Cement paste yield stress and self-compacting mortar stability

Abstract

Self-compacting concrete (SCC) has been extensively used because of its high-performance. This is mostly due to the integral stability of its components predominantly driven by the cement paste rheology and influences the viscosity of the overall suspension. Referring to Stokes law, solid particles exerting downward forces sink through the liquid phase only once the drag force fails. This work argues that the stability of self-compacting cement mortar does not only depend on the overall viscosity of the cement suspension but also on the yield stress of the suspending medium, the cement paste. Rheological measurements in shear steady mode, conventional column apparatus and total organic carbon measurements were done. Results showed that, cement mortars with higher yield stress pastes exhibited more stable suspensions while those with lower yield stresses resulted in unstable mortars with higher segregation. No correlation was found between rheological parameters and bleeding of cement pastes and corresponding cement mortars.