A team of Washington State University (WSU) and Pacific Northwest National Laboratory researchers has discovered a method to create stronger cement by putting nanoparticles from shrimp shells into cement paste. The innovation could lead to reduced seafood waste and lower carbon emissions from concrete production.

The findings were reported in the journal Cement and Concrete Composites. The research team created nanocrystals and nanofibers of chitin, a biopolymer widely present in nature, especially in marine invertebrates, insects, and fungi, from waste shrimp shells. When the chitin was added to cement paste, the resulting material was up to 40% stronger. The set time was also extended by more than an hour, which is a desired quality for long-distance transport and hot-weather concrete work. 

“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.”

Seafood waste is also a major issue for the fishing industry as it generates between six million and eight million pounds of waste annually worldwide, with most of it dumped into the sea. 

In prior studies, researchers worked to improve concrete with a similar common biopolymer called cellulose. Its effectiveness in concrete, however, was inconsistent. The WSU team found that, compared to cellulose, chitin at the molecular scale has an additional set of atoms that allows the researchers to control the charge on the surface of the molecules and, as a result, how they function in cement. 

In addition to the 40% increase in strength, the chitin nanoparticles in the cement saw a 12% improvement in the ability to compress the material. 

“Those are very significant numbers,” said WSU Regents Professor Michael Wolcott, a corresponding author of the study. “If you can reduce the amount that you use and get the same mechanical function or structural function and double its lifetime, then you're able to significantly reduce the carbon emissions of the built environment.”

The researchers are hoping to scale up the work to start producing the additive at large scales. The research also needs to achieve the same level of results at the concrete scale as at the cement paste scale.