, Port Arthur, Texas

October 19, 2009

Entergy, researchers developing concrete from 'fly ash'

MONROE, La. (AP) — Where many coal-fired power plants see waste, researchers at Louisiana Tech University see an opportunity to curb greenhouse gas emissions, protect aquifers and change engineering forever.

The researchers, led by Erez Allouche, an assistant professor of civil engineering and associate director of the Trenchless Technology Center, and Sven Eklund, an assistant professor of chemistry, are working with a group of students to create a geopolymer concrete, or GPC, made from a waste byproduct produced by coal-fired power plants called "fly ash."

The power plants typically store the ash, one of the most abundant industrial byproducts on earth, in massive lagoons and storage facilities. That method of storage puts aquifers and surface bodies of fresh water in danger if storage goes awry, and takes up thousands of acres. But GPC can help eliminate the need for that storage.

Fly ash is often mixed into concrete, and researchers around the world are studying ways to use it as a substitute.

"It is important research for the U.S. because it's environmentally friendly," said Ivan Diaz, a PhD candidate who has been working on the research team for several years.

"We're keeping the fly ash out of the landfills and we're creating a valuable material."

The researchers use another byproduct from the paper pulp industry, sodium hydroxide, to start the reaction that turns fly ash into GPC.

The goal is to market GPC as a substitute for Portland cement, the most widely produced man-made material on earth and one scientists have pegged as a major contributor to global warming.

An estimated 5 percent to 8 percent of all human-generated atmospheric carbon dioxide (CO2) worldwide comes from the concrete industry. More than 2.6 billion tons of Portland cement are produced per year, and production is growing 5 percent annually.

Compared to Portland cement, GPC produces 90 percent less CO2 during production.

According to Allouche, GPC offers several additional advantages compared to Portland cement.

GPC features greater resistance to corrosion, more fire resistance, greater strength and less shrinkage.

Companies have tried a mixture that used 85 percent Portland cement and 15 percent GPC, but "why use 15 percent we can use 100 percent?" Allouche asked.

So far, the Tech research team has produced a 5,000 pound block of GPC and constructed a 100-square foot gazebo made entirely of GPC.

The researchers are working with about 30 power plants to provide fly ash for the research, including Louisiana companies like Cleco Power of Pineville and Entergy.

Allouche said he foresees GPC being used for road and bridge construction, as well as for other civil-engineering products like sewer piping.

The researchers could reach that goal sooner rather than later, as Allouche said they are currently on the verge of marketing a sprayable geopolymer product.

"We're not out to replace concrete, but we'd like to offer a complementary product," he said.

Diaz said GPC is unlikely to replace Portland cement, but not because GPC isn't a superior product.

"It's not because it can't do it, but because it's really hard to change the minds of the civil-engineering community," he said.

GPC currently costs about 15 percent more than Portland cement, "but that does not take into account savings (produced) by not having to store fly ash or 'green' tax credits," Allouche said.

Allouche and Eklund, the other lead researcher, said the success of GPC will ultimately be determined by companies' willingness to try something new.

"It's up to the industry to accept it," Allouche said.