Construction company Heijmans Infra used self-healing concrete to build a pilot project, a railway underpass in Rijen, the Netherlands, for the first time.

The pilot project is a collaboration between Heijmans and railway company ProRail, and aims to test the waterproofness of self-healing concrete. Self-healing concrete needs only half the amount of horizontal reinforcement steel than traditional concrete, which can lead to major savings in CO2 emissions. In addition, self-healing concrete lives up to its name by filling cracks in the material by itself, which increases the lifespan of structures.

Self-healing concrete is made by certain additives, which consists of bacteria and nutrients The microbiological procedure was developed at TU Delft (read more about it here) and has been commercially available for a few years now. The bacteria are activated when they come into contact with oxygen and moisture, like the concrete is damaged. When activated, they create a layer of limestone, filling the cracks.

For the project in Rijen, a mixture of six kilograms of bacteria spores and nutrients was used for every cubic metre. A wall of self-healing concrete was applied in a basement located under one of the concrete tunnel entrances. By using self-healing concrete, Heijmans was able to reduce the amount of horizontal reinforcement steel with 35 per cent across the 25-metre wall. It is the first project in which a combination of self-healing concrete and the reduction of horizontal reinforcement was used.

Photo: Heijmans Infra