Shrimp Strength: How the fishy ingredient makes cement stronger

By Gwyn Wright via SWNS

Cement can be made stronger by adding shrimp shells, according to new research.

Scientists found that using tiny particles from the crustaceans makes the building material up to 40 percent tougher and 12 percent easier to compress.

The amount of time the paste needs to set was extended by around an hour when the shrimp shells were added.

To make it, the team created tiny crystals and fibers from chitin- the second most abundant natural polymer in nature- from waste shrimp cells.

The bits of chitin are around 1,000 times smaller than human hair.

Researchers in the US say the innovation can cut carbon emissions from cement production and reduce seafood waste.

The study’s corresponding author Professor Michael Wolcott from Washington State University said: “Those are very significant numbers.

“If you can reduce the amount you use and get the same mechanical or structural function and double its lifetime, then you’re able to significantly reduce the carbon emissions of the built environment.”

The team says their invention will reduce the amount of cement needed, lowering carbon emissions overall.

Cement is currently the second most used material on Earth after water and accounts for five percent of global greenhouse gas emissions.

The material also accounts for around 15 percent of global industrial energy consumption.

It needs lots of fossil fuels to reach the 1,500°C needed to produce it and the limestone it needs also has to be decomposed, which produces additional carbon dioxide.

People consume high volumes of it because it cracks easily and needs to be replaced often.

Lead study author Professor Somayeh Nassiri from the University of California, Davis said: “The concrete industry is under pressure to reduce its carbon emissions from the production of cement.

“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 produces between six million and eight million pounds a year of waste worldwide, with most of it being dumped in the sea.

For the study, the team studied the chitin materials at a microscopic level.

Crab, shrimp and lobster shells are made up of about 20-30 percent chitin with much of the rest being calcium carbonate, another useful additive for cement.

Scientists have previously tried to improve cement with similar material, cellulose, but sometimes it has worked and sometimes it has not.

The team found chitin has another set of atoms which 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.

Professor Walcott added: “Being able to control the charge on the surface is an important piece to controlling how they function in cement.

“We could do that quite simply on the chitin because of the carboxyl group that sits in the chitin polymer.

“The chitin nanoparticles repel individual cement particles enough so that it changes the hydration properties of the cement particle within the system.”

As the team added the processed nanocrystals of chitin to the cement, they were able to improve and target its properties, including its consistency, the setting time, strength and durability.

The authors now want to make the shrimp shell additive at larger scales and make the material as good at strengthening concrete itself.

The findings were published in the journal Cement and Concrete Composites.