The influence of silica-coated nanoscale titanium dioxide on the microstructure, mechanical properties, and carbonation resistance of cementitious materials

Nanomaterials possess great application prospects in improving the performance of cementitious materials. However, their high agglomeration hinders their efficient utilization in cementitious matrices. Consequently, surface modification has recently attracted attention as a method to enhance dispersibility. In this study, silica was employed to modify the surface of nanoscale titanium dioxide (NT), resulting in the synthesis of silica-coated nanoscale titanium dioxide (SCNT) composite material. In particular, the dispersibility of SCNT was investigated, and its influence on the compressive strength development of modified cement paste was analyzed. Additionally, the mechanisms affecting cement hydration behavior and microstructure evolution were comprehensively analyzed. Lastly, the impact of SCNT on the carbonation resistance of cementitious materials was further explored. Interestingly, the research results indicate that the surface SiO2 coating treatment improves the dispersibility of NT. More precisely, compared to 3% NT, the addition of 3% SCNT can increase the compressive strength of cement paste by 20.52% at 3 days and 16.52% at 28 days. Specifically, the incorporation of SCNT promotes cement hydration, refines the crystal size of Ca(OH)2, reduces the crystal orientation growth index of Ca(OH)2, and enhances the polymerization degree of calcium silicate hydrate (C-S-H), optimizing the pore structure. Furthermore, the 28-day permeability coefficient of 3% SCNT mortar is reduced by 99.98% compared to the blank group, effectively enhancing the carbonation resistance of cementitious materials. Overall, the findings of this study will contribute to the development of high-performance and multifunctional nanocomposite cementitious materials.