Self-healing Concrete – In recent days, there have been many innovations in every aspect of architecture. Materials that already exist have been experimented extensively, and there have been new inventions. The new materials aim to be more durable and corrosion-resistant. With the environment and surroundings in mind, the emerging materials are proven safer to the climate and are comparatively sustainable. A lot of research goes behind coming up with such solutions.
Why the Need of Self-Healing Concrete?
Concrete is one of the abundantly used construction materials. While it has its advantages, concrete is prone to cracks. It resists compressive stress but does not resist tensile stress, tending it to crack when tension is applied. Liquids seep through the cracks, reach the reinforcement and corrode it. Corrosion of reinforcement questions the stability and durability of the structure. Self-healing concrete is an invention in the construction field solving the problem of deterioration of concrete.
How Does it Work?
Hendrick Jonkers and a team of biologists, after long research, invented self-healing concrete. Hendrick got nominated for the European award of 2015 for the invention. As the name suggests, this material heals itself during any cracks. Concrete is mixed with a healing agent or bacteria that gets converted into limestone when cracks appear. Bacteria like genus Bacillus, along with calcium lactate, nitrogen, and phosphorus, are used. The bacterial spore is in the form of tiny water-permeable capsules when added to the concrete. Inert by nature, they become active when they come into contact with water. Bacteria germinate and move towards the water.
The activated bacteria consume oxygen, and the soluble calcium lactate within it converts into limestone. It solidifies when it comes in contact with the atmosphere. Since oxygen is one of the main reasons for corrosion in steel, consumption of it by bacteria proves self-healing concrete is more durable. The bacteria live for over 200 years and do not cause any harm to humans, allowing us to use them more efficiently. According to research, it takes seven days for a crack to heal in a laboratory but several weeks in outside conditions.
Advantages
Also called bio or bacterial concrete, self-healing concrete is more durable and long-lasting. The material is alkaline-resistant and has a higher compressive and flexural strength. Structures made from this material resist freeze-thaw attacks well and have reduced permeability. Though the initial cost of self-healing concrete is almost 40% greater than conventional concrete, it is efficient in the long run. It is estimated that European scientists could save 120 million simply by reducing maintenance costs.
Self-Healing Concrete: A Sustainable Material
The construction industry is the reason for 8% of the total carbon dioxide emissions in the world. Cement production releases a large amount of carbon dioxide. The usage of large amounts of concrete has an adverse effect on the environment. Self-healing concrete is a sustainable alternative to it. It is possible to reduce carbon dioxide emissions by using lasting concrete. The use of this material reduces the number of construction materials used overall. Self-healing concrete works on the concept of refilling instead of demolition. Adding more stability to the building effectively prevents destruction due to insufficiency of strength.
Applications
Large-scale and medium-sized buildings commonly use self-healing concrete. Most of the structural elements of buildings constitute concrete. Self-healing reduces the need for concrete demolition. Along with being used in buildings, it can also be found in bridges, roads, tunnel linings, and marine structures. Self-healing concrete cuts down maintenance costs and increases the safety of the building by filling the cracks. It is also advantageous to use self-healing concrete in water-retaining buildings and high-strength structures with more bearing capacity.
Construction materials undergo several tests and a lot of research before being used. Self-healing concrete is still in the stages of testing and is not yet on the market. Hendrick Jonkers tested them in many small pieces called prisms and put them at the corners of the buildings. Later, he constructed a canal and irrigation system. There were a few panels made of self-healing concrete, while the other was of traditional concrete. The structures were under observation for three to five years. Researchers have also tested alternative approaches of self-healing concrete instead of using bacteria. These include fiber that shrinks when contacted with water and squeezing concrete.
Cons
Though self-healing concrete is durable and sustainable, it has its own set of disadvantages. In contrast to natural concrete, the initial cost is nearly twice as high. Not all environmental conditions are suitable for the growth of bacteria. The effect of it reduces if the bacteria mixes with clay pellets. The study of calcite is expensive. Skilled labor is required in the construction using self-healing concrete which adds to the cost. There is no specific code available to standardize the self-healing concrete.
In spite of the fact that it has some cons, self-healing concrete might still be better for the long haul. Bio-mineralization is good for the environment. Self-healing concrete is a sustainable material ensuring the durability and safety of the structures. Improvement of buildings leads to improvements in society as a whole. Many new materials like self-healing concrete have come into the market. It is a hope that these bring a positive change to the architecture, environment and create a sustainable world for future generations.
