1] presented an investigation into the durability of geopolymer materials manufactured using class F fly ash and the alkaline activators when exposed to a sulfate environment. 12% and 35% strength increase was measured in sodium hydroxide and mixture of sodium hydroxide and potassium hydroxide as activators respectively and 24% strength decline was measured in sodium silicate activated samples. The diffusion of alkali ions into the solution caused significant stress and formation of deep vertical cracks in the specimens prepared using a mixture of sodium and potassium hydroxides. The mixtures were cured for 24 h at room temperature. The best performance in different sulfate solutions was observed in the geopolymer material prepared using sodium hydroxide and cured at elevated temperature. The more crystalline geopolymer material prepared with sodium hydroxide was more stable in the aggressive environment of sulfuric and acetic acid solutions than amorphous geopolymers prepared with sodium silicate activator. . [2] had investigated the durability of geopolymer materials using class F fly and sodium silicate. which contributed to a loss of strength. when exposed to 5% solutions of acetic and sulfuric acids. formation of ettringite was also observed. Bakharev. In acidic environment. The chemical instability would also depend on the presence of the active sites on the aluminosilicate gel surface. while low performance geopolymers deteriorate through crystallization of zeolites and formation of fragile grainy structures. high performance geopolymer materials deteriorate with the formation of fissures in amorphous polymer matrix.23 geoplolymers. replacement of Na and K cations by hydrogen and dealumination of the geopolymer structure. which improved their strength. Good performance was attributed to a more stable cross-linked aluminosilicate polymer structure. which appeared to increase in presence of K ions. sodium hydroxide and a mixture of sodium hydroxide and potassium hydroxide as activators. In material prepared using sodium silicate. The significant degradation was observed in geopolymer materials prepared with sodium silicate and a mixture of sodium hydroxide and potassium hydroxide as activators. The deterioration was due to depolymerisation of aluminosilicate polymers and liberation of silicic. thus causing minimal damage to the geopolymer matrix. The strength increase in fly ash geopolymers is also partly sintering reactions of un-reacted fly ash particles.. Both types of geopolymers were synthesized with sodium silicate and potassium hydroxide solutions. The strength of fly ash based geopolymer increased after exposure to elevated temperatures (800°C). The paper concludes that the fly ash based geopolymers have large number of small pores which facilitate the escape of moisture when heated.. Activated fly ash concretes and pastes were found to be more porous and contains large fraction of pores greater than 10µm in size as compared to activated GGBFS mixtures. pore structure features and microstructure of concretes containing Class F fly ash or ground granulated blast furnace slag (GGBFS)as a sole binder was reported. the strength of the corresponding metakaolin based geopolymer decreased after similar exposure. [5] described the influence of the concentration of the activating agent(sodium hydroxide solution) and activator to binder ratio on the compressive strength. Ravikumar et al. Statistical analysis of the strength results show that the activator concentration has influence on the compressive strength of activated concretes made using fly ash and the activator to binder ratio influences the compressive strength of activated GGBFS concretes to a greater degree. The starting material content and the curing parameters (temperature and duration) were optimized to provide the highest compressive strengths. . metakaolin geopolymers do not possess such pore distribution structures. On the other hand.24 Kong et al. [4] studied the effect of elevated temperatures on geopolymers manufactured using metakaolin and fly ash of various proportions. However. Thus materials were found unsuitable for refractory insulation applications.09-0. materials remained mostly amorphous up to 1200°C.35.25 Bakharev. Geopolymer materials prepared using class F fly ash and sodium and potassium silicate show high shrinkage as well as large changes in compressive strength with increasing fired temperature in the range 800-1200°C. [3] reported a study of thermal stability of properties upon firing at 800-1200°C of geopolymer materials prepared using class F fly ash and Na and K alkaline activators. The materials were prepared at water/binder ratios in a range of 0. Compaction at 1-10 MPa reduced shrinkage on firing in all materials. Materials prepared using fly ash and potassium silicate had better thermal stability than geopolymers prepared using Na containing activators. deterioration of strength started at 1000°C. made from metakaolin and alkaline activators. In the samples prepared using sodium containing activators rapid deterioration of strength at 800°C was observed. After firing these materials remained amorphous with reduced average pore size and significantly increased compressive strength. Initially amorphous structures were replaced by the crystalline Na feldspars. using compaction pressures up to 10 MPa and curing temperatures 80°C and 100°C. which was connected to a dramatic increase of the average pore size. 2. It has great potential to be used as a building material alternative to ordinary Portland cement concrete because of its strength. stiffness and other mechanical properties which are . In materials prepared using fly ash and potassium silicate compressive strength was significantly increased on heating.5 SUMMARY OF LITERATURE Geopolymer concrete was first introduced by Davidovits. Most of the published research on geopolymer concrete studied the effect of compressive strength. Geopolymer becomes highly flexible material at a temperature around 700°C. higher curing temperature and longer curing duration. The production of geopolymer requires relatively low temperature and emits less CO2. which allows the material to accommodate large strains without fracturing and gains strength when exposed to fire.26 comparable to OPC concrete. higher activator solution to binder ratio by mass. dairy floors and other acid industrial applications.4 to 2. The compressive strength of geopolymer concrete was increased by using higher concentration of activating agent. On the long-term properties.5. by varying ratio of sodium silicate solution to sodium hydroxide solution in the range of 0. This provides technical advantages in applications such as sewer pipes. fly ash-based geopolymer concrete undergoes low creep and very little drying shrinkage. the cost of fly ash based geopolymer concrete was about 10 to 30 percent cheaper than that of Portland cement concrete. On the economic benefits. . Geopolymer also possesses excellent resistance to acid environments. Reasonable strength was developed in a short period at room temperature and in most cases. 70% of the ultimate compressive strength is developed in the first 4 hours after mixing. The physical properties of fly ash were determined as per IS: 1727-1967 and given in Table 3. alkaline liquids.2. It falls in the category of class F grade and its chemical composition was given in Table 3.27 CHAPTER 3 EXPERIMENTATION AND METHODOLOGY 3.1. mixture proportions. 3. .2 MATERIALS AND THEIR PROPERTIES The materials used for making fly ash-based geopolymer concrete specimens were low-calcium fly ash. the mixing process and the curing conditions of geopolymer concrete were discussed in this chapter.1 Fly ash The fly ash used in this study was obtained from Ennore Thermal power plant. 3. . extra water and super plasticizer. aggregates.1 GENERAL The physical and chemical properties of materials.2. 96 0.13 99. The coarse aggregate passing through 20mm and retaining 4.2.75mm was used for experimental work.2 Physical properties of fly ash Sl. Percentage 2.78 2.28 Table 3..2 Coarse aggregates Locally available crushed granite stone aggregate of 20mm maximum size was used as coarse aggregate. [3] Loss Components SiO2 Al2O3 Fe2O3 TiO2 CaO MgO Na2O K2O on ignition % by mass 56.1% 3 passing on 90 µm sieve 3.39 0.6% 2 passing on 150 µm sieve Fineness.82 2. Percentage 98. No Properties Test Results 1 Specific gravity of fly ash Fineness.93 Table 3.1Chemical composition of Ennore fly ash as reported by Naik et al.88 2.68 1.77 31.77 0. The . 65 0.60 20mm 16mm 12.29 following properties of coarse aggregates were determined as per IS: 23861963 and given in Table3.40 Cumulative Weight Passing (%) 55 17 2 0.0 38.1.0 83. Table 3.35 99. The gradation curve for coarse aggregate was shown in Figure 3.35 0.7mm 45. No 1 2 3 4 Properties Specific gravity Fineness modulus Bulk density Water absorption Test results 2.68 8.0 15.3 and sieve analysis were presented in a Table 3.0 1.05 .3 Properties of coarse aggregate Sl.4 Sieve analysis of coarse aggregate IS Sieve Size Weight retained (%) Cumulative Weight retained (%) 45.4.5mm 10mm 4.65 1540 Kg/m3 0.0 98.5% Table3.0 99. 3 Fine aggregates The locally available river sand.75 mm was used in this experimental work. No 1 2 3 4 Properties Specific gravity Fineness modulus Bulk density Water absorption Test results 2.2. passing through 4.30 10 120 100 80 Cumulative Passing (%) 60 40 20 0 10 100 IS Sieve Size (mm) Figure 3.2.5 and sieve analysis were presented in a Table 3.65 2. The following properties of fine aggregates were determined as per IS: 2386-1963 and given in Table 3. The gradation curve for coarse aggregate was shown in Figure 3. Table 3.6.5 Properties of fine aggregate Sl.49 1260 Kg/m3 1% .1 Gradation curve for coarse Aggregate 3. 15 1.6 4.36mm 1.85 98.1 1 10 IS Sieve Size (mm) Figure 3.75mm 2.85 25.5 120 Cumulative Passing (%) 100 80 60 40 20 0 0.15 77.4 Cumulative Weight Passing (%) 98.75 20.6 48.4 51.18mm 600µm 300µm 150µm 1.31 Table 3.55 29.6 Sieve analysis of fine aggregate IS Sieve Size Weight retained (%) Cumulative Weight retained (%) 1.75 22.6 20.2 Gradation curve for Fine Aggregate .9 98.15 0.85 22.25 77.1 1. 3.4% and water 55. In contrast. water in the mixture chemically reacts with the cement to produce a paste that binds the aggregates.9% by mass) was used. The super plasticizer was a dark brown solution containing 42% solids. a sulphonated. The sodium with 97-98% purity.32 3.The reason being the sodium silicate solution was cheaper than the sodium hydroxide solution. SiO2=29. ie (Na2O = 14.2.2.2. the water in a low-calcium fly ash-based geopolymer concrete mixture does not cause a chemical reaction. naphthalene formaldehyde condensate-based super plasticizer was used for the concrete mixtures as water reducing agents. 3.7%. In fact. The concentrations of sodium hydroxide solution as 8 Molar. in flake or pellet form was used. The solids must be dissolved in water to make a solution with the required concentration.5 Super Plasticizer In order to improve the workability of fresh concrete.4 Alkaline solution A combination of sodium silicate solution and sodium hydroxide solution was used as alkaline solution.5. The sodium silicate solution A53 with SiO2 to Na2O ratio by mass approximately 2.6 Water Content of Mixture In ordinary Portland cement (OPC) concrete. The ratio of sodium silicate solution to sodium hydroxide solution by mass was fixed as 2. the chemical reaction that occurs in geopolymers produces water that is eventually . to find out the influence of other parameters on the compressive strength of Geopolymer concrete. the total mass of water is the sum of the mass of water contained in the sodium silicate solution. In this parameter. and the mass of solids in the sodium silicate solution. water to geopolymer solids ratio by mass. water content in the geopolymer concrete mixture affected the properties of concrete in the fresh state as well as in the hardened state. The compressive strength of hardened concrete and the workability of fresh concrete are selected as the performance criteria. In order to meet the performance criteria.26 a constant value. . 3. However.33 expelled from the binder. the mass of water in the sodium hydroxide solution. the heat curing temperature and the heat curing time are selected as parameters. the coarse and fine aggregates occupy about 75 to 80% of the mass of geopolymer concrete. The performance criteria of a geopolymer concrete depend on the application. The water content in the geopolymer concrete mixtures was expressed by a single parameter called „water to g eopolymer solids ratio by mass. the alkaline liquid to binder ratio by mass. In this project work. and the mass of extra water added to the mixture. The mass of geopolymer solids is the sum of the mass of fly ash. the „water to geopolymer solids‟ ratio was fixed as 0. the mass of sodium hydroxide solids.3 MIXTURE PROPORTIONS As in the case of Portland cement concrete. 22 0. by mass Workability strength (wet mixing time of 4 minutes.8. The above proposed method for the design of mixture proportion was adopted in this project work. steam curing at 60°C for 24hrs after casting).45 were given in Table 3.7 for the design of low calcium fly ash based geopolymer concrete were proposed. 0.34 Rangan has proposed guidelines for the design of heat cured low calcium fly ash based geopolymer concrete. The mixture proportions for various alkaline solutions to fly ash ratios such as 0.7 Data for Design of low calcium fly ash based geopolymer concrete mixtures as reported by Rangan [1] Design compressive Water to geopolymer solids ratio. MPa 0. Table 3.35 has been reported in Appendix A.40 & 0. the data in Table 3.18 0. Based on the results obtained from numerous mixtures made in the laboratory over a period of four years.35. The mix design for low–calcium fly ash based geopolymer concrete for alkaline solution to fly ash ratio of 0.24 Very stiff Stiff Moderate High High 60 50 40 35 30 .20 0.16 0. The mass of NaOH solids in a solution varied depending on the concentration of the solution expressed in terms of molar. NaOH solution with a concentration of 8M consisted of 8x40 = 320 grams of NaOH solids (in flake or pellet form) per liter of the solution.4 1260 540 429 49 122 0. and water was the major component.4. The sodium silicate solution and the sodium hydroxide solution were mixed together at least one day prior to use to prepare the alkaline liquid. For instance. The mass of NaOH solids was measured as 262 grams per kg of NaOH solution of 8M concentration. Note that the mass of NaOH solids was only a fraction of the mass of the NaOH solution.8 Mixture proportion per m3 of geopolymer concrete Materials Alkaline solution /fly ash (by mass) Coarse aggregate Fine aggregate Fly ash Sodium hydroxide solution Sodium silicate solution 0.35 1260 540 444 45 111 Mass( Kg/m3) 0.45 1260 540 414 53 133 3. M.1 Preparation of Liquids The sodium hydroxide (NaOH) solids were dissolved in water to make the solution.4 MANUFACTURE OF GEOPOLYMER CONCRETE 3.35 Table 3. where 40 is the molecular weight of NaOH. On . The fresh concrete could be handled up to 120 minutes without any sign of setting and without any degradation in the compressive strength.36 the day of casting of the specimens.4. For compaction of the specimens. each layer was given 60 to 80 manual strokes using a roding bar. the fly ash and the aggregates were first mixed together in the pan mixer for about 3 minutes.The fresh concrete was cast into the moulds immediately after mixing. the alkaline liquid was mixed together with the super plasticizer and the extra water (if any) to prepare the liquid component of the mixture. .3. In the laboratory. in three layers for cubical specimens of size 100mm x 100mm x 100mm.2 Manufacture of Fresh Concrete and Casting Geopolymer concrete can be manufactured by adopting the conventional techniques used in the manufacture of Portland cement concrete. The fresh concrete was shown in Figure 3. The aggregates were prepared in saturated surface dry condition. The alkaline solution was then added to the dry materials and the mixing continued for further about 4 minutes to manufacture the fresh concrete. 3. 4.3 Fresh Geopolymer concrete (At VGN lab. the gain in strength was only moderate. Both curing time and curing temperature influence the compressive strength of geopolymer concrete. Compressive strength of dry cured geopolymer concrete is . The curing time varied from 4 hours to 96 hours. Heat curing substantially assists the chemical reaction that occurs in the geopolymer paste. Heat curing can be achieved by either steam curing or dry curing. Higher curing temperature of geopolymer concrete resulted in higher compressive strength.3 Curing of geopolymer concrete Heat curing of low calcium fly ash based geopolymer concrete is generally recommended.37 Figure 3. Nungambakkam) 3. Longer curing time improved the polymerization process resulting in higher compressive strength. The rate of increase in strength was rapid up to 24 hours of curing time and beyond 24 hours. geopolymer concrete specimens were cured immediately. The specimens were oven-cured at 60OC and 100OC for 24 hours in the oven. . they were kept under ambient conditions for curing at room temperature. After the curing period.e. Oven curing and Ambient curing. such a delay in the start of heat curing substantially increased the compressive strength of geopolymer concrete. The temperature required for heat curing can be as low as 30°.4.38 approximately 15% more than that of steam cured geopolymer concrete. the specimens were left to air-dry in the laboratory until the day of testing. the start of heat curing of geopolymer concrete can be delayed for several days. For Oven curing. the test specimens were left in the moulds for at least six hours in order to avoid a drastic change in the environmental conditions. Two types of curing were used in this study. In tropical climates. 3. This may be due to the geopolymerisation that occurs prior to the start of heat curing. the test specimens were cured in the oven and for Ambient curing.4 Curing of Test Specimens After casting. After demoulding. In fact. i. Also. The delay in the start of heat curing up to five days did not produce any degradation in the compressive strength.4 & Figure 3. this range of temperature can be provided by the ambient conditions. The oven cured specimens and the specimens under ambient curing were shown in Figure 3.5. Nungambakkam) .4 Oven cured specimens (At VGN lab.39 Figure 3.Nungambakkam) Figure 3.5 Specimens under ambient curing (At VGN lab. 6.5 EXPERIMENTS CONDUCTED 3. The compressive strength test was performed as shown in Figure 3.5.5. the slump value of the fresh concrete was maintained in the range of 30mm to 40mm. 3. the slump value of the fresh concrete was measured using slump cone. . 14days and 28days. Totally 81 number of cubical specimens of size 100mm x 100mm x 100mm was casted and tested for the compressive strength at the age of 7days. Before the fresh concrete was cast into moulds. placed. Each of the compressive strength test data corresponds to the mean value of the compressive strength of three test concrete cubes. In this project work.1 Workability Test Workability is the property of freshly mixed concrete that determines the ease with which it can be properly mixed.2 Compressive Strength Test The compressive strength test on hardened fly ash based geopolymer concrete was performed on standard compression testing machine of 3000kN Capacity. The workability of the fresh concrete was measured by means of the conventional slump test as per IS: 1199(1989).40 3. as per IS: 516-1959. consolidated and finished without segregation. 6 Compressive Strength of cube specimen (At VGN lab. Nungambakkam) .41 Figure 3. 42 CHAPTER 4 RESULTS AND DISCUSSION 4. 4.The test results reveals that the compressive strength of geopolymer concrete ranged from a minimum of 3. Compression test is the most common test conducted on hardened concrete.1 to 4. . and partly because most of the desirable characteristic properties of concrete are qualitatively related to its compressive strength.7. concentration of alkaline solution and curing conditions were found at 7. 4. the experimental results are discussed and presented in the form of tables and graphs.1 INTRODUCTION In this chapter. The test results are tabulated in Tables.1 to 4.2MPa to a maximum of 27MPa. curing conditions that are manipulated in this experimental study.2 COMPRESSIVE STRENGTH The compressive strength different of geopolymer concrete specimens for various alkaline solutions to fly ash ratio. partly it is an easy test to perform. The results show that the strength development is related to variables such as alkaline to fly ash ratio.4 and plotted in Figures 4. 14 and 28days. 35 Concentration of Curing condition NaOH liquid(in Molars) Ambient curing Oven curing at 60oC Oven curing at100oC 8M 8M 8M Compressive strength at various ages (N/mm2) 7 days 14 days 3.7 18.3 21.5 24.40 Concentration of Curing condition NaOH liquid (in Molars) Ambient curing Oven curing at 60oC Oven curing at100oC 8M 8M 8M Compressive strength at various ages (N/mm2) 7 days 5.2 14.4 Table 4.8 16.8 28days 16.4 20.2 .43 Table 4.5 16.7 28 days 14.3 21.7 14days 11.1 Compressive Strength of geopolymer concrete for Alkaline solution to fly ash ratio of 0.5 20.6 16.2 17.2 22.9 8.2 Compressive Strength of geopolymer concrete for Alkaline solution to fly ash ratio of 0. by mass. Curing conditions.35. The alkaline solution to fly ash ratio by mass has considerable effect on the compressive strength of geopolymer concrete.3.1 Ratio of Alkaline solution to fly ash The effect of alkaline solution to fly ash ratio on compressive strength of geopolymer concrete specimens were given in Table 4.5 24.4 and shown in Figures 4.40 & 0. 2.4 14days 12.45 Concentration of Curing condition NaOH liquid(in Molars) Ambient curing Oven curing at 60oC Oven curing at 100oC 8M 8M 8M Compressive strength at various ages (N/mm2) 7 days 9.45.1 to 4.3. 0.9 22. 4.44 Table 4. The alkaline solution to fly ash ratio by mass was varied as 0. .1 28days 18. Ratio of alkaline solution to fly ash.3 EFFECT OF SALIENT PARAMETERS The following parameters which affect the compressive strength of geopolymer concrete were considered in this project: 1.4 17.5 24 27 4.4 22.3 Compressive Strength of geopolymer concrete for Alkaline solution to fly ash ratio of 0. 45 was about 22% and 35% with respect to 0. The reason for increase in compressive strength was concluded by previous researchers as. only the glassy phases in fly ash were the source of Al and Si to form aluminosilicate gel and also the reaction product was quickly formed that engulfs the fly ash particle and slowing down the further activation of the fly ash particles.2 26.4 16.40 and 0.4 Effect of alkaline solutions on Compressive Strength Compressive strength at 28th day Concentration of NaOH sol (in molars) Ratio of alkaline solution to fly ash (by mass) 8M 8M 8M 0. Table 4.3 18.2 21. in lower alkaline solution to fly ash ratios.5 24.0 Ambient Oven cured Curing at 60°C (N/mm2) Oven cured at 100°C 22. in a higher alkaline solution to fly ash ratios the quartz and mullite phases in fly ash were completely dissolve and increases the amounts of reaction product formation thereby increases the compressive strength.5 20. thus resulting in only low to moderate degrees of reaction.4 24. Increase in the alkaline solution to fly ash ratio.45 14.40 0.35 respectively.0 .35 0.45 Increase in compressive strength at alkaline solution to fly ash ratio of 0. increased the compressive strength of concrete irrespective of other factors. However. 6 0.45 Alkaline solution to fly ash ratio 7 days 14 days 28 days Figure 4.3 16.4 0.5 20.4 16.35 0.2 21.7 26 24.2 Effect of alkaline solution to fly ash ratio on compressive strength of oven cured concrete at 100°C .2 20 15 10 5 0 21.9 24.1 Effect of alkaline solution to fly ash ratio on compressive strength of oven cured concrete at 60°C Compressive Strength N/mm2 30 25 20 15 10 5 0 22.7 16.1 22.5 17.40 0.40 0.8 17.35 0.2 24 22.7 14.46 Compressive Strength N/mm 2 30 25 20.4 18.45 7 days 14 days 28 days Alkaline solution to fly ash ratio Figure 4. compressive strength significantly increases with age up to 28 days.9 8.45 7 days 14 days 28 days Alkaline solution to fly ash ratio Figure 4.8 3.4 to 4. alkaline solution to fly ash ratio and concentration of sodium hydroxide solution.40 0.5 11.5 9.25 times more than that of ambient cured specimens at 7 and 28 days respectively.5 12. The compressive strength of oven cured specimens was more than that of ambient cured specimens irrespective of age. In oven . In ambient curing.3 14.3 Effect of alkaline solution to fly ash ratio on compressive strengthof ambient cured concrete 4. In ambient curing.5 and 1.4 18.3.4 5.2 0.45 ratio was 4. compressive strength at 28 days was about 3 times and 1.6. The test results revealed that compressive strength of oven cured specimens at 0.4 times higher than 7 and 14 days respectively.47 Compressive Strength N/mm2 20 18 16 14 12 10 8 6 4 2 0 16.2 Curing conditions The effect of curing conditions on the compressive strength of geopolymer concrete for various alkaline solutions to fly ash ratios are depicted in Figures 4.35 0. 4 8. Since the chemical reaction of oven cured geopolymer concrete is due to substantially fast polymerization process.2 times and 1.4 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.45 ratio compressive strength was about 1.4 16.60oC o Oven curing-100 7 days C Curing Conditions 14 days 28 days Figure 4.1 times higher than 7 days 14 days respectively. In oven curing 28 days at 0.7 20. the compressive strength did not vary with age of concrete.6 16.7 3.5 14.35 . 60°C curing temperature was recommended for oven cured concrete to produce desired compressive strength. The effects of curing temperature on compressive strength are shown in Figure 4. compressive strength of geopolymer concrete has not increased substantially after 7 days.2 22.7. The rate of increase in compressive strength of oven curing at 100⁰ C was about 12% with respect to curing temperature at 60°C.48 curing. Increase in curing temperature from 60°C to 100°C.9 20 15 10 5 0 14.2 Ambient curing Oven curing. increases the compressive strength but not significantly. 30 Compressive strength N/mm2 25 18. From the test results. 3 16.60oC Oven curing.5 18.1 27 Ambient curing Oven curing.5 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.6 Variation of Compressive Strength with Curing Conditions for alkaline solution to fly ash ratio of 0.5 5.4 24.7 N/mm 15 10 5 0 2 Ambient curing Oven curing.9 9.60oC Oven curing.5 12.3 11.8 16.2 20.8 17.40 30 Compressive strength N/mm2 25 20 15 10 5 0 22.4 17.2 21.100oC 7 days 14days Curing Conditions 28days Figure 4.100oC 7 days 14days 28 days Curing Conditions Figure 4.45 .49 30 Compressive strength 25 20 24.5 21.4 24 22. 2 27 24.3 14.35 AL/FA =0.7 Effect of curing temperature on Compressive strength .50 30 25 20 15 10 5 0 24 18.4 Ambient 60 100 AL/FA =0.5 20.45 Curing temperatue Figure 4.4 21.2 22.4 AL/FA =0.5 16. 6.45. In ambient curing. for alkaline fly ash ratio of 0.35 3. for alkaline fly ash ratio of 0. 4. Fly ash-based geopolymer concrete cured in the laboratory ambient conditions gains compressive strength with age. 28 days compressive strength of oven cured specimens at 60 ⁰ & 100⁰ C is 1. for alkaline fly ash ratio of 0. the following conclusions are drawn: 1. alkaline solution to fly ash ratio. compressive strength at 28 days is about 3 times and 1. 28 days compressive strength of oven cured specimens at 60 ⁰ & 100⁰ C is 1.1 times more than that of ambient cured specimens.3 times and 1.4 times more than that of ambient cured specimens. .4 times higher than 7 and 14 days respectively.51 CHAPTER 5 CONCLUSIONS Based on the test results.3 times and 1. 28 days compressive strength of oven cured specimens at 60⁰ & 100⁰ C is 25% and 35% more than that of ambient cured specimens. The compressive strength of oven cured concrete was more than that of ambient cured concrete irrespective of age.4. 5. 2. iii.9 times respectively greater than the 0. after 14 days for 0. results in increase in the compressive strength of fly ash-based geopolymer concrete. The maximum compressive strength achieved in this project work for low calcium fly ash based geopolymer concrete is 27MPa.45 ratio was seen to be 1.35 ratio and by percentage it is 11%&22% higher comparatively. Likewise at the interval of 28 days for 0. Similarly. ii. 8.45 ratio was seen to be 1.8 & 2. Increase in alkaline solution to fly ash ratio by mass.45 ratio was seen to be 1. i. When compressive strength was plotted against alkaline solution to fly ash ratio.3 times respectively greater than the 0.4 & 0. 0.3 & 1. There is no substantial gain in the compressive strength of oven-cured geopolymer concrete with age beyond 7days.4 & 0.35 ratio and by percentage it is 26% &34% higher comparatively.1 & 1.4 & 0. 9.5 times respectively greater than the 0.52 7.35 ratio and by percentage it was 44% &66% higher during the initial 7 days. . RECCOMMENDATION APPLICATION 1. Increase in curing temperature in the range of 60°C to 100°C.high-alkali activating solutions).g. causes marginal increase in compressive strength of fly ash-based geopolymer concrete. It is also used in precast structural elements and decks as well as structural retrofits using geopolymer-fiber composites. 10. . During ambient curing the compressive strength was increased by 77% from 7 days to 28 days.53 i. during oven curing the compressive strength was increased by 24% from 7 days to 28 days. Geopolymer technology is most advanced in precast applications due to the relative ease in handling sensitive materials (e.. 2. ii. Similarly. 54 LIMITATIONS The followings are the limitations of geopolymer concrete 1. Safety risk associated with the alkalinity of the activating solution. 3. Practical difficulties in applying steam curing/high temperature curing process . High cost for alkaline solution 2. 75*2400 = 1800 Kg/m3 = (2400 – 1800) = 600 Kg/m3 2.35) = 444 Kg/m3 = (600 – 444) = 156 Kg/m3 5.5) = 45 Kg/m3 7. Ratio of alkaline liquid to fly ash by mass 4. Mass of fly ash and alkaline liquid 3.55 APPENDIX – A MIX DESIGN PROCEDURE FOR GEOPOLYMER CONCRETE Assume that normal density aggregates in SSD condition are to be used and the unit weight of concrete is 2400 Kg/m3 Take the mass of combined aggregates as 75% of the mass of concrete. Mass of alkaline liquid Take the ratio of sodium silicate to sodium hydroxide solution by mass as 2.35 = 600/(1+0. Mass of sodium hydroxide solution = 156/(1+2. Mass of sodium silicate solution = (156 – 45) = 111 Kg/m3 . Mass of fly ash = 0. 1. Mass of combined aggregates = 0.5 6. 559*111 = 62 Kg Solids = (111– 62) = 49 Kg In sodium hydroxide solution.262*45 = 12 Kg Water = ( 45 – 12) = 33 Kg Therefore total mass of water Mass of geopolymer solids Hence water to geopolymer ratio by mass = 62+33 = 95 Kg = 444+49+12 = 505 Kg = 95/505 = 0. the workability of fresh geopolymer concrete is expected to be moderate. super plasticizer has to be added to the mixture to facilitate ease of placement of fresh concrete. the workability of fresh geopolymer concrete is moderate. Water = 0.19. If needed.56 For trial mixture water to geopolymer solids ratio by mass is calculated as follows: In sodium silicate solution. . In general.19 For water to geopolymer ratio of 0. Solids = 0. T. “Structure and strength of NaOH activated concretes containing fly ash or GGBFS as the sole binder”.J. 36. 35.M. Deepak Ravikumar. Sumajouw. pp. 1233-1246. Bakharev. Cement and Concrete Research. pp. pp. 2007. T. Vol.57 REFERENCES 1. 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