Aluminum-induced structure evolution and mechanical strengthening of calcium silicate hydrates: an atomistic insight

作者：Kai, Ming-Feng; Li, Gen; Yin, Bin-Bin^*; Akbar, Arslan^*

来源：CONSTRUCTION AND BUILDING MATERIALS, 2023, 393: 132120.

DOI：10.1016/j.conbuildmat.2023.132120

• Calcium aluminosilicate hydrate (CASH)
• Atomic structure
• Diffusive characteristics
• Mechanical properties
• Reinforcing mechanisms

How Al3+ dissolved from supplementary cementitious materials influences the performance of cement paste is far from being fully understood, especially from an atomistic insight. Herein, Al3+ is introduced into calcium silicate hydrate (CSH, the main phase of cement paste) to evaluate its effect using atomistic simulation. Structurally, Al3+ heals defects in the silicate chains, forms cross-links between calcium aluminosilicate layers, and reduces interlayer space and H2O content. The chemical stability of interlayer H-bonds and Ca-O bonds is also improved. The diffusion of the interlayer H2O and Ca2+ is decelerated, attributed to Al-induced channel blocking and stronger interfacial adhesion with the calcium silicate layers. Mechanically, the Al-induced chain bridging enhances the load-bearing capacity of aluminosilicate chains along y direction, resulting in - 57.1% and - 100.4% enhancement of Young's modulus and tensile strength. In z direction, the cross-links provide ultra-strong connections between the layers by raising Young's modulus and strength by - 4 and - 6 times. This study provides profound guidance for future design of environmental-friendly cement with promising mechanical properties and durability.