The Influence of Selected Material Variables of Photocatalytic Cementitious Composites on the Self-Cleaning Properties and Air Purification Efficiency from NOx Pollutants

Abstract

This work aimed to investigate the influence of selected material variables on the self-cleaning and air purification efficiency in NOx pollutants of cement-based photocatalytic composites. Tests were performed on cement mortars, with seven independent variables considered: the mass ratio between cement and quartz powder to sand, the water to cement ratio, the total mass amount of photocatalysts (two different types), the mass content of nanoparticulate silica, the percentage of quartz powder replacing part of cement, and the ratio between two sands of fine granulation. Photocatalytic cementitious materials had their self-cleaning properties tested via two methods (spectrophotometry—the degradation of rhodamine B under UVA irradiation, and the change in the contact angle—via a goniometer). Air purification properties were tested in the reaction chamber under UVA and visible light at low irradiance (0.2 W/m2 for UVA, 150 W/m2 for visible). It was found that TiO2 content and the mass ratio between cement and quartz powder to sand were the most influential variables within the selected ranges of variability, with the ratio between sands and quartz content being the least significant variable of the tested properties.