Scientists have been trying for at least a decade to develop concrete that fixes itself, but commercialization's been difficult because the product requires costly materials like glass capillaries or bacteria transmitters.
University of Rhode Island (URI) graduate student Michelle Pelletier, however, has found a way to target only the areas that need repair using less-expensive materials. The process increases strength by 26% compared to 10% for standard concrete mixes.
Her process implants microencapsulated sodium silicate healing agents directly into the concrete matrix. When the concrete cracks, the capsules rupture - allowing the sodium silicate to react with calcium hydroxide in the concrete, forming and releasing a gel-like healing agent into the affected areas that hardens within seven days.
"'Smart' materials usually have an environmental trigger that causes the healing to occur," she says. "What's special about our material is that it can have a localized and targeted release of the healing agent only in the areas that need it."
When tests showed the process protects steel rebar by reducing the rate of corrosion, Pelletier began adding more capsules into the concrete mix to prevent corrosion entirely and to increase strength after damage.
She's working to patent the "smart concrete" before marketing it to businesses for further development.