Synthesis and characterization of synthetic sand by geopolymerization of industrial wastes (fly ash and GGBS) replacing the natural river sand

The diminution of the natural sources in the form of dredging the riverbanks and blasting the mountain ranges has always dented the balance of the ecosystem which in turn results in disasters as well at times. This alarming situation accelerates the global warming, threatens the biota life in riverbanks, diminishes the ground water level, harms the aquatic life, and affects the growth of agriculture. This study is an attempt to synthesis fine aggregates from the industrial byproducts, namely, fly ash and GGBS through the process of geopolymerization. This enables the formation of aluminosilicate networks upon the addition of the alkaline activator solution (Na₂ SiO₃ + NaOH) into the byproducts. The dry mix is then allowed for oven drying as well as air drying to accelerate the geopolymerization process. The fly ash-geopolymerized fine aggregate (F-GFA) and the GGBS-geopolymerized fine aggregate (G-GFA) were noted to exhibit adequate physiochemical and mechanical properties in par with the natural sand. The production of GFA is considered eco-friendly process since it ceases the extensive usage of river sand and incorporates the effective usage of industrial byproducts (fly ash and GGBS), thereby minimizing the land pollution and its consequent harmful hazards. Though the F-GFA and G-GFA showcased higher water absorption ratio than the natural sand due to the presence of unreacted fly ash and GGBS particles, the complete replacement of fine aggregate with geopolymerized sand initiated the adequate compressive strength attainment up to 90% of natural sand, by reacting with the lime expelled out of the hydration process of cement in the mortar specimens developed in this experimental study. The geopolymer itself is hydrophilic in nature, and it will also aid for the higher water absorption ratio of the polymer sand. The microstructure of the samples was further examined through optical microscope, scanning electron microscope, and X-ray diffraction analysis in order to corroborate the experimental results of this study. The results thus obtained strongly recommend the potential of the F-GFA and G-GFA as an ideal replacement material for natural sand.