Photocatalytic activity and stability of TiO2/ZnAl layered double hydroxide based coatings on mortar substrates

The surface properties and photocatalytic activity of the cement and pozzolanic mortar samples coated with TiO₂/ZnAl layered double hydroxides were studied with the intention to design suitable protective, hydrophilic coatings. In order to underline the existing correlation between the water uptake characteristics and the surface features, the coated mortars were subjected to water absorption test by capillarity, to photo-induced surface water absorption test and to photo-induced hydrophilicity test by contact angle measurements. The self-cleaning behavior of the mortar systems was evaluated by monitoring the photocatalytic rhodamine B removal efficiency in correlation with the development of photo-induced surface hydrophilicity. The coating durability was assessed towards the weathering effect of rain (essential for the coating self-cleaning properties). The positive result of the coating deposition was the improvement of photocatalytic activity, photo-induced hydrophilicity and the decrease of mortar systems surface roughness. The study revealed that the developed coating promotes self-cleaning effect.