Infrastructure innovation: Self-healing concrete

Michelle Pelletier

Here at Infrastructure US, we are big fans of any form of building material that helps cut costs, emissions and is beneficial to the environment, and this latest news covers all of those.

At the University of Rhode Island, a graduate has developed a form of self-healing concrete that is able to 'repair' itself should cracks form. The student, Michelle Pelletier, has achieved this by embedding a micro-encapsulated sodium-silicate healing agent directly into a concrete matrix. When stress cracks appear or form in the concrete, the capsules rupture, releasing a 'healing agent' into the affected areas.

According to The Engineer, the sodium silicate reacts with the calcium hydroxide naturally present in the concrete to form a 'calcium-silica-hydrate product' that repairs the cracks by filling in the pores in the concrete. This chemical reaction creates a gel-like material that hardens in about one week making the concrete solid once more.

Smart materials

Speaking to The Engineer, Pelletier, who is working on the project with URI Chemical Engineering professor Arijit Bose, said, "Smart materials usually have an environmental trigger that causes the healing to occur."

"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."

When Pelletier's methods were tested against a standard concrete mix to her concrete mix containing two percent sodium-silicate healing agent, Pelletier's mix recovered 26 percent of its original strength (after being stressed to near breaking) versus 10 percent recovery by the standard mix.

It is believed that an increase in the quantity of healing agent would likely further improve the recovered strength of the concrete.

Pelletier's research project is one of several from around the globe aimed at developing bio-concrete and smart materials:

Hopes
It is hoped that the introduction of smart materials such as the self-healing agent will extend the lifespan of buildings and reduce repair costs, as well as have environmental advantages. By having self-healing agents in a concrete mix, you drastically reduce the amount of CO2 emissions that result from concrete production, which includes mining, transportation and those that come from concrete plans.

"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 CO2 emissions," Pelletier said.

It is estimated that the concrete/construction industry is responsible for about 10 percent of all CO2 emissions in the US.

Relevant articles:

Is sustainable design purely political? | Sustainable construction projects | First steps to a sustainable city? | Green buildings

Timon Singh

Timon Singh is a graduate of Liverpool University where he received a degree in Social and Economic History. He has previously worked for BBC Magazines on BBC Who Do You Think You Are? Magazine, the publication for the popular genealogy show.

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