Self-healing concrete

To create the self-healing material, Michelle Pelletier embedded a microencapsulated sodium-silicate healing agent directly into a concrete matrix. When tiny stress cracks begin to form in the concrete, the capsules rupture and release the healing agent into the adjacent areas.

The sodium silicate reacts with the calcium hydroxide naturally present in the concrete to form a calcium-silica-hydrate product that heals the cracks and blocks the pores in the concrete. The chemical reaction creates a gel-like material that hardens in about one week.

’Smart materials usually have an environmental trigger that causes the healing to occur,’ explained Pelletier, who is collaborating on the project with URI Chemical Engineering professor Arijit Bose. ’What’s special about our material is that it can have a localised and targeted release of the healing agent only in the areas that really need it.’

In tests comparing a standard concrete mix to concrete containing two per cent sodium-silicate healing agent, Pelletier’s healing mix recovered 26 per cent of its original strength (after being stressed to near breaking) versus 10 per cent recovery by the standard mix. Pelletier said that an increase in the quantity of healing agent would likely further improve the recovered strength of the concrete.