Self-cleaning ability of titanium dioxide clear paint coated architectural mortar and its potential in field application

The self-cleaning property of building materials is a much desirable function. It not only improves the aesthetic appearance of the building, but also effectively reduces the costs of routine maintenance. Normally, titanium dioxide (TiO2) incorporated cementitious materials display multiple photocatalytic functions, including the self-cleaning ability. However, attaining a photocatalytic functional building product with both a high photocatalytic efficiency and a robust weathering resistant ability still remains challenging. This study investigated the strategy of directly applying a TiO2containing paint (clear in colour) on the surface of self-compacting architectural mortars (SCAM). Its self-cleaning (in terms of rhodamine b (RhB) degradation) and weathering resistant ability (accelerated façade weathering) were evaluated under both Ultraviolet-A (UV-A) and visible light irradiation. For comparison, 5% P25-TiO2-intermixed and dip-coated SCAM samples were also prepared and tested. The results showed that the TiO2paint coated SCAM sample displayed both a high photocatalytic RhB removal ability and a robust weathering resistance under all conditions. In contrast, the 5% P25-TiO2-intermixed samples only achieved a significantly lower RhB removal efficiency. Although the P25-TiO2-coated SCAM delivered a satisfactory self-cleaning performance, it suffered a significant loss in the RhB abatement after subjecting to the façade weathering process. The overall results suggest that the TiO2coated SCAM has the potential to be used as a resource and energy efficient product for air-purifying and self-cleaning applications.