Roles of water film thickness in fresh and hardened properties of mortar

Supplementary cementitious materials (SCM) are commonly added to improve the performance of concrete. However, the effects of SCM on the behaviour of cement paste/mortar/concrete depend on many factors and have so far remained elusive, making the mix design of high-performance concrete containing SCM rather difficult. This paper evaluates the effects of SCM, the fresh and hardened properties of mortar made with superfine cement and condensed silica fume added at different water/cementitious materials ratios. First, the packing densities of the solid particles in the mortar samples were measured directly by a new wet packing method. Then, based on the measured packing densities, a mix parameter called water film thickness (WFT) was quantitatively evaluated. The results showed that the WFT plays important roles in the fresh and hardened properties of mortar, as demonstrated by the good correlations established between the WFT and the rheology as well as the strength of the mortar samples tested.