Twenty-seven tracks host NASCAR Cup races that pay points in 2022. Only the Nashville Superspeedway is designed with concrete racing. Martinsville installed concrete in the bends in 1976, while Bristol and Dover switched from asphalt to concrete in 1992 and 1995, respectively.
The 1.33-mile Nashville runway has a D-oval and is the longest of the four runways containing concrete. At 14 degrees the banking is slightly sloping from Martinsville (12 degrees) but much less than Dover (24 degrees) or Bristol (24-28 degrees). If we count half of Martinsville, concrete represents 13% of NASCAR Cup Series Surfaces. Dirt accounts for 3.7%, with asphalt accounting for the remaining 83.3%.
Concrete against asphalt
Both concrete and asphalt are composite materials: an aggregate (also known as “small rocks”) bonded together with an adhesive-like material called a binder. The concrete dates back to the Roman Empire, until the first paved roads were built until 1848. The nature of the binders explains the difference in timelines.
Concrete usually uses Portland cement binder, a mixture of limestone and clay. Asphalt uses bitumen, a tarry black substance derived from the heaviest components of crude oil, as a binder. Binders determine the route of administration. While the concrete is pouring and hardening, the asphalt must be heated to a high temperature before extrusion and allowed to cool.
Because asphalt is more flexible than concrete, asphalt can be laid on long, continuous slopes. The concrete must be poured in sections to prevent damage from expansion and contraction caused by time. The lines between the concrete sections also help drain the water. This is necessary because concrete is less porous than asphalt.
The flexibility of asphalt means that it does not distribute loads. Asphalt experiences higher, more concentrated stresses than concrete. The figure below shows typical stress distributions (in red) for asphalt and concrete.
As you can guess – from this graphic or from your personal experience with holes, asphalt is more easily damaged by concrete. Asphalt simply cannot withstand the high forces of racing cars, which take narrow turns at high speeds.
Transport engineer Van Walling compiled the fascinating (as yet unpublished) collection Almanac with an oval track. The three volumes document 45 years of in-depth study of more than 1,000 songs in the United States and abroad.
Martinsville, Walling explained, turned to concrete because racing cars damaged asphalt in corners. Trucks can damage asphalt in circles outside the motorway ramp in the same way.
“Between the high temperature and the power of vehicles,” Walling said, “asphalt can be moved, creating a texture like a washing board.”
While “pushing,” as the phenomenon is called, is annoying for off-ramp, these bumps create real problems for racing cars. Rail operators have no choice but to make frequent repairs or reconstructions – or switch to concrete.
This does not mean that concrete tracks are impermeable. In 2004, Jeff Gordon lost a race in Martinsville due to concrete coming off the track. In 2018, a piece of Dover’s concrete surface loosened and damaged James McMurray’s car. Debris from the impact broke the windows of a pedestrian crossover over the racetrack. This episode made Dale Earnhard Jr. do tweet that “Asphalt is for racing. Concrete is for sidewalks. “
Walling, who studied the original drawings for Daytona International Speedway, said NASCAR founder Bill France Sr. did not have to agree.
“He intended to have the corners of Dayton concreted,” Walling said. “The problem was the price.”
Concrete required much larger initial investment, and France was already struggling for funding.
“Initially, he planned a 60-foot racing surface,” Walling said, “but eventually stopped at 40 feet.”
If France hadn’t found the money, Walling says, Daytona could have been a much flatter track. Preliminary costs are the reason why almost all new tracks are built with asphalt, although maintenance is more expensive in the long run.
How the concrete changes the competitions
The main traction mechanism of each race track is the tire deforming around the unit. Concrete is inherently smoother than asphalt. When NASCAR measured track surface roughness in 2019, Martinsville, Dover and Bristol were the three smoothest tracks.
The second gripping mechanism is the adhesive interaction between the rubber molecules on the track and the tire. Although Goodyear designs its tires to lay rubber on concrete tracks, the tire does not stay in place.
“At speed,” said Greg Stucker, Goodyear’s racing director, “the track will gradually turn black as the cars lie rubber on the concrete surface and then turn white again under the precautionary flag as the tires collect much of that tire.” Maintaining this transition is an important element of the competition strategy. “
The driver loses traction on a concrete track much faster than on asphalt. Drivers have already turned more in 2022 with the next generation car than in the whole of 2021. The accident rate is also rising.
The concrete surface of Nashville can be a real challenge. Dover, the only race on 2022 on a full concrete track so far, had 13 warnings. That’s almost twice the number of warnings in each of the two races before and a tripling of each of the two before.
One positive result is that concrete does not wear out as quickly as asphalt. Although the car is new, the surface will not have changed much since last year. Tires are also familiar. The teams ran Nashville’s left tire three times (including in Dover) and the right six times this year. They have even held the same left-right configuration twice: in Charlotte and the All-Star Race in Texas.
black and white
The color of the track matters.
The sun emits a spectrum of electromagnetic waves. The small strip we can see is what we call light. But the sun also provides infrared waves, such as the heat lamps that restaurants use to keep food hot. Its ultraviolet waves are the reason you wear a lot of sunscreen on the track.
Different colored surfaces interact differently with the sun’s waves.
We see objects because they reflect, emit and / or transmit light. A red car absorbs all wavelengths of light except those corresponding to red. Only red wavelengths reach our eyes.
White surfaces reflect most wavelengths of light. That’s why you see concrete as white – white light is the sum of all the colors of light. Black surfaces, on the other hand, absorb a lot of light. Since the light is not reflected, you see black. The same thing happens with infrared waves, which cause black surfaces to heat up faster than white ones.
White marks also reflect more light in the driver’s eyes. Drivers will need to peel off tinted visors for the local start at 16:00 (17:00 east), which will be broadcast on NBC.
The heat causes the bitumen in the asphalt to release oils, which make the track more slippery. This does not happen with concrete.
The end result is that the concrete track does not change as much during the race as the asphalt track. Nashville Superspeedway should be easier for crew leaders, as temperature changes will not change the race surface so much.
On the downside, if a team misses the setup, they are much less likely to come across the track during the race.