Self-Healing Phenomena in Cement-Based Materials — State-of-the-Art Report, TC 253-MCI
About this book
The RILEM State-of-the-Art Report on Self-Healing Phenomena in Cement-Based Materials (TC 253-MCI), published as part of the RILEM State-of-the-Art Reports series, synthesizes the scientific and engineering knowledge on the spontaneous or engineered ability of concrete and other cement-based materials to repair damage — particularly cracks — without human intervention. RILEM (Réunion Internationale des Laboratoires et Experts des Matériaux, Systèmes de Construction et Ouvrages) is the international union of testing and research laboratories for materials and structures. Self-healing in cement-based materials has been recognized as a natural phenomenon since the early twentieth century: narrow cracks in concrete structures exposed to water frequently seal themselves through continued cement hydration, precipitation of calcium carbonate (autogenous healing), or deposition of material transported by water flowing through the crack.
The report provides a comprehensive scientific account of these natural healing mechanisms, quantifying the conditions (crack width, water availability, age of concrete, temperature) under which autogenous healing reliably occurs and the degree of strength and impermeability recovery that can be achieved. Beyond autogenous healing, the report addresses a range of engineered self-healing approaches that have been developed to enhance and extend the natural capability. These include the incorporation of bacteria into concrete mix designs — spore-forming bacteria that survive the curing process, become activated by water entering cracks, and precipitate calcite to fill the crack; the encapsulation of healing agents such as epoxy, cyanoacrylate, or isocyanate adhesives in microcapsules or hollow glass fibres that rupture when a crack passes through them; the use of polymers and crystalline admixtures that promote crystal formation in crack networks; and intrinsic healing through the addition of supplementary cementitious materials and fibres that distribute damage more finely.
The application context for self-healing concrete includes infrastructure where crack formation is expected but repair access is difficult — buried structures, marine foundations, tunnels, and water-retaining structures — and where the consequence of water ingress and reinforcement corrosion are severe. The economic and environmental life-cycle benefits of reduced maintenance and extended structural life are analyzed. Sources: RILEM (rilem.net); RILEM TC 253-MCI State-of-the-Art Report; Springer publication; journal Self-Healing Materials.