Integrated Design of Photocatalysis and Structure for Cement Mortar Using Nano-TiO2 Hydrosol

AbstractDue to the large specific surface area and strong van der Waals force, bulk aggregation of nano-TiO2 immediately occurs when it is mixed with fresh cement mixture, limiting its reinforcing efficiency to cement-based materials. This study proposes a novel strategy to improve the mechanical and photocatalytic properties of cement mortar using nano-TiO2 hydrosol instead of conventional nano-TiO2 powder. Compared with pure mortar, the 28-day compressive and flexural strength of mortar with 0.6% by weight nano-TiO2 hydrosol were enhanced by 51% and 15%, respectively, the water absorption and chloride ion diffusion coefficient were decreased by 21% and 31%, respectively. The observed improvements were attributed to the denser microstructure and enhanced micromechanical properties in the bulk matrix and around interfacial transition zone (ITZ), resulting from the better dispersion of nano-TiO2 hydrosol in alkaline environment. In addition, compared with the mortar with nano-TiO2 powder, the degradation efficiency of Rhodamine B and NO by the mortar with nano-TiO2 hydrosol (0.6% by weight) was enhanced by 18.3% and 17.1% at 28 days, respectively. The enhancement resulted from the higher intrinsic photocatalytic activity and larger exposed surface area of nano-TiO2 hydrosol due to better dispersion. The research outcomes demonstrate the potential of using nano-TiO2 hydrosol in cement mortar to significantly increase the mechanical strength, durability, and photocatalytic activity, which can lead to the development of cement-based constructions with the integrated design of functionality and structure.