  The forces exerted by growing crystals on the surrounding materials play a
major role in many geological processes, from diagenetic replacement to rock
weathering and uplifting of rocks and soils. Although crystallization is a
nonequilibrium process, the available theoretical prediction for these forces
are based on equilibrium thermodynamics. Here we show that nonequilibrium
effects can lead to a drop of the crystallization force in large pores where
the crystal surface dissociates from the surrounding walls during growth. The
critical pore size above which such detachment can be observed depends only on
the ratio of kinetic coefficients and cannot be predicted from thermodynamics.
Our conclusions are based on a physical model which accounts for the
nonequilibrium kinetics of mass transport, and disjoining pressure effects
within the thin liquid film separating the crystal and the surrounding walls.
Our results suggest that the maximum size of the pores that can sustain
crystallization forces close to the equilibrium prediction ranges from
micrometers for salts to a millimetre for low solubility minerals such as
calcite. These results are discussed in the light of recent experimental
observations of the growth of confined salt crystals.
