Tag Archives: science

How self-healing concrete could fortify America’s crumbling roads

As Congress navigates another last-minute scramble to approve funding for the nation’s highways ahead of a July 31 deadline, engineers far-removed from the Capitol Hill gridlock are hard at work improving the stuff that sustains our nation’s roads and bridges: concrete.

Recent innovations point to stronger and higher-performing highways and bridges in the future. Some products are already on the market; others are a long way off.

It may sound far-fetched, but the technology exists for self-healing concrete. The auto-mending material contains limestone-producing bacteria that activates when wet. The bacteria can lie dormant for up to 200 years, according to the European Patent Office, where the technology is registered.

When a structure made of self-healing concrete develops a crack, water inevitably seeps in, prompting the bacteria to feed on calcium lactate in the concrete. The feeding process breaks down different minerals in the concrete and consumes oxygen from the air. This sets in place a process that converts the calcium lactate, which can be dissolved in water, to limestone, which fills the crack.

“This is kind of ‘The Jetsons’ stuff,” says Georgene Geary, with a laugh. Ms. Geary is principal engineer at GGfGA Engineering in Georgia, and chairs the Task Force on Nanotechnology-Based Concrete Materials at the Transportation Research Board in Washington.

“This is the future,” she says.

Hendrik Jonker, a microbiologist in the Netherlands who owns the patent to the technology, came up with the idea by considering how the human body repairs broken bones through mineral processes. The process for concrete works on a crack of any length, as long as it is no wider than 0.03 inches, according to the European Patent Office.

New technology also opens the door for self-cleaning concrete. Engineers such as Kimberly Kurtis, professor at the Georgia Institute of Technology in Atlanta, are studying ways to use light as a catalyst for cleaning the surface of concrete or binding pollutants in the surrounding air.

Ms. Kurtis’ team has examined the use of a special form of the mineral titanium dioxide, which has been manipulated to make the mineral react to light. When light hits the surface of a concrete structure containing this special type of titanium dioxide, it begins a chain of events that eventually destroys organic material on the surface of the concrete, such as bacteria. Moss and fungi that feed on bacteria are unable to grow without the food source.

“They can also interact with pollutants in the air – things like nitrogen oxides or volatile organic compounds – and bind those to surfaces to essentially clean the air,” Kurtis says.

Kurtis noted that the high cost of self-cleaning concretes make them best suited for smaller scale projects in particularly dirty environments, such as a section of wall facing a street with heavy pollution.

While self-cleaning concrete has been commercially available for the past decade, its use remains limited. Sculptures near the new Interstate 35 bridge across the Mississippi River in Minneapolis – built after the 2007 collapse of an earlier bridge  – use self-cleaning concrete, as does the Jubilee Church in Rome, a building celebrated for its stunning white walls and unique architecture.

If special concretes can kill bacteria, could they also purify water? Researchers at the University of Central Florida are working to develop a cleansing coating for concrete surfaces that will kill bacteria. According to Boo Hyun Nam, assistant professor of civil, environmental, and construction engineering, the idea is to cover the inside walls of pipelines and storage tanks with the coating to purify the water inside and prevent contamination. Mr. Nam would not specify what the coating is made of.

“It’s their secret recipe,” he says.

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VIDEO: The 3-D-printed arms race


In May of 2013, the online organization Defense Distributed publicly released the blueprints for a plastic 3-D printed handgun they designed and built. Within two days, the U.S. Department of Defense ordered the group to remove this information, but it was too late. By then, over 100,000 people had downloaded the plans for the single-shot pistol, dubbed the Liberator.

The process of 3-D printing involves the layering of an additive, such as plastic, to create a model based on a digital file. This technology has the potential to revolutionize several industries and sectors, including manufacturing, medical implantation and art, but some are fearing the dangerous implications of 3-D printed firearms.

Last year, Illinois State Senator Ira Silverstein (D-Chicago) and Illinois State Representative Elgie Sims (D-Chicago) proposed respective bills in the Illinois Senate and House that would ban the production of 3-D printed firearms without a Federal Firearms License. Both proposals are active in the Illinois General Assembly.

The current federal law, the Undetectable Firearms Act, outlaws firearms that could go unnoticed by a metal detector. That means a gun must have at least a 3.7-ounce metal component.

However, gun control advocates argue that 3-D printed firearms can be built with a purely superficial metal piece that can be removed and still yield the gun operable. Furthermore, the guns tend to have a short shelf life, making them particularly dangerous.

“They’re not reliable,” said Mark Walsh, program director for the Illinois Council Against Handgun Violence. “There are only a certain number of opportunities to fire a bullet before the weapon malfunctions and has the potential to injure the person using it or someone else.”

The Liberator, a plastic 3-D printed gun, disassembled. (Photo: Justin Pickard)

The Liberator, a plastic 3-D printed gun, disassembled. (Photo: Justin Pickard)

Julie Friedman Steele, founder and CEO of the 3-D Printer Experience, a Chicago facility that manufactures 3-D printed objects, disagrees with restrictions placed on the technology.

“The first human innovation was fire, you could either use it for good or you could be an arsonist,” Friedman Steele said. “No matter what innovation it is, you’re going to find people using it for good or using it for bad, but if you take away the ability to use it, then there is so much innovation for good that we won’t be able to access.”

Back in 2013, Philadelphia became the first U.S. city to ban the production of 3-D printed firearms. That same year, the United Kingdom passed strict legislation banning all 3-D printed guns or gun components. Violators in Great Britain could face up to 10 years in prison.

In a city like Chicago that’s no stranger to gun violence, gun control advocates are hoping for similar legislation.

(Editor’s note: This story originally appeared on Medill Reports: Chicago.)


Defense Department shows off cutting-edge tech

WASHINGTON — More than 100 display booths popped up in the Pentagon courtyard for the first-ever Defense Department Lab Day. These innovations, most of which are still under development, were designed by about 38,000 scientists and engineers.

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