Led by a team of researchers from Cardiff University, the first major trial of self-healing concrete in the UK is being undertaken at a site in the South Wales Valleys.
Prof Bob Lark, the principal investigator on the project from Cardiff University’s School of Engineering, said: “Our vision is to create sustainable and resilient systems that continually monitor, regulate, adapt and repair themselves without the need for human intervention.
The Materials for Life (M4L) project is piloting three separate concrete-healing technologies for the first time in real-world settings, with a view to incorporating them into a single system that automatically repairs concrete in the built environment.
At present, billions of pounds are spent every year maintaining, fixing and restoring structures such as bridges, buildings, tunnels and roads. According to Cardiff University, Britain spends around £40bn a on the repair and maintenance of structures, most of which are made from concrete.
The overall aim of the Cardiff-led project is to develop a single system that can be embedded into concrete when it is initially set, and then automatically sense when damage occurs. Once damage is detected, the system will be able to repair itself autonomously without the need for human intervention.
The trial is being undertaken in collaboration with Costain, and is taking place at the Heads of the A465 Valleys road improvement scheme in South Wales.
The research team, which includes academics from the Universities of Bath and Cambridge, is testing three separate technologies at the site.
The first technique uses shape-memory polymers to repair large cracks in concrete. When these materials are heated with a small current, they can transform into a different shape that the material has ‘memorised’. The researchers believe that these materials can be embedded into concrete and used to close cracks or make them smaller.
In the second technique, researchers will pump organic and inorganic healing agents through a network of thin tunnels in the concrete to help repair damage.
In the third technique, the team will embed tiny capsules, or lightweight aggregates, containing bacteria and healing agents into the concrete. It is anticipated that once cracks occur, these capsules will release their cargos and, in the case of the bacteria, the nutrients that will enable them to function and produce calcium carbonate, which the researchers envisage will heal the cracks in the concrete.
The researchers have cast six concrete walls at the test site, each containing the different technologies. Over time the team will load the concrete at specific angles to induce cracks, and then monitor how effective each of the self-healing techniques is.
“From this trial we should gain an insight into the feasibility of constructing a full-scale structure using these techniques and their early-stage effects on structural properties,” said Oliver Teall, a civil engineer at Costain. “We will be monitoring properties such as stiffness, permeability and the mechanical damage recovery of the trial walls in comparison with conventional reinforced concrete walls.”