The Fresh State: From Macroscale to Microscale to Nanoscale

There is a need to increase fundamental knowledge about the rheological behavior of cement-based materials. Cementitious fluids have complex rheologies and typically exhibit shear-thinning viscosity, yield stress, elasticity, and thixotropy; this complex rheological behavior results from the heterogeneity of the material and the finite time that it takes for the in situ structure to rearrange when it is subjected to shear-induced stresses. The specific cause of the rearrangement depends on interactions at the molecular level, which, unfortunately, are poorly understood. The rheological behavior of cement-based materials is directly linked to the aggregation, deaggregation, reaggregation, and dispersion of the solid particles. Research that can provide information about any of these phenomena would advance the state of knowledge of the flow behavior of cement-based materials. This paper presents an approach to characterization of the fresh-state structure of cement paste suspensions. It is shown that this method can be used to investigate the flocculation and floc properties of cement pastes.