Atomistic modelling of crystal structures of Friedel's salts Ca2Al(OH)6(Cl,CO3,OH)·mH2O: Its relation to chloride binding
Journal article, 2025

The diffusion of chloride critically affects the durability of reinforced concrete in exposure environments. Hydrocalumite-like (AFm) phases can bind chlorides to form Friedel's salts, retarding chloride ingress. However, the stability and structural parameters of Friedel's salts with mixed-anion interlayers are not fully understood. First principles computation was performed to provide the energy-minimum crystal structures for Friedel's salt and AFm phases with various substitutions and water contents. It shows that the mixing of Cl− and OH− significantly changes the lattice parameters. However, the mixing of 1/2CO32− and Cl− anion presents little effect on structural parameter. It is energetically favourable and hardly measurable by XRD but decreases chloride binding capacity. The interlayer hydroxide ions show considerable flexibility in terms of occupied sites, which may be a key factor for the stability of AFm phases. The modelling results align with the the structural changes of Friedel's salts reported in previous experiments.

Chloride binding

First principles computation

Friedel's salts

AFm

Author

Liming Huang

Chalmers, Architecture and Civil Engineering, Building Technology

Erik Bialik

Molecules in Motion

Arezou Baba Ahmadi

Chalmers, Architecture and Civil Engineering, Building Technology

Cement and Concrete Research

0008-8846 (ISSN)

Vol. 191 107821

Subject Categories (SSIF 2025)

Physical Chemistry

DOI

10.1016/j.cemconres.2025.107821

More information

Latest update

3/7/2025 1