Effect of Cement Substitution with Mineral Fillers on NOx Air-Purification Efficiency and Photocatalytic Reaction Selectivity of Nano-TiO2-Modified Cementitious Composites

Abstract

This research investigated the properties of photocatalytic cementitious composites, including their air-purification efficiency. A method of characterizing the removal of airborne pollutants (nitrogen oxides), simulating the actual NOx concentration and irradiation conditions in Warsaw, Poland, in the autumn/winter season was established. The study analyzed the impact of changes in the composition of cement mortars—partial substitution of the binder with mineral fillers—on the properties of the external photoactive surface of the composite. The designed experimental plan included both quantitative and qualitative variables (type and amount of fillers used). It was found that the photocatalytic performance of the composite was correlated with its pore total content and pore size distribution—the higher the content of mineral fillers, the lower the porosity and the less effective its photocatalytic properties. The selectivity of the photocatalytic NOx reactions also deteriorated as the content of the mineral fillers increased. The study confirmed the validity of increasing the binder content in cementitious composites to enhance their photocatalytic performance.