A time-varying model for predicting crack closure in microbial self-healing concrete after incorporating encapsulated agent

Cracks in concrete might undermine structural integrity, accelerate harmful substances to pass through, result in deterioration of concrete matrix and potential reinforcement corrosion, and then increase the maintenance and repair costs of structure. To mitigate these effects, the microbial self-healing concrete (MSC) has emerged as a promising solution among self-healing technologies. This paper presents an integrated numerical model to predict crack closure in MSC by combining simulated crack spaces with two sub-models, i.e., agent release model and self-healing model. The crack spaces created through digital image processing (DIP) method or Rigid Body Spring Model (RBSM) are used as initial boundary conditions for the agent release model. The agent release model can quantitatively describe the transport of self-healing agents, while the self-healing model is able to reproduce the reduction of local crack widths induced by Microbially Induced Calcium Carbonate Precipitation (MICP). Key features of the proposed model include accounting for the effects of boundary fluctuations and local crack width variations on crack closure process. Parametric analyses reveal that the healing ratio is significantly influenced by factors such as healable depth, environmental conditions, as well as the diffusion and consumption coefficients of healing agents. Moreover, the reduction in local crack widths (i.e., crack closure) is also presented through visualizing the formation of calcium carbonate within both cracked MSC specimens and simulated crack spaces.