Roles of water film thickness and SP dosage in rheology and cohesiveness of mortar

In recent studies, the authors have demonstrated that the combined effects of water content, packing density and solid surface area on the rheology of mortar may be evaluated in terms of the water film thickness (WFT). However, in addition to these factors, the superplasticizer (SP) dosage also has some effects. In order to study the roles of the WFT and SP dosage in the rheology and cohesiveness of mortar, a number of cement-sand mortar samples with different SP dosages and water contents were made for packing density, rheology and cohesiveness measurements. The results showed that the packing density and WFT would increase significantly with the SP dosage. At low SP dosage, the rheology of mortar is dependent on both the WFT and SP dosage while at high SP dosage, the rheology of mortar is dependent solely on the WFT. On the contrary, the cohesiveness of mortar is always dependent on both the WFT and SP dosage. Lastly, regression analysis of the test results was carried out and very good correlations of the measured rheological parameters to the WFT and SP dosage have been achieved.