Effects of calcium silicate hydrates/polycarboxylate on the rheological behaviour and hydration performance of cement paste

In order to enhance the early hydration evolution as well as improve the fluidity property of cement paste, calcium silicate hydrates (C-S-Hs)/polycarboxylate (PCE) was self-synthesised by way of the co-precipitation method, and was added into cement paste. The rheological performance and hydration process of the cement paste were analysed. Results showed that adding C-S-Hs–PCE could improve the rheological performance of cement paste. With a low amount of C-S-Hs–PCE adopted, the viscosity and shear stress reduced slightly, while a high amount of C-S-Hs–PCE led to sharply decreased viscosity and shear stress. Adding C-S-Hs–PCE could shorten the cement hydration induction period and improve the hydration heat release rate significantly. The crystalline nuclei provided by C-S-Hs–PCE promoted the nucleation growth of hydration products. When C-S-Hs–PCE content increased, the hydration reaction products in the hardened cement slurry increased remarkably, and a large number of hydration products effectively filled into the micro-pores, leading to reduced large pores and increased nanopores. Adding 1.0% C-S-Hs–PCE increased compressive strength at 1 day by 12.9%, the 3 day compressive strength by 18.2%, 7 day compressive strength by 20.5% and 28 day compressive strength by 12.6%. The findings could provide a theoretical reference for the performance regulation of cementitious materials.