Innovative Concrete That Repairs Itself When Damaged

In 2015, researchers at Delft University in the Netherlands, led by microbiologist Hendrik Jonkers, unveiled a type of concrete material that could fix itself when damaged. This 'bioconcrete' uses bacteria to heal cracks that develop over time. These bacteria are embedded into the concrete while it goes through the mixing process. Along with these bacteria (Bacillus species) are particles of calcium lactate. When the concrete develops a crack, water seeps in and activates the dormant bacillus bacteria, which feed on the calcium lactate. Over time (estimated three weeks), they combine oxygen, calcium ions, and carbonate ions to produce limestone, effectively filling up the crack and thus repairing it from the inside. This discovery is significant because one of the leading causes of structural failure in buildings is tension that accrues from minor internal fractures within their concrete structures. If these micro-cracks enlarge and reach the building's reinforcement bars, it might lead to rusting, which may ultimately result in total failure of the structure. Jonkers' idea was inspired by our human body’s ability to naturally heal itself from cuts and bruises. He wanted to incorporate a similar concept into civil engineering to make better, more sustainable materials. While this self-healing bio-concrete holds excellent potential for future construction projects due to its durability and resistance properties, its cost is also a challenge compared to traditional concrete. However, Jonkers’ team foresaw this problem earlier on and introduced another solution: ‘repair mortar,’ which contains only healing agents in dry form. If any part/tile/outside layer of your building begins cracking too fast or before you expected, this repair mortar - in paste or liquid form - can be applied to the damaged part. This way, only problem areas must be treated at a fraction of the cost. Details of this research were published in research papers found on the Delft University website, and a TED Talk by Jonkers is available for further information.