Bending the rules to create a better infrastructure for our environment

Sugarcane bagasse ash collection in Louisiana’s sugar mill
Sugarcane bagasse ash collection in Louisiana’s sugar mill(LSU/WAFB)
Published: Jan. 14, 2021 at 1:11 PM CST
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BATON ROUGE, La. (WAFB) - The use of concrete is firmly cemented in human history with structural uses going back to ancient times. A research team is taking that ancient material into the future by creating a bendable product that will last longer and prove better for the environment.

Yes, bendable. You read that right. It goes against everything you think you know about concrete and the way it performs. The cracks in your house, the potholes in the road - those are all things that could become a distant memory with what’s being developed today.

“The lack of flexibility causes it [concrete] to crack,” explains Gabriel A Arce Amador, assistant professor in the Department of Construction Management at LSU. “Because of the cracking, water and other detrimental agents can penetrate into the structure. Concrete is usually made with stele reinforcements and it can corrode because of the agents coming in from those cracks.”

Our concrete cities are crumbling around us. In fact, the American Society of Civil Engineers completed a study in 2017 that ranked the country’s infrastructure at a D – just barely passing. The process of fixing all that crumbling infrastructure isn’t cheap. And it’s a cost that doesn’t just come with dollars and cents.

“The process [of making cement] releases significant amounts of CO2 in the environment. CO2 is a greenhouse gas and the scientific community agrees that this gas can cause harm, so there’s a lot of interest in the community to make concrete more sustainable.”

The part of the process that creates CO2 is in the production of cement.

“Concrete itself is a very ecofriendly,” explains Arce. “It’s a mixture of sand, gravel, and water. If you mix that together, it’s going be mud. When you add cement, that’s the product that acts as glue and binds it together to make the rock-like material.”

Cement is made when you take lime, silica, alumina, iron, and other materials, mix it, then heat it to 2,700 degrees. This is the step in the process that is producing all that CO2.

“One of the key aspects is to reduce the use of cement or completely replace the use of cement.”

So that’s what Arce and his teammates are working to do. And they’ve made some significant progress.

“We’re replacing cement and making it from clays,” Arce said. “Clay is calcinated soil at low temperatures, so there is less CO2 emissions.”

But that is only one piece of the puzzle. Remember when you were teased with the idea of bendable concrete? Let’s go back to that topic.

Bendable concrete is not necessarily new. Its invention is credited to Victor Li, a professor of civil and environmental engineering at the University of Michigan. In the early 1990s, he created what is called Engineered Cementitous Composites (ECC), which, to me and you, means bendable concrete.

“He came up with some phenomenal theories,” Arce explained. “The way to do it was not to make it not crack, but to use its cracking ability as an advantage.”

Rather than an unintended crack that occurs over time, Li sought to create a material that would crack on purpose.

“The idea is to control the cracking,” Arce noted. “Instead of one big crack, you distribute that into multiple hairline cracks. When you control that, you produce a concrete that will crack a lot, but in these very controlled micro cracks.”

These small cracks improve the strength of the material, while also making it more flexible.

“You will not be able to see the cracks except on a microscopic level.” Arce said. “This is good for structural purposes.”

Sounds great, right? Well, hang on, there’s a catch.

“Bendable concrete uses a lot of cement, more than traditional concrete,” Arce noted.

Although worse for the environment, it is better for infrastructure projects. That’s why it’s important to create a cleaner form of cement.

“This is something that will develop significantly in the next couple years,” Arce said. “There are so many unknowns right now.”

Arce’s team has found a way to create a more sustainable product that has environmental benefits.

“For quite a long time now, it’s been common practice to use coal fly ash in the cement.”

Coal ash is the residue that is created when coal is burned. This typically comes from power plants. Fly ash is a very fine, powdery material that comes from the burning of finely ground coal in a boiler.

According to the EPA, the powerplants will dispose of all this coal byproduct in landfills, discharge it in the waterways, or recycle it in concrete or wallboard.

“There was a professor at LSU [Dr. Michele Barbato] who started working on using sugarcane bagasse in conventional concrete,” Arce said. “We partnered to work on it together. When we were experimenting, we had the idea [to use sugarcane fly ash] and said that the properties of these ashes could be a perfect fit for this bendable concrete.”

Just like coal, ash is created during the disposal processing of the sugarcane.

“When you’re processing [sugarcane], you crush it, and you end up with these fibers. Then, they burn it, and they produce energy from the burning process,” Arce explained. “The result is this fine black powder, and this is the powder that we’re using to add into our bendable concrete.”

What was once destined for the landfill is now a viable component to improve the process of making bendable concrete.

“It’s replacing sand,” he noted. “Sand in conventional concrete isn’t a problem, but when you do bendable concrete, it is a special kind of sand called micro silica sand.”

That special sand is artificial produced, so that drives up the cost. Replacing this expensive sand with the sugarcane ash could bring the price down, which would make it more viable in the commercial market.

Sugarcane is already a vital part of Louisiana’s economy. According to the American Sugar Cane League, the industry employs roughly 17,000 people, is produced in 22 parishes, and has a $2 billion economic impact.

“It would be a very positive thing for the economy. You’re using a product that’s a waste and now it has value,” Arce noted. “It could create several jobs and would allow Louisiana to have a more resilient infrastructure.”

Additionally, making it more cost efficient will make it more attractive for those infrastructure projects.

“We can make infrastructure last longer. It should be significantly longer,” he noted. “Pavements, for example, we can significantly reduce the thickness, which means you use less, so now the cost isn’t as much.”

So, in the next 5 to 10 years, you could have a choice when hiring someone to add a concrete slab to your home. You could use traditional concrete, which is bad for the environment and would crack after a few years. Or you could spend a little more to get something that is better for the environment and will last twice as long, if not longer, without any cracks.

A second project has the potential for even greater benefits, but will take a bit longer before it comes to market.

“It’s the same concept as bendable concrete, but this would replace the cement with clays,” Arce explained. “Clay is calcinated at low temperatures, so it produces much less CO2. You use that as your cement and use chemical reagents that are solid, but bendable.”

This project is a collaborative effort with a team from Texas A&M, being led by Professors Miladin Radovic and Svetlana Sukhishvili.

“This is something that will develop significantly in the next couple years. There are so many unknowns,” he said.

What we do know is that there are better ways to fix the cracks of our crumbling infrastructure, and we can do so in a way that will minimize harm to the environment.

“This is a very, very sustainable product,” Arce said. “The main product that causes pollution is the use of cement. If you remove it, then you have a product that is very environmentally friendly and sustainable.”

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