1. Iowa State engineers don’t need a plow to clear snow from the heated test slabs they installed at the Des Moines International Airport. Larger photo. Photos courtesy of Halil Ceylan.
2. A thermal image of the heated airport pavements.
Engineers have installed 2 test slabs of electrically conductive concrete and the pavement has effectively cleared ice and snow. Iowa State University’s Halil Ceylan picked up his smartphone, opened up an app and called up the remote controls for the first full-scale test slabs. When a winter storm approaches, Ceylan can use that app to turn on the heated pavement system and, thanks to real-time video capability, watch as snow and ice melts away.
Late last fall Prof. Ceylan and his team from Iowa State’s Program for Sustainable Pavement Engineering and Research installed two, 15-by-13.5-ft test slabs of electrically conductive concrete into the apron at the southwest corner of the Elliott Aviation hangar on the north side of the Des Moines International Airport. “We have proven this technology does work,” Ceylan said. “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.” It’s the first thing Ceylan brings up after noting the success of the test slabs at the Des Moines airport: “People wonder how much this costs.”
Using 333 watts/ square meter (about the energy used by 3 light bulbs) for 7 hours, the operating cost is about 19c/ sq m. 7 hours “is way more than enough to melt an inch of ice or snow,” Ceylan said. 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. Thus far, the benefits are greater than the costs.
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. 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 12 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 and Sajed Sadati, doctoral students in 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.
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 degrees. After early success with heated pavements in his campus lab, Ceylan and his research group were ready to move on to larger-scale studies. That led to discussions about airport tests with Bryan Belt, the director of engineering and planning at the Des Moines International Airport. With Ames and Iowa State only about 40 miles away and the FAA as a major partner of the airport, he thought the airport should find a way to participate.
Ceylan noted that aprons are the most congested areas at airports and it takes a long time to clear them of snow and ice because big plows and other heavy equipment can’t work in such busy areas. So Belt identified a site and with the help of a project team from Foth Infrastructure and Environment, the test slabs were installed last October and November. Belt has checked on the test slabs three times during snowy or icy weather.
Belt said he can see the technology being useful in and around gates where there are lots of airport ground-handling equipment and employee activity. He also said heated pavements would be a big help at the front of the terminal with its sidewalks, crosswalks and ramps – he said it takes a lot of work to keep the areas clear and safe. In addition to collecting more data on the electrically conductive concrete, he said the team will soon be adding a hydrophobic coating to one of the test slabs. The water-repelling coating is designed to keep snow and ice from sticking to the pavement, making it much easier to keep clear and dry.
“We’re looking at hybrid heated pavements systems,” Ceylan said. “We think we can take advantage of multiple technologies to keep airports open and safe during the winter.”
http://www.news.iastate.edu/news/2017/03/28/heatedairportpavements
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