Researchers aim to use seafood waste to improve concrete
WSU researchers have received a Department of Energy (DOE) grant to use seafood waste from shrimp and crab shells to improve concrete.
The work could lead to more durable concrete and in doing so, reduce the significant carbon emissions that go into concrete production. Led by Somayeh Nassiri, assistant professor, Michael Wolcott, Regents Professor, and Hui Li, research assistant professor in the Composite Materials and Engineering Center, the interdisciplinary team also includes researchers from Pacific Northwest National Laboratories.
About 10 billion tons of concrete are produced every year, making it the second most used material on earth after water. It can be made from locally available materials, forms easily, and is very strong when it sets. At the same time, due to massive use, the cement and concrete industry is one of the most energy and carbon-intensive of all manufacturing industries. Making cement requires high temperatures (1500°C) and combustion of fuels. The limestone used in its production also goes through decomposition that produces carbon dioxide. Cement production is responsible for between seven and 10% of total carbon emissions worldwide.
Furthermore, while concrete is used around the world for a huge variety of purposes, it easily cracks and must be repaired or replaced often, says Nassiri. Water penetrates unrepaired cracks and can cause corrosion in reinforced concrete, which is another expensive repair job. Once the cracks develop, whether in bridges, pavements, or a dam, they need to be treated.
One reason for cracking is that the amount of water needed in concrete production is not an exact science. Sometimes concrete sets as it is being transported to a site or waits at the job, which means the load has to be rejected. Sometimes, if it has set prematurely, contractors will add water to keep the concrete workable, which makes for a weaker final product and could lead to cracking.
As part of the two-year, $644,000 grant from the DOE’s Advanced Research Projects Agency-Energy (ARPA-E) program, the researchers have used bio-based nanomaterials made from shrimp and crab shells to strengthen cement paste at the atomic scale. The ARPA-E program supports innovative and unconventional energy technology projects that could lead to disruptive technologies.
“What we propose to do is to increase the durability and mitigate cracking issues of concrete, so that it doesn’t have to be repaired so often,” said Nassiri. “By doing that, we don’t have to use so much carbon-intensive cement.”
Shrimp and crab shells are made of chitin, an organic polymeric molecule with a highly ordered structure. The researchers are using the chitin to create an additive to improve the concrete.
“We looked at a very unconventional biomass source that is abundantly available in seafood waste,” Nassiri said. “It’s very underutilized and often discarded, making it a prime candidate. Maybe we can turn that unwanted waste into a wished-for additive for concrete.”
The researchers have worked with a similar biopolymer, cellulose, and believe they could derive properties from the chitin to enhance desirable engineering properties for the concrete.
“We knew the physical, chemical, and engineering properties that this new product will have and had a really good understanding of what we’re going to get,” she said. “Everything was on the theory side on paper, but we had scientific justification for it. That’s how we formed our hypothesis.”
As they add the processed nanochitin to the concrete, they are able to improve and target its properties, including its fluidity, the setting time, strength, and durability.
“It can be engineered to give you exactly those sought-after, looked for properties that you want to get with your concrete,” she said. “We’re getting an improvement in strength, and we would like to be able to customize and tune the fluidity of the concrete.”
As part of the project, the researchers are studying the market feasibility of their product for the concrete industry, such as how to meet production demand, its cost effectiveness, and its shelf life.
“If we’re developing a concrete that uses less water and less cement and is stronger and more durable, we can reduce the need for replacement and repair jobs and achieve a more cost-effective infrastructure that could transform the U.S. construction market,” Nassiri said. “So, to all those large seafood companies, don’t throw out your shrimp or your crab shells. We can use it in concrete.”