Self-healing concrete could end cracked walls
When buying a brand new apartment or house, you need to keep in mind that it can take a few months or even years for these properties to settle after construction, and minor cracks in walls are likely to occur.
However, wouldn’t it be nice if we could build buildings that are crack resistant and not have to worry about filling in the cracks?
The most common type of building material is concrete due to its long life, non-combustible material which makes it fire-safe as well as being an economical material. However, concrete is susceptible to cracking, especially under tension as well as becoming weaker over time when exposed to harsh elements including, wind, rain and temperature changes.
Henk Jonkers and Eric Schlangen, researchers from Delft Technical University in Netherlands have come up with a solution called Bioconcrete, a brand new self-healing material.
Bioconcrete is a concrete mixture embedded with calcite-precipitating bacteria which gives concrete self-healing capabilities. The two components bacillus spores and calcium lactate nutrients are each separately set into expanded clay pellets which are just a few millimetres in size and then added to the wet concrete mix.
When cracks do start to form in the concrete, water that enters the concrete will open up the pellets allowing the bacteria to germinate and feed on the lactate. This in turn mixes with the calcium and carbonate ions to form calcite or limestone.
By using bioconcrete this can lead to dramatic cost savings, especially in steel reinforced concrete and the time and money it takes to repair or replace these cracked walls. It would also be ideal to use when constructing underground retainers for hazardous waste materials, due to no one needing to go and repair the damage, as well as helping to decrease CO2 emissions, benefiting the environment.
Both Jonkers and Schlangen have been working on this material for 10 years now and full scale testing has already begun, where a building in the South of Holland has been covered with bioconcrete and will be monitored closely over two years. Currently, cracks up to 0.5mm in size can be healed and the researchers are now looking to heal much larger cracks.
But bioconcrete does not just help repair cracks. It can also filter rain water, turning it into safe drinking water. This occurs when the bioconcrete is placed on the roof of a building, allowing it to set the pH to the correct range and soften the rain water. This rainwater then runs from the roof and into a cistern providing drinking water that is safe to drink without the need to add chemicals.
With only a limited amount of freshwater available around the world, the use of bioconcrete could certainly provide many solutions to the world’s sustainability issues.
Published on 9th of February 2015 by Marty Stanowich