Roles of water film thickness and CaCl2/TEA dosage in mobility and hardening performance of cement-based materials

Abstract

Water film thickness (WFT) has been discovered to significantly affect the performance of cement-based materials in previous studies. The purpose of this study is to apply the WFT theory to cement-based materials with early-strength agents. To this end, calcium chloride (CaCl2) and triethanolamine (TEA) were used to prepare 32 groups of fresh pastes with varying water-cement ratios and different dosages of CaCl2/TEA. These pastes were tested for flow performance, setting time, and hardening performance. The comprehensive effects of WFT and early strength agents on the mobility and hardened properties of cement-based materials were discussed from the obtained results. Results show that WFT is still one of the main elements affecting the performance of cement-based materials in the presence of early strength agents. CaCl2 increased the packing density of the paste, enhancing the excess water between particles and enlarging the WFT, which positively impacted the performance of the paste. In contrast, TEA decreased the WFT, increased the cohesion between particles, and declined the fluidity. Furthermore, as the water-cement (w/c) ratio raised, the WFT of the paste also increased. This caused cement particles to be enveloped in excess water, improving slip capacity and consequently increasing fluidity but reducing strength. Overall, WFT and admixture dosage can effectively predict the fluidity and mechanical properties of the paste.