Enhancing the carbonation of γ-C2S through MgCl2 incorporation

Abstract

With the growing awareness of CO2 emissions reduction in the cement industry, minerals like γ-C2S with lower calcium content and formation temperatures have shown potential as sustainable alternatives to ordinary Portland cement. Although γ-C2S possesses considerable carbonation reactivity, incorporating additives can further optimize its carbonation hardening performance. This study investigated the effect of different dosages of internally incorporated MgCl2 on the carbonation behavior of γ-C2S. Test results demonstrated that incorporating 1.87 % MgCl2 led to the maximum compressive strength and CO2 uptake. The compressive strength and CO2 uptake following 24 h of carbonation increased from 63.2 MPa and 18.23 % to 84.2 MPa and 23.95 %, respectively. XRD and TG analyses indicated that Mg2+ promoted the transformation of amorphous calcium carbonate into more stable crystalline calcite and the formation of magnesium calcite and nesquehonite. SEM imaging revealed that the generated carbonation products tightly filled the pores, enhancing the compactness and strength. However, excessive MgCl2 coating on particle surfaces hindered further carbonation. These findings reveal opportunities to further optimize the carbonation hardening properties of calcium silicate minerals and precisely tailor the morphology of calcium carbonate products for sustainable construction.