Concrete is the most commonly-used building material in the world, but it has a significant problem. It tends to develop cracks and if the cracks become large enough, the steel rods used to reinforce the concrete can corrode, weakening the concrete and thereby weakening the structure. Builders usually compensate for this by using more steel reinforcing rods, but steel is expensive. If there were a way to prevent these cracks, or to easily repair them, (1) the cost of building with concrete might be reduced because less steel would be required and (2) the concrete structures could be made to last much longer.
When they experience deterioration, living things typically possess the ability to heal themselves. What if concrete could be given some degree of “aliveness” so that it could somehow heal itself? That is exactly what some researchers at the Delft University of Technology in the Netherlands are trying to do. Dr. Henk Jonkers is experimenting with bacteria which can not only withstand the extremely alkaline environment in concrete, but produce calcite – basically limestone – which would in effect build new concrete to repair a crack. Initial testing has shown that the bacteria can indeed survive this environment. Like many new technologies, the cost of this technique is currently high. But – also like many new technologies – the cost is expected to drop significantly as development proceeds.
It seems very reasonable to believe that, as the costs come down, a break-even point will be reached where the cost of implementing this technique just equals the repair and replacement costs saved. After that, it seems like it would be a very viable way of reducing the life-cycle cost of a concrete structure. Furthermore, if the physical sciences and the biological sciences can be combined to produce self-healing materials, what other materials might be able to fix themselves – heal themselves – in the not-too-distant future. Whatever materials come out of this fascinating technology are sure to be of use to architects, designers, and builders.