Understanding the role of different phases in γ-C2S based carbonatable clinkers

Abstract

Accelerated carbonation of carbonatable clinkers into building products is an effective way of CO2 utilization. However, due to insufficient understanding on the phase characteristics of carbonatable clinkers, there is still a lack of guidance on the selection and design of carbonatable clinkers. In this study, three γ-C2S based carbonatable clinkers were designed and synthesized, covering the carbonation active phase, the unavoidable C2AS and amorphous glass phases when using industrial feedstocks. The differences in the carbonation activity, mechanical properties and microstructure were compared. Results show that the uncarbonated phases have a significant impact on the mechanical properties of carbonated matrix. The presence of unreacted γ-C2S with self-pulverization induced cleavage planes and the amorphous glass phase with poor binding to the adjacent calcium carbonate crystals leads to reduced compressive strength. The carbonation reactivity of γ-C2S formed in composite system is significantly higher than that of pure γ-C2S. Benefiting from the higher degree of carbonation, carbonatable clinkers only need to contain >40 wt% of γ-C2S to obtain comparable compressive strength as the pure γ-C2S system.