Concrete self-healing cracks

New materials capable of repairing small cracks and holes are no longer far-fetched for construction science researchers.

Civil construction: Concrete can now heal itself of weather-induced injuries. A new construction material capable of repairing small cracks and holes is no longer out of reach for scientific researchers in construction.

Concrete is a key material useful in the construction industry, but it has some disadvantages compared to other materials, especially with construction stone in terms of its ability to withstand weather. Salt and ice are often the cause of small cracks and holes, making concrete structures vulnerable to penetration of water. So the consequences are costly and labor-intensive for repairing and upgrading concrete structures.

Concrete can heal the 'weathering' itself.(Artwork: Alamy)

Self-healing concrete is not a new idea. Since 2009, the Delft University of Technology research team in the Netherlands has shown the feasibility of combining some special bacteria capable of secrete chemicals to heal cracks into concrete before pouring. These bacteria keep the concrete structure stronger, but they only work when they are alive. But the tests showed that bacteria only lasted no more than a year.

Dr. Chan-Moon Chung, Yonsei University Korea is also one of the breeding scientists hoping to create a material that can heal itself. Instead of approaching biological research, Dr. Chung uses chemical research methods.

He and his colleagues discovered that, when two substances called methacryloxypropyl-terminated polydemetylsiloxane and benzoin isobutyl ether were mixed together, along with the presence of sunlight, they would be transformed into a waterproof polymer. water, easily adheres to concrete. The problem is how to preserve it until it is needed to release that chemical. The solution is to place a healing resin in microcapsules made of urea and formaldehyde. They keep the chemical mixture safe and break when the concrete is cracked, freeing the mixture.

To make capsules, the team mixed and stirred the solution, including water, urea, ammonium chloride and a benzene derivative called resorcinol. The team then added methacryloxypropyl-terminated polydemetylsiloxane, isobutyl etheric benzoin and formaldehyde, and cooked the mixture at a temperature of 55 degrees C for four and a half hours. If this process is successful, the resulting capsule will contain the two chemicals that heal the concrete as desired.

To deploy the use of capsules, Dr. Chung mixed with thin polymers, sprayed the mixture onto several concrete blocks and allowed the membrane to freeze. Later, he in turn broke each concrete block and left it in the sun for four hours, hoping that cracks in the concrete would break the polymer film containing the capsules, liberating substance inside. After exposure to the sun, it will create a waterproof layer. After that he soaked the concrete blocks in the country, and in fact proved the chemical process was successful.

24 hours later, Mr. Chung measured and weighed the amount of water in the concrete blocks. As a result, average concrete contains 11.3g of water; concrete has 3.9g water-filled capsules, but it is impressive that the concrete is coated with polymer layer containing capsules to absorb only 0.4g of water. So Dr. Chung's aspirations and efforts paid off, concrete blocks healed the cracks themselves.