Halil Ceylan, Civil, Construction and Environmental Engineering Professor–Iowa State University’s Program for Sustainable Pavement Engineering and Research in Ames, Iowa, USA, held his smartphone, opened an app, and called up the remote controls for the first full-scale test slabs of electrically conductive concrete installed at an American airport. When a winter storm approaches, Ceylan can use the app to turn on the heated pavement system and watch as snow and ice melts away—through real-time video capability.
After early success with heated pavements in his campus lab, Ceylan and his research group were ready to move on to larger-scale studies, which led to discussions about airport tests with Bryan Belt, Director of Engineering and Planning-Des Moines International Airport. By late fall 2016, Ceylan and his research team installed two, 15 x 13.5-foot test slabs of electrically conductive concrete into the apron at the southwest corner of the Elliott Aviation Hangar on the north side of the airport. The hangar is centrally located in the general aviation apron devoted to smaller aircraft.
Ceylan’s pictures of the slabs taken during one of this winter’s rare snowfalls show the apron all around the test slabs covered with an inch or two of white snow, while the two heated slabs, marked by diagonally painted red stripes, were clear and drying. “We have proven this technology does work. Our goal is to keep airports open, safe and accessible. We don’t want any slips or falls, or any aircraft skidding off runways. Our technologies can contribute to providing a safe environment and fewer delays,” Ceylan said.
The cost of heating pavement
Ceylan and his research group have run the numbers: Using 333 watts per square meter (about the energy used by three light bulbs) for seven hours, the operating cost is about 19 cents per square meter. Seven hours “is way more than enough to melt an inch of ice or snow,” he said.
Ali Nahvi, Graduate Student-Civil, Construction and Environmental Engineering and part of Ceylan’s research group, has been analyzing the economics of heated runways at airports. So far, Nahvi’s data says the benefits are greater than the costs. While the installation costs would be higher than regular pavements, the heated pavement technology also saves on the cost of plows, de-icing chemicals and wastewater treatment of chemical runoff.
How it works
The test slabs of electrically conductive concrete are made up of 1 % carbon fiber and a special mix of cement, sand and rocks. The carbon fiber allows the concrete to conduct electricity, but there is some resistance to the moving electrons, which creates heat. With help from the National Concrete Pavement Technology Center (CPTech Center-Iowa State University), Alireza Sassani, Doctoral Student-Civil, Construction and Environmental Engineering, led studies of the concrete mix and prepared hundreds of concrete samples in the lab to find the right combination of:
- compressive strength
- tensile strength
- workability
- durability and
- electrical conductivity
The test slabs at the Des Moines airport are 7.5 inches thick in two layers – the bottom 4 inches are regular concrete, the top 3.5 are electrically conductive concrete. Between the layers are twelve metal electrodes, six per slab, running the width of each slab. The electrodes are wired to the nearby hangar’s power supply. The slabs are also wired with various sensors: temperature probes, strain gauges, humidity sensors and more. There are two surveillance cameras mounted nearby; and the team just acquired its newest research tool—a high-grade thermal camera.
Hesham Abdualla, Sajed Sadati and Ali Arabzadeh, Doctoral Students-Civil, Construction and Environmental Engineering, recently demonstrated the camera by sending 70 volts of power through a test sample of electrically conductive concrete that was 14 inches long, 4 inches wide and 4 inches thick. Ali set the thermal camera nearby to watch the electrodes heat up, creating thermal images in reds and whites. As the carbon fibers in the test sample spread electricity and heat, the camera’s images turned from blues to greens to yellows. After several minutes, the camera recorded a sample temperature of about 75°.
Airport perspective
Ceylan’s heated pavement research is part of the Federal Aviation Administration’s (FAA) Center of Excellence “PEGASAS”—Partnership to Enhance General Aviation Safety, Accessibility and Sustainability—established in 2012, led by researchers at Purdue University with other core members from Iowa State, The Ohio State University, Georgia Institute of Technology, Florida Institute of Technology and Texas A&M University. They’ve establish cost-sharing research partnerships with the federal government, universities and industry.
To read the entire article and for more details, please go to: http://www.newswise.com/articles/iowa-state-engineers-test-heated-pavement-technology-at-des-moines-international-airport.
Photos: Halil Ceylan/Iowa State University