The Super Bowl of NASCAR does not have comical commercial breaks to fall back on, but it put on one heck of a halftime quiz show last February.
Crews worked feverishly for 1 hour and 40 minutes during the running of the Daytona 500 to fix a pothole that sprouted from the historic pavement on turn 2 about halfway into the race. For those TV viewers and spectators who held on during the panic-laden delay, it quickly became a game of “How Are They Going to Fix It?” Engineers and asphalt specialists with the North American Testing Co. threw everything but the kitchen sink at the problem, and ended up using something that probably a few plumbers carry in their toolbox. They ended up gathering polyester resin products from racing teams, mixed them with a hardener and heated the concoction up so the putty mixture turned into a jelled substance.
Jamie McMurray recovered to win the 2010 Daytona 500, but the emotional cut clearly hit a nerve with track officials.
“This is not supposed to happen,” track president Robin Braig told the Associated Press shortly after the race. “We know how to fix it. We know how to do it right. I apologize for it. This is hallowed ground. We understand that. We accept the responsibility.”
Leading up to the 2010 Daytona 500 upper-brass confidence was at the very least stable. Even though the 2½-mile trioval had not been resurfaced since 1978, the next project was not scheduled until 2012. Then the crazy climate pattern that had been toying with much of the U.S. for the past year spun Florida around like a top. The combination of unusually cold and wet weather weakened the pavement, and sealing its fate on turn 2 was the stress caused by the racing tires during the event.
Days after the NASCAR season opener, Daytona’s team of pavement experts prescribed a more permanent fix to the pothole: reinforced concrete measuring 6 ft wide and 18 ft long. And track officials stiffly defended their turf.
“We have addressed that area of concern,” Daytona spokesman Andrew Booth told Roads & Bridges. “It was fixed about five or six days after the Daytona 500, and we have since had motorcycle races in that area without any issues. We have had the Richard Petty Driving Experience without any issues, so we are confident in that area and what we have done to address it.”
Still, in an effort to avoid another world infamous incident, the Daytona International Speedway bumped its reconstruction to July 2010.
Breaking ground after Zero
Not long after the Coke Zero 500 drops the checkered flag, crews will be breaking ground on the Daytona International Speedway repaving project. Lane Construction Corp., coincidentally the Richard Petty of racetrack construction that has repaved the likes of Talladega in 2006 and Darlington in 2008, will be on hand to execute the Daytona work, with HNTB Corp. serving as the lead designer. There also will be other “supervisors” from afar.
“You are working right across the street from the headquarters of the International Speedway Corp., which owns Daytona, and the NASCAR offices,” Jason McLear, Lane’s district manager who will be overseeing the Daytona project, told Roads & Bridges. “I think from their office they can see inside the track, so that brings another level of interest from the owner. Before they have not been as visible during construction.
“We are looking forward to putting our guys in the spotlight and certainly providing the owner with the smoothest and safest track yet.”
As a contractor, they will dig down to the deepest. The track was first paved in 1959, and 19 years later in 1978 another asphalt surface was dropped on the original. Starting on July 4, Lane Construction will remove both racing surfaces and replace them with 7 in. of new asphalt. Crews will use a track hoe with teeth to rip the pavement in turns 1, 2, 3 and 4. According to McLear, the machine will essentially “pull down, from the bottom, the existing hot-mix surface.”
A motor grader and soil compactor will come in and execute the fine grading operations after the surface is removed on the turns. Here is where Lane’s innovation comes into play. Before grading begins, Lane will remove the catch fence and safer barrier and drop in a dirt backfill behind the outside wall. The backfill will serve as a service road for Caterpillar D8 and D9 dozers, which will use “cables and winches” to hold the grader and compactor at the 30° banking angle of the turns. A standard milling machine and grader will handle the work on the straightaways.
The first asphalt layer to be applied will be a 2-in. open drainage layer (ODL) that will contain larger aggregate to assist in pulling water off the track. McLear said crews also will be installing an under-drain system to carry the water away from the track.
“The ODL layer is used to get any water that gets into the different joints and into the track up against the wall,” said McLear. “It acts as a base to carry that water down to the bottom of the track.”
A 2-in. asphalt base will go on top of the ODL, followed by a 1½-in. asphalt “level up” course. All three will carry a PG 76-22 binder. The 1½-in. surface layer will contain an 82-22 binder. At press time, McLear could not go into much detail concerning the asphalt mixes, saying it would be similar to the one that was produced at Talladega and Homestead-Miami, but Daytona is calling the surface layer a “polymer-modified asphalt [mat] with an elevating softening point.”
A portable asphalt plant located in the parking lot of Daytona will supply the material. The asphalt paving train will consist of an ABG Titan paver with tamping bars for compaction, a Shuttle Buggy and one or two rollers, depending on where they are laying down the mat. The turns call for just one steel double-drum roller, held up by a Cat dozer. The straightaways will use two steel double-drum rollers. The paving width will be 40 ft.
Lane Construction also will be reconstructing pit road, replacing the asphalt surface in the pit stalls with 6-in.-thick concrete pavement.
McLear hopes to carry what was learned during the Talladega and Darlington jobs over to the Daytona reconstruction. Perhaps the most valuable lesson was conducting effective project development up front.
“What we are doing right now in preparing for the job is working hand in hand with our designer, HNTB Corp.,” said McLear. “That really is the key. Our project manager and his team, and the owner and designer, [are] coming up with the grades and model of the track surface.”
“From a managing standpoint, we have the best of the best as far as the people doing the physical work,” added McLear. “We have a lot of confidence in them. —Bill Wilson ”
Grappling with grip
Race cars are built as light as possible within their technical regulations, so you might think they don’t impose much wear and tear on the pavement under them.
You would be wrong.
The reality on the ground is that a Formula One race car, for example, experiences up to 5 g’s of deceleration in some braking zones. That means the car is shoving the asphalt horizontally with a force five times the weight of the car. Even with a relatively lightweight car, that adds up to a tremendous force and can easily result in bumps in the asphalt where the cars are trying to slow down to make a turn.
Braking zones occur on road courses, racetracks that have a mixture of right and left turns with a variety of radii and little if any banking. Some road courses are laid out to simulate a drive through the country; others are made up of city streets that carry public traffic when they are not closed for racing. Road courses pose—to drivers and to pavers—challenges that are unlike anything on an oval speedway.
To prevent shoving in braking zones, paving contractors try to ensure a good bond between layers of asphalt, the favorite choice of pavement for road courses.
“We are more stringent in our tack coats, making sure we get a uniform tack coat,” Brian Prowell, Ph.D., P.E., principal engineer at Advanced Materials Services LLC, Auburn, Ala., told Roads & Bridges.
Advanced Materials Services is warming up to pave one new road course at the Kansas City Speedway and another near New Orleans, beginning on about Sept. 1.
The thickness of the asphalt layers also can help resist shoving.
“The pavement that we typically use for a racetrack ends up being somewhat thicker than what you would need from a structural design standpoint,” said Prowell, but the extra mass is needed to resist shoving.
Racetrack pavements have different requirements for aggregate, too. They need to give the racing cars good grip throughout the life of the racetrack.
One possibility is a friable aggregate such as slag, where bits will break off and expose new sharp edges. The other possibility is a hard aggregate like granite, which will resist polishing.
Prowell said the biggest difference between racetrack pavement and public road pavement might be the liquid asphalt cement.
Where racing rubber meets the road course, the predominant failure mode is raveling. To prevent raveling, racetrack designers increase the softening point of the asphalt cement.
The friction of the tires can heat the track. Add sunshine and the asphalt can reach a temperature where it softens, aggregate particles work loose and the pavement begins to crumble.
A polymer modifier might raise the softening point. Other additives can raise the softening point, too.
One spot that is susceptible to wear is a joint, so racetracks try to eliminate transverse joints as much as possible. If a transverse joint is necessary, the track designer will put it in a straightaway, where the lateral forces are insignificant, or at an angle, so the racing car does not have two tires crossing the joint at once.
Advanced Materials Services recently did some work on Lime Rock Park, a historic 1.53-mile-long road course in a park-like Connecticut setting. Lime Rock Park underwent a major reconstruction in 2008 and now has multiple configurations the cars can race on.
Many road courses have optional track layouts, where some segments of the track are used by all the cars and other segments offer a choice. Different classes of car may use different configurations, depending on their handling characteristics. For some cars, a turn may be too fast for safety, so they take an optional route that forces them to slow down.
At the interfaces where the different track segments meet, the joints require careful paving techniques, techniques that are not required for oval speedways.
International Speedway Corp., the owner of the Kansas City Speedway, had not decided at press time whether the road course would be built inside or outside of the existing oval, so many factors, such as drainage, were still unknown. Wherever the new racetrack is built, it is certain to be a unique challenge to pave. —Allen Zeyher
