Nanoparticles extracted from waste prawn shells are being added to cement to make concrete stronger in construction.

Researchers from the Washington State University and Pacific Northwest National Laboratory created nanocrystals and nanofibres of chitin from waste prawn shells. When these nanoparticles were added to cement paste, they created a material that was up to 40% stronger and took longer to set – an ideal attribute for long-distance transport of concrete as well as hot weather construction work. The setting time for the cement was delayed by more than an hour, the researchers reported.

The results of the study could positively impact the environment through reduced seafood waste and lower carbon emissions from concrete production.

The research study was published in the journal Cement and Concrete Composites.

“The concrete industry is under pressure to reduce its carbon emissions from the production of cement,” said Somayeh Nassiri, an associate professor at the University of California, Davis, who led the research at WSU. “By developing these novel admixtures that enhance the strength of concrete, we can help reduce the amount of required cement and lower the carbon emissions of concrete.”

Concrete is widely used around the world in critical infrastructure such as building, bridges and roads. However, cement – an important component of concrete – is produced through a carbon intensive process, requiring the use of fossil fuels. Cement production accounts for about 15% of industrial energy consumption and about 5% of total greenhouse gas emissions worldwide.

Similarly, seafood waste is a significant problem for the fishing industry, with millions of kilograms of waste generated annually worldwide, most of it dumped into the sea.

“In the current world, dealing with climate change through the circular economy, we want to use waste materials as much as possible. One person’s waste is another person’s treasure,” says Hui Li, research assistant professor in WSU’s Composite Materials and Engineering Center, and a corresponding author on the paper.

During the course of their study, the researchers found that chitin at the molecular scale had an additional set of atoms that allowed them to control the charge on the surface of the molecules and, consequently, how they behave in the cement slurry.

“The chitin nanoparticles repel individual cement particles enough so that it changes the hydration properties of the cement particle within the system,” says WSU Regents Professor Michael Wolcott, a corresponding author on the paper.

Adding the processed nanocrystals of chitin to the cement, the researchers were able to improve and target its properties, including consistency, setting time, strength and durability. They saw a 40% increase in strength in how the concrete can bend and a 12% improvement in the ability to compress it.

The researchers are now looking to scale up the work to begin producing the cement additive.

Image: Somayeh Nassiri and Li Hui measure properties of cement formulas that contain nanoparticles of chitin (Source: Washington State University)

Branko Miletic

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