Synergistic mechanism of mechanical strength, photocatalysis and carbonation resistance in cementitious matrix doped with nanosilica and nanotitania

This is the authors' abstract. We don't add key points for this paper.

The dosage-dependent synergistic effects of nano-silicon dioxide (NS) and nano-titanium dioxide (NT) on the compressive strength, photocatalytic activity and carbonation resistance of cement pastes were investigated. Compressive strength, methyl orange degradation, accelerated carbonation, mercury intrusion porosimetry and X-ray diffraction were used to correlate macroscopic performance with microstructural evolution. The hybrid mixture containing 2 wt% NT and 1 wt% NS (T20S10) achieved a 28-day compressive strength of 67.1 MPa, 21.6% higher than that of the plain paste. Photocatalytic activity was mainly governed by NT content, while NS affected nanoparticle dispersion and titania active-site accessibility. T20S10 exhibited the lowest carbonation depth among the hybrid mixtures, corresponding to a 34.6% reduction relative to the control, although it did not outperform the best single-NS mixture. Microstructural analyses indicated that the pozzolanic effect of NS and the nucleation/filling effects of NT promoted hydration, reduced portlandite content and refined the pore structure. Overall, multi-functional performance depended on balancing synergistic modification against nanoparticle agglomeration rather than simply increasing the nanomaterial dosage.