Comparative effects of CO2-curing condition on phase assemblage and mechanical response of C3S pastes: Insights from atomic, crystallographic, and macroscopic deformations

초록

This study investigates the microstructural characteristics of C3S pastes subjected to various CO2-curing regimes and their deformation mechanics at atomic, crystallographic, and macroscopic scales. Specifically, the effects of CO2 delivery methods and curing pressure are compared. Flowable CO2 and enclosed atmospheric CO2 resulted in carbonation degrees of C3S by 44.5% and 44.1% within 48 h. In contrast, enclosed high-pressure CO2 contributed to only 26.5% owing to concurrently promoted hydration induced by pressure and the restrictive propagation of CO2 through extensively carbonated exterior layer. Despite its significant carbonation degree, flowable CO2 showed severe decalcification represented by the highly polymerized silicate structure (49% of Q4 species) with substantial submicron porosity (17.5%). Highly pressurized CO2 with enclosure resulted in the lowest porosity of 12.4% and Q0 fraction (38%)—despite exhibiting the lowest carbonation degree—owing to the enhanced reaction by both hydration and carbonation induced by high pressure. However, these conditions resulted in severe oscillation in the crystal and atomic scale stress–strain curves due to significant inhomogeneity in the matrix, as evaluated based on the radial distribution of pores. Enclosed CO2 with atmospheric pressure induced the formation of homogeneous and interlocked structures imparting constant strain propagation. This multiscale stress–strain analyses suggest that a uniform phase distribution facilitates load transfer between reaction products, thereby possibly improving mechanical performance. Additionally, these findings provide advanced insights into the relationships between CO2-curing conditions, phase assemblage, and mechanical response.

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