Effects of Silica Fume on Workability and Compressive Strength Properties of Aluminosilicate Based Flowable Geopolymer Mortar under Ambient Curing

In this study, the effects of silica fume on setting time, mortar flow and compressive strength properties of fly ash based flowable geopolymer mortar had been studied. The aluminosilicate binder of 70% fly ash and 30% GGBFS with 2 M of sodium silicate solution (Na2SiO3) is considered as control mix. In the aluminosilicate binder, fly ash had been partially replaced with silica fume (0-30%). The test results indicate that the increase in silica fume up to 20% had shown increment in the geopolymer properties, due to the fine particle size and large surface area of the silica fume. The percentage of silica fume increases beyond 20% decrease in geopolymer properties but, still the mixes shown higher properties than control mix. Later, to improvise the fresh and strength properties, the mix containing 50% fly ash, 30% GGBFS and 20% silica fume is considered as aluminosilicate binder and examined with varying molarity of sodium silicate solution in the region of 1.5 < M< 2. However, the test results are significantly improved with decreasing the molarity of sodium silicate solution. The optimum level of 1.75 M of sodium silicate solution is considered in terms of setting time, mortar flow and compressive strength properties.