Is Rice Nice—for Concrete?
Water, aggregate, cement—the standard recipe for concrete is pretty simple.
But a few Concrete Industry Management students are hoping they have identified a secret ingredient—rice straw.
A small team of students are working under the guidance of program coordinator Feriadon Ataie to determine if incorporating the agricultural waste product can reduce concrete cracking and shrinkage. If successful, they not only will have created a better product for their industry, but helped the producers of one of California’s largest crops deal with a major waste product as well.
“Any time you can be a part of trying to make something better is always rewarding,” said junior Henry Freimuth. “What’s cool about this—if it works—is not only are we helping make concrete better, we are helping other facets outside of the industry. We are taking what would have been burned off in piles and repurposing it into something that could last another 100 years.”
Last fall, with support from the CSU’s Agricultural Research Institute and the California Rice Research Board, students whipped up 10 batches of high-performance concrete, which is often used in residential buildings and bridges. One remained pure, as a control group, and the other nine incorporated varying percentages of rice straw, which was provided by area farms and ground into a fine pulp by students.
Extracting a slim strand of straw, Ataie held it up in demonstration, yanking on both ends to show its resiliency. Like a spider’s web, it looks fragile but boasts incredible strength.
Ataie had done previous tests using rice straw ash, made from burned straw, but wanted to test the viability of the straw itself. He pushed his students to employ their critical thinking skills.
‘These are my heroes on the project,” he said. “They always come up with ideas on how we can make it better.”
For every ton of rice that is grown, 500 pounds of rice husks and straw are created. As a byproduct, it is often burned as waste or used for cattle fodder or insulation. Other studied uses have included fiberboard, sugar syrup, paper pulp, and industrial products but none were economically promising.
“They’ve tried a lot of things but nothing has worked,” Freimuth said. “I think we have a shot.”
In February, he and project member Joanne O’Hara were chosen as one of 10 student research groups to present their groundbreaking work at the 30th Annual CSU Statewide Student Research Competition in April.
“It’s just cool to be part of something that could one day change the way we do everything,” said O’Hara, a junior who is also president of the Women in Concrete Club.
With rubber gloves and protective glasses, the students traded off running the mixer and hefting scoops into molds on a recent afternoon. The concrete cylinders and beams they produced then were placed in the curing lab to be tested weekly for three months.
The concrete testing lab has several machines by which it can test pressures ranging from 60,000 up to 674,000 pounds.
“We mess with the designs and compare it against historical data to see how it compares to sidewalks and parking garages,” Freimuth said. “This is actually behaving pretty well.”
With a few taps on his keyboard, he watched the pressure start spiking upward on the screen. At 75,000 pounds or 6,000 pounds per square inch, the cylinder popped, sending concrete fracturing off in chunks.
“That’s about the equivalent of 24 Volkswagen Bugs sitting on it,” Freimuth said, as he took the cylinder out of the chamber and gave it closer examination.
Next was the flexion machine, where the top of the beam is compressed and the underside flexes outward—testing the strength of each.
“Concrete doesn’t like to move that way,” Freimuth said, as it snapped in half at just 6,429 pounds—about two Volkswagen Bugs.
Freimuth admits he is much more interested in concrete than he was with recreation management, his first bachelor’s degree. A veteran, he worked briefly as a prison guard after his service in the Navy until he heard about a program for veterans to return to school, and discovered Chico State’s Concrete Industry Management program—one of only four in the nation.
“This is what I want to make a career out of,” he said. “It’s great to have the opportunity to do research, and it’s nice to be able to have all the instrumentation and a lab to do this kind of work—there are not many labs out there and few opportunities within the industry.”