No matter where you are in Canada, you're most likely going to come across a building made with concrete. It's been an integral part of infrastructure for decades. The formulations have changed over the years but most modern mixtures contain rocks, sand, limestone and clay. The end product is touted to last for decades without succumbing to decay and offer the perfect backbone to any development.
But while total collapse won't happen for generations, the integrity of these structures can falter, particularly in the form of fissures. Many start at the microscopic level, only a few thousandth of a millimetre in size. But they can grow quickly and become visible within a matter of days to weeks taking the shape of large cracks and gaps. Without proper remediation, the entire structure could be at risk.
Most of the problems may appear to be unpreventable as they are caused by factors we cannot control such as weather or a necessity for use. The only answer appears to be reactionary in nature; as soon as a crack or hole is seen, it's patched up by construction crews. But this is by no means perfect and many problems go unresolved. At this point, urban decay can set in and lead not only to eyesores but also to public health concerns.
But there may be a preventative measure: add bacteria. Although it may seem illogical, the idea of adding microbes to concrete may offer the hope we need to heal those microscopic fissures and cracks before they become troublesome. In the last few months, the concept has jumped from the research lab to the commercial arena and is now being considered by numerous areas worldwide.
The idea of a bioconcrete has been around for about 15 years although getting to a point of a viable usable option has been somewhat difficult. The process is rather straightforward. When putting the concrete together, add in some bacteria and also food for growth. It seems simple enough but in order to meet the requirements for tensile strength, the bugs and the nutrients would have to meld in the mixture without causing any problems.
The answer came in the form of bacteria that literally use salts for food and energy. They are known as the Bacillus and Sporosarcina genera. These bacteria are naturally found in alkaline environments and survive there using a rather interesting mechanism. They use milky-like substances, such as calcium lactate, a main component of baking powder, for nutrition. Then, when done, they send out the waste in the form of calcium carbonate, also known as limestone.
There was an added advantage. Unlike most bacteria, these genera had the ability to form spores, meaning they could lie dormant for years, if not centuries and still remain viable. This offered the opportunity to not only maintain concrete in the short-term but also to ensure troubles would not arise for decades or longer meaning less costs for maintenance and a reduced chance of creating those eyesores.
The combination of characteristics made these bacteria seem perfect. But they still needed to be tested. This happened in 2007. The bacteria passed the tests with flying colours. As expected, the cells ate up the nutrients inside the concrete and then formed a strong, tensile, limestone byproduct. The crack eventually disappeared. But even more exciting was the fact the concrete in that area was just as if not more sturdy than before. Not only had the concrete been healed, it had been made stronger.
There was however a small catch. The bacteria seemed to work quite effectively over the first few months. But then their ability to heal seemed to wane as time went on. The reason came down to the overall degradation of the bacteria over time in the harsh climactic conditions. But this was easily aided by switching the concentration of the clay to protect the spores.
This initial testing confirmed the premise yet the system could be optimized. By 2013, several species and strains of bacteria showed higher levels of limestone production than others. This not only improved crack-healing ability but also provided focus to the concept. With the strains in place, upscaling could begin so bioconcrete could be made available for commercial interests.
The concrete is almost ready to make its debut in the marketplace and so far there seems to be good interest. The only issue seems to be the cost, which is about twice the amount of regular concrete. Yet the front-end expenditure may balance out with less maintenance and repair costs over time. As for those structures already in place but in dire need of help, there may also be a solution. Bacteria-based fillers are being developed so they can be added straight to existing structures.
Bioconcrete is nearly at the tipping point and appears to be just a few months to years away from being the next wave of concrete development. Although this may start off as a fad, there is good reason to hope it lasts. For countries where concrete issues are common, this may be the perfect option to help stabilize the next generation of buildings. More importantly, it may help prevent unnecessary urban decay and the associated troubles it brings.
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