Sunday, September 25, 2022

Shrimp shell nanoparticles make for significantly stronger cement

A new study has suggested that putting nanoparticles from shrimp shells into cement paste could make the material significantly stronger. The innovation could lead to reduced seafood waste and lower carbon emissions from concrete production.

Concrete is the second-most consumed material in the world after water. The production of this immense amount of cement is carbon-intensive, requiring the use of fossil fuels to reach the required high temperatures. It is responsible for almost 15% of industrial energy consumption and about 5% of total greenhouse gas emissions worldwide.

Meanwhile, seafood waste is a significant problem for the fishing industry, which generates between 6 million and 8 million pounds of waste annually worldwide.

The team of Washington State University and Pacific Northwest National Laboratory researchers created nanocrystals and nanofibers of chitin, the second most abundant biopolymer in nature, from waste shrimp shells. When these tiny bits of chitin, which are about 1,000 times smaller than human hair, were added to cement paste, the resulting material was up to 40% stronger.

The set time for the cement was also delayed by more than an hour, the desired property for long-distance transport and hot weather concrete work.

In their work, researchers studied the chitin materials at the nanoscale. Crab, shrimp, and lobster shells are made up of about 20-30% chitin, with much of the rest being calcium carbonate, another useful additive for cement. Compared to cellulose, chitin at the molecular scale happens to have an additional set of atoms – a functional group – that allows the researchers to control the charge on the surface of the molecules and, consequently, how they behave in the cement slurry.

The success in strengthening the cement paste came down to how the particles suspend themselves within the cement slurry and how they interact with the cement particles. The chitin nanoparticles repel individual cement particles enough so that it changes the hydration properties of the cement particle within the system.

As they added the processed nanocrystals of chitin to the cement, they were able to improve and target its properties, including its 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.

Researchers are now hoping to scale up to work to begin producing the additive on large scales. The research also needs to continue to achieve the same level of enhancements seen at the cement paste scale at the concrete scale.

“The concrete industry is under pressure to reduce its carbon emissions from the production of cement,” said Somayeh Nassiri, 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.”

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