Sound-absorption and NOx-removal performances of TiO2-incorporated porous concrete made with bottom ash aggregates

The sound-absorption and NOx-removal performances of TiO2-incorporated porous concrete made with bottom ash aggregates were investigated. Concrete samples made with bottom ash aggregates having different paste-to-aggregate volume ratios (i.e., 0.2, 0.3 and 0.4) and TiO2 contents (i.e., 0%, 1% and 3%) were fabricated. The correlation between the voids and the mechanical strength values of concretes made with bottom ash aggregates was investigated through void ratio measurement and compressive strength tests to derive a proper aggregate size. The influence of target void and TiO2 content on the void ratio, compressive strength, sound-absorption, and NOx-removal performances of the samples was explored through compressive strength, void ratio, sound-absorption, and NOx-removal performance tests. The test results indicated that the sound-absorption and NOx-removal performances of the concrete samples were greatly influenced by the total void ratio, and the NOx-removal efficiency of the concrete samples was further promoted with an increase in the TiO2 content. These coupled effects were possibly attributed to the fact that the photocatalytic reaction is surface-oriented and can be affected by an increase in the total void ratio, increasing the available number of TiO2 particles on the surface that can facilitate the photocatalytic reaction when exposed to light.