Long term self-cleaning and photocatalytic performance of anatase added mortars exposed to the urban environment

• A 2-year natural exposure campaign of photoactive and standard mortars is proposed.
• Lightness and solar reflectance are better maintained if mortars contain TiO2.
• Aging decreased the materials photoactivity due to soiling.
• Accelerated cleaning with UV and light rinsing restored 70% of initial photoactivity.
• Self-cleaning materials contribute to preserve aesthetics and mitigate heating.

Building envelope materials containing titanium dioxide have been proposed to exploit their photoactivated depolluting and self-cleaning potential, but a full appraisal of their durability and long-term performance is still missing. This study reports a two-year campaign of natural exposure in Milano, Italy, of photoactive and non-photoactive fiber-reinforced mortars, analyzing the evolution of lightness, solar reflectance, porosity and photoactivity. After aging, photoactive samples showed limited color variation. The photocatalytic activity of TiO2 containing samples, characterized with dye degradation tests, was minimal after aging. Then, after alternated cycles of UV–Vis irradiation and rinsing, almost 70% of the initial photocatalytic efficiency was recovered.

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