Atomistic mechanisms govern nanoscale friction and instability in cement hydrate

An atomistic movie of a sliding friction between a tip and substrate that represent cement hydrate. While the electrostatic forces govern the interfacial interaction at short and large inter-particle distances, the van der Waals force are more pronounced for variations in the normal force at intermediate distances.

Calcium-Silicate hydrate (C-S-H) gel is the primary binding phase in cement paste and the main source of mechanical properties in concrete. C-S-H is typically considered as an assemblage of discrete nanoscale particles whose interactions are governed by nano-scale friction and cohesion. For a particulate material such as C-S-H, interparticle forces are of paramount importance when it comes to mechanial properties. However, due to variable stoichiometry, adsorbed surface ions and disordered nature of C-S-H at the nanoscale, it is quite difficult to measure or model the interparticle forces. This project employs a multiscale computational framework utilizing the fundamentals of material science rooted in subatomic properties to tackle this issue and link non-intutive nonoscale features to macro scale properties through overlapping hierarchical modeling techniques. In particular, reactive atomistic simulation can serve a “powerful lens” to decode the complex nanoscale interactions. The overarching goal is to study how intrinsic interparticle interactions, such as nanoscale friction, defects, cracking and fracture in cement hydrates impact the mechanics and safety of concrete infrastructures. Here, we are particularly interested to identify atomistic deformation-based mechanisms or “unit processes” that govern defect nucleation, strain localization, instability and fracture in cement hydrate. The research outcomes are expected to pave a path toward a predictive design of cementitious materials while devising strategies to curb their negative environmental impacts.