Experimental Investigation of the Influence of Fly Ash Fineness on the Mechanical Properties of M50 Grade Geopolymer Concrete
Abstract
The manufacture of Ordinary Portland Cement (OPC) is a significant source of global carbon dioxide emissions, creating a strong need within the construction sector for more sustainable binder alternatives. Fly ash-based geopolymer concrete (FAGC) has developed as a potential sustainable alternative to conventional cement concrete by completely replacing OPC with Class F fly ash activated using sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃). Although many investigations have studied the effects of alkali-activator type, molarity, and proportion on geopolymer concrete, relatively limited attention has been given to the influence of fly ash fineness, expressed through particle size and specific surface area, on highstrength M50 geopolymer concrete. The present investigation compares two fineness levels from the same fly ash source—an asreceived coarse fraction and a processed/ground fine fraction—to determine their effect on the mechanical behaviour of M50 geopolymer concrete while maintaining the alkali-activator composition and other mix parameters unchanged. Specimens are evaluated for compressive, split-tensile, flexural, shear, and pull-out strength in accordance with the applicable Indian Standard (IS) codes to identify the fly ash fineness that provides the most favourable overall mechanical performance. The findings are intended to contribute to the development of sustainable high-strength geopolymer concrete and promote its potential use as a structural substitute for conventional M50 grade cement concrete