Micro-capsules and bacteria to be used in self-healing concrete
01 June 2013
A new research project aims to develop novel self-healing concrete that uses an inbuilt 'immune system' to close its own wounds and prevent deterioration.
The life of concrete structures is reduced when the material cracks and water is able to get at the steel reinforcement, causing rust and degradation.
The project, funded by a £2m EPSRC grant and matched by an additional industrial contribution of just over £1 million, will involve researchers from the University of Bath in collaboration with Cardiff University (the lead partner) and the University of Cambridge.
The team at Bath aims to develop a concrete mix that contains bacteria within microcapsules, which will germinate when water enters a crack in the concrete to produce limestone (calcite), plugging the crack before water and oxygen has a chance to corrode the steel reinforcement.
Self-healing concrete could vastly increase the life of concrete structures, and would remove the need for repairs, reducing the lifetime cost of a structure by up to 50 percent.
Over seven per cent of the world’s CO2 emissions are caused by cement production, so reducing the amount required by extending the lifetime of structures and removing the need for repairs will have a significant environmental impact.
The team at Bath will be assessing different species of bacteria to find one that is able to form abundant spores and which will survive and germinate in this environment. The work will involve finding alkaline-tolerant isolates and testing their biology and physiology.
Concrete becomes more dense as it cures, so the pore size decreases to a level where bacteria may be crushed. The researchers are looking at enclosing the bacteria in micro-capsules, along with nutrients and calcium lactate which the bacteria will convert when water becomes present and use to fill cracks in the concrete.
Including bacteria in concrete offers a double layer of protection in preventing steel corrosion. Not only do the bacteria work to plug cracks in the concrete, the process of doing so uses oxygen present which would otherwise be involved in the corrosion process of the steel bars.
The research team will assess the survival of different species of bacteria in the concrete over time. They’ll allow the concrete to mature over certain time periods and then grind it down to create a suspension which can be assessed by biologists for surviving bacteria.
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