Carbonation characteristics of γ-dicalcium silicate for low-carbon building material

Abstract

γ-Dicalcium silicate (γ-C2S) is characterized by its high carbonation reactivity and has the potential to be utilized as a construction material with the added benefit of CO2 sequestration. The present work addresses the characteristics of pressure-molded γ-C2S samples subjected to accelerated carbonation curing, including the developments in microstructure, carbonation degree and mechanical strength. The results indicate that the mechanical strength and surface density of carbonated γ-C2S block correlate well with its carbonation degree, which is attributed to the generation of more voluminous carbonation products. This strengthens the structure and densifies the matrix. The carbonation products include calcite as the primary morphology and aragonite as the minor phase, and amorphous Ca-modified silica gel formed by coordinated SiO4 tetrahedrons. Conductivity and ion concentration measurement elucidates the accelerated Ca2+ ion dissolution in the presence of CO2 is the reason for the high carbonation reactivity of γ-C2S. A conceptual model of carbonation process is proposed based on the distribution of Ca-modified silica gel and calcium carbonates. Additionally, the ecological evaluation demonstrates that γ-C2S would hopefully reduce 40% of the CO2 emissions compared to ordinary cement, which opens up a new area of a novel low-carbon construction material.