The Effect of Sodium Hydroxide Concentration in Alkaline Activator on the Formation, Compression Strength and Morphology of Heat-Treated Fly Ash Geopolymers

Abstract

The construction industry’s reliance on Ordinary Portland Cement (OPC) significantly contributes to global carbon dioxide (CO₂) emissions and exacerbating climate change. This study addresses the urgent need for sustainable alternatives, focusing on Geopolymer Concrete (GPC) made from industrial by-products like fly ash (FA). However, existing research lacks insights into raw FA containing high levels of unburned carbon content and impurities, which can adversely affect GPC’s properties. Furthermore, the optimum concentration of NaOH solution that gives highest compressive strength in GPC remains unclear. The objectives of this study are to investigate the effects of unburned carbon content in FA on the morphology, compressive strength, and functional groups in GPC and to determine the optimum concentration of NaOH solution that enhance the compressive strength of the GPC.