Influence of different amounts of natural pozzolan from volcanic scoria on the rheological properties of portland cement pastes

Abstract

In this study, design of experiments is used to investigate the influence of ratio of Portland cement (PC) / natural pozzolan (NP) on the yield stress and plastic viscosity of blended pastes. A set of pastes specimens was made with 0%, 25%, 35% and 45% of NP. NP from a Cameroonian volcanic scoria (CVS) with four differents colors were used. The results showed that the yield stress and viscosity of pastes were generally decreased when the NP replaced part of the cement. The reduction of yield stress is around 3.72 to 29.04%, 21.12 to 44.26% and -1.99 to 58.96% for 25, 35 and 45% of replacement respectively. The reduction of plastic viscosity is around -7.60 to 26.57%, 16.67 to 34.23% and 37.5 to 56.26% for 25, 35 and 45% of replacement. However, NP exhibited a significant reduction of yield stress and plastic viscosity when amount of replacement is higher than 25%.