Atomistic origin of kinetics in hydrated aluminosilicate gels upon precipitation

Cheng Zhao; Jiahui Yu; Xuyong Chen; Qiaoyun Wu; Wei Zhou; Mathieu Bauchy

doi:10.1063/5.0165937

Atomistic origin of kinetics in hydrated aluminosilicate gels upon precipitation

J Chem Phys. 2023 Oct 14;159(14):144501. doi: 10.1063/5.0165937.

Authors

Cheng Zhao^{1

2}, Jiahui Yu^{1

2}, Xuyong Chen^{1

2}, Qiaoyun Wu^{1

2}, Wei Zhou³, Mathieu Bauchy⁴

Affiliations

¹ School of Civil Engineering and Architecture, Wuhan Institute of Technology, Wuhan 430074, China.
² Hubei Provincial Engineering Research Center for Green Civil Engineering Materials and Structures, Wuhan 430074, China.
³ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China.
⁴ Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA.

PMID: 37811823
DOI: 10.1063/5.0165937

Abstract

Calcium-alumino-silicate-hydrate (CaO-Al2O3-SiO2-H2O, or C-A-S-H) gel, which is the binding phase of cement-based materials, greatly influences concrete mechanical properties and durability. However, the atomic-scale kinetics of the aluminosilicate network condensation remains puzzling. Here, based on reactive molecular dynamics simulations of C-A-S-H systems formation with varying Al/Ca molar ratios, we study the kinetic mechanism of the hydrated aluminosilicate gels upon precipitation. We show that the condensation activation energy decreases with the Al/Ca molar ratio, which suggests that the concentration of the Al polytopes has a great effect on controlling the kinetics of the gelation reaction. Significantly, we demonstrate that 5-fold Al atoms are mainly forming at high Al/Ca molar ratios since there are insufficient hydrogen cations or extra calcium cations to compensate the negatively charged Al polytopes at high Al/Ca molar ratios during accelerated aging.