The effect and mechanism of C–S–H-PCE nanocomposites on the early strength of mortar under different water-to-cement ratio

Abstract C–S–H-PCE nanocomposites (CPNs) serving as nucleation sites are a promising material to accelerate the cement hydration and gain high early strength for cementitious materials. This study aimed to investigate the effects of CPNs on the properties and hydration of cement mortar under different water-to-cement (w/c) ratios. CPNs were prepared via the co-precipitation method in MAPEG-PCE solution and characterized by means of XRD, FT-IR, DLS, TEM, TGA, and TOC. The mechanism and effect of CPNs on the early hydration of cement mortar with w/c ratios of 0.50, 0.40, and 0.35 were assessed in terms of mechanical properties, isothermal calorimetry, setting time XRD, TGA, SEM, and MIP. The results showed that CPNs significantly promoted the early strength development of mortar and a higher enhancement ratio was brought at a lower w/c ratio. Calorimetry and setting results also showed a greater hydration acceleration of samples dosed CPNs with lower w/c ratio. From the analysis of XRD and TGA, the content of CH and C–S–H in the samples dosed CPNs increased with the decrease of w/c ratio in 6 h, while exhibited an opposite trend in 12 h and 3 d. MIP and SEM results showed that CPNs led to a refinement of pore structure and dense morphology, especially at a low w/c ratio. Moreover, the underlying acceleration mechanism of cement hydration versus w/c ratio was that the seeding ability was enhanced for the low distance between cement and CPNs at a low w/c ratio. According to this research, the use of CPNs may be more practical in high-strength concrete.