CO2 Sequestration in Pervious Concrete and its Impact on Concrete Strength and Alkalinity

Carbonation curing (CC) of cement-based materials is one attractive way for carbon utilization and sequestration, which is crucial to mitigate the greenhouse effect. The pervious concrete with high permeability and continuous pores is an ideal candidate for the CC to attain a homogeneous carbonation and high CO₂ sequestration efficiency. The aim of this article is to investigate the effect of CC conditions, including pre-curing time, CC time and pressure, on CO₂ sequestration in pervious concrete. Also, the impact on the concrete compressive strength and alkalinity was evaluated. Besides, the microstructure of CO₂ cured pervious concrete was characterized for revealing the mechanism of CO₂ sequestration. The results show that the CO₂ sequestration, alkalinity, and compressive strength of previous concrete are obviously affected by the above CC parameters. As the pre-curing time increases, the amount of CO₂ sequestration first increases and then decreases. Also, when the CC time and pressure raise, the amount of CO₂ sequestration is increased. CC can greatly improve the early-age compressive strength of pervious concrete and make the cement matrix denser, but excessive carbonation results in a decrease in early-age compressive strength. CC can reduce the early-age alkalinity of concrete to some extent, but the effect of CC on the alkalinity is not obvious in the long curing age. Thermodynamic modeling based on GEMS software indicate correctly the CC process of cement.