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Improving Concrete Production—by Adding Corn
UNK researcher Mahmoud Shakouri believes Nebraska’s most common crop could play an important role in addressing America’s infrastructure needs. He is studying how corn stover—the cobs, stalks, leaves and husks left over after harvest—can improve and strengthen concrete, the most widely used manmade material in the world.
Ten billion tons of concrete are produced across the globe each year—a figure that’s expected to continue growing as developing nations urbanize and countries like the United States look to replace aging infrastructure. “Most of the infrastructure in our country—roads, bridges and buildings—is made of concrete,” says Shakouri, an assistant professor of construction management at the University of Nebraska at Kearney. Many of these structures were built decades ago and are showing their wear.
Compounding the need to replace worn infrastructure: the durability of today’s concrete. “Although the production process has been automated over time, the durability of concrete is concerning,” says Shakouri. He points to the Roman Empire as an example of this decline. Ancient Roman concrete gets stronger over time. But while many of their structures—including the Pantheon and Colosseum—are still standing nearly 2,000 years later, roads built today begin to crack and deteriorate within a year or two.
This is especially noticeable in cold-weather states like Nebraska, where one of the primary causes of deterioration in concrete bridges and roads is the use of salt and anti-icing chemicals during snow and ice removal. When these chemicals seep into concrete, they corrode the reinforcing steel inside—weakening the structure and shortening its life span.
Concrete production has an environmental impact as well. Producing cement—which is used in concrete—generates 8% of greenhouse gas emissions worldwide. For every ton of cement produced, a nearly equal amount of carbon dioxide is released into the atmosphere. “It’s a major research topic from an environmental perspective,” Shakouri said.
A Different Approach to Concrete
Shakouri, who has degrees in architectural engineering, construction management industrial engineering, and civil engineering, is a concrete expert. “There are a lot of opportunities for research in this field,” he says, “including looking at supplementary materials that can replace a portion of the cement used in concrete.” Supplementary materials can improve concrete’s strength and reduce production costs.
The most common supplementary material added to cement is fly ash—a byproduct from coal-fired power plants. But fly ash is getting harder to come by as environmental regulations impact power plants, many of which have been shut down or converted to fuels other than coal. According to Shakouri, the current supply of supplementary materials can only meet about 15% of the concrete demand worldwide.
“There is a real push to find alternatives for that material,” says Shakouri. “In countries like India, China and Brazil, they are testing different types of agricultural waste in concrete, such as rice and sugarcane. I thought: Why not corn? It’s abundant here in Nebraska, and has similar characteristics to the other crops.”
Just Add Corn
Nebraska is one of the top corn-producing states in the U.S., harvesting 1.8 billion bushels in 2018. Corn stover is typically used as livestock feed or to make biofuels, but Shakouri believes it can be a sustainable source of supplementary cementitious material for the concrete industry.
“There’s definitely an economic advantage to producing concrete this way. Using corn byproducts could boost the state's economy and give farmers another revenue source. It’s a win-win situation.”
He is currently conducting research on whether corn stover ash can meet industry standards to be used as a supplementary material in concrete. He is also studying whether corn stover ash can improve the durability of concrete and reduce its permeability.
“We’re still in the beginning stage,” Shakouri said, noting that a new type of cement must go through several years of research and testing before it’s approved. “But this could have tremendous implications when it comes to construction.”
In addition to boosting concrete’s physical properties, Shakouri sees other reasons to consider adding corn stover ash to cement. Unlike coal, which takes millions of years to form, corn is planted and harvested each year, making it a more sustainable option than fly ash.
He spoke to the Nebraska Corn Board in December, and their division of research was very interested in expanding the application of corn stover. “They're supportive of any idea that allows us to reuse corn waste, because it helps the economy of the state,” he said. “There’s definitely an economic advantage to producing concrete this way. Using corn byproducts could boost the state’s economy and give farmers another revenue source. It’s a win-win situation.”