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The search to unravel concrete’s ‘DNA’

MIT researchers aim to make it more versatile, environmentally friendly

Deepak Jagannathan uses toys to mix concrete for some serious research in associate professor Krystyn Van Vliet’s lab at MIT. Deepak Jagannathan uses toys to mix concrete for some serious research in associate professor Krystyn Van Vliet’s lab at MIT. (David L. Ryan/Globe Staff)
By Carolyn Y. Johnson
Globe Staff / August 8, 2011

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CAMBRIDGE - To most people, it is utterly mundane: the stuff of humble sidewalks, bridge supports, and building foundations. But intrigued by the sheer complexity of concrete, Massachusetts Institute of Technology researchers have been leveraging the tools of statistical physics, materials science, chemistry, and civil engineering to find ways to make the most widely used man-made material on earth more environmentally friendly.

This week, about 600 people from industry, academia, and government will flock to Cambridge for a symposium that tackles the big questions about this seemingly ordinary material, with sessions on the science of concrete, insights from the architecture and design community, and updates on efforts to measure and decrease its carbon footprint.

“Concrete is the backbone material for infrastructure . . . for housing, for shelter, for bridges,’’ said Franz-Josef Ulm, a professor of civil and environmental engineering and member of the self-proclaimed “liquid stone gang,’’ a multidisciplinary group of MIT scientists and engineers with a shared interest in concrete. “There’s no material in the foreseeable future that can replace concrete.’’

Each member became interested through a different path. A leading cement chemist, Hamlin Jennings, began studying concrete on a bet; senior research scientist Roland Pellenq was drawn in by fundamental questions about its porousness. Ulm notes interest in concrete runs in the family - his mother is a structural engineer who has consulted on projects such as reinforced concrete buildings and bridges.

Concrete has been used in some form or another since at least the days of ancient Rome and is ubiquitous at construction sites - a far cry from the pristine confines of the laboratory. This basic building block of infrastructure may seem simple, or at the very least, a solved scientific problem.

But in fact concrete is mysterious - at least at the molecular level.

The MIT group saw in the lack of detailed scientific understanding of concrete an opportunity: If scientists could, using computer models and imaging technology, understand the basic molecular structure, they could develop ways to manipulate concrete to make it stronger or harder, or decrease its environmental impact.

In 2009, the MIT gang became a bit more official, forming the basis of the Concrete Sustainability Hub, funded by a $10 million, five-year grant from the cement and concrete industry, with a focus on leveraging sophisticated scientific tools to make its manufacture and use more sustainable.

The research was sparked by one particular problem with concrete: Producing it is energy intensive and accounts for 5 to 10 percent of annual emissions of carbon dioxide, a heat-trapping greenhouse gas.

Making the manufacturing process more efficient or making concrete more durable so less of it is needed could have far-reaching environmental repercussions.

The research hub is also trying to devise modeling tools that could help engineers and architects make more informed decisions about how to minimize the environmental impact of any use of the material. The team is working on developing a computer program that would make it easy to track the carbon footprint of a building or paving project over its lifetime.

To do that, they are calculating the amount of carbon dioxide emitted in the manufacturing process and when the material is in use - in a building, for example, that includes heating and cooling.

Balancing the benefits and drawbacks is essential, so that engineers and architects can make informed decisions about what building options have the lowest overall environmental costs.

Scientists have made huge strides in deciphering the “DNA of concrete’’ and are building computer models that could help them create formulations that have different properties, such as increased stiffness or strength. The idea is that just as biologists have been empowered by understanding the structure and code of DNA, a truly molecular understanding of concrete can enable scientists to optimize the material to meet the needs of a job or make the manufacturing process more efficient.

“How can we change the [properties of concrete] by changing the composition and structure down at the atomistic scale,’’ said Krystyn Van Vliet, associate professor of materials science and engineering at MIT. “Could you make a cement sidewalk that never cracks?’’

Carolyn Y. Johnson can be reached at cjohnson@globe.com.


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