Elucidating deposition process of calcium carbonate and mechanical properties of precipitation via molecular dynamics simulation

Abstract

Brittle cracking is a critical issue affecting the load bearing capacity and service life of concrete. Microbially induced calcium carbonate precipitation can heal concrete cracks, but the relation between its microscopic morphology and macroscopic mechanical properties remains poorly understood. This study employs molecular dynamics simulations to investigate the deposition processes of calcite and aragonite unit cells on calcium carbonate substrates. The deposition process of a single unit cell can be divided into two stages: collision rebound and adsorption. The deposited unit cells combine to form amorphous calcium carbonate. Local disordering of substrate upper-surface caused by unit cell collision reduces the tensile strength of the substrates, while the ductility of amorphous precipitations enhances its failure strain. The deposition velocity significantly impacts the mechanical properties of the precipitations. At higher temperature, greater molecular mobility enhances cohesive strength within the precipitations. Aqueous environments can weaken the collisional impacts of deposited unit cells on the substrate. Matching the substrate and deposited unit cell types facilitates ordered structures and strengthens precipitations. This work deepens the understanding of deposition process of calcium carbonate on the substrate and the mechanical properties of precipitations.