Research on the purification efficiency and mechanism for road runoff pollutants in pervious concrete with recycled aggregates.

The use of recycled aggregate (RA) in pervious concrete (PC) is a green approach that can effectively mitigate urban waterlogging, excessive RA, and runoff pollution, thereby enhancing the urban ecological environment. This article focuses on the long-term purification efficiency of runoff pollutants by PC at different porosities and RA dosages. Moreover, the purification mechanism of pollutants by recycled aggregate pervious concrete (RAPC) was revealed utilizing particle size analysis, microstructure, and elemental analysis. Finally, the recovery effects of different maintenance approaches on the purification capacity of RAPC were explored. The results indicate that an increase in the RA dosage reduced the effective porosity of PC, thereby decreasing the permeability of RAPC. In addition, PC with a lower porosity demonstrated a slightly greater purification effectiveness for pollutants. However, the utilization of RA significantly enhanced the purification capacity of PC for various pollutants, primarily by leveraging advantages in terms of pore structure, micromorphology, and surface chemical composition. Additionally, RAPC exhibited nearly 100 % retention effectiveness for particles larger than 68.95 μm but relatively lower purification efficiency for particles ranging from 1.541 to 17.11 μm. In particular, it displayed the poorest purification performance for particles with a diameter of 6.396 μm. The surface of RAPC's pore channels exhibited a loose state with high porosity and appeared rough and uneven with numerous pits and grooves. RAPC had a larger surface area and contained more components, such as SiO2, CaCO3, and Al2O3, than regular PC. Therefore, RAPC possessed a higher purification capacity. High-pressure flushing (HPF) and sodium citrate flushing (SCF) under different maintenance frequencies significantly contributed to the recovery of the purification efficiency of RAPC. However, overall, a lower maintenance frequency led to a less favorable recovery effect. Furthermore, SCF had a better recovery effect than HPF.