The influence of additive MgO and its content on the carbonation resistance of alkali-activated slag concrete with different activators

Abstract

The influence of additive MgO and its content on both the compressive strength and carbonation depth of alkali-activated slag concrete (AASC) was investigated under an accelerated carbonation environment. Furthermore, the modification mechanism of MgO on the carbonation resistance of AASC was explored by multiple analytical techniques. Results showed that the incorporation of MgO effectively enhanced the post-carbonation compressive strength and diminished the carbonation depth of concrete. As the MgO content increased, there was a gradual reduction in carbonation depth. The incorporation of MgO promotes the hydration of slag, altering the Al environment, and promoting the formation of C-S-H and Mg-Al hydrotalcite phases. Moreover, the addition of MgO resulted in the emergence of magnesium carbonate and calcium magnesium carbonate in the carbonation products, which filled the pores and prevented the further diffusion of CO2 into the interior. In addition, the improvement effects are more pronounced in the water glass system compared to the NaOH system.