Augmenting Microbially Induced Carbonate Precipitation of Soil with the Capability to Self-Heal

Microbially induced carbonate precipitation (MICP) is increasingly being explored as a potential ground improvement mechanism, both for improved mechanical performance and groundwater control. However, the formation of a brittle cemented monolith will produce structures susceptible to chemical or physical deterioration over time, requiring potentially costly maintenance in the future. We present a demonstration of the potential for a simple and durable self-healing mechanism to be incorporated within the MICP process that allows the monolith to automatically respond to and heal damage. By selecting a bacterium capable of both causing MICP and surviving long periods and harsh conditions as a spore, it is demonstrated that such an organism can be entombed within calcium carbonate precipitates of its own making, survive in a senescent state, and ultimately germinate upon damage to the encapsulating precipitate matrix. The organism is then capable of producing further calcium carbonate to heal the damage. It has further been shown that this mechanism can be used to initially cement a mass of sand, survive damage and deterioration, and respond to restore the functionality of the stabilized mass, exhibiting the potential for such a system to provide "smart" autonomous stabilized soil structures that offer enhanced durability and reduced maintenance. (c) 2020 American Society of Civil Engineers.