WEST LAFAYETTE, Ind. – Purdue University researchers say fusing concrete with microscopic wood nanocrystals could make concrete even stronger.
The researchers are hoping to build a bridge in California with the new material: cellulose nanocrystals - byproducts generated by the paper, bioenergy, agriculture, and pulp industries fused into concrete.
“Simply getting out there where people can actually drive on it, I think, is a huge step because you can't just say it's a lab curiosity at that point. It has real-world implications,” said Jeffrey Youngblood, a Purdue professor of materials engineering.
An electron microscope shows cellulose nanocrystals, tiny structures derived from wood. A cellulose nanocrystal is 100 nanometers long and five nanometers wide - much too small to be seen in an ordinary microscope. For reference, a human hair is 100,000 nanometers wide.
The cellulose nanocrystals make the concrete stronger through a chemical reaction that increases the hydration of the cement particles, making the concrete stronger, the researchers say. “The strength of concrete scales with the degree of hydration. So the more hydrated it is, the stronger it is,” Youngblood said. “So you’d think if you add more water it would be stronger. The problem is, water adds pores that make it weaker. But cellulose nanocrystals enhance hydration with less water, making the concrete stronger.”
Strengthening concrete could have other implications, such as making items made with concrete thinner and lighter while retaining the same strength with a potential side benefit of decreasing carbon dioxide released into the atmosphere. Cement plants account for an estimated 8 percent of global emissions of carbon dioxide, a main cause of climate change.


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Jason Weiss, the Miles Lowell and Margaret Watt Edwards Distinguished Chair in Engineering at Oregon State University, who previously was a professor at Purdue, said the cellulose nanocrystals make concrete more efficient because less mass is needed to make something that is equally strong.

“So it can be more sustainable and more efficient,” he said.
Youngblood said another benefit is that the cellulose-infused concrete sets faster, which means less waiting for concrete to cure when using forms to make bridges or for oil drilling.
Cement samples embedded in epoxy.
The researchers say the cost of using the cellulose nanocrystals may be offset by being able to use less cement, but the exact cost hasn’t been determined. They say how widely cellulose nanocrystals are used will be a factor. But even if only a small percentage of all the concrete produced used the cellulose nanocrystals, it would have a big impact just because concrete use is so ubiquitous.
The researchers say the work in scaling to concrete and preparing for the bridge in California is a partnership between Purdue, Oregon State University, P3Nano and others. P3Nano is a public-private partnership designed to support the commercialization of cellulosic nanomaterial.  P3Nano has been actively involved in the full-scale trials and is the sponsor of the project at Oregon State University to demonstrate full-scale applications of cellulose nanocrystals in bridges and flat slabs. The exact bridge in California where the cellulose-infused concrete will be used has not yet been determined.     
Blaine Kunkel, CEO of Nano-Green Biorefineries Inc., which has a license agreement with the  Purdue Research Foundation Office of Technology Commercialization to commercialize the technology, said the company is excited about the potential of cellulose nanocrystals.
“We view this as transformational technology,” he said. 
Images and story provided by Purdue University

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