February 23, 2005
Mixture includes bottom ash from coal Researcher develops new concrete compositeCARBONDALE, Ill. -- When construction begins on the Southern Illinois Research Park's first new building this spring, a new kind of concrete developed at Southern Illinois University Carbondale will help it take shape.
Bottom ash, part of the waste generated when power plants burn coal, will substitute for some or all of the sand used in conventional concrete. Contractors will use this new mix in the foundation and slab of the one-story, 19,920-square-foot facility as well as in surrounding curbs and their gutters and in sidewalks and driveways.
"This is a waste product that would otherwise go into landfills and ash ponds," said Sanjeev Kumar, SIUC associate professor of civil engineering who, with the help of his students, created the composite.
If, after seeing how well it works at the research park, the building trades adopt this new material, everyone comes out ahead. Construction companies could save as much as 10 percent on concrete costs. Utility companies would save big bucks by not having to pay landfill charges. And the environment would benefit from having one less product in the waste stream.
Right now, the research team is in the lab, tinkering with percentages of cement, sand, gravel, water and bottom ash needed to meet the design team's strength and stiffness specifications. In March, they'll build a test pad out at the construction site to make sure the mix works as it should and do some tweaking if it doesn't. Kumar expects construction to begin in spring.
While this is the first full-scale use of bottom ash in a construction project, Kumar and his team have been working on ways to make it into a building material for about five years. They began with a series of laboratory experiments designed to test concrete made with different amounts of the stuff for strength, stiffness and durability.
Encouraged by the results, the researchers next tried out their altered concrete by building make-believe foundations at the Illinois Coal Development Park in Carterville and testing them under field-loading conditions.
"The performance of the concrete composites was almost as good as and in some cases better than the equivalent conventional concrete, " Kumar said.
Last summer, the Illinois Department of Transportation agreed to give the SIUC concrete composite a whirl in constructing the temporary road barriers used to divert traffic during road repairs.
"We'll know more with the passage of time, but the performance we have seen so far is similar to that of the barriers made with equivalent conventional concrete," Kumar said.
"The work with IDOT lets us test under real-world conditions. This current project (at the research park) takes us a step further because we're using these composites on an actual building."
New products always meet with some hesitation in the marketplace precisely because they are new and therefore have no track record, Kumar noted.
"Unless they have been tested for several years, end users are reluctant to adopt them," he said.
"Even though we have done extensive lab testing that shows results similar to conventional concrete, (this product) has never been used on an actual project. That was one of the troubles with taking it into commercial production."
Kumar anticipates that those in the building trades will have to see several more projects with good results before they begin to feel confident about using the new concrete. But he thinks that will happen.
"I have talked to several industrial partners who have shown interest in what we are doing," he said.
Leading in research, scholarly and creative activity is among the goals of Southern at 150: Building Excellence Through Commitment, the blueprint for the development of the University by the time it celebrates its 150th anniversary in 2019.
(Caption) Concrete feat - Workers at the Egyptian Concrete Co. in Salem pour concrete made with bottom ash, a type of coal waste, into forms used in making temporary road barriers. Researchers at Southern Illinois University Carbondale developed the experimental material, which performs as well as conventional concrete.