Evaluation of the Performance of Pervious Concrete Inspired by CO[sub.2]-Curing Technology

Urban runoff is acidic in nature and mainly consists of heavy metals and sediments. In this study, the pervious concrete samples were cured in a CO[sub.2]-rich environment and their performance under runoff conditions was evaluated by passing different solutions containing clay particles, heavy metal ions, and acid species. The compressive strength of these samples was reduced by up to 14% when they were cured in water instead of a CO[sub.2] environment. Heavy metal ions, including lead and zinc, in the simulated runoff were adsorbed in these pervious concrete samples by up to 96% and 80% at the end of the experiment, but the acid species in this runoff could leach calcium ions from the cement components during passage. Clay particles in the runoff were trapped in the flow channels of samples, which marginally reduced the percolation rate by up to 14%. Concrete carbonation reduced the release of calcium ions under runoff conditions, and zinc removal was relatively lower because of the nonavailability of hydroxyl sites in the interconnected pore structure. The weight and strength losses in the carbonated concrete samples were relatively lower at the end of the acid storage experiment, suggesting that CO[sub.2] curing reduces cement degradation in aggressive chemicals. The SEM and tomography images revealed the degraded microstructure, while the XRD results provided data on the mineralogical changes. CO[sub.2] curing improves the strength gain and service life of pervious concrete in runoff environments.