Improved Water Retention and Positive Behavior of Silica Based Geopolymer Utilizing Granite Powder

This research aims to study the behavior of silica based geopolymeric material (22–28%Si) from granitic waste. Granitic waste in powder form was used as main precursor in combination of activating alkaline-solution (18% Na2SiO3, 7% NaOH and 75% distilled water). The ratio between Na2SiO3 and NaOH was kept constant (2.57) in all experiments to achieve appropriate geopolymerization but solid to liquid ratio was varied. Five different compositions of geopolymeric material were prepared with varying proportions of granite waste in the range of 70–78%, combined-alkaline-solution in range of 28–20% and 2% water. Curing of the samples was done in a heating oven at 70 °C for 24 h. After that samples were de-moulded and placed in a heating furnace for further curing at 220 °C for 2 h. After curing, compressive strength, density (bulk, apparent and true) and porosity (open, close and total) were measured. Phase analysis, degree of geopolymerization and microstructural analysis were evaluated by XRF (X-ray Fluorescence), FTIR (Fourier Transform Infrared Spectroscopy) and SEM (Scanning Electron Microscopy), respectively. XRF analysis revealed 28.38% Si and 5.96% Al which are the main constituents for the synthesis of geopolymer. Maximum achieved compressive strength was 22 MPa with minimum porosity of 19.487% in 78% granite based geopolymer. Minimum bulk density of 1.441 g/cm3 was achieved using 70% granite waste. FTIR results confirmed geopolymerization and optimized composition in the resultant samples which is 78% granite and 20% combined-alkaline-solution. Further, SEM results revealed most homogenous and dense structure in the same composition. The durability of the geopolymeric samples was evaluated by water absorption index. Maximum water absorption index of 3.09 was found in 72% granite based sample having 26.79% Si while minimum 2.018 in 78% granite based geopolymeric material having 22.97% Si. Positive compositional effect on various construction properties has been achieved in this study.