Critical Review of Nanomechanical Properties of Calcium (Alumino) Silicate Hydrates: Test Methods, Influencing Factors, and Enhancing Strategies
Jiawei Wang, Stuart McElhany, Zhangli Hu, Jiaping Liu, Carlo Carraro, Paulo J.M. Monteiro, Roya Maboudian
Abstract
The mechanical properties of calcium (alumino) silicate hydrates (C-(A)-S-H) represent a critical focus within the cement and concrete industry. This review begins by summarizing particle- and subparticle-scale models of C-(A)-S-H. Building on these models, the effects of chemical composition and microstructure on the intrinsic mechanical properties of C-(A)-S-H, as determined by high-pressure X-ray diffraction, are described. Existing studies have demonstrated that increasing the Ca/Si ratio and Al incorporation enhances the intrinsic mechanical properties of C-(A)-S-H. Advanced techniques, such as high-pressure Raman spectroscopy and synchrotron radiation-based techniques, have been employed to elucidate the origins of intralayer sliding and preferred intragranular orientation, offering insights into the fundamental mechanisms of creep. Compared with intralayer sliding, the preferred intragranular orientation of cement-based materials significantly contributes to creep in C-(-A)-S-H, establishing a direct link to macroscopic creep behavior. Based on these findings, this review summarizes several “bottom–up” strategies for strengthening and toughening C-(A)-S-H.