Roles of superplasticiser dosage, water film thickness and slurry film thickness in flowability of cementitious paste

Cementitious paste samples proportioned with blended ordinary Portland cement, pulverised-fuel ash and condensed silica fume (CSF), with different water/cementitious materials ratios and varying superplasticiser (SP) dosages, were produced for packing density and flowability measurements. The results showed that increasing the SP dosage significantly increased the packing density and water film thickness (WFT) of the cementitious paste, and increases in SP dosage and WFT contributed to increasing the flowability of the cementitious paste. At the same SP dosage and WFT, cementitious pastes containing CSF tended to have higher flowability. It is postulated that this is because the finest portion of CSF and water flowed together as a slurry that coated the larger sized particles with a certain slurry film thickness (SFT). Regression analysis of the test data revealed a very good correlation of flowability to SP dosage and SFT.