A Boeing 747 jumbo jet can weigh more than 800,000 pounds at full capacity and have a takeoff speed of 180 miles per hour. Now imagine 350 aircraft of varying weight and speed operating on one runway daily.
With that kind of force hitting the pavement, the construction specifications for the runway must be strictly adhered to, and the contractor responsible for paving must do so with surgical precision.
If that isn't difficult enough, try to stay on time and under budget. Tilcon Connecticut Inc. did just that this past spring when it rehabilitated runway 6-24 at Bradley International Airport in Hartford, CT.
Tilcon Connecticut Inc. is a leading asphalt producer and contractor in New England. The company began in 1923 handling roadbuilding projects with only a steam shovel and has grown to become a statewide conglomerate of 23 locations and plants.
Tilcon produces not only asphalt but also crushed stone and ready-mix concrete. It has nine paving crews and assumes a majority of state contracts for the Connecticut DOT, such as highway roadbuilding and repair. One such state contract was Bradley International Airport.
"Runway 6-24 is the main runway at Bradley," says Richard Birge, manager of construction for Tilcon. "The backup runway 15-33 was open to air traffic, but both runways had to be shut down for three consecutive weekends while we milled and paved the intersections of the two. It was imperative we kept to the schedule."
Bradley is managed by ConnDOT and services more than 6 million passengers annually (2008 statistics), second only in New England to Boston's Logan International Airport. Runway 6-24 handles approximately 60% of all daily air traffic.
The Federal Aviation Administration (FAA) recommends rehabilitation of airport runways every 20 years. This $17 million project was funded through the FAA Airport Improvement Program and passenger facility charges. Renovation of runway 6-24 entailed not only resurfacing, but also upgrading of the water main line and installation of all new lighting along the runway.
The project began the last weekend in April with a drop-dead completion date of June 23, 2009. Like all state highway jobs, if Tilcon missed the completion date, ConnDOT would assess fines. To accommodate such a tight timeline, crews were scheduled around the clock with up to eight crews working each 12-hour shift.
"There were no rain dates in the schedule," explains Birge. "If it rained a lot, we had to change the hours worked. At times we had milling and paving going 24 hours a day."
Runway 6-24 is 9,500 feet in length and 250 feet wide. The project called for milling and repaving the runway with a 4-inch-thick mat - 62,900 tons - of FAA-approved hot mix asphalt. Tilcon's asphalt plant is 24 miles away from the airport, one hour by truck. Tilcon had a convoy of 30 trucks running back and forth during the day, and less during the night shifts. Approximately 1,800 tons of asphalt were used per shift.
"One very productive day we used 3,100 tons," says Birge.
Paving a wide berth
The specifications for paving and compaction were very stringent. Test strips were laid prior to the project start, which had to be tested for compaction density and quality of the asphalt.
"We did a couple test strips at our facility, making adjustments to see what gave the best result for texture and mat consistency," says Birge. "Then test strips at the airport were inspected by ConnDOT and the FAA before we could begin work."
The project called for each pass to be a minimum of 20 feet wide; however, it was Tilcon's choice to pave 25 feet wide. With the continuous work within an already tight schedule, Birge wanted to ensure as much efficiency on the job as possible.
"We paved across the runway in 10 passes that were 6,000 feet in length," explains Birge. "The less time you take to back up, the more efficient the job."