The concrete truth about the Nashville Superspeedway – NASCAR Talk

Twenty-seven tracks will host points-paying NASCAR Cup Series races in 2022. The Nashville Superspeedway is built only with a concrete racing surface. Martinsville installed concrete in turns in 1976, while Bristol and Dover switched from asphalt to concrete in 1992 and 1995, respectively.

The 1.33-mile Nashville Trail is a D-shaped oval and is the longest of the four concrete trails. At 14 degrees banking, the bank is slightly more than Martinsville (12 degrees), but much lower than Dover Bank (24 degrees) or Bristol (24-28 degrees). Cup chain surfaces. Dirt makes up 3.7%, leaving asphalt making up the remaining 83.3%.

Concrete vs. asphalt

Both concrete and asphalt are composite materials: aggregate (also known as “little rock”) held together by a glue-like substance called a binder. Concrete dates back to the Roman Empire, while the first asphalt roads were not built until 1848. The nature of the volumes explains the difference in timelines.

Concrete usually uses a Portland cement binder, which is a mixture of limestone and clay. Asphalt uses bitumen, a black, tarry substance derived from the heaviest component of crude oil, as a binder. Folders define the method of application. During concrete pouring and curing, 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 paved in long, continuous spaces. Concrete must be poured in sections to prevent damage from expansion and contraction caused by weather. The lines between the concrete sections also help with drainage. This is required because concrete is less porous than asphalt.

The flexibility of asphalt means that it does not distribute the loads. Asphalt is subjected to greater and more concentrated stresses than concrete. The figure below shows typical stress distributions (in red) for asphalt and concrete.

A graphic showing how concrete and asphalt handle stress differently.  Concrete spreads pressure while asphalt does not

As you might imagine – from this drawing or from your personal experience with potholes, asphalt is damaged more easily than concrete. Asphalt simply cannot stand up to the high forces of racing cars that take tight curves at high speed.

tangible costs

Transportation Engineer Van Walling compiled the awesome (as yet unpublished) compendium. Oval track calendar. The three volumes document 45 years of extensive research of more than 1,000 tracks in the United States and abroad.

Walling explained that Martinsville switched to concrete because the race cars damaged the asphalt in the corners. Trucks can damage asphalt in highway loops away from slopes in the same way.

“Between the high temperatures and the strength of the vehicles, the asphalt can be moved around, creating a washboard-like feel,” Walling said.

While the “scramble,” as the phenomenon is called, is annoying for a slope, these bumps create a real problem for racing cars. Track operators have no choice other than frequent resurfacing or rebuilding – or switching to concrete.

This does not mean that concrete tracks are impervious. In 2004, Jeff Gordon lost the Martinsville race due to concrete getting off the track. In 2018, a portion of Dover’s concrete surface softened and damaged Jaime McMurray’s car. Debris from the collision shattered windows at a pedestrian intersection above the racing roof. That episode prompted Dale Earnhardt Jr. to tweet That “Asphalt for racing. Concrete for sidewalks.”

Walling, who studied the original blueprints for the Daytona International Speedway, said NASCAR founder Bill France Sr. would not necessarily agree.

“He intended the corners of Daytona to be concrete,” Walling said. “The problem was the cost.”

Concrete required a much larger upfront investment, and France was already struggling with financing.

“He initially planned to run 60 feet, but ended up going to 40 feet,” Walling said.

Walling says that if France hadn’t found the money, Daytona might have ended up as a flatter track. The initial cost is the reason why almost all new tracks are built with asphalt, although maintenance is more expensive in the long run.

How concrete changes the race

The primary grip mechanism on any racetrack is to deform the tire around the pile. Concrete is inherently softer than asphalt. When NASCAR measured track surface roughness in 2019, Martinsville, Dover and Bristol had the smoothest tracks.

The second grip mechanism is the adhesive interaction between the rubber particles on the track and on the tire. Although Goodyear designs its tires to put rubber on concrete tracks, the rubber doesn’t stay in place.

“At speed, the track will gradually turn black as the cars lay rubber on the concrete surface and then turn white under the warning flag while the tires recover a lot of that rubber,” said Greg Staker, Goodyear Racing Director. Keeping pace with this transition is an important component of racing strategy. “.

The driver loses traction on a concrete track much faster than on asphalt. Drivers have already managed to spin more in 2022 with the next generation car than in all of 2021. The accident rate has also increased.

Nashville’s concrete surface can be a real challenge. Dover, the only 2022 race on a full concrete track so far, has received 13 warnings. That’s nearly double the number of alerts in each of the previous two races, and three times each before that.

One positive thing, though, is that concrete does not erode as quickly as the asphalt. Although the car is new, the surface hasn’t changed much since last year. Tires are also familiar. Teams have run the left side tire from Nashville three times (including at Dover) and the right side six times this year. They’ve even run the same configuration left and right twice: in Charlotte and Texas All-Star Race.

black and white

The color of the track is important.

The sun emits a spectrum of electromagnetic waves. The little strip that we can see is what we call the light. But the sun also provides infrared waves, like the heat lamps restaurants use to keep food hot. His ultraviolet waves are the reason why you should wear so much sunscreen on the track.

Different colored surfaces react differently to the sun’s waves.

We see things because they reflect, emit, and/or transmit light. Red car absorbs all wavelengths of light Except That corresponding to red. Only red wavelengths reach our eyes.

A graphic showing how white light (light of all colors) hits a red surface.  The surface absorbs all light except red.  This light is reflected back to 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. On the other hand, black surfaces 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 surfaces.

Drawing comparing light hitting black and white surfaces

The white tracks also reflect more light into the drivers’ eyes. Drivers will need to peel off a colorful mask for the start of 4 p.m. (5 p.m. ET), 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 path does not change over the course of the race as much as the asphalt path does. The Nashville Superspeedway should be easier for crew chiefs to keep up with because changes in temperature won’t change the racing surface much.

On the downside, if the team gets the setup wrong, there’s much less chance the track will come to them during the race.

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