By Day Greenberg The Daily Northwestern

Northwestern researchers may have made it possible to have spiral buildings in the Chicago skyline someday.

Recent findings from Northwestern researchers and the National Institute of Standards and Technology have found a way to measure the exact amount of water in concrete structures, which could ultimately lead to the creation of longer-lasting materials and allow for more experimentation in design.

The research, published in the April issue of Nature Materials, could also lead to the reduction in carbon dioxide emission caused by the process of creating concrete and a decrease in the amount of money spent on maintenance and repair.

Hamlin Jennings, a civil and environmental engineering professor at NU who was the primary author of the study, said the findings could also lead to producing more environmentally friendly materials.

“I think most people find concrete a boring material,” Jennings said. “That’s because a lot of it is used and it’s not fun to look at. But concrete is conceivably the most important material on earth when we look at the infrastructures that we rely on on a daily basis. Improving that material is important to improving the quality of life.”

Portland concrete is the most widely used construction material in the world – 11 billion metric tons are consumed every year. It is made with cement, water, sand and gravel. However, until now, scientists could only estimate how much water is chemically bonded with the cement and how much water is sitting in the sponge-like concrete structure.

Civil and environmental engineering Prof. Jeffrey Thomas, also an author of the study, said the result of this new research pins down the composition and density of the solid particles in the concrete by measuring the exact amount of water present in the mixture.

“It is hard to design concrete to have all the properties you need,” Thomas said. “You don’t know how durable it’s going to be in the long run,” he added.

Thomas and Jennings worked with Andrew J. Allen of NIST and finalized their data from separate experiments over many years. The last improvements made to the physical structure of concrete occurred in 1824.

Cement is made from limestone and clay. It is heated at a very high temperature of 1,400 degrees Celsius in a kiln to form a powdery cement material. Water, sand and usually gravel are then added to make the final, usable product, concrete. The process of extracting calcium from the limestone is responsible for up to 10 percent of carbon dioxide emissions, Thomas said.

Researchers found the amount of water in the concrete by submerging a piece into neutron-rich heavy water. The water replaced the non-bonded water in the concrete. By blasting this heavier concrete with more neutrons, scientists were able to measure the amount of water that was not bonded. The research was conducted using equipment at the NIST Center for Neutron Research and the Advanced Photon Source at Argonne National Laboratory in Argonne, Illinois.

“We’re hoping this result will give people kind of a starting point, one thing that they can hang their hat on,” said Thomas. “It’s one precise measurement that we think people need.”

Researchers said this discovery opens up the opportunities for more creativity in construction without sacrificing safety. Buildings like a recently proposed spiral skyscraper in Chicago could be the norm with more advanced building materials, said civil and environmental engineering Prof. Raymond Krizek.

“I think (the research) is absolutely fascinating,” said Kevin Bedi, president of Chicagolandconstruction.com, a directory that helps construction companies network. “The ideas and possibilities are limitless … for its uses in high-rises and everything else.”

Reach Day Greenberg at [email protected].