Synergistic enhancement of hydration and polymer network structure in in-situ polymerization cement composites by nano-silica

In-situ polymerization is an effective approach to enhance the toughness of cementitious materials; however, the associated hydration retardation often leads to significant compressive strength loss. In this study, low-dosage nano-silica (NS) was incorporated into in-situ polymerization-modified cement systems (IPMCs) to regulate hydration kinetics and strengthen the polymer-cement interaction. Calorimetry, phase analysis, polymerization characterization, and microstructural observations revealed that 0.2% NS markedly accelerated hydration and increased the overall reaction degree. Consequently, the 28-day compressive and flexural strengths increased to 50.17 MPa and 17.73 MPa. These enhancements stem from the synergistic effects of NS, including its nucleation-induced hydration acceleration, pozzolanic production of additional C-S-H, and refinement of pore structure. Moreover, hydrogen bonding between NS and polymer chains increased the polymer network’s crosslink density, while C-S-H formed from NS-driven rehydration bridged with polymer chains via Ca 2 ⁺, reinforcing the organic-inorganic interface. This coupled mechanism effectively offsets the hydration inhibition caused by polymerization and provides new insights for designing high-performance polymer-cement composites.