Please see the end of this post below for a related and most interesting December 7, 2016 update on a related new development on an experimental material called programmable cement.
While nearly all new technologies, products and services vigorously try to keep any bugs out, a modern improvement in an ancient technology that nearly everyone in the world still, well, heavily relies upon is based upon deliberately keeping all of its bugs in.
A microbiologist named Henk Jonkers at Delft University of Technology in the Netherlands, has created self-healing concrete involving bugs of a biological rather than electronic nature. The remarkable story of how he has accomplished this was reported in an article on Smithsonianmag.com entitled With This Self-Healing Concrete, Buildings Repair Themselves, by Emily Matchar, posted on June 5, 2015.
I will sum up, annotate and ask a few additional microbe-free questions.
Taking his inspiration from human biology, Jonkers has created this self-healing material by embedding concrete with limestone capsules. When the limestone is activated by “cracks, air or moisture”, it will then produce one of two forms of bacteria plus another compound called calcium lactate. In turn, these bugs will commence reacting with the calcium lactate to convert it to another chemical called calcite which then seals the cracks.
This advance could potentially solve an enduring problem when concrete is used in construction: Micro-cracks that develop later and, over time, may affect the structural integrity of a building. Moreover, further “leakage” like this in a structure can eventually result in a collapse. Jonker’s creation could put a halt this corrosive activity. The two strains of bacteria that emerge from the limestone can potentially remain “dormant for as long as 200 years”. *
Since 2011, Jonkers has been field testing his self-healing concrete on a lifeguard station which is subject to the corrosive forces at the beach. To date, it remains “watertight”.
The material will be brought to market in 2015 in the forms of “self-healing concrete, a repair mortar and a liquid repair medium”, costing between $33US to $44US per square meter. Because of this relatively high expense, it will only be used at first in structures where “leakage and corrosion” are potentially significant factors. Nonetheless, Jonkers is working on less costly alternatives to his formulation. He also expects to scale up production of his new concrete by mid-2016.
Self-healing concrete mixtures have also been under development elsewhere at the following universities:
- In the UK at the University of Bath, Cardiff University, also based upon bacteria (details described here)
- In the US at MIT using “sunlight to activate polymer microcapsules” to fill in cracks (details described here), and
- At the University of Michigan by embedding microfibers in conjunction with calcium carbonate (details described here)
Another potentially environmental benefit from self-healing concrete might be a reduction in the worldwide amount of energy used to produce concrete. Currently, it generates 5% of all of global carbon emissions and demand for concrete continues to rise as a result of growing urbanization. Thus, the increasing usage of self-healing concrete may lower the demand for the more carbon-emitting production of new concrete.
My questions are as follows:
- Can added bacteria likewise bring self-healing capabilities to other building materials such as wood, glass, iron, marble and others?
- In addition to self-healing, are there other beneficial properties that microbes can add to concrete as well as other construction materials?
- Conversely, can microbes be similarly and safely somehow used in the demolition of buildings and the clearing of the resulting debris?
- Are there any possible applications of metamaterials, as covered in the April 10, 2015 Subway Fold post entitled The Next Wave in High Tech Materials Science, to concrete formulations?
There is a common expression among software programmers and developers to try to explain instances when end-users find flaws in their work. They will often, half-jokingly, say “It’s not a bug it’s a feature“. In the case of self-healing concrete, it turns out to be both.
* For a fascinating journey through the several-millennia history of concrete, I very highly recommend Planet Concrete (Prometheus Books, 2011), by Robert Courland. The author has skillfully enlivened and fully engaged his readers in what might otherwise sound like a somewhat dull topic for a book.
December 27, 2016 Update:
A story was posted on Phys.org today entitled Scientists Develop ‘Programmable’ Cement Particles to Attain Enhanced Properties. (No author is credited.) Scientists at Rice University have created a new form of “programmable” cement that, at the microscopic level, forms new shapes that make the resulting hardened product more durable while less porous. In turn, this may result in “stronger structures that require less concrete”. I highly recommend clicking through for a full read of this fascinating news.