Novel procedure of CO2 capture of the CaO sorbent activator on the reaction of one-part alkali-activated slag

Abstract

CaO derived naturally from limestone or dolomite is an inexpensive and widely available sorbent. Understanding the mechanisms of CaO carbonation at ambient temperature under the assistance of H₂O is important for predicting the reaction of CaO in complex environments and designing novel CaO materials. In this study, we found that the reaction rate of alkali-activated slag is controlled by the CaCO₃ layer on a partially carbonized CaO alkali activator. The size of the sorbent increased after the adsorption reaction and the physically adsorbed water in the pores accelerated the carbonation. The carbonation process was governed by CO₂ diffusion. When the carbonation conversion rate reached 2–6%, the setting time increased rapidly with the increase in the carbonation rate. This is because the surface of the activator was modified by the thickened CaCO₃ product layer, which increased the diffusional resistance and thus prolonged the setting time of the alkali-activated slag.