Effect of coral powder on the carbonation behavior of γ-C2S

Abstract

γ-dicalcium silicate (γ-C2S) is a potential sustainable binder owing to its high carbonation reactivity and self-pulverization properties. In this study, porous coral powders were used as a partial replacement of γ-C2S, and the effect on the degree of carbonation, the characteristics of carbonated products, and the compressive strength were investigated. Results suggest that the introduction of coral powders is conducive to the ingress of CO2 and thus the enhanced degree of carbonation, which is evidenced by both the increase of carbonation temperature rise and the extension of the sustained carbonation period. The incorporation of coral powders leads to a significant suppression in the content of amorphous calcium carbonate and an enrichment in crystalline phases. The compressive strength of γ-C2S compacts is increased from 79.1 MPa to 88.5 MPa after γ-C2S is partially replaced with 30%wt coral powders, while the same level of partial replacement by quartz powders results in a proportional reduction in compressive strength which is 52.8 MPa. The mechanical enhancement by coral powders is found to be associated with the unique porous structure which introduces more gas transport channels to increase the internal degree of carbonation, and favors the formation of denser interfacial transition zone between coral powders and the carbonated matrix. In addition, the tiny aragonite crystals in the coral powders are believed to induce the transformation of amorphous calcium carbonate into the crystalline phase, which contributes to the strengthening effect.