Contribution of turbidimetry on the characterisation of cement pastes bleeding

Abstract

The aim of this paper is to examine the contribution of turbidimetry measurements in the characterisation of cement pastes bleeding. In some cases (e.g. the presence of superplasticiser), the bleed water becomes turbid due to dispersion of the finest particles, and the boundary between the bleed water and the consolidated paste becomes difficult to detect. A Turbiscan device allows this boundary to be detected more accurately than in traditional tests. The role of superplasticiser and solid volume fraction in bleeding is examined. The bleeding measurements highlight the role of the superplasticiser in bleeding and its kinetics. The effect of superplasticiser may be explained by better dispersion leading to the release of water trapped between agglomerates. Furthermore, the existence of a critical volume fraction is shown, above which no bleeding occurs, and close to that corresponding to the appearance of contacts between particles. Finally, using rheological measurements, the correlation between the yield stress and bleeding has been possible.