Structure of C-S-H/PCE Prepared from PCE with Different Side Chain Densities and Its Effects on Early Hydration Properties of Cement

The development of prefabricated buildings increases the demand for using early strong agents in the production of prefabrication. As a new type of crystal early strength agent, synthetic calcium silicate hydrate (C-S-H) can significantly enhance the early strength of cement-based materials, but its poor dispersibility limits its application. In this paper, the polycarboxylate superplasticizers (PCE) with different side chain density were used as a dispersant to synthesis a series of C-S-H/PCE by means of co-precipitation method. The influence of C-S-H/PCE on the structure of C-S-H was studied with XRD, FT-IR, DLC. Moreover, its influence on the cement hydration behavior, hardened body strength and composition structure was investigated. The results show that the smaller the side chain density of PCE, the better the dispersion of C-S-H seeds and the smaller the particle size; the median particle size can reach 339.5 nm; the increase of the number of seed particles can provide more nucleation sites. The incorporation of C-S-H/PCE can significantly accelerate cement hydration, advance the exothermic peak of hydration acceleration by 1.3 h, and increase the heat release by 10.8% at 8 h. After the incorporation of C-S-H/PCE, the porosity of the hardenite of the cement slurry decreases at 8 h and 1 d and the compressive strength increases by 13% and 15%, respectively.