On Self Healing Concrete
How does self-healing concrete leverage modern technology to address durability and environmental concerns in infrastructure?
Concrete is an integral material to modern infrastructure, widely used due to its reliability. However within concrete structures, cracks can occur during any stage of its lifetime, due to a multitude of internal and external contributors, such as harsh environmental exposure or design flaws.[1]
As cracks negatively impact the concrete’s mechanical performance and durability, engineers and scientists have begun developing ‘self-healing’ concrete, a more robust material that can gradually be implemented into everyday construction. This essay explores the concept of self-healing concrete, and its potential bearing on engineering and the environment.
The composition of self-healing concrete was derived from the Ancient Romans, who included volcanic ash and quicklime in concrete structures such as the Pantheon. Quicklime lime casts after mixing, creating a brittle nanoparticulate formation. Due to this, if a crack formed and water infiltrated these particles, crystallisation would occur, ‘healing’ the concrete.[2] Similarly, contemporary self-healing concrete partially mimics this idea by embedding capsules filled with healing agents into the concrete matrix. Upon these capsules being activated, the agents are released, producing a material that seals the damage. The majority of the capsules are made of glass, whilst magnesium has also been discovered to be an effective component in the healing agent itself.[3]
Sensicon[4], a company that specialises in self-healing concrete, has included bacterium in their embedded capsules. When a crack in the concrete occurs, and the bacterium come into contact with water, the reaction between them produces limestone, effectively sealing the cracks. This method known as extrinsic self-healing, is more widely used. However, the rising potential of intrinsic self-healing is also gaining attention. It entails the material itself containing substances that can undergo reversible reactions. The primary limitation with extrinsic self-healing is that once the capsules have been broken and the healing agent released and activated, the healing ability of the affected area has essentially been ‘used up’. If another crack occurs in that same place, there are no unbroken capsules that can be used. However, intrinsic self-healing is not limited by this, and can undergo an infinite number of healing cycles in the same area, though it compromises the material’s mechanical strength. Engineers are still divided on which method is more efficient.[5]
Nevertheless, the increase production and use of self-healing concrete offers a plethora of benefits. Ultimately, structures will last longer, reducing reparation costs and the need for sealants. Furthermore, concrete production currently contributes to 7% of global carbon emissions. By reducing the production of additional cement used to repair cracks, carbon emissions will also decrease. Similarly, the heavy use of cement within concrete largely contributes to the material’s overall environmental impact, so the composition of self-healing concrete, which includes more healing agents and less cement, also substantially reduces the level of carbon embedded into the concrete. Additionally, self-healing concrete has the potential to offer more than just damage repair. For example, a fire-resistant form of self-healing concrete is being developed[6], which would considerably enhance building safety and integrity.
Self-healing concrete is a groundbreaking development that appears to have boundless potential. Further exploration and adaptation would almost certainly lead to self-healing concrete playing a huge role in a more sustainable future for infrastructure.
Ivie Avwenagha is an A-level student with big engineering dreams and a love for all things writing, too. This usually manifests as many STEM-related essays, poems and narratives.
Bibliography
Choi, K., Noh, A., Kim, J., Hong, P. H., Ko, M. J., & Hong, S. W. “Properties and Applications of Self-Healing Polymeric Materials: A review.” (2023) Polymers, 15(22), 4408.
Hou, S., Li, K., Wu, Z., Li, F., & Shi, C. “Quantitative evaluation on self-healing capacity of cracked concrete by water permeability test – A review.” (2022) Cement & Concrete Composites, 127, 104404.
Pollock, A. “Building a Sustainable future: the Incredible Potential of self-healing Concrete” Rics.org. 2024
Sensicon Ventures. “Sensicrete - self healing concrete.” [https://www.sensicon.co.uk/sensicrete-self-healing-concrete/]
Stevens Institute of Technology. “This 'Smart Concrete' Heals Its Own Cracks, Resists Fire — and Cleans the Air.” (2019). [https://www.stevens.edu/news/smart-concrete-heals-its-own-cracks-resists-fire--and-cleans-air]
Yang, Y., Lepech, M. D., Yang, E., & Li, V. C. “Autogenous healing of engineered cementitious composites under wet–dry cycles.” Cement and Concrete Research, 39(5), (2009): 382–390
[1] Yang, Y., Lepech, M. D., Yang, E., & Li, V. C. “Autogenous healing of engineered cementitious composites under wet–dry cycles.” Cement and Concrete Research, 39(5), (2009): 382–390
[2] Pollock, A. “Building a Sustainable future: the Incredible Potential of self-healing Concrete” Rics.org. 2024
[3] Hou, S., Li, K., Wu, Z., Li, F., & Shi, C. “Quantitative evaluation on self-healing capacity of cracked concrete by water permeability test – A review.” (2022) Cement & Concrete Composites, 127, 104404.
[4]Sensicon Ventures. “Sensicrete - self healing concrete.” [https://www.sensicon.co.uk/sensicrete-self-healing-concrete/]
[5]Choi, K., Noh, A., Kim, J., Hong, P. H., Ko, M. J., & Hong, S. W. “Properties and Applications of Self-Healing Polymeric Materials: A review.” (2023) Polymers, 15(22), 4408.
[6] Stevens Institute of Technology. “This 'Smart Concrete' Heals Its Own Cracks, Resists Fire — and Cleans the Air.” (2019). [https://www.stevens.edu/news/smart-concrete-heals-its-own-cracks-resists-fire--and-cleans-air]