Aluminum-Induced Interfacial Strengthening in Calcium Silicate Hydrates: Structure, Bonding, and Mechanical Properties

Calcium aluminosilicate hydrate has attracted significant interests, because of its low carbon footprint, while basic questions persist concerning its molecular-level properties. In this work, the material chemistry of C-A-S-H is systematically investigated, and its microstructure at atomic scale is reexamined based on first-principles modeling and simulation. We find that the cross-link between interlayers is crucial for mechanical strengths, which is responsible for similar to 36.2% enhancement of the bulk modulus and similar to 10.0% of shear modulus. Anomalous C-A-S-H exhibits zeolitic features with interatomic Al-O-Si bonding. With the reversible structural transformation and other physical incentives, C-A-S-H can be categorized into soft porous crystals. Aluminum substitution induces interfacial strengthening in calcium silicate hydrates by raising tensile and compressive strength by, similar to 76.1 and similar to 16.9%, respectively. Uncovering these reinforcement mechanisms, including the interlayer strengthening, provides theoretical underpinnings for future design for green cement with ultrahigh performance.