Structural Evolution and Characterization of gamma-C2S (gamma-C2S) Compacts during Carbonation

gamma-C2S has high potential for use as a construction material with the additional benefit of CO2 absorption due to its high carbonation reactivity. This study quantitatively investigates the evolution and influencing factors of the microstructure of the gamma- C2S compact molded by cold isostatic pressing, including microhardness, porosity, pore structure, and carbonation degree at different reaction depths. Results show that the carbonation reaction of the gamma-C2S compact is a sequential process from outside in, and the whole process can be divided into three stages. The carbonation degree decreases gradually with the increase of depth of the compact and finally forms a gradient structure, and the microhardness and backscatter results can also quantitatively demonstrate this evolution. In addition, the gamma-C2S compact with a lower forming pressure is beneficial to obtain a higher reaction depth after carbonation; with the progress of carbonation, the reaction depth shows a trend of rapid growth in the early stage, followed by a tapered-off development in the later stage of carbonation. This study provides a meaningful insight and shows the practical significance for the study and development of related gamma-C2S-based carbonation products.