Smart Concrete? Self-repairing concrete seems to belong more in Stars Wars and Superman than in metropolitan architecture and industrial skyscrapers. Michelle Pelletier, graduate student at the University of Rhode Island, plans to transform this structural legerdemain from fiction to fact. Currently pursuing a Master’s degree, Pelletier, corroborating with chemical engineering professor, Arijit Bose, has developed the revolutionary, inexpensive and self-repairing smart concrete.
Pelletier has delved into a new and exciting arena: self-repairing concrete. This fiction-esque concept is the alchemy of architecture, a veritable goldmine for structural engineers and construction workers. Self-repairing concrete could diminish maintenance, transportation, manufacturing and labor costs. Unfortunately, most current smart concretes, such as those using glass capillaries or bacteria transmitters to secret repair agents, are tremendously expensive, making them about as practical as light sabers and x-ray vision for buildings. Pelletier believes that her novel conception, due to its simplicity of design and easy manufacturing requirements, could alter that situation permanently.
In order to create self-healing concrete, Pelletier injected microencapsulated sodium silicate agents into the concrete. After stress, cracks or fissures, the microcapsules split and release their chemicals into the affected area. The sodium silicate reacts with calcium hydroxide to create a thick jelly which disperses into targeted cracks and broken areas. This gel hardens after approximately seven days. Traditional fillers take anywhere from three to thirty days to fully cure and solidify. Calling the reaction “targeted” and “local,” Pelletier proudly believes that not only is her material less costly than current alternatives, but has a leg up on performance as well.
Smart concrete has an unanticipated but providential benefit. Structural concrete commonly has steel bars set inside to reinforce the concrete’s strength. Unfortunately, these bars are easily corroded when exposed to air, which can be caused by chinks in the concrete. By repairing these ruptures using Pelletier’s healing gel, the steel is protected from corrosion and fracture. Also, the resulting surface film from the sodium silicate may further prevent erosion.
Not only is this concrete intelligent, Pelletier claims, it is eco-friendly too. The U.S. concrete industry is responsible for 10% of America’s carbon dioxide (CO2) emissions. By reducing extraneous maintenance repairs, and by extension, transportation and manufacturing processes, this smart concrete can drastically reduce CO2 emissions, helping to control climate change and increasing air healthiness.
Set aside all the scientific foo-fa-rah, and only one question remains: “Does it work?” In tests comparing standard concrete to the self-healing concrete, when stressed to the near-breaking point, Pelletier’s creation regained 26% of its original tensile strength, next to a regular 10%.
So where’s the kryptonite; where’s Darth Vader in this happy-go-lucky story? Meet traditional concrete. He doesn’t want to leave. And he is the biggest obstacle to self-healing, "smart" concrete.