Exploring crystallization pressure limits via molecular simulation

Crystallization pressure can cause significant damage to various materials, particularly cementitious materials and geomaterials. Understanding the mechanism behind this pressure is essential to preserve these materials and limit their degradation. Although the phenomenon has been known for a long time, the results from theoretical calculations and experimental observations remain very heterogeneous. The confined crystallization process relies on the presence of a nanometric wetting film at the interfaces to sustain crystal growth. The conditions for the existence and stability of these nanometric films, as well as their transport properties, remain largely unknown due to the great difficulty of studying them experimentally. In this paper, we determine by molecular simulation the limits of the crystallization pressure phenomenon at the finest scale. We perform hybrid configurational bias Monte Carlo-molecular dynamics simulations to determine the critical pressure at which the wetting film separating the crystal from the pore surface disappears under various temperature and pressure conditions. We illustrate the influence of the wetting film's composition on the crystallization process by comparing a confined pure water film to a confined brine solution film. The obtained results enable us to establish both an upper and a lower boundary for the crystallization pressure, to define the range of applicability for the existing theoretical equations, and to identify the limiting factors affecting the transport properties in the constrained films.