Two chemical engineering researchers take on the challenge of concrete
klykins@tntech.edu
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We walk on it, work in structures built with it, drive on it and for the most part take for granted our use of the most abundant synthetic material on earth—Portland cement concrete.
But researchers around the world remain baffled in many ways about the behavior of a material made from the most plentiful and simple raw materials. It’s hard to predict how long it will last, how badly it will crack and how much negative environmental impact it will make.
At Tennessee Tech University, colleagues and chemical engineering researchers Joe Biernacki and Don Visco are working to help unravel some of the mystery surrounding concrete. The American Ceramic Society, ACerS, recently featured their work in a publication dedicated to highlighting cement researchers who are working to bring new strength, flexibility, self-healing capacities and a smaller CO2 footprint to concrete.
Biernacki says modern concrete just doesn’t last long enough, and one way to reduce the environmental impact is to double, triple or even quadruple its life expectancy in the field.
“In an ideal world, we would produce cements that had no carbon footprint. The work we do we link to the environment,” Biernacki said. “If we can make concrete last twice as long, just a factor of two would be remarkable. It would certainly make concrete more environmentally friendly.”
The TTU duo developed a technique for encoding the structure of molecules that have a particular performance behavior. They run the data through a computer model to correlate performance and predict new molecular structures to enhance performance.
“We hope to design entirely new molecules with targeted performance enhancing characteristics,” Biernacki said. “This has the potential to enable the design of concrete mixtures with unique rheological [the flow under stress and strain] properties, for example.”
Biernacki also summarized the enigmatic challenges of concrete research in a recent article.
He says more than 2,000 years after the Romans built great and enduring structures using hydraulic cements, modern science is still baffled about the behavior of concrete because there is no unifying theory.
“It’s limestone, shale, stones and water. What’s so baffling? It’s simple, burn the limestone and shale to produce some calcium silicates and calcium aluminates, add a bit of gypsum, grind into a powder, put some stones in, mix with water and let it set. No big deal, right?
“Unfortunately, the resulting concoction turns out to be incredibly complex,” Biernacki explained.
To add to the challenge, the final and important steps to creating concrete take place in the field by necessity. Environmental conditions play a huge part in the final product.
Finally, concrete is not one material, but a spectrum of materials designed to match the application. Some must be strong, some porous, and some tough.
“Controlling the properties is the key,” said Biernacki. “Not just making a lot of it the same every day.
“Ultimately, we are working to alter the kinetics of hydration to unlock the elusive secrets of this important material.”
