Reactive Molecular Dynamics Study on Thermal Stability of Type I Defect C-S-H Gel Phase

doi:10.16552/j.cnki.issn1001-1625.2024.1301

Abstract

Abstract: Under high temperature conditions, the presence of defects and confined water in C-S-H gel significantly affects its strength and durability. This study employed reactive molecular dynamics to investigate the molecular structural characteristics and reactivity of type I defect C-S-H gel under high temperature environments. The findings reveal that the increase in temperature and Ca/Si ratio enhances the mobility of water molecules, accelerating their penetration into the layered structure, reducing structural order and connectivity, leading to an increase in Q¹ and Q⁰, and weakening the thermal stability of C-S-H gel. Type I defect causes the C-S-H gel to expand along the interlayer direction, and the expansion rate increases with rising temperature and Ca/Si ratio. Under high temperature and high Ca/Si ratio conditions, the reactivity of water molecules is enhanced, promoting hydrolysis reactions and the formation of hydroxyl groups, and type I defect rapidly expands, significantly affecting the structural stability of gel. The results of this study provide theoretical support for improving the performance of concrete in extreme environments such as fires.

Key words: C-S-H gel, high temperature environment, type I defect, Ca/Si ratio, molecular dynamics simulation, reactive molecular dynamics

CLC Number:

TU528.1

SUN Ming, TANG Qingyin, GUO Haoran, WANG Pan, YUAN Xiongzhou. Reactive Molecular Dynamics Study on Thermal Stability of Type I Defect C-S-H Gel Phase[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2025, 44(6): 2046-2059.

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