Concrete is one of the most important inventions of modern infrastructure, making up buildings, roads, and bridges worldwide. But this vital material is prone to cracking, which shortens its lifespan and requires expensive repairs. In response, researchers have developed innovative solutions to prolong the durability of concrete, and one of the most promising is self-healing concrete. This groundbreaking approach uses living organisms, such as fungi, to mend cracks in concrete, offering a sustainable alternative to traditional construction methods.
What is self-healing concrete?
Self-healing concrete is a type of concrete embedded with biological agents that can repair small cracks autonomously. These agents, typically microorganisms like bacteria or fungi, are mixed into the concrete during production. When cracks form, the microorganisms become active and start repairing the damaged area, preventing the cracks from spreading. This significantly reduces the need for maintenance and extends the lifespan of the concrete structure. Detecting cracks in traditional concrete often requires specialized equipment and can be labor-intensive, particularly in large-scale infrastructures like bridges and highways. Self-healing concrete addresses these challenges by minimizing the need for human intervention.
How do fungi work in the healing process?
The process begins when fungal spores are mixed into the concrete. These spores remain dormant during the early stages of concrete curing, as the harsh conditions of high pH (around 13) and elevated temperatures make it impossible for fungi to grow. However, once cracks form in the concrete, the conditions inside the cracks become less severe—pH levels drop to around 9, and moisture becomes trapped in the fissures. These conditions are ideal for fungal germination.
When activated, the fungi begin to grow and form calcium carbonate (CaCO₃), a material similar to limestone. This calcium carbonate fills in the cracks, restoring the concrete’s structure. The fungi’s ability to produce CaCO₃ is a key factor in their effectiveness. By precipitating this material, the fungi essentially “patch” the cracks from within, preventing further damage and water infiltration, which can cause additional degradation.
A recent study published in AIMS Bioengineering highlighted the effectiveness of this process. The researchers screened 18 strains of fungi for their ability to survive and perform in the extreme environment of concrete, making them excellent candidates for further development.
Sustainability benefits
The environmental impact of conventional concrete production is staggering. Concrete manufacturing is responsible for around 8% of global CO₂ emissions. This is largely due to the high energy demands of producing cement, one of concrete’s primary ingredients. The extraction of raw materials like limestone and clay also has significant ecological consequences, including habitat destruction and pollution.
By incorporating fungi into concrete, we reduce the need for new concrete production. Self-healing concrete can repair itself, reducing the frequency of repairs and replacements which directly lowers the demand for new materials and, consequently, decreases the environmental footprint of the construction industry. As highlighted in the AIMS Bioengineering study, self-healing concrete could significantly cut down on energy consumption and CO₂ emissions by reducing the need for and frequency of new construction.
Fungi used and why they are effective
The type of fungi used in self-healing concrete must be able to withstand the extreme conditions during the initial stages of concrete formation. The high pH and elevated temperatures pose significant challenges for most microorganisms. However, certain strains of fungi, such as Scopulariopsis brevicaulis, which the researchers determined was fungi most suited for this purpose, have shown remarkable tolerance to these conditions. This species was found to survive concrete’s harsh environment and effectively germinate in cracks, making it ideal for self-healing.
The screening process for selecting fungi involves several steps. First, fungi are tested for their ability to grow in high-pH environments. Then, their spores are subjected to temperatures as high as 55°C to simulate the concrete hydration process. Finally, the fungi must demonstrate the ability to remain dormant during concrete curing and become active once cracks appear. This careful selection ensures that only the most resilient fungi are used in self-healing concrete.
Impact on future construction
The potential applications of self-healing concrete are vast, particularly as the global population grows and demand for infrastructure increases. According to the International Energy Agency (IEA), by 2060, the world’s building floor area is expected to double, putting immense pressure on the construction industry to find sustainable solutions. Self-healing concrete could revolutionize how we build, maintain, and sustain our infrastructure.
In the future, self-healing concrete could become a standard practice in construction projects, particularly in regions prone to extreme weather or high seismic activity, where the integrity of concrete structures is often compromised. This technology not only offers a cost-effective solution but also holds promise for reducing the ecological impact of the construction industry. As the construction industry seeks to lower its environmental impact, solutions like fungi-based self-healing concrete offer a path toward a more sustainable future. With continued research and development, fungi could play a crucial role in building the resilient, eco-friendly infrastructure of tomorrow.
