Photocatalytic NO_x removal efficiency and surface reflectance of carbonated mortars

Photocatalytic concrete containing titanium dioxide (TiO₂) nanoparticles can convert airborne nitrogen oxides (NO_x) into nitrate byproducts when exposed to light in the UV-A spectrum, which can reduce the impact to the environment and humans. In this study, the photocatalytic degradation of NO_x by mortars containing anatase TiO₂ was analyzed through photoreactor testing. Mortar mixtures were prepared with white and gray cements and varying TiO₂ and fly ash contents to quantify the effects of carbonation and surface reflectance on each mix design's NO_x removal potential. Carbonation of the mortar specimens significantly reduced photocatalytic NO_x removal efficiency, but this could be offset by the replacement of cement with fly ash. Specimens containing photocatalytic white cement were highly reflective in the UV-A spectrum and demonstrated a NO_x removal rate significantly greater than less reflective samples cast with gray cement. After carbonation, mixes with 15% fly ash replacement of cement produced the highest NO_x removal efficiency for specimens containing the same source of cement.