Insight into the Decalcification Mechanism of Calcium Silicate Hydrate under a Water–Heat–Salt Environment

Author

Wei Zhang
Boya Zhang
Jia Sun
Juntao Dang
Xiangke Guo
Keliang Li
Bo Tao Huang
Biqin Dong
Hongyan Ma, Missouri University of Science and TechnologyFollow
Dongshuai Hou

Abstract

Understanding the decalcification mechanism of calcium silicate hydrate (C–S–H) under marine environments is crucial for concrete durability. In this study, the decalcification behavior of C–S–H under a water–heat–salt environment was systematically investigated through immersion experiments and reactive molecular dynamics simulations. Experimental results showed that elevated temperature and NaCl solution significantly accelerated Ca leaching and reduced the Ca/Si ratio of C–S–H. Simulation results further revealed that both high temperature and NaCl reduce the dissolution free energy of Ca, making its release more thermodynamically and kinetically favorable. Local structure analysis indicated that Cl^– disrupts Ca–Os (O atoms in silicate tetrahedra) connection through electrostatic attraction, while Na⁺ competes with Ca for silicate coordination sites. Elevated temperature further weakens the Ca–Os interactions and enhances the ion mobility. In contrast, the dissolution of Si atoms shows a clear energy barrier and requires higher energy due to strong Si–Os bonding. Based on these findings, an atomic-scale decalcification mechanism is proposed involving thermal activation, Cl^– attraction, and Na⁺ competition, providing new insights into the degradation processes of C–S–H under the water–heat–salt environment.

Recommended Citation

W. Zhang and B. Zhang and J. Sun and J. Dang and X. Guo and K. Li and B. T. Huang and B. Dong and H. Ma and D. Hou, "Insight into the Decalcification Mechanism of Calcium Silicate Hydrate under a Water–Heat–Salt Environment," ACS Sustainable Chemistry and Engineering, vol. 14, no. 1, pp. 483 - 496, American Chemical Society, Jan 2026.

The definitive version is available at https://doi.org/10.1021/acssuschemeng.5c10232

Department(s)

Civil, Architectural and Environmental Engineering

Comments

National Key Research and Development Program of China, Grant 2022YFE0133800

Keywords and Phrases

calcium silicate hydrate; decalcification; dissolution free energy; reactive molecular dynamics; water-heat-salt

International Standard Serial Number (ISSN)

2168-0485

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 American Chemical Society, All rights reserved.

Publication Date

12 Jan 2026