Tuning interfacial properties of C-A-S-H gels through Al/Si ratio control: Multiscale simulation insights

ABSTRACT Understanding the role of aluminum incorporation in calcium-aluminosilicate-hydrate (CASH) gels is crucial for enhancing cement-based materials’ durability. The presented research employs molecular dynamics simulations and quantum chemical calculations to examine how changing the Al/Si ratio affects the interfacial tension of CASH gels with water. The results reveal that initial aluminum addition increases interfacial tension, while further increases in the Al/Si ratio lead to a gradual reduction, indicating an optimal aluminum content for minimizing solution transport. Analysis of the interface microstructure and lamellar interfacial tension suggests that increased Al/Si ratios contribute to a more homogeneous interface. Molecular interaction analysis shows that calcium is a key factor in interfacial bonding, with aluminum enhancing calcium adsorption and inhibiting its detachment. Quantum chemical analysis confirms that calcium adsorption occurs via electrostatic interactions, with weaker electron localization in aluminum-containing structures. These findings shed light on the mechanism by which aluminum in CASH gels inhibits transportation at the molecular level, offering valuable guidance for designing durable concrete materials.