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

Abstract

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.