The idea of a concrete that could heal cracks and decay by itself is one that has fascinated materials science researchers for decades, particularly following evidence that a similar system could have helped preserve Ancient Roman concrete buildings and monuments.
What was believed to have been a mistake is now believed to have been part of Roman experiments into improving the durability of concrete.
However, to what extent is self-repairing concrete feasible, and could it change how concrete repairs are undertaken?
Self-repairing concrete typically consists of pockets of calcium, and when combined with moisture, it reacts and releases calcium-rich minerals that fill in the gaps.
A similar approach, nicknamed “living concrete”, uses bacteria to induce the process and create stronger repairs.
A study published in Innovative Infrastructure Solutions aimed to not only prove the principle that concrete mixed with this calcium-producing bacteria can help to seal cracks, but also how different cracks and concrete mixing methods can affect this process.
The study, led by Yongchao Zhou from Chang’an University, found that the biggest difference in the performance of living concrete came from the type of crack. Horizontal hairline cracks were easiest to fix, with vertical and diagonal cracks demonstrating increased issues.
The study did not examine the effects of different methods of mixing concrete, which can affect the ability of bacteria to heal the concrete; limited food, curing heat and drying rate could all affect the survival of bacteria and thus their ability to repair the concrete around them.
These elements have kept an undeniably transformative material in the testing phase, but the benefits are particularly significant.
Sealing cracks as soon as possible can help structures to corrode slower, leak less, remove the need for some emergency patching and keep concrete structures functioning for longer.
It cannot entirely heal concrete and larger damage will need specialist repair crews, but it can help reduce the level of work needed and the potential delays caused.