Title: Geo-polymer reinforced concrete beam with low calcium fly ash

Abstract

Cement production is accountable for billions of tons of waste materials. Researchers are trying to replace conventional cement with alternative cementation material to reduce carbon emissions and improve the overall efficacy. However, studies on eco-friendly materials with low calcium fly ash and different chemical compositions in structural performance are very limited. The research aim of this study is to investigate the influence of Low Calcium on Geopolymer Reinforced Concrete Beam (GB) in flexural behaviour compared with Conventional Cement Reinforced Concrete Beam (CB). The following are the research objectives of this study. To evaluate and to find the Flexural Strength of the Geo-Polymer Reinforced Concrete Beam(GB) and to compare it with the Conventional Cement Reinforced Concrete Beam. To identify the suitability of the Geo-Polymer Reinforced Concrete Beam for the application. Materials and Methods of the study: Class–F Fly ashes have been used in Geo-polymer concrete. Low calcium fly ash, fine and coarse aggregates, and alkaline liquids are used for making Geopolymer concrete. The grade of concrete used is M20. The nominal mix ratio (1:5.5:3) of M20 grade, is the minimum grade of concrete as per I.S 456-2000. For the analytical approach, the Finite Element method has been adopted using ANSYS APDL Programming in finding out the deflection of the beams and it is validated with the experimental investigation. 2D Beam 188 is the selected element type, which is based on Timoshenko beam theory (a first-order shear-deformation theory), which includes shear deformation effects. Transverse-shear strain is constant through the cross-section. The element includes unrestrained and restrained warping of cross-sections, i.e. apart from the regular six degrees of freedom, the seventh degree of freedom-warping magnitude can also be included. Stress stiffening is always included in geometrically non-linear analysis. Element type ignores Poisson's ratio, which affects the shear-correction factor and shear-stress distribution. Beam does not account for coupling of bending and twisting at the section stiffness level. In the Experimental Investigation, Specimens are made with the size of 125 mm x 250 mm x 3200 mm and designed under reinforced sections with Fe 415 Steel bar of 10 mm Ф of two numbers at the top and 12mm Ф of two numbers at the bottom with the clear cover of 20 mm. 8mm Ф bars were used for two-legged stirrups at 150 mm CC. The yield strength of the steel bars is 435.6 N/mm2. The young's modulus of Geopolymer concrete (GB) was 2.21 X 104 N/mm2 and the Poisson's ratio is 0.12. The reinforced cement concrete control beams (CB) were designated as CB-1, CB-2 and CB-3. Similarly, the Geopolymer Concrete beams are designated as GB-1, GB-2 and GB-3. The two-point loads are applied at an equidistant of 500mm from the Centre on both sides. The load applied is in the steps of 2.5 KN. Conclusion: 1. The average first cracking load of Geopolymer beam was around 22% higher than control concrete and it gives higher deflection, indicating the binding between inner matrixes of GB mix has more bond strength compared to conventional concrete. 2. In the service stage and yield stage GB exhibited better performance in the aspects of load-carrying and deflection compared to CB which shows GB have more ductility compared to CB because of its Modulus of Elasticity of geopolymer concrete beam. 3. The crack width increased gradually with an increase in load. In the case of GB, crack width increased slowly up to the service stage. However, when it reached the ultimate stage, it increased rapidly. The average Spacing between cracks in GB is more when compared to conventional concrete. It may be due to less porosity because of the finesse of fly ash. 4. The application of Low calcium Fly ash based Geo-polymer concrete was suggested effectively in the replacement of conventional concrete as it shows better performance and reduced Environmental issues. It gives better performance in all aspects by using industrial waste as a binder.