Concrete is the backbone of modern civilisation, supporting everything from homes and skyscrapers to bridges, tunnels and dams. Yet even this remarkably strong material has a costly weakness. Tiny cracks inevitably develop over time because of ageing, weather, heavy traffic and earthquakes, allowing water to penetrate and corrode the steel reinforcement inside. Repairing damaged concrete infrastructure costs governments and businesses billions of dollars every year. What if these structures could repair themselves just as human skin heals after a cut? That once far-fetched idea became reality when Dutch microbiologist Professor Henk Jonkers developed self-healing concrete using bacteria that produce calcium carbonate, commonly known as limestone, enabling cracks to seal themselves naturally and potentially extending the lifespan of buildings while reducing maintenance costs.
Who is the Dutch scientist behind self-healing concrete?
The breakthrough was pioneered by Professor Henk Jonkers, a microbiologist at Delft University of Technology (TU Delft) in the Netherlands. Unlike traditional civil engineers, Jonkers specialised in microbiology and wondered whether living organisms could solve one of construction’s oldest problems.Inspired by the human body’s ability to heal wounds, he spent years studying bacteria capable of surviving in extremely harsh conditions. His research eventually led to the development of self-healing concrete containing dormant bacterial spores that remain inactive until cracks appear.Jonkers’ work gained international recognition after receiving support through European research programmes and has since become one of the world’s best-known examples of bio-inspired engineering.
How do bacteria repair cracked buildings?
The secret lies in a group of naturally occurring bacteria from the Bacillus family, including species such as Bacillus pseudofirmus and Bacillus cohnii. These bacteria are specially selected because they can survive the highly alkaline environment inside concrete.During construction, bacterial spores are mixed into the concrete along with tiny capsules containing nutrients such as calcium lactate. Under normal conditions, the bacteria remain dormant for decades because there is no moisture inside healthy concrete.When a crack develops, rainwater enters the concrete and activates the bacteria. The microorganisms consume the nutrients and convert them into calcium carbonate, commonly known as limestone. This newly formed limestone gradually fills the crack, preventing further water penetration and protecting the steel reinforcement inside the structure.Once the crack has been sealed and moisture disappears, the bacteria become dormant again until they are needed.
What studies proved that self-healing concrete works?
One of the earliest landmark studies was “Application of bacteria as self-healing agent for the development of sustainable concrete,” published in the journal Ecological Engineering. The study was authored by Henk M. Jonkers, Arjan Thijssen, Gerard Muyzer, Oğuzhan Çopuroğlu and Erik Schlangen, and demonstrated that bacteria could successfully seal cracks by producing biologically formed limestone.Further research by TU Delft’s Microlab and the university’s Department of Materials and Environment showed that the bacteria remained viable inside concrete for many years and could repeatedly heal small cracks after exposure to water.Another influential publication, “Bacteria-based concrete: From concept to market,” by Henk M. Jonkers, explained how the technology progressed from laboratory experiments to pilot-scale applications, highlighting its ability to improve the durability and watertightness of reinforced concrete structures while reducing maintenance requirements.Researchers around the world, including teams in the United Kingdom, Belgium, China, South Korea and India, have since validated and expanded upon Jonkers’ work, making self-healing concrete one of the fastest-growing areas of sustainable construction research.
How much damage can the bacteria repair?
Current versions of bacterial concrete can typically repair cracks measuring up to around 0.5 to 1 millimetre wide, depending on the concrete mixture and environmental conditions.Although that may sound small, these hairline cracks are often the starting point for much larger structural problems. By sealing them early, the bacteria prevent water, oxygen and salt from reaching the reinforcing steel, dramatically slowing corrosion and extending a building’s lifespan.Researchers are now developing improved bacterial strains and nutrient delivery systems capable of healing wider cracks and functioning for even longer periods.
Could this technology save billions in repair costs?
Concrete is the world’s most widely used construction material after water. According to the American Society of Civil Engineers (ASCE), ageing infrastructure requires enormous investment to repair deteriorating bridges, tunnels, highways and public buildings.By automatically repairing small cracks before they become serious, self-healing concrete could substantially reduce maintenance costs, extend service life and minimise disruption caused by repair work.The technology is particularly valuable for structures where repairs are difficult or expensive, including offshore platforms, underground tunnels, dams, railway bridges, parking structures and marine infrastructure.Beyond financial savings, reducing repair work also lowers carbon emissions because producing new cement is one of the largest industrial sources of carbon dioxide worldwide.
Has self-healing concrete been used outside the laboratory?
Yes. Since its invention, bacterial concrete has been tested in several pilot projects across Europe.The Netherlands has incorporated self-healing concrete into experimental infrastructure projects, while researchers in Belgium, Italy and the United Kingdom have conducted field trials on bridges, tunnels and retaining walls.Several companies inspired by Jonkers’ research have also begun commercialising bacteria-based self-healing concrete products for specialised construction projects. However, the technology has not yet been widely adopted in mainstream construction because it remains more expensive than conventional concrete. Researchers believe wider use is likely as production costs fall and the long-term economic benefits become more apparent.
Why could self-healing concrete transform construction?
For decades, engineers have focused on repairing concrete after it fails. Professor Henk Jonkers reversed that thinking by creating a material that repairs itself before serious damage occurs. His bacteria-powered concrete combines microbiology with civil engineering, offering a sustainable solution to one of the construction industry’s biggest challenges.While scientists continue refining the technology, the concept has already changed how engineers think about infrastructure. Instead of constantly repairing ageing buildings, future cities could be built using materials that quietly maintain themselves for decades, reducing costs, improving safety and making construction far more sustainable.
