Effective Interactions between Calcium-Silicate-Hydrate Nanolayers

Calcium-silicate-hydrate (C-S-H), the main binding phase in cementitious materials, possesses a complex multiscale porous texture where nanosized particles interact effectively and contribute to the macroscopic properties of concrete. Engineering the morphology and properties of cementitious materials can thus be obtained by, first, studying the impact of the variable chemical composition on the cohesion and properties of nanolayers of C-S-H at the nanoscale arid, then, translating these information to the mesoscale so that a textural analysis can be accomplished. Here, we aim to establish a foundation for such a comprehensive study. First, we construct variable atomic structures of C-S-H nanolayers and validate them against experimental measurements. Then, we conduct free energy perturbation analysis to measure the potential-of-mean-force (PMF) between C-S-H nanolayers with varying chemical compositions. We find a strong correlation between the chemical composition as well as polymorphic structure of C-S-H and characteristics of measured PMFs. In particular, we observe a transition in PMF shape from a single minimum to multiple minima, indicating the emergence of metastable states in the interparticle interactions. We show that key mechanical properties of C-S-H calculated via the PMF approach are in a reasonable agreement with the available experimental data. The proposed PMFs can be directly used to investigate the textural attributes as well as the study of the hydration process in cementitious materials.