Mechanisms of ice crystal growth in nanoconfined spaces of cementitious composites at low temperatures: Insights from molecular dynamics simulations

This study investigates the dynamics of ice crystal growth and stress distribution in nanoconfined spaces using molecular dynamics simulations. First, the interaction between the pore wall and coarse-grained water is modified, leading to the development of pore models with varying wettability. Subsequently, the process of ice crystal growth within pores of 10 nm diameter is examined under different temperatures and hydrophobicity conditions. Results unveil that ice crystal growth induces substantial energy and enthalpy alterations within the system. Hydrophobic nanopores demonstrate a protective function by limiting ice crystal growth and water transport, thereby mitigating freezing damage. However, hydrophobic nanopores exhibit increased stress levels when saturated with water. The study employs the Zener pinning theory and mass transfer rates to qualitatively scrutinize the thermodynamic and kinetic interplay between the ice crystal interface and the degree of supercooling. These findings offer insights into the mechanisms of ice formation and stress evolution in nanoconfined environments.