The Healcon European Project aims to develop self-healing concrete for improving the durability of structures.
The partners in the project are studying PU-based polymer precursors, bacteria and superabsorbent polymers as materials for self-healing concrete.
Encapsulated PU-based precursors have demonstrated great potential for cracked concrete healing applications. They have enabled good regain in liquid-tightness and mechanical behavior. So far, researchers have used glass tubes as the encapsulation material in tests, and going further they intend to optimize the technique by using polymeric spherical microcapsules. PU-based precursors can also help the healing agents to increase their resistance to cyclic loading, which would enable dynamic cracks to be healed.
Micro-encapsulated CaCO3 bacteria hold promise as concrete healing agent. They are initially dormant, and become active when the concrete cracks and water enters into the concrete. Pure bacterial cultures are effective but expensive, hence mixed cultures are being used. The researchers studied ureolytic and non-ureolytic alkali-resistant spores of Bacillus which are incorporated into Liapor particles. These spores can help protect and immobilize the biogenic healing agent.
Superabsorbent polymers have the ability to absorb huge quantities of water. They can help induce healing and sealing of cracks. As part of this project, the researchers have developed new synthetic superabsorbent polymers that demonstrate better pH sensitiveness and swelling abilities that are favorable for efficient healing of cracks. During the process of concrete mixing, macropores are created when the superabsorbent polymers absorb the water, and the project partners are trying out ways to prevent this macropore creation.
The partners in the Healcon project have modeled a bio-based self-healing mechanism. They modeled the Liapor particles as spheres. The degree of healing was found to be independent of the crack’s depth but dependent on the crack’s width. Further research is to be done on more realistic cracks, while considering properties of Liapor particles and the cement paste.
The Healcon project utilized non-destructive testing methods to assess the Young’s modulus, strength and defects – both visible and invisible. The various methods included acoustic emission analysis, time-of-flight diffraction technique, resonance frequency measurements, and modal analysis.
The project is coordinated by the Ghent University in Belgium.