Effect of carbonation on development of reactive MgO-based pervious concrete

Abstract

Pervious concrete, developed to solve urban flooding and overloaded drainage issues, has limited strength due to its large void ratio. Reactive MgO cement (RMC) is a sustainable cement gaining strength through carbonation, which can have a more pronounced carbonation-induced enhancement in mechanical properties compared with Portland cement. However, its carbonation degree was limited due to the dense microstructure. To address both issues, pervious concrete using RMC was developed, and its void ratios were leveraged to facilitate the carbonation of RMC. Experimental results revealed that compared with that of samples cured under ambient environment (i.e. 4.7–15.7 MPa), the compressive strength of RMC-based pervious concrete cured under accelerated carbonation (11.2–39.7 MPa) and water/CO2 cycles (10.3–29.6 MPa) was enhanced by 77–278%. As the design void ratio increased from 0.15 to 0.30, the permeability coefficient of pervious concrete increased from 0.1 to 2.3 mm/s, while the carbonation of RMC-based pervious concrete also benefited from high void ratio, with the highest 28-day carbon sequestration ratio reaching 12.7%, as indicated by XRD, TGA tests and SEM observations. Furthermore, a mathematical model was established to estimate the thickness of cement paste on aggregates in pervious concrete, which was less than 1 mm and decreased as the design void ratio increased.