SOUTH KINGSTOWN – Tiny capsules of sodium silicate could hold the key to producing self-healing concrete at an affordable price, University of Rhode Island graduate student Michelle Pelletier says.
Pelletier placed microencapsulated sodium silicate into concrete mix and allowed the concrete to harden. When stress cracks later appeared they popped the capsulate and released the sodium silicate. That reacted with calcium hydroxide naturally present in the concrete to form a calcium-silica-hydrate substance to heal the cracks.
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“Self-healing concrete is a big research field right now,” Pelletier said. “But many of the approaches being taken by other researchers have not ended up being economically feasible for commercial production.”
Pelletier’s chemical engineering professor, Arijit Bose, said what sets this process apart is that it targets only areas that need healing.
URI said that in tests comparing a standard concrete mix to concrete containing 2 percent sodium silicate healing agent, Pelletier’s healing mix recovered 26 percent of its original strength (after being stressed to near breaking) versus 10 percent recovery by the standard mix. Upping the amount of the agent could increase recovery strengths, Pelletier said
She is also studying whether her mixture could prevent corrosion.
Besides lowering costs for builders, self-healing concrete could reduce carbon dioxide emissions because builders would require the production of less concrete. URI said the production of concrete – from mining to transportation – accounts for about 10 percent of all carbon dioxide emissions in the United States.
“If self-healing concrete can lengthen the life of the concrete and reduce maintenance and repairs, it will ultimately reduce the production of excess amounts of concrete and result in a decrease in [carbon dioxide] emissions,” Pelletier said.
