Roles of Packing Density and Water Film Thickness in Rheology and Strength of Cement Paste

Lowering the water/cementitious materials (W/CM) ratio is the key for the production of high-strength concrete and high-performance concrete, but there is a limit to lowering the W/CM ratio because the water added must be enough to fill the voids between solid particles and form water films coating the solid particles. Hence, an increase in packing density of the cementitious materials would allow a lower W/CM ratio to be adopted. This research aims to evaluate the effects of adding superfine cement (SFC) and condensed silica fume (CSF) on the packing density of cementitious materials, and study the roles of packing density and water film thickness in the rheological properties and compressive strength of cement paste. The results showed that the addition of SFC and/or CSF can significantly increase the packing density and water film thickness, and thereby greatly improve the rheological and strength performances of cement paste.