Investigation on strength, drying shrinkage and photocatalytic efficiency of TiO2 cement composite mortar by the layering method

Nano-TiO 2 (NT) cementitious materials are usually prepared by the internal mixing method, which is characterized by simplicity and high photocatalytic efficiency. However, this method leads to low NT utilization. In this study, nano-TiO 2 cement composite mortar was prepared using the layering method to investigate the influence of NT layer on mechanical properties, drying shrinkage, carbonation resistance and photocatalytic properties of the mortar. The results showed that the NT top layer mortar in NT cement composite mortar with 5 mm thickness and 5 % NT doping was optimal, and its compressive strength and flexural strength were 52.2 MPa and 8.0 MPa, respectively. Due to the reduced contact angle, the surface hydrophilicity of NT cement composite mortar was enhanced, which led to the increase of its drying shrinkage. However, the NT doping optimized the internal pore structure of the mortar. The type and intensity of light significantly affect the early degradation rate of rhodamine B (RhB). After 60 min of irradiation, the highest RhB degradation rate of 87 % was achieved by sunlight, followed by the degradation rate of up to 85.54 % by UV light with a wavelength of 365 nm and 200 W, and the lowest by tungsten iodine lamp, which was 21.34 %. Additionally, the carbonation depth of NT cement composite mortar increased with higher NT dosage. Despite the reduced carbonation resistance, the RhB degradation rate remained as high as 74.5 % even with increased carbonation time and depth. Overall, the NT cement composite mortar prepared by the layering method demonstrated good mechanical properties, with drying shrinkage and carbonation resistance increasing as NT dosage increased. Moreover, NT cement composite mortar maintained effective photocatalytic properties under various lighting conditions.