Living concrete

Tomorrow’s materials for ecosystem protection

29/04/2024

Use and problems of concrete

At present, the materials used in the construction of urban spaces and dwellings are an increasing problem because of their not insignificant environmental impact.

This aspect is made even more evident when one considers that among the primary needs of a human being is the need to have a shelter in which to feel protected, a home, and that concrete, i.e. the material through which this need is mostly met, registers about 5% of global CO2 emissions.

Therefore, there is an urgent need for a review of the ways in which we build. Before we even delve into the world of the most advanced research technologies in the world of bioengineering, it is first necessary to take stock of the materials we already have, concrete for that matter, and identify why this is now to be considered obsolete.

An initial clarification should be made regarding the term cement, with which it is too often confused: if concrete is the main element for erecting a dwelling, cement is nothing more than the glue, an ingredient in a more complex recipe that includes, in addition, large quantities of water, aggregates and additives. And it is this binder that pollutes disproportionately: contained within it is clinker, a component made of limestone and clay that, when fired at 1,400°C, are responsible for the emission of roughly one ton of CO2.

With these considerations in mind, researchers around the world are increasingly turning to designing new materials whose production process is less polluting. Among the proposed innovations is so-called living concrete.

Futuristic vision: living concrete

Also known as the «Frankenstein material» because of its ability to self-regenerate, living concrete stands as one of the most promising solutions in construction.

Born from the ingenuity of Wil Srubar, an American engineer as well as an associate professor at the University of Colorado Boulder, it was first heard of in 2020 when it appeared to the general public in Matter magazine, and then was also mentioned by Amos Zeeberg in the New York Times in the January 15 edition of that year.

As the article makes clear, the revolutionary material literally comes to life by questioning a «frozen» and antiquated method of making concrete, thus leaving room for creativity: the interdisciplinary team did nothing more than combine cyanobacteria of the genus Synechococcus, which through the process of photosynthesis absorb carbon dioxide and produce sugars, with warm water, sand and gelatin. Stored in a dry place and at room temperature, over the course of a few days these undergo a gradual process of sedimentation, giving rise to a compound with a gel-like consistency; thus the equivalent of concrete but sustainable is obtained.

From theory to facts: the pros and cons

Many pros and just as many cons emerge from the avant-garde project. In its conceptual form, in fact, the material enjoys several advantages: first of all, it is obtained in a relatively short time (about 24 h) and, more importantly, it does not pollute at the various production stages.

It is also capable of reproducing in considerable quantities precisely by virtue of the fact that we are talking about a living compound: once the cyanobacteria are left in a nutrient-poor and dehydrated environment, they enter a state of quiescence allowing the material to harden, a fundamental characteristic for any building material. The moment, however, they are returned to a condition of moisture and sustenance, the bacteria reactivate and thus allow the brick to regenerate. In potency, therefore, cutting a living concrete brick in half and adding water, sand and gelatin to it yields two; this process can be repeated more than once.

Among the application areas in which the longevity of living concrete comes in most handy are all those cases in which there is damage to a building: in fact, standard concrete, however strong it may be, once cracked is difficult to repair. With Dr. Srubar’s invention, on the other hand, is sufficient to reactivate the feeding circle of bacteria and the «injured» part repairs itself.

However, not all that glitters is gold: in fact, living concrete is not without its flaws, chief among them being the lack of strength equal to that of its more polluting counterpart. As Wil Srubar himself explains, it is more accurate to describe his invention as a compound more akin to mortar.

How far does bioengineering go?

In the light of such technology, it now arises to reflect on the question related to the macro-category of engineered living materials (also known as ELMs).

In fact, from the synergy between studies in the purely engineering field and the established notions derived from biology comes the attempt to respond to all those needs and tasks we are «victims» of and witnesses to on a daily basis, starting from finding a solution to help people with disabilities, to applications in favor of the environment.

The Massachusetts Institute of Technology (MIT), of the Department of Engineering and Materials Science, is working in this direction, aiming to develop engineered solutions that positively affect society. The aim is to understand and manipulate materials in order to create new, less impactful ones.The scope of research ranges from studying technologies exploited by ancient peoples in America (think ceramics, glass rather than the characteristic tumbaga of the Incas), to perfecting metal production techniques, to using X-rays and spectroscopy to investigate the chemical and physical structure of what the team calls soft matter materials, namely polymers, foams and gels.

At this point the question begs to be asked: what other milestones will be conquered by bioengineering?

Sofia Martino

Graduated in Journalism, Editorial Culture and Multimedia Communication from the University of Parma, she loves interfacing with new realities. An aspiring traveller, she has a keen eye for ecology and human rights. In Atmosphera Lab she has found a valuable ally to communicate what is closest to her heart.