Insight into Early-Age Performance of Cement Paste/Mortar with C-S-Hs-PCE and Aluminum Sulfate

This work aimed to perform the insight into the performance at early age of cement paste/mortar with calcium silicate hydrate seeds-polycarboxylate (C-S-Hs-PCE) and aluminum sulphate. The performance was evaluated using the setting behavior and compressive strength. Hydration heat liberation, chemical shrinkage, X-ray diffraction, and differential thermal analysis were performed to explore the related mechanism. The results indicate that C-S-Hs-PCE can reduce the setting times of paste and increase the compressive strength of mortar with aluminum sulfate at 6 and 12 h and 1 and 28 days. These results are mainly related to the acceleration hydration of tricalcium silicate and facilitation of ettringite and calcium hydroxide formation. Aluminum sulfate and C-S-Hs-PCE promote the cement hydration in two manners: (1) they significantly enhance the heat flow and end the acceleration period earlier; and (2) aluminum sulfate prolongs the induction period, whereas C-S-Hs-PCE shortens it. These findings provide theoretical guidance for the development of a new alkali-free accelerator as well as the application of C-S-Hs-PCE.