Hydration characteristics, structure evolution of marine cement composites with high durability modified by colloidal nano-silica for low carbon footprints

The porous structure of cement composites provides channels for the invasion of chloride ions in marine environment, which limits their service life and low carbon footprints. Colloidal nanosilica (CNS) with the particle size of 10-30 nm theoretically can refine the pore structure, block the chloride ion transport channel. Thus, it is beneficial to improve the service life of cement composites and reduce the consumption of cement and carbon dioxide emission. In this paper, the CNS was introduced to partially replace high sulfate resistance Portland cement (HSRPC) preparing HSRPC-CNS composite. The hydration characteristics, strength property, porous structure and chloride ion resistance were investigated. The results revealed that the addition of CNS was effective in improving the properties of HSRPC-CNS composite, and the most suitable content of CNS was 3 wt%. In this case, the hydration process of HSRPC-CNS composite was accelerated, and the 28-days compressive strength increased by 12.26%. Additionally, as the CNS content increases to 3 wt%, the porosity and chloride diffusion coefficient decreased by 32.39% and 41.99%, respectively. Therefore, CNS can be used as a sustainable nano additive that improved compactness, alleviated chloride ion permeability and reduced carbon dioxide emissions in HSRPC-based composites.