2025 Volume 78 Issue 1 Pages 35-43
In this study, white cement paste powder with particle sizes less than 75μm was utilized to investigate the effects of carbonation on cement hydration products. The T2 relaxation time was measured using 1H-NMR relaxometry, which enabled the evaluation of changes in the distribution of mobile water and the total specific surface area within calcium silicate hydrate（C-S-H）due to carbonation. Additionally, powder X-ray diffraction（XRD）measurements were conducted to quantify the phase composition, providing insights into the degree of carbonation of C-S-H. These analyses were crucial for understanding the carbonation process and the subsequent alterations in the pore structure of the cement paste. Experiments were conducted under natural carbonation conditions with relative humidity set at 60％ and 95％. It was observed that, after a carbonation period of 14 days, the extent of carbonation in C-S-H was approximately the same for both humidity conditions. However, the study revealed that relative humidity levels significantly influenced the speed of the carbonation reaction and the changes in pore structure post-carbonation. Specifically, at a relative humidity of 60％, the carbonation reaction progressed more slowly, and the resulting changes in the pore structure were less pronounced compared to the conditions at 95％ relative humidity, where the reaction occurred more rapidly, leading to more significant alterations in the pore structure. These findings indicate that humidity plays a critical role in the carbonation behavior of C-S-H and its physical properties.
