Performance of Zero Cement Concrete Synthesized from Fly Ash: A Critical Review

Abstract

Since the invention of the reinforced concrete (RC) technique, RC buildings have comprised the majority of extant building systems. The shift from traditional materials to green or low/zero carbon designed materials that are energy efficient, such as fly ash (FA), is recognized as one of the desirable approaches to reduce CO2 emissions and the climate change crisis. This review aims to summarize the performance of fly ash based Zero Cement Concrete (FA − ZCC) according to the main parameters: Fly ash types (ASTM FA Class F and Class C), precursor activator, molarity (Sodium Hydroxide concentration), modulus ratio (SiO2/Na2O), mixture design, mixing approach, compressive strength (f’c), modulus of elasticity (MOE), splitting tensile (ft), curing time, and curing technique. The findings of this critical review show that the compressive strength of FA-ZCC Class C is higher in comparison with Class F FA − ZCC. Ambient curing for ZCC made from FA Class C was more suitable compared with Class F, which needed high-temperature curing. Increasing molarity up to 14 led to better ZCC regardless the type of FA. Modulus of elasticity and tensile strength of FA − ZCC was found to be similar to or lesser than those for normal cement concrete. Besides, standard approaches should be provided to enhance the mixture design technique, mixing procedure approach, mechanical properties of ZCC synthesized by FA.