Impact resistance of geopolymer concrete blended with class F and C fly ashes by ambient sun light curing

Abstract

Evolution of eco-friendly, sustainable mode of construction can overcome the undesired carbon-dioxide emission into the environment with the expansion of the use of geopolymers in the conventional concrete structures. This research work is focused on the inducement of geopolymerization in Class F fly ash (FFA) under ambient sunlight by incorporating Class C fly ash (CFA). The FFA: CFA ratios of 100:0, 95:5, 90:10, 85:15, 80:20, 75:25 and 70:30 are used as the blended base materials for the geopolymer formation. For the efficient geopolymer formation, two alkaline activators such as sodium hydroxide (NaOH) and sodium metasilicate (Na2SiO3) solutions are utilized. The experimental result reveals that the optimal proportion of CFA in the FFA-CFA blends can improve the polymerization and hydration process simultaneously, with an increment in the mechanical strength of the geopolymer mortars. The high calcium content of CFA also contributes to the strengthening of the geopolymer matrix structure. This enhancement in the mechanical strength and impact resistance of the geopolymer concrete is by the virtue of the inherent hidden, latent cementitious properties of CFA and because of the interlinking of calcium silicate hydrate (C-S-H) gel in conjunction with the alumino-silicate (Si-O-Al-O) geopolymeric gel.