Segregation is always on the mind of Seppanen and others at Peab Asfalt. The efforts start at the plant, with proper loading of the trucks. The trucks themselves have rounded, not flat, bed bottoms. This prevents sticking when the materials are end-dumped into the Cat® AP600D later in the process.
The trucks travelled about 70 km (43 miles) from the plant to the airport. Traffic was light given the area and the fact much of the paving was done at night. Shorter truck cycle times, combined with other segregation fighting efforts, paid off.
"Our trucks are insulated, so the asphalt stays hot," Seppanen said. "The asphalt is covered as well. There was no problem keeping the asphalt in the trucks hot because the job took place in the middle of the summer."
The mix left the plant at 170º-180°º C (338º-356º° F), and was dumped into the hopper at about 160º-165º° C (320º-329º° F). Plant production, paving speed and trucking were all calculated to keep the paver moving at a consistent pace. "We move continuously," Seppanen said. "That's one of the key efforts we make to prevent segregation."
Another segregation-fighting technique is allowing mix to collect in the sides of the hopper throughout the shift. "We don't close the (hopper) sides between lifts to loosen material," Seppanen said. "The asphalt on the sides is cold, and we don't want to shake it loose and mix it with the hotter material. When the work is done for the day, we clean the sides."
The AP600D was a newcomer to the site, with the company previously using a different manufacturer's product.
"I really like the Cat paver," Seppanen said. "It's silent compared to others." He also appreciated its fuel efficiency. "It doesn't take a lot of diesel—it's very stingy with the fuel.," he said. Crews also found the screed adjustments easy to make.
The paver worked at a pace of about 4-5 m (13-16') per minute, placing a single lift of 40 mm (1.5"). The Cat paver worked at a width of 4.5 m (14.8'). Ten passes were required to cover the entire width of the 45 m (148') runway.
"The middle of the runway is the highest point because of drainage," Seppanen said. "We started at one side, then made five passes until we reached the middle. Then we started at the opposite side, and worked our way back to the middle."
The width of the project led to many longitudinal joints. Peab Asfalt crews placed the new, hot mat slightly higher than the adjacent cold mat. A breakdown compactor used a small side roller to compact the joint.