COMPARATIVE STUDY OF EXPERIMENTAL AND ANALYTICAL RESULTS OF GEO POLYMER CONCRETE

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 7, Issue 1, Jan-Feb 2016, pp , Article ID: IJCIET_07_01_018 Available online at Journal Impact Factor (2016): (Calculated by GISI) ISSN Print: and ISSN Online: IAEME Publication COMPARATIVE STUDY OF EXPERIMENTAL AND ANALYTICAL RESULTS OF GEO POLYMER CONCRETE D. Annapurna Assistant Professor, Civil Engineering Department, University College of Engineering, Osmania University, Hyderabad, INDIA Prof. Ravande Kishore Professor, Civil Engineering Department, University College of Engineering, Osmania University, Hyderabad, INDIA M. Usha Sree P.G. Scholar, Civil Engineering Department, University College of Engineering, Osmania University, Hyderabad, INDIA ABSTRACT Geo polymer concrete is a recently developed construction material which is environment friendly and perhaps best alternative to conventional concrete. In the present scenario, where global warming is a big issue due to Co2 emissions, no cement concrete like Geo Polymer Concrete is the big boon for construction industry. The research work carried out on Geo Polymer Concrete and documented in the present paper is a step forward in the direction to encourage the development of Geo Polymer Concrete for its wide application in construction industry. The present paper describes experimental work and analytical work pertaining to Finite Element Analysis using ANSYS software to simulate the flexural behavior of Reinforced Geo Polymer Concrete Beams. The alkaline solution used for present study was the combination of sodium silicate and sodium hydroxide solution with the varying ratio of NaoH solids with 97-98% purity is purchased from commercial source and mixed with water to make solution with a concentration of 16 molarity. The standard test specimens viz., cube, cylinder and prism were cast to understand compressive strength, flexural strength, stress-strain behavior, Poisson s ratio. These properties are incorporated for modeling the flexural behavior of Reinforced Geo Polymer Concrete Beams using ANSYS software, which will simulate the load-deflection behavior, crack pattern, ultimate load etc. The model thus developed is validated using the data generated during experimental investigations on Reinforced Geo Polymer Concrete Beams in flexure. The results of theoretical investigations match closely with that of editor@iaeme.com

2 D. Annapurna, Prof. Ravande Kishore and M. Usha Sree results obtained from experimental work, thus making the developed model useful for predicting the flexural behavior of Reinforced Geo Polymer Concrete Beams. Key words: Geo Polymer Concrete, Fly Ash, Molarity, Sodium Silicate, Sodium Hydroxide, ANSYS. Cite this Article: D. Annapurna, Prof. Ravande Kishore and M. Usha Sree, Comparative Study of Experimental and Analytical Results of Geo Polymer Concrete, International Journal of Civil Engineering and Technology, 7(1), 2016, pp INTRODUCTION Concrete is the most widely used material in the world, with Ordinary Portland Cement being the current most utilised concrete binder. Although there are variations in the estimates of the total global concrete production, roughly 3 billion tones of Portland cement was recorded to have been manufactured during last decade. This rate of concrete usage is increasing semi-exponentially due to continuous global industrialization. The current usage is estimated at 4 tones per capita. Concrete s environmental impact, especially during the manufacturing process, is ranked as one of the worst in the world as 1 tone of Portland cement production results in 1 tonne of CO 2 emissions. Portland cement manufacture therefore accounts for 5-8% of global man-made CO 2 emissions. Pozzolans such as blast furnace slag and fly ash may be activated using alkaline liquids to form a binder and hence totally replace the use of OPC in concrete. In this scheme, the alkalinity of the activator can be low to mild or high. In the first case, with low to medium alkalinity of the activator, the main contents to be activated are silicon and calcium in the by-product material such as blast furnace slag. The main binder produced is a C-S-H gel, as the result of a hydration process. In the later case, the main constituents to be activated with high alkaline solution are mostly the silicon and the aluminium present in the by-product material such as low calcium (ASTM Class F) fly ash (Palomo, Grutzeck et al. 1999). The binder produced in this case is due to polymerization. Davidovits in 1978 named the later as Geo polymers, and stated that these binders can be produced by a polymeric synthesis of the alkali activated material from geological origin or by-product materials such as fly ash and rice husk ash. In the case of geo polymers made from fly ash, the role of calcium in these systems is very important, because its presence can result in flash setting and therefore must be carefully controlled. The source material is mixed with an activating solution that provides the alkalinity (sodium hydroxide or potassium hydroxide are often used) needed to liberate the Si and Al and possibly with an additional source of silica (sodium silicate is most commonly used) Need of present research Construction industry requires huge amount of Concrete which in turn consumes tones of Cement. However the production of Cement causes environmental degradation in view of huge amount of co 2 emissions during the production of Cement. It is therefore desired that the dominant construction material like Concrete needs to be manufactured using the least amount of Cement. Research in that direction has resulted into development of Fly Ash Concrete with partial replacement editor@iaeme.com

3 Comparative Study of Experimental and Analytical Results of Geo Polymer Concrete of Cement. But in view of the fact that the demand for Concrete production is rising in geometric proportion, production of no Cement Concrete, such as Geo Polymer Concrete is the need of the hour. Several pozzolanic materials can be considered for producing Geo Polymer Concrete. Fly Ash is one of the pozzolanic material which is abundantly available. It is a byproduct from thermal power plants and considered to be marginal material posing disposal issue. Hence Fly Ash based Geo Polymer Concrete is a construction material of huge potential providing solution to the environment related issues. Considerable research is being carried out on Fly Ash based Geo Polymer Concrete. While properties and performance of Geo Polymer Concrete to a limited extent has been understood, the critical review of the related literature reveals that very limited published results are available for Geo Polymer Concrete with higher alkaline liquid ratio above 0.5. Further, very little work seems to have been carried out on the flexural behavior of Reinforced Geo Polymer Concrete (RGPC) analytically. Hence, an attempt is made to study the effect of alkaline liquid ratio of 0.55 and 0.6 with 16 molarity NaOH on mechanical properties and flexural behavior of Reinforced Geo Polymer Concrete beams both experimentally and analytically. 2. RESEARCH METHODOLOGY In this project fly ash is used as the base material for making geo polymer concrete. NaOH of 16 molarity and alkaline liquid ratios of 0.55 and 0.6 are used in the present work. Standard specimens were cast to know the mechanical properties of Geo Polymer Concrete. ANSYS software is used to model the flexural behavior of Reinforced Geopolymer Concrete Beams. Ultimate load carrying capacity, Maximum deflection and crack pattern are observed. Reinforced Geo Polymer Concrete Beam model results will be validated with experimental results. 3. EXPERIMENTAL PROGRAM 3.1. Materials The materials used for making fly ash-based geo polymer concrete specimens are dry fly ash as the source material, aggregates, alkaline liquids, water, and super plasticizer if necessary. Fly Ash Chemical analysis of fly ash is shown in Table 3.1 and is within the limits specified by IS 3812(Part 1) Characteristics Table 3.1 Properties of Fly ash Results /% by mass Loss on Ignition 1.80 Silica, SiO Alumina, Al2O Iron, Fe2O Magnesium, MgO Nil Calcium, CaO editor@iaeme.com

4 D. Annapurna, Prof. Ravande Kishore and M. Usha Sree Sodium Hydroxide: Sodium hydroxide solids in the form of flakes with 97% purity were used in the preparation of alkaline activator. Sodium Silicate: Sodium silicate in the form of solution was used in the preparation of alkaline activator Mix Design and concrete production Design of Geo Polymer mixtures have been carried out by considering coarse aggregate and fine aggregate together as 75% of total mixture by mass with 30% of it being fine aggregate. This is similar to the aggregate content required for design of conventional concrete. Further, assuming design of Geo Polymer Concrete same as that of conventional concrete and following the guidelines of mix design given by Rangan [2010], the mixture proportions are arrived at and the same is tabulated at Table 3.2. Alkaline liquid ratio Table 3.2 Mix proportion of different alkaline liquid ratios Na 2 Sio 3 NaOH Water for NaOH Fly ash Fine Agg Coarse Agg Mechanical properties Standard specimens were cast to determine the mechanical properties and the same are tabulated in Table 3.3. S.No. Table 3.3 Mechanical properties of geo polymer concrete for 0.55 and 0.6 alkaline liquid ratios Alkaline liquid ratio Compressive strength (N/mm 2 ) Flexural strength (N/mm 2 ) 3.4. Reinforced Geo polymer Concrete Beam Reinforced geo polymer beams were cast with the dimensions of 1500mmx230mmx150mm. All beams were reinforced with 16mm of main reinforcement at the bottom face with the yield strength of 420 N/mm 2. Testing were carried out to find out the first crack load and ultimate load at the central deflection using Universal Testing Machine. 4. ANALYTICAL MODELING USING ANSYS As stated above, the details of modeling are described in the following text. Modulus of Elasticity, MPa Geometry and Modeling The Finite Element Analysis included modeling of geo polymer composite reinforced concrete beams with the dimensions and properties corresponding to beams tested experimentally in the laboratory. By taking the advantage of the symmetry of the beam and loading, one quarter of the full beam was used for finite element modeling editor@iaeme.com

5 Comparative Study of Experimental and Analytical Results of Geo Polymer Concrete This approach reduces computational time and Computer disk space requirements significantly Element Types Eight noded solid brick elements (Solid 65) were used to model the concrete. This solid element has eight nodes with three degrees of freedom at each node translations in x, y, and z directions. The element is capable of plastic deformation, cracking in three orthogonal directions, and crushing. Flexural and shear reinforcements were modeled as discrete reinforcement by using beam188 as shown in Figure 4.1. Figure 4.1 Beam model showing solid 65 and beam188 elements 4.3. Real Constants Real Constant Set 1 is used for the Solid 65 element. Real Constant Sets 2 and 3 are defined for the beam188 element Material properties The Solid65 element with reference to ANSYS software requires linear isotropic and multi-linear isotropic material properties to model concrete. As required for modeling using ANSYS software the material properties such as compressive strength, Modulus of Elasticity etc. obtained from the experimental work on mechanical properties of Geo Polymer Concrete given in Table 3.3 has been used as input data Meshing To obtain satisfactory results from the Solid 65 element, a rectangular mesh was considered. Further beam 188 is considered for discretization of reinforcement such that the concrete and reinforcement share the same node. For concrete and reinforcement the assigned Mesh attributes are 1, Loads and Boundary Condition Displacement boundary conditions are needed to constraint the model to get a unique solution. To ensure that the model acts the same way as the experimental beam boundary conditions need to be applied at points of symmetry, and where the support exist. The symmetry boundary conditions were set first. Since this is a simply supported beam so constraints given at one support is in UX, UY and at the other supports UY is given. The loads and boundary conditions applied to the model are shown in Figure editor@iaeme.com

6 D. Annapurna, Prof. Ravande Kishore and M. Usha Sree Figure 4.2 Loads and boundary conditions 5. RESULTS AND DISCUSSIONS The results of Reinforced Geo Polymer Concrete beam obtained both experimentally and analytically are discussed in the following text Displacement and crack pattern For the nonlinear analysis, automatic time stepping in the ANSYS program predicts and controls the load step sizes. The longitudinal displacement at ultimate load is shown in Figure 5.1. Final Crack patterns observed in experimental and theoretical studies are found to have similar pattern, which is depicted in Figure 5.2 and 5.3 Figure 5.1 Longitudinal Displacement vector sum at ultimate load

7 Comparative Study of Experimental and Analytical Results of Geo Polymer Concrete Figure 5.2 Final crack pattern at ultimate load Figure 5.3 Experimental cracks at ultimate load From Table 5.1 clearly reveal that, at first, second and third cracks, the load predicted by theoretical model are 15%, 14% and 13% higher than the experimental values. This implies that the theoretical model overestimating the load for the model therefore warrants further refinement for estimation of crack loads. However, for crack at ultimate load the theoretical model underestimates the load marginally by 3%. Hence, for ultimate load condition the model can be carried as reliable and dependable. Further, at first, second and third cracks, the deflection predicted by theoretical model are 6, 10 and 14% higher compared to experimental results. Hence the theoretical model which overestimates the results pertaining to deflection is acceptable. However for deflection at ultimate load the theoretical model is

8 Load in KN D. Annapurna, Prof. Ravande Kishore and M. Usha Sree underestimating the result marginally by 3%. Hence, this model could be refined or the theoretical results are to be cautiously considered. In general the model to predict the results for loads at different crack and deflection at different stages of loading, there is a scope for improvement in the model to satisfy all the requirements simultaneously. Table 5.1 Comparison between Experimental and Theoretical results Beam ID First crack Second crack Third crack Ultimate load GPC Load (KN) Def. (mm) Load (KN) Def. (mm) Load (KN) Def. (mm) Load (KN) Def. (mm) Exp Ana Load deflection curves of reinforced geo polymer concrete beam Load deflection curves are plotted using experimental and theoretical results and in shown in Fig From this figure, it is observed that both curves representing experimental and theoretical results are very close and at some points overlapping to each other Deflection in mm EXP ANSYS Figure 5.4 Load Deflection curve 6. CONCLUSIONS At various stages of cracking except, at the final crack theroretical model overestimates the loads in the range of 13 to 15%. The theoretical model estimates the load at final crack within acceptable limit of -3%. At different stages of cracking except at failure the theoretical model overestimates the deflection in the range of 6 to 14%. Thus enabling the use of theoretical model for prediction of deflection. The predicted and experimental deflection profile match closely, indicating the dependability of theoretical model editor@iaeme.com

9 Comparative Study of Experimental and Analytical Results of Geo Polymer Concrete REFERENCES [1] Rangan,B.V (2010) Fly-ash based geo polymer concrete Proceedings of international workshop on Geo polymer cement and concrete, Allied Publishers Private Limited, Mumbai, India, December 2010, pp [2] Abdul Aleem M. I, Arumairaj P.D (2012) geo polymer concrete- a review, International Journal of Engineering Sciences & Emerging Technologies, ISSN: Vol.1, Issue 2. [3] Dattatreya.k, Rajamane.NP (2011) Flexural behaviour of reinforced geo polymer concrete beams, International journal of civil and structural engineering Volume 2, issue 1. [4] Fareed Ahmed, M., Fadhil Nuruddin, M and Nasir Shafiq (2011) Compressive strength and workability characteristics of low calcium fly ash based self compacting geo polymer concrete, International Scholarly and Scientific Research & Innovation volume 5, issue 2. [5] Kannapiran. K, sujatha. T and nagan. S (2013) Resistance of reinforced geo polymer concrete beams to acid and chloride migration, Asian journal of civil engineering (BHRC) vol.14, issue 2. [6] Kumarave. S, Thirugnanasambandam. S (2013) Flexural Behaviour of Low Calcium Fly ash Based Geopolymer Concrete Beams, International Journal of Structural and Civil Engineering ISSN: Volume 2 Issue 11. [7] Madheswaran C. K, Dattatreya J. K, Ambily P.S, Karansingh (2014) Investigation on behaviour of reinforced geo polymer concrete slab under repeated low velocity impact loading International Journal of Innovative Research in Science, Engineering and Technology Vol. 3, Issue 3. [8] Pateel Alekhya, S. Aravindan (2014) Experimental investigations on geo polymer concrete, International journal of civil engineering and technology (ijciet) volume 5, issue 4. [9] Ruby Abraham, Deepa Raj. S, Varghese Abraham (2013) Strength and behaviour of geo polymer concrete beams, International journal of innovative research in science, engineering and technology, volume 2, special issue 1. [10] Shaishav R. Viradiya, Tarak P. Vora (2014) Comparative study of experimental and analytical results of frp strengthened beams in flexure, International Journal of Research in Engineering and Technology (ijret) Volume 03, issue 04. [11] Sameer Ul Bashir, Effect of Alkali Materials on Geo Polymer Concrete, International Journal of Civil Engineering and Technology, 6(1), 2015, pp [12] Sameer Vyas, Neetu Singh, Rp Pathak, Pankaj Sharma, Nv Mahure and Sl Gupta, Behaviour of Alkali Activated Fly Ash-Based Geopolymer Concrete on Thermal Activation, International Journal of Civil Engineering and Technology, 5(4), 2014, pp [13] Srinivas murthy T.V, Ajeet kumar Rai (2014) Geo polymer concrete, an earth friendly concrete, very Promising in the industry, International journal of civil engineering and technology (ijciet) volume 5, issue 7. [14] Uma.k, Anuradha.R, venkatasubramani. R (2012) Experimental investigation and analytical modeling of reinforced geo polymer concrete beam, International journal of civil and structural engineering volume 2, issue editor@iaeme.com