Influence of Sand-Cement Ratio and Polycarboxylate Superplasticizer on the Basic Properties of Mortar Based on Water Film Thickness

Previous studies demonstrated that water film thickness (WFT) is a key factor that affects the fluidity of mortar. Changes in the sand-cement (S/C) ratio and polycarboxylate superplasticizer (PCE) dosage will affect the WFT. In this study, several mortar samples with different S/C ratios and different PCE dosages were prepared, and the basic properties of the mortar were measured. The results show that as the S/C ratio increases, the packing density of the mortar will decrease, the WFT will decrease, and the cohesiveness will increase, resulting in a decrease in the flow spread and strength of the mortar. When the PCE dosage is increased, the packing density of the mortar will increase, the WFT will increase, and the cohesiveness will decrease, which increases the flow spread of the mortar. When the water-cement (W/C) ratio is low, the S/C ratio has a significant effect on the strength, and the strength will increase with the increasing of the PCE dosage. When the W/C ratio is high, the strength of the mortar will be reduced once the PCE dosage exceeds the saturation value. In the case of different S/C ratios or different PCE dosages, the WFT can be used as a measure of mortar cohesiveness and flow spread.