Self-Healing Concrete Produced From Bacteria-Coated Fibers Can be the Future of Sustainable Construction

Inspired by biological self-healing tissues, Drexel University's Advanced Infrastructure Materials laboratory developed self-healing concrete called BioFiber, which prevents cracks from widening and upholds the structural integrity of the concrete.

By integrating fibers coated with bacteria and a hydrogel layer into the concrete, dormant bacteria that were previously inactive can be activated upon the formation of cracks.

(Photo : Pexels/Kyla Rose Rockola )

Development of Self Healing Concrete

The Advanced Infrastructure Materials laboratory at Drexel University drew inspiration from biological self-healing tissues. BioFiber performs three primary roles: it is capable of self-healing, prevents cracks from becoming wider, and maintains its integrity within the concrete even when no cracks are present. These gaps are bridged by the strong core fibers of BioFiber, which also prevent the fissures from getting wider as the healing process progresses.

The hydrogel layer encircles the core fiber and is composed of a molecular-level polymer chain lattice that exhibits an attractive property toward water. Due to its sponge-like structure, hydrogels are capable of absorbing and retaining vast quantities of water. Calcium is added during the manufacturing process to facilitate the hydrogel's solidification.

Accordingly, hydrogel is made up of alginate, a natural polymer found in seaweed. Alginate possesses unique qualities that enable it to trap bacteria. Its use in biomedical applications, such as medication delivery and tissue engineering, is safe and free of adverse effects.

In addition, dormant bacteria are known as endospores and are contained within the hydrogel. The endospores can promote spontaneous healing upon cracking the outer shell and awakening from its latent state.

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How to Activate BioFibers

The combination of cement, sand, gravel, and water results in concrete having the characteristics of a solid and durable substance. While mixing the concrete, scientists incorporate the BioFibers into the mixture and spread them out to guarantee that they are dispersed uniformly throughout the mixture.

However, it is no longer possible for the activated BioFiber to heal once the self-healing process has been completed and the bacteria have passed away. On the other hand, because the concrete has many BioFibers dispersed throughout it, another fiber can repair the subsequent break.

The number of cracks that can be repaired by BioFiber concrete is currently unknown to us, and we are conducting additional studies to find out how many fractures it can fix.

In addition, water is required for endospore activation. Fortunately, the hydrogel layer in the middle is very good at absorbing water. The spores become active when water evaporation from rain, humidity, or street runoff occurs through an aperture in the concrete. Aside from the calcium in the concrete, the spores consume carbon, which is mainly added to the concrete mix.

When the bacteria are given these ingredients, they facilitate a chemical reaction known as microbially induced calcium carbonate precipitation or MICCP. The calcium carbonate crystals produced as a result of this reaction accumulate and fill in the fractures in the concrete.

Thus, crystals can take on various shapes, ranging from spheres to needles, and each of these shapes is robust enough to repair cracks successfully. By altering the pH level, calcium source, and type of bacteria, researchers can change the crystals produced by the bacteria organisms.

The amount of food that the bacteria require to be alive and repair the cracks is determined by the number of cracks that they expect to need to cure. This reportedly gives them the opportunity to feed the bacteria. Once the bacteria have exhausted their food supply, the process will end. The microorganisms have an estimated lifespan of two weeks during the healing process.

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