The microstructure and NOx degradation ability of alkali-activated steel slag-based pervious concrete doped with g-C3N4/CoAl-LDH

A new nanocomposite g-C3N4/CoAl-LDH was synthesized and implemented to make alkali-activated steel slagbased photocatalytic pervious concrete (ASSPPC). The water permeability, compressive strength, microstructure, and NOx degradation ability of ASSPPC were investigated. The results show that at lower dosages (1 wt% and 3 wt%), the spherical structure facilitates excellent dispersion of g-C3N4/CoAl-LDH within the matrix, which leads to reduced matrix porosity, resulting in improved compressive strength and reduced water permeability in ASSPPC. Compared to control previous concrete, the compressive strength of ASSPPC with 1 wt% g-C3N4/CoAl- LDH increased by 6.3%, and water permeability of which decreased by 15.4%, respectively. However, at higher dosages (5 wt%), g-C3N4/CoAl-LDH tends to agglomerate, causing lower hydration degree and higher matrix porosity. Moreover, owing to the remarkable alkali resistance of g-C3N4/CoAl-LDH, ASSPPC with this photocatalyst only marginally decreases its NOx degradation ability as the curing age increases. When considering water permeability, compressive strength, and NOx degradation ability, ASSPPC with 3 wt% g-C3N4/CoAl-LDH demonstrates optimal performance, which gives both compressive strength and water permeability equivalent to pervious concrete without photocatalyst while exhibiting a NOx degradation rate 0.58 times higher than that of ASSPPC with 3 wt% g-C3N4.