Effect of fly ash and silica fume on rheology, compressive strength and self-compacting in cement mixtures

Abstract

In this research the effect of the addition of silica fume (SF) and fly ash (FA) to the ordinary Portland cement (OPC), individually and in combination, on rheology, compressive strength and self-compacting capacity in mixtures of cement were evaluated. At the beginning, the physicochemical characterization of the raw materials was carried out using XRF, SEM and PSD. Subsequently the rheological analysis was done in order to determine yield stress and plastic viscosity, then the compressive strength was measured at 7 and 28 days of normal curing. Finally, the measurement of the selfcompacting capacity by means of a V-funnel was performed. It was found that the FA influences positively because it reduces yield stress and selfcompacting test times, but decreases the compressive strength in comparison to control sample. The addition of SF increases the yield stress and selfcompacting times, but positively influences the compressive strength. By analyzing the combinations of FA and SF additions the effects of each one are maintained allowing finding an addition range that delivered efficient values for the performance of fresh and hardened state of the blended cement pastes.

Keywords

• cement rheology
• mineral additions
• yield stress
• viscosity
• self-compacting cements