Study on the molecular structure and mechanical properties of potassium ion uptake in calcium silicate hydrate

HL Gao and RR Yu and J Liu and W Zhang and MM Li and YY Jia and YB Ye and SJ Zhong and C Zhuang and H Zhu and QY Su and BT Huang and H Wu and J Sun and DS Hou, CONSTRUCTION AND BUILDING MATERIALS, 481, 141651 (2025).

DOI: 10.1016/j.conbuildmat.2025.141651

The effect of potassium (K) ions on the structure and mechanical properties of calcium silicate hydrate (C-S-H) at the nanoscale is rarely reported, as most studies focused on the macroscale or microscale experiments. This paper aims to investigate the molecular structure and mechanical properties of C-S-H under varying K ion content through molecular dynamics simulations. The results show that K ions uptake in C-S-H reduces the basal spacing, which is consistent with the experimental results, and leads to the formation of K-Os and K-Ow bonds in the interlayer region. In addition, the TCF value of K-Os bond is lower than that of Caw-Os bond, suggesting that the K-Os bond is less stable than the Caw-Os bond. The partial substitution of Caw with K ions improves the tensile Young's modulus and tensile strength of C-S-H, which is in agreement with the nanoindentation test. However, when the interlayer Caw was completely replaced by K ions, the fracture strain and fracture energy decrease. Unlike previous studies focusing on macroscale effects, this work provides a nanoscale perspective on the influence of K ions on interlayer bonding and fracture behaviour, offering insights for optimizing cementitious materials.

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