Understanding the formation and structure of bio-mineralization for self-healing of marine concrete: An experimental and thermodynamic approach

In marine engineering, infrastructures are facing serious issues of deterioration resulted largely from concrete cracking due to the hostile seawater environment. Microbial induced carbonate precipitation (MICP) is an effective and environmentally friendly way to achieve self-healing of concrete cracks. However, the formation and structure of MICP products for crack healing in seawater remain unclear, thus hindering the application of MICP in self-healing of marine structures. By means of experimental and thermodynamic approaches, this work first investigated the evolution of aqueous species as well as the phase assemblages and microstructures of biominerals in compound solutions simulating concrete cracks in seawater. The coupling effects of Mg2+ and bacteria on bio-mineralization kinetics result in significant discrepancy between experimental results and thermodynamic outputs in terms of phase assemblages in seawater, yet the morphology depends on Mg2+ rather than bacteria. A comparative analysis on healing products collected from real concrete cracks in seawater revealed a fast abiotic precipitation of brucite followed by the MICP process, which is more conducive to attain a high-efficient self-healing in marine environment.