Effect of C-S-Hs-PCE and sodium sulfate on the hydration kinetics and mechanical properties of cement paste

Abstract

This study reports the effects of combined application of calcium silicate hydrate seed-Polycarboxylate (C-S-Hs-PCE) and sodium sulfate (SS) on the hydration kinetics and mechanical properties of cement paste. The setting time, compressive and flexural strengths, and chemical shrinkage were evaluated. The mechanism of synergistic utilization of C-S-Hs-PCE and SS was explored on basis of the hydration heat releases, pore structures and crystalline phases. The results show that the setting time is shortened and the strengths of cement pastes are improved dramatically with the addition of C-S-Hs-PCE and SS. The incorporation of C-S-Hs-PCE increases the chemical shrinkage, while the co-doped C-S-Hs-PCE and SS can mitigate it. Overall, it accelerates the hydration process especially at early age, the pore structures are refined and the volume of gel micro pores increases due to more formation of gel. In the hardened pastes, the content of calcium hydroxide (CH) increases with the C-S-Hs-PCE and SS dosages, attributed to the further hydration of dicalcium silicate (C2S) and tricalcium silicate (C3S). This study could be viewed as a reference for the application of C-S-Hs-PCE and SS in cement paste, which is of great significance for its enhancement of early strengths.