Effect of simulated weathering conditions on the NOX and SOX removal rates of permeable concrete blocks with porous materials

Abstract

This study examined the effects of simulated weathering conditions on the NO_X and SO_X removal rates of permeable concrete blocks with embedded porous materials. To provide NO_X and SO_X removal, titanium oxide (TiO₂) nanoparticles or coconut shell carbon (CS) powders and zeolite beads (ZB) were embedded in permeable concrete blocks during their production. Permeable concrete blocks were produced with different embedding ratios of TiO₂ nanoparticles or CS powders using an actual factory production line of Company C in Korea. Leaching, freeze–thawing, and high and low temperatures were applied to each block to simulate weathering conditions. Test results reveal that the specimens with a 5% TiO₂ nanoparticle embedding ratio experienced reductions in NO_X and SO_X removal rates of approximately 17.7% and 19.5% respectively, after exposure to 10 leaching cycles and 300 freeze–thawing cycles, compared to unexposed specimens. However, the values were not affected by the high or low temperatures and remained similar to those of the unexposed specimens. In particular, the NO_X and SO_X removal rates of the specimens with a 5% CS powder embedding ratio exceeded 25.8% and 97.5%, respectively, and maintained similar values after exposure to leaching, freeze–thawing, and high- and low-temperature weathering conditions. Considering that TiO₂ nanoparticles can only be removed in an environment with ultraviolet light and NO_X removal rates were reduced in water environments, such as leaching and freeze–thawing, CS powders and ZB are promising materials for the stable reduction of NO_X and SO_X even in external weathering conditions.