Experimental concrete that patches up cracks by itself is to undergo outdoor testing. The concrete contains limestone-producing bacteria, which are activated by corrosive rainwater working its way into the structure. The new material could potentially increase the service life of the concrete – with considerable cost savings as a result.
The work is taking place at Delft Technical University, the Netherlands. Concrete is the world’s most widely used building material. But it is prone to cracks, which means that structures need to be substantially reinforced with steel. “Micro-cracks” are an expected part of the hardening process and do not directly cause strength loss. Fractures with a width of about 0.2mm are allowed under norms used by the concrete industry. But over time, water – along with aggressive chemicals in it – gets into these cracks and corrodes the concrete.
For durability reasons – in order to improve the service life of the construction it is important to get these micro-cracks healed. The main challenge is to ensure the healing agent is robust enough to survive the mixing process. In order to do so they have to apply coating to the particles, which is very expensive”.
The team is currently trying to reduce the cost this adds to the process. But it’s expected to improve in about six months. The outdoor tests should begin after this, the team is already talking to several construction firms that could provide help.
The concrete will then have to be monitored for a minimum of two years to see how it behaves in this real-world setting.
If the results are good, they will try to commercialise the product. By extending the concrete’s service life the cost will drop extensively.