2023 Volume 77 Issue 1 Pages 308-316
The microstructure evolution of cement paste along the carbonation depth under different RH conditions （23-80％） was characterized using SEM image analysis, complementing the phase quantification of each depth by XRD. From the microstructure analysis of binarized SEM images used to determine local porosity, a sudden reduction of local porosity occurred from the non-carbonated zone to the carbonated zone, and the lowest porosity was observed at the carbonation front. According to the ratios of macro-pores and microcracks to the total voids along the carbonation direction, calcium carbonate tends to precipitate in the microcracks, which could also explain the lowest ratio of microcracks occurring at the carbonation front. At low RH （23％） conditions, the ratios of microcracks and pores are similar to the non-carbonated zone because of the microcracks newly formed from the connection between the pre-existing microcracks by decalcification of C-S-H and remaining unfilled pores.
