Self-Healing Concrete Inspired by Bones

Innovation: Industry

Hendrik Marius Jonkers

2015

Image: Jayakumar / Shutterstock / CC BY NC - Creative Commons Attribution + Noncommercial

Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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Physically Assemble Structure

Living systems use physical materials to create structures to serve as protection, insulation, and other purposes. These structures can be internal (within or attached to the system itself), such as cell membranes, shells, and fur. They can also be external (detached), such as nests, burrows, cocoons, or webs. Because physical materials are limited and the energy required to gather and create new structures is costly, living systems must use both conservatively. Therefore, they optimize the structures’ size, weight, and density. For example, weaver birds use two types of vegetation to create their nests: strong, a few stiff fibers and numerous thin fibers. Combined, they make a strong, yet flexible, nest. An example of an internal structure is a bird’s bone. The bone is comprised of a mineral matrix assembled to create strong cross-supports and a tubular outer surface filled with air to minimize weight.

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Manage Impact

An impact is a high force or mechanical shock that happens over a short period of time, such as a hammer hitting a nail rather than a hand pushing slowly against a wall. Because of their speed and force, impacts don’t allow materials to slowly adjust to the force, which can lead to cracks, ruptures, and complete breakage. Therefore, living systems have strategies that can absorb, dissipate, or otherwise survive that force without the need to add large amounts of material. For example, the Toco toucan’s large beak is very lightweight, yet can withstand impacts because it’s made of a composite material with rigid foam inside and layers of a hard, fibrous material outside.

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Patents

Self-repairing concrete contains bacteria that produce limestone to fill any cracks that occur.

Benefits

Reduced emissions
Reduced cost

Applications

Construction
Building materials
Infrastructure

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure
Goal 11: Sustainable Cities & Communities
Goal 12: Responsible Production & Consumption

Bioutilization

Sporosarcina pasteurii
Bacillus pseudofirmus

The Challenge

Cement is the second most consumed product on Earth after water. Concrete production is one of the largest producers of carbon dioxide, a greenhouse gas. These gases absorb solar energy and keep heat close to the Earth, known as the greenhouse effect, leading to global warming. In addition, repairing cracked concrete in roads and buildings costs governments and companies billions of dollars every year.

Innovation Details

Self-repairing concrete utilizes a limestone-producing bacteria, which is normally dormant inside the concrete. When a crack emerges, it lets in air and moisture. This forces the bacteria out of dormancy, where they start to feed on the calcium lactate inside the concrete. They also consume oxygen, which converts the soluble calcium lactate into insoluble limestone. The limestone solidifies in the cracks, sealing them again. This process was inspired by the ability of bones to self-heal after damage.

Biological Model

Osteoclasts and osteoblasts work together to help bones heal by encouraging cell growth and mineralization. The osteoblasts work in groups to deposit calcium and phosphate crystals into the damaged site, which combine with collagen to form new bone. Osteoclast cells remove any unwanted bone around the fracture site, until the repaired bone assumes a shape similar to its appearance before injury.