Carbonation of Dicalcium Silicate Enhanced by Ammonia Bicarbonate and Its Mechanism

The strength development law of gamma-type dicalcium silicate (gamma-C2S) under different carbonation processes was investigated, and the carbonation mechanism of gamma-C2S under the action of NH4HCO3 was clarified by using a wide range of test methods, including XRD and SEM. A method of saturated NH4HCO3 solution as a curing agent was identified to improve the carbonation efficiency and enhance the carbonation degree of gamma-C2S, and then a high-strength carbonated specimen was obtained. Microhardness analysis and SEM morphology analysis were conducted on the carbonised specimens obtained under atmospheric pressure carbonisation conditions using the curing agent. It was found that gamma-C2S could perform carbonisation well under atmospheric pressure, which promoted the carbonisation efficiency and decreased the carbonisation cost simultaneously. Therefore, a new carbonisation process solution was proposed for the rapid carbonisation of gamma-C2S.