Effects of CO₂ Curing on the Properties of Pervious Concrete in Different Paste-Aggregate Ratios

To improve the comprehensive performance of pervious concrete, the properties of pervious concrete in different paste-aggregate ratios were subjected to both early CO₂ curing and uncarbonated curing conditions. The mechanical properties, water permeability, porosity, and chemical composition of pervious concrete under two curing conditions were investigated and compared. The effects of CO₂ curing on the properties of pervious concrete with different paste-aggregate ratios were derived. Through mechanical experiments, it was revealed that early CO₂ curing can enhance the mechanical strength of pervious concrete by about 15-18%. Meanwhile, with the increase in the paste-aggregate ratio, the improvement effect induced by early CO₂ curing became more significant. The water resistance of carbonated concrete was not significantly reduced. And with the increase in the paste-aggregate ratio, the carbonation degree of pervious concrete was reduced; the differences in porosity and water resistance became less significant when the paste-aggregate ratio exceeded 0.39. Micro-structural analysis shows that the early CO₂ curing reduced both total porosity and the volume of micropores with a pore diameter of less than 40 nm, while it increased the volume of pores with a diameter of more than 40 nm. This is also the main reason that the strength of pervious concrete under early CO₂ curing is higher than that without CO₂ curing. The effect of varying paste-aggregate ratio and curing methods adds to the limited knowledge of the performance of pervious concrete.