Concrete is the most commonly used construction material on earth. It’s made from mixing cement, sand, stone and water, and is used in everything from roads and buildings to bridges and sewers.
Although concrete is strong and can withstand a lot of compression, it’s prone to cracking. Steel rods are often used to reinforce concrete structures, so these cracks are a problem, as they allow water to get in and rust the steel, damaging the structure.
To solve this problem, researchers from the University of Bath are investigating how certain species of Bacillus bacteria could be used to make concrete that heals itself.
The three Bacillus species used by the team naturally produce crystals of calcite (a form of calcium carbonate that makes up limestone) when exposed to calcium and CO2. Adding these species to concrete would allow them to seal up cracks as they form, and so prevent any structural degradation.
Repairing concrete structures currently takes a lot of time and money – but it also has a significant impact on the environment. Cement manufacture is responsible for around ~5% of global CO2 emissions, so increasing the lifespan of structures by using self-healing concrete could dramatically reduce their carbon footprint.
The team is currently looking at ways of sealing bacterial spores in capsules that will protect them inside the concrete. Once cracks appear, the capsules will dissolve and provide food and calcium to the bacteria, allowing them to plug the gaps with calcite.