A type of bacteria-based living concrete could one day help reduce the construction industry's environmental impact.
Wil Srubar at the University of Colorado and his colleagues used a type of bacteria, Synechococcus, to create living concrete building blocks in different shapes.
The team combined the bacteria with gelatin, sand and nutrients into a liquid mixture, then placed it into a pre-formed mold. With heat and sunlight, the bacteria produced calcium carbonate crystals around the sand particles, in a process similar to what leads to the formation of shells in the ocean.
Once cooled, the gelatin solidified the mixture into a gelatinous form. Once this gel thus obtained was dehydrated (a process that lasted several hours) the material reached the hardness necessary for use in construction.
The team compared the living material to cement and concrete. It is a mixture of gravel, sand and cement combined with water. But its mechanical properties are more similar to mortar, a weaker material usually made with cement and sand. It does not yet have the strength of normal bricks, but they are working on it.
The advantage of living cement? It multiplies by itself
An advantage of using bacteria to create concrete is that if they are not completely dehydrated, they continue to grow. One brick can be split to create two, just add sand and nutrient solution. The team demonstrated that a living brick can “reproduce” itself into eight bricks after several divisions.
“If we refine the process and use species of bacteria that grow at faster rates, we can theoretically move from a linear production approach to an exponential production approach”, he claims Šrubař.
The process can make the production of cement, which is otherwise wasteful for the environment, more eco-sustainable. Concrete is the second most consumed material on earth after water. For this reason this research, and others on the biocemento, they are really important.
The work was funded by DARPA (US Defense Advanced Research Projects Agency), and Srubar says the team is now in talks with the US Department of Defense to scale up production of this biomaterial and pilot its use in construction.
Research reference: Matter, 10.1016 / j.matt.2019.11.016
