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October 5, 2020
South Dakota State University is researching how cellulose fibers made from crop residue and forest byproducts can be used as an asphalt binder.
Asphalt binder is a thick, sticky substance produced as part of crude oil processing. It holds the sand, gravel and crushed rock in the asphalt mixture together.
Replacing a portion of the petroleum-based binder with cellulose can improve the performance of asphalt pavement, says Rouzbeh Ghabchi, assistant professor in the Department of Civil and Environmental Engineering. Plus, cellulose fiber is a renewable resource.
Because asphalt is so widely used in the U.S., “if we can engineer and produce a paving material that reduces material production and maintenance costs by as low as 1%, this will result in a substantial amount of savings for taxpayers,” Ghabchi says.
The SDSU researchers are making cellulose nanofibers to use in asphalt. To produce the fibers, they dissolve cellulose in a solution and pump it through a syringe. High voltage is applied to create an electrical field that draws the solution from the syringe tip. The solution dries as it emerges from the syringe tip into aligned nanofibers that are deposited on a collector plate.
The SDSU team tested various amounts of cellulose in different solvents to get the right type of cellulose nanofibers to use in the asphalt binder.
“We were able to produce cellulose nanofibers that gave us a consistent material in terms of quality and structural strength,” Ghabchi says.
They modified asphalt binders with different levels of cellulose nanofibers and tested the formulations with different aggregates.
“If it is not a good glue, it is not useful,” Ghabchi says. The asphalt mixture must be flexible, yet strong enough to resist cracking.
One of the tests involved subjecting the asphalt mixes to a freeze-thaw cycle and conditioning them in water to test their susceptibility to moisture.
“Freeze-thaw, rain and snow can result in the asphalt binder stripping from the aggregates — then we get potholes,” Ghabchi said.
They used a laboratory wheel tracking device that simulates rutting and moisture-induced damage on the highway.
“We were able to compare and rank mixes with various amounts of cellulose nanofibers and different types of asphalt binders, and to see the effect of the fibers on mechanical properties of asphalt mixes,” Ghabchi says.
Although further testing will be necessary, Ghabchi said their small-scale study showed that “plant-based additives are a promising technology for developing sustainable highway construction materials.”
Anamike Prasad, assistant mechanical engineering professor at SDSU, graduate student Marco Paulo Castro and doctoral student Ruhuit Sinha also worked on the project. The North Central Regional Sun Grant Center help fund the research.
Source: SDSU, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.
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