Published: Fri Sep 7, 2012
Civil engineering graduate student Jared Thompson and civil engineering technician Mark Davis recently unveiled a small parking slab at Tennessee Tech University that is also a giant leap toward green planning on campus and a promotion of student competitions in the American Society of Civil Engineers.
The 21-by-10-foot slab east of the TTU football stadium was constructed of pervious concrete, which allows water to filter back into the groundwater supply.
“We built the slab to provide all-weather parking for the TTU ASCE student chapter, which participates annually in competitions like the concrete canoe and steel bridge contests sponsored by the Southeastern ASCE student chapters,” said L.K. Crouch, a TTU civil and environmental engineering professor who has been involved in porous concrete research for 10 years. “It will serve as a display area for competition-related items like the ASCE student chapter trailer, which is sort of a mobile billboard for the student chapter, and will also serve as a research field demonstration venue in water quality.”
Crouch said he hopes displaying these items on the slab will increase industry and alumni support of the student chapter’s costs of traveling to compete, which are normally covered by student fees, funds from the Student Monies Allocations Committee, the civil and environmental engineering department and private donations. He hopes the slab also will be a centerpiece for tailgating, fundraising and networking with potential employers at TTU football games.
The slab also promotes research in the use of pervious concrete, as it can be used in environmentally sound planning.
“The system captures rainfall on the slab and transmits it to the base, which serves as a holding area to permit time for the runoff to percolate into the subgrade,” Crouch said. “Theoretically, runoff is decreased, and the captured runoff is filtered to some degree prior to recharging local groundwater.”
Thompson said perforated pipe networks are installed in both the base and the subgrade to allow water quality sampling.
“Projects like this are important to finding better ways to deal with runoff water and ensure better water quality,” said Dennis George, director of the Center for the Management, Utilization and Protection of Water Resources, which financially sponsored the project by splitting the cost of the concrete and No. 57 limestone base with TTU. “Runoff affects our overall water quality because it carries with it all the pollutants or anything that is on the ground that it crosses.”
The use of pervious concrete is slowly expanding. A driveway in Baxter, Tenn., was constructed using a pervious concrete mixture similar to that used for the ASCE trailer slab. One thing researchers must do, though, is determine whether or not the porous concrete has the same strength as regular concrete.
“Pervious concrete is permeable and thereby contains much smaller quantities of sand than normal concrete,” Crouch said. “Unfortunately, the strength of pervious concrete is inversely related to its permeability.”
In other words, the more permeable, the weaker the concrete. According to Crouch, “a balance must be achieved between compressive strength and permeability for the particular application.”
TTU ASCE students built the demonstration slab under the direction of Alan Sparkman, executive director of the Tennessee Concrete Association.
“Sparkman was ideal for the job for a variety of reasons. He teaches National Ready Mix Concrete Association Pervious Concrete Installer Classes, has all the necessary special tools and has long supported TTU pervious concrete research,” Crouch said.
TTU Facilities personnel dug the slab. Davis served as both foreman and quartermaster and was the driving force behind the project, Crouch said.