Self-Healing Bio-Concrete from a Process-Driven Perspective: A Review of Mechanisms, Challenges and Multi-Scale Simulation Methods

Abstract

Microcracks in concrete are a key factor affecting structural durability, and traditional repair methods struggle to achieve the long-term sealing of deep-seated microcracks. Self-healing bio-concrete, based on the technology of microorganism-induced calcium carbonate precipitation, utilises pre-embedded microbial repair agents to mimic the self-healing mechanisms of living organisms, thereby offering a solution to the problem of microcracks in concrete. However, current research in this field has yet to establish a quantitative framework linking the successive stages from damage perception to functional recovery. To this end, this paper critically reviews the core process-driven mechanisms of this technology, covering the complete chain from damage sensing and triggering, mass transport and microbial metabolism to the formation of mineralisation products and functional recovery. Furthermore, this paper identifies three major bottlenecks: the survival of bacteria in harsh matrix environments, the adverse impact of carriers on mechanical properties, and performance discrepancies between laboratory conditions and on-site conditions. Building on this, this paper further explores key influencing factors such as the selection and cultivation of alkali-tolerant microbial strains, the optimisation of carrier systems, and temperature control. In particular, the paper introduces multi-scale numerical simulation methods to establish coupled convection–diffusion–reaction mass transfer equations within cracks as well as kinetic models for substrate consumption and urease-catalysed microbial processes. These models enable the quantitative prediction of reagent concentration fields, the evolution of supersaturation, and the time required for complete crack sealing whilst taking into account the regulatory role of extracellular polymers. This paper aims to advance research into self-healing bio-concrete from an empirical trial-and-error approach towards predictable, rational design. It also recommends that future efforts should focus on the development of self-sensing and self-adaptive healing systems and on the durability assessment of self-healing bio-concrete under real-world service conditions.