Characteristics and efficiency of photocatalytic cementitious materials: Type of binder, roughness and microstructure

This work aims to study the effect of addition of photocatalyst on the characteristics of TiO2 modified mortars and the influence of type of binder, surface roughness and microstructure, on their photoactivity for self-cleaning of organic dyes (rhodamine B and methylene blue) and NOx degradation. Mortars with four different types of cements and three levels of roughness were prepared. From the results, it was found that the available active surface is a parameter more influential than surface roughness for assessing photocatalytic efficiency. Concerning the composition of the mixes, the classification according to photocatalytic efficiency was the same for both NOx and self-cleaning, being, in decreasing order: Portland cement (quite similar to calcium aluminate cement for NOx), fly ash and slag mortars. The difference has been explained on the basis of oxidation-reduction potentials and photoabsorption energy of the different constituents of cementitious matrix.