Influence of silica fume and class F fly ash on mechanical and rheological properties and freeze-thaw durability of self-compacting mortars

Abstract

This paper investigates the effect of different dosages of fly ash (FA) and silica fume (SF) in self-compacting mortars (SCMs) on the freeze-thaw (F-T) resistance as well as fresh and hardened properties. Nine mortar mixtures were prepared at 640 kg/cm3 of unit weight and water/binder (w/b) ratio between 0.43 and 0.50. All SCMs contained either FA or SF, but the control mixture contained only portland cement. The fresh properties of SCMs were determined using viscosity, slump flow, and V-funnel flow time tests. The compressive strength of SCMs containing SF was generally found to be higher than that of SCMs with FA and the control mixture. At 28 and 91 days, the control mixture had the highest flexural tensile strength in all blends except SF20 at 91 days. In addition, with increasing replacement rates of FA and SF in SCMs, the sorptivity of SCMs with FA resulted in an increase, whereas a reduction in the sorptivity of SCMs with SF was observed. Finally, as replacement ratio of FA and SF increased, the relative dynamic elastic modulus of SCMs showed a reduction, and the decreases in the elastic modulus of SCMs containing SF occurred sharply compared with SCMs incorporating FA because of the deleterious effects of SF on F-T cycles. Moreover, as SF and FA content increased, the dynamic elastic modulus of SCMs decreased at 28 days. © 2018 American Society of Civil Engineers.