Concrete is the most produced material in the entire world and contributes to more than 8 per cent of global CO2 emissions. Introduced as a new form of concrete in 2006 by Professor Henk Jonkers, a microbiologist at Delft University of Technology in the Netherlands, self-healing concrete ‘heals’ or ‘repairs’ damaged surface cracks on occurrence. It contains microcapsules and fibres that release healing agents like bacteria and fungi into the concrete mix. When cracks forms on the surface of the concrete, these agents come in contact with oxygen and water and release calcium carbonate to fill the cracks automatically, this heals the concrete and restores its structural integrity and durability for years. Applications Self-healing concrete’s primary application is structures that are not easily accessible for repair and maintenance, like heavy bridges, underground tunnels, marine structures, etc. It also has strong application in marine and offshore construction that is prone to water seeping in, affecting the reinforcement and leading to structural failure. While there are projects where self-healing concrete is used as a replacement for conventional concrete in some parts of the structure, a structure solely made from self-healing concrete is not yet present. R&D Much research is underway to increase the effectiveness of self-healing concrete. Professors from IIT Roorkee and some NITs, including others, have published papers on this subject. A company called Prions Biotech provides a self-healing compound that could be mixed with concrete while companies like Basilisk, Penetron, Krypton, and Hycrete are currently working to develop self-healing concrete. The impact Conventional concrete is made using conventional materials; the mix design is modified and based on the required strength. But as it can’theal its own cracks, lifespan is limited to 30-50 years. In fact, even over a decade, buildings start showing visible cracks owing to harsh weather conditions and internal stresses. On the other hand, self-healing concrete addresses cracks from their micro stage and does not let them grow larger; thus, the bond between concrete and reinforcement is never affected, increasing durability and lifespan. Every year,$ 40billion worth of concrete is used in the repair and restoration of structures that could be prevented to a large extent. This bio concrete will not only reduce the concrete used in repair and retrofitting but also increase the lifespan of new structures, resulting in less consumption of concrete. Current methods of repair and retrofitting require toxic chemicals and heavy machinery, which cause a lot of pollution and affect the environment.Self-healing concrete does not require any external treatment and maintenance, which saves a lot of effort and money for contractors and, in turn, the construction industry. Making self-healing concrete SIDDHARTH KABRA shares his experience “Making concrete that has not been developed before requires much more than physical materials, admixture or microbes. It needs a great deal of research, trials and observations. The concreteI developed has the basic raw materials that go into the making of conventional concrete, namely cement, sand, aggregate and water. But what makes it self-healing are the microorganisms infused in the right way, using special microbiological processes for the microbes to survive in the highly alkaline environment of concrete. There are several parameters to keep in mind while mixing the microorganisms in the concrete, like temperature, medium, method of mixing, proportion, mixing time, adding the right nutrients for microorganisms to grow and survival of microbes in the concrete. The selection of the right nutrients for the microbe is as crucial as selecting a microbe itself as different microbes respond to different nutrients. Even after successfully keeping all the important factors in mind, there is a high chance the healing process will not initiate. There are several parameters, like methods of curing and water temperature,which also need to be considered postmixing and casting a cube of self-healing concrete to achieve observable results and retrieve calcium carbonate samples from it to conduct confirmatory tests.”About the authors: Prof Bhargav Tewar has been teaching at CEPT University for over 13 years. He is associated with subjects such as concrete technology, construction technology and project estimation. His research interest is in the development of special concrete and industrial waste utilisation in construction. Siddharth Kabra is a civil engineering student pursuing his bachelor’s in construction technology at CEPT University. His curiosity and enthusiasm lie in the field of material sciences and research to address real-world challenges.