TTU Engineering Students Take Top Prizes in International Concrete Cube Competition

To win the American Concrete Institute's Lightweight High-Strength Concrete Cube Competition, six Tennessee Technological University civil engineering students had to learn to work under pressure: at least 8,000 pounds of pressure per square inch, to be exact. That's what the 2-inch lightweight concrete cubes they created withstood to win first and third places in the competition in Montreal in November.

Two teams from the university mailed in their entries last October. According to contest rules, the cubes could weigh no more than 230 grams Q about 70 percent of the weight of standard concrete. L.K. Crouch, associate professor of Civil and Environmental Engineering at Tennessee Tech, supervised both teams in the design and construction of the cubes. He attributes the wins to the students' diligence and innovative thinking, as well as superior materials: a lightweight aggregate donated by the Stalite Corporation and concrete admixtures donated by Master Builders Technologies.

Coming up with a workable recipe for mixing the concrete was among the most difficult parts of the process, according to Neal Whitten of Kingsport, a member of the first-place team. What they were trying to accomplish within the limitations of the contest rules was "kind of difficult," says Whitten. "It's different than what we learn in class. We all did a lot of extra reading and came up with a couple different mixes."

Crouch notes that the students experimented with the proportions of paste and admixture, using about five times more liquid admixture than is recommended for regular concrete. "It's tricky," says Crouch. "At about eight times the regular amount, the concrete won't even set."

The mixes were placed in molds, allowed to set, refrigerated and then placed in a lime bath solution that speeds up the concrete's aging process. The molds, which Crouch says are at least as old as some of the students, posed problems by leaking. "For every 12 cubes we cast, we got about seven we could use!" says Whitten.

The strict specifications on weight and dimensions also presented a challenge, says Jason Burgess of Greeneville, another member of the first-place team. "We even had to do some sanding to get the cubes to within .05 inches of the size limit."

Although the Montreal event marked Tennessee Tech's first time in the international competition, the university beat out teams from a number of large, well-known schools, including the University of Virginia and Penn State University. Fourteen universities submitted 27 entries, and cubes were tested for compressive strength. The first-place entry withstood over 10,000 pounds of pressure per square inch, while the third-place entry stood up to 8,000 pounds of pressure.

"We all had some experience in classes and in other contests making high-strength concrete," says Lee Williams of Jackson, a member of the third-place team, "so we were confident we'd do well."

Lightweight, high-strength concrete is used to decrease the dead load in buildings and bridges. It also occupies less space than standard concrete.

The ACI announced the winners in a letter dated January 11. Whitten, Burgess and Jason Blankenship of Lafayette created the first-place entry. They won a plaque, "seeMIX" computer software for optimal concrete mix design, ACI watches and coffee mugs. The third-place winners, Williams, Austin Bateman of Fairview and Todd Wheeler of Hixson, won a plaque and ACI coffee mugs. Both teams received a year of free ACI membership and will be recognized in the association's monthly magazine, Concrete International.

For the past two years, Tennessee Tech students have won the high-strength category of the American Society of Civil Engineers' Southeast Regional Competition, competing against 23 universities. Tennessee Tech civil engineering students plan to compete in future ACI competitions as well as regional events.