Relationship among particle characteristic, water film thickness and flowability of fresh paste containing different mineral admixtures

This paper aims to study the influences of particle characteristic on flowability of cement paste containing different mineral admixtures. Fly ash (FA), ground granulated blast furnace slag (GGBS) and limestone powder (LS) were added by 10-30% of cement weight to prepare binary system. SEM observation, particle size distribution and packing density were carried out for every single and binary cementitious system. Fresh pastes of every cementitious system were prepared with variable solid volume fractions, and slump flow and flow times (T150, T200 and T250) were recorded in the mini-slump test to evaluate the rheological performance. The results show that the packing density of cementitious system is increased significantly by addition of LS due to the wider particle size distribution and decreased by addition of GGBS due to the irregular shape. FA has a little increasing effect on the packing density due to its finer and sphere particles. For different cementitious systems with similar particle shape, the closer to the Fuller distribution the particle size distribution, the higher the packing density is. The packing density of solid particles increases linearly with the lower n value of Rosin-Rammler distribution and the particle shape has little influence on this tendency. A flowable paste containing mineral admixture can be prepared with the higher threshold solid volume fraction and lower water film thickness (WFT) value. For every cementitious system, the relationship between the relative flow diameter (RFD) and WFT value can be described by the equation of RFD = b/(WFT + a) + c, and the relationship between flow time (T) and WFT accords with the equation of T = 1/(d + e * WFT).