Accelerated Carbonation and Performance of Steel Slag Concrete with Pressurized CO2 Curing

The carbonation of various alkali industrial wastes has been widely investigated owing to its potential permanent sequestration of CO₂. To make use of the carbonated products is of great significance, which may not only facilitate to cut the cost of CO₂ sequestration, but also economically utilize the industrial wastes. In this study, steel slag with relatively high contents of MgO and CaO was used as the aggregate to cast concrete and then the pressurized CO₂ (0.10-0.55MPa) was employed to curing the concrete. The carbonation front, mechanical strength, microstructure, and carbonate products of the concrete were investigated. Results shown that the compressive strength of the slag concrete after CO₂ curing (0.1MPa CO₂ and 14d) was significantly increased, obtaining an up to three-fold increase in comparison to that of the same concrete cured in normal moist curing condition for 28d. This may not only attribute to the densification of the concrete microstructure caused by the formation of Mg/Ca-bearing carbonates, but also relate to the binding properties of the carbonate products. According to the results obtained in this study, concrete with low-carbon emissions can be produced via the accelerated carbonation of steel slag.