For centuries, concrete has been a go-to building material for everything from residential foundations to parking garages. However, concrete has always had the problem of cracking associated with it. A beautiful driveway or patio can easily be marred by a huge crack developing through its center. Worse, a building foundation with cracked concrete can compromise the integrity of the entire structure and allow moisture to enter the building. At least that’s the way things used to be. Today, self-healing concrete can give home and business owners the sleek, professional look of concrete without having to worry about cracking and costly repairs.
What is self-healing concrete?
Self healing concrete, also known as self mending concrete or bio concrete, uses a variety of new technologies to create a building product that will actually mend any cracks that appear in the concrete due to wear, changing temperature, shifting ground or other occurrences. This not only makes the concrete more attractive, but also more durable.
Making concrete more durable also makes it more environmentally friendly, since it won’t have to be disposed of and replaced nearly so often, nor will it have to be repaired using extra concrete. According to Nima Rahbar, an associate professor of civil and environmental engineering at Worcester Polytechnic Institute, concrete production is responsible for as much as nine percent of the world’s carbon dioxide emissions. In fact, if concrete producers were a country, it would be the third-largest climate polluter in the world.
Autogenous vs autonomous self-healing
Self-healing generally appears in two forms for typical service crack conditions. Autogenous healing relies on continued cement hydration and calcium carbonate precipitation to seal microcracks. Autonomous healing adds agents, such as microcapsules or bacteria, that activate at cracking and supply repair material.
How self-healing concrete works
One of the most exciting new building products on the market, this new type of concrete can be made using a variety of processes. One uses an enzyme found in human red blood cells to “heal” the concrete. Another, developed by a researcher at Delft University of Technology in the Netherlands, uses bacteria. Some types of bacteria can thrive in arid, harsh environments, such as found in and around concrete. The bacteria used can produce spores that can live up to four years without any food or oxygen. The researcher used bacteria that would produce limestone, which kept the bacteria alive and provided material to repair the cracked concrete.
Most bacteria-based systems need moisture and available calcium to precipitate limestone within cracks. Enzyme-assisted mixes use carbonic anhydrase, which speeds carbonate formation when water, CO2, and calcium ions are present. Sodium silicate microcapsules rupture as cracks open, reacting with pore solution to form sealing gels.
Another method of producing self healing concrete, developed by an engineering student at the University of Rhode Island, uses a microencapsulated sodium silicate healing agent that ruptures as the crack forms and acts to repair the crack
Typical crack-size ranges and timeframes for healing
Reported healing ranges help set expectations for projects and product claims. Autogenous mechanisms commonly seal microcracks up to about 0.2 to 0.3 millimeters under wet conditions. Bacteria and sodium silicate systems are effective to 0.3 to 0.5 millimeters over days or weeks.
Examples of self healing concrete
Self healing concrete is already being tested in the real world. One example was spearheaded by three universities in the UK. They used a concrete mixture with microcapsules of sodium silicate to build mock retaining walls and highway sections in South Wales, UK. The project was a test, and one section used traditional concrete while the other used the concrete mixture. The test was a success, with all the self-healing concrete panels exceeding the performance of those made using traditional concrete construction materials.
How performance is measured
Performance is documented through water permeability recovery and visual crack-closure ratios from image analysis. Labs track regained mechanical properties, including flexural stiffness and limited compressive strength recovery after healing. Durability tests like chloride permeability, ASTM C1202, or sorptivity, ASTM C1585, indicate reduced ingress and support credible claims.
Typical applications where self-healing adds value
Use cases cluster where limiting leakage and ingress matters most in service. Water-retaining structures like basements, tunnels, and tanks show strong results in studies. Bridge decks, pavements, precast, and repair mortars reduce maintenance cycles, supporting owner value propositions.
The future of self-healing concrete
Self-healing concrete changes how we look at using concrete for buildings and surfaces. It can totally eliminate invasive building maintenance and expensive repairs and replacements to foundations, driveways, sidewalks and patios.
Most types of self mending concrete are much more expensive to produce than traditional concrete. While you can argue that the ultimate price of this building material is less, for contractors trying to compete on price, this can be a disadvantage. The self healing concrete price right now is about double that of traditional concrete.
This new type of concrete mix is still in the development stages, and it remains to be seen which formula will become the most commercially viable. However, look for this exciting product to be a game-changer in the construction industry in the next few years.
FAQs
Self-healing concrete, also known as self-mending concrete or bio-concrete, is a type of building material designed to repair cracks that appear due to various factors like wear, temperature changes, or shifting ground.
Self-healing concrete can be produced using different methods, such as incorporating enzymes from human red blood cells or bacteria that produce limestone, which mend the cracks as they form. Another method involves microencapsulated sodium silicate that ruptures to repair cracks.
Self-healing concrete increases durability, reduces maintenance costs, and is more environmentally friendly by minimizing the need for disposal and replacement, thus lowering carbon dioxide emissions associated with concrete production.
Yes, self-healing concrete has been tested in various applications. For instance, in the UK, mock retaining walls and highway sections were constructed using a concrete mixture containing microcapsules of sodium silicate, demonstrating superior performance compared to traditional concrete.
Currently, self-healing concrete is approximately twice as expensive to produce as traditional concrete. While it may offer long-term cost savings, contractors may find it challenging to compete on price in the short term.
