Effect of the color of natural pozzolan from volcanic scoria on the rheological properties of portland cement pastes

摘要

The objective of this study is to examine the effect of the color of natural pozzolan (NP) from Cameroonian volcanic scoria (CVS) on the rheological properties of blended Portland cement (PC) pastes. A set of pastes specimens was made with 0%, 25%, 35% and 45% of NP. Four differents NP were used (black, dark red, red and yellow). The results showed that rheological properties of cement pastes were decreased when the NP replaced part of the cement. The reduction of yield stress is around 26.06 to 55.20%, 20.14 to 39.23%, 29.04 to 58.96% and -1.99 to 21.12% for replacement by black (BP), dark red (DRP), red (RP) and yellow (YP) NP, respectively. The reduction of viscosity is around 20.88 to 52.78%, 26.57 to 56.26%, 19.89 to 50.70% and -7.60 to 37.51% for replacement by BP, DRP, RP and YP respectively. The replacement by BP, DRP and RP exhibited a significant reduction. But the replacement YP exhibited a slow reduction. The results also showed that the inclusion of YP at levels of 25% and 45% resulted in an increase of yield stress and plastic viscosity for 1.99% and 7.60% respectively.