Experimental Study of Carbonation Resistance of Alkali-Activated Slag Concrete

This paper studies the effect of carbonation resistance on alkali-activated slag (AAS) concrete. To be specific, this paper investigates the effect of alkali content and type of activators on the carbonation depth of AAS concrete, and analyzes the changes in volume stability, water absorption rate, and carbonation depth of the AAS system after the addition of active MgO. As is shown by the results, while early carbonation is slower, the later carbonation rate of concrete with a high alkali content is higher than that of concrete with a low alkali content. After 28 days and 56 days, the carbonation depth with NaOH as the activator is smaller than that with sodium silicate as the activator; the strength of concrete after carbonation is slightly increased when sodium silicate is used as the activator. The addition of 3% active MgO decreased the water absorption rate of slurry, reduced the shrinkage of concrete, and improved the impermeability of concrete. Moreover, the incorporation of active MgO promoted the formation of hydrotalcite-like compounds and retarded the decomposition of C-S-H gel, thereby reducing the carbonation degree of concrete.