Concrete facts about the Nashville Superspeedway – NASCAR Talk

Twenty-seven tracks host paying points of NASCAR Cup Series races in 2022. Only the Nashville Superspeedway is designed with a concrete racing surface. Martinsville installed concrete in turns in 1976, while Bristol and Dover moved from asphalt to concrete in 1992 and 1995, respectively.

The 1.33-mile Nashville track is a D-shaped oval and the longest of the four concrete-containing tracks. At 14 degrees of banking, it is slightly lower than Martinsville (12 degrees), but lower than Dover (24 degrees) or Bristol (24-28 degrees.) If we count half of Martinsville, the concrete accounts for 13% of the NASCAR Surfaces Cup Series. Dirt makes up 3.7%, leaving asphalt to account for another 83.3%.

Concrete Vs. asphalt

Concrete and asphalt are both aggregate: aggregate (also known as “pebble”) held together by a glue-like material called a binder. The concrete dates are in the Roman Empire, while the first asphalt roads were not made until 1848. The nature of the binders explains the difference in timelines.

Concrete typically uses portland cement binder, a mixture of limestone and clay. Asphalt uses bitumen, a tarry black substance derived from the heaviest part of crude oil, as a binder. The binders determine the method of application. As the concrete is being poured and treated, the asphalt must be heated to a high temperature before being extruded and allowed to cool.

Because asphalt is more flexible than concrete, asphalt can be placed in long, continuous swaths. Concrete should be poured in sections to prevent damage from expansion and shrinkage caused by weathering. The lines between the concrete sections also help with drainage. That is necessary because concrete is less porous than asphalt.

The flexibility of asphalt means that it does not spread loads. Asphalt experiences greater, more concentrated stress than concrete. The figure below shows typical stress distributions (in red) for asphalt and concrete.

A graphic showing how concrete and asphalt deal differently with stress.  Concrete spreads stress whereas asphalt does not

As you can guess – from this graphic or your own personal experience with potholes, asphalt is easier to break than concrete. Asphalt is unable to withstand the high force of racing cars taking tight curves at high speeds.

Concrete costs

Transportation engineer Van Walling has compiled the fascinating (in-yet-to-be-published) compendium Oval Track Almanac. The three volumes document 45 years of extensive research of more than 1,000 tracks in the United States and abroad.

Martinsville, Walling explained, became concrete because race cars damaged the asphalt on turns. Trucks can damage asphalt on expressway off-ramp loops in the same way.

“Between the high temperature and strength of the vehicles,” Walling said, “the asphalt can move, creating a texture like a washboard.”

While “shoving”, if you call the phenomenon, is annoying for an off-ramp, those bumps create a real problem for race cars. Track operators have no option beyond frequent resurfacing or reconstruction – or moving to concrete.

This does not mean that concrete metals are invulnerable. In 2004, Jeff Gordon lost a Martinsville race because of concrete coming off the track. In 2018, a chunk of Dover’s concrete surface loosened and damaged Jaime McMurray’s car. Debris from the impact shattered windows at a pedestrian crossover above the racing surface. That episode motivated Dale Earnhardt Jr tweet that “Asphalt is for racing. Concrete is for sidewalks. “

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

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

Concrete requires larger up-front investment, and France is already struggling for funding.

“He initially planned a 60-foot racing surface,” Walling said, “but ended up at 40 feet.”

If France hadn’t found the money, Walling said, Daytona could have ended up as a flatter track. The upfront cost is the reason why almost all new tracks are made using asphalt, although maintenance is more expensive in the long run.

How concrete changes careers

The main grip mechanism on any racetrack is the wheel that deforms around the aggregate. Concrete, in its nature, is smoother than asphalt. When NASCAR measured track surface roughness in 2019, Martinsville, Dover and Bristol were the three smoothest tracks.

The second grip mechanism is the adhesive interaction between the rubber molecules on the track and the wheel. Although Goodyear designed their tires to put rubber on concrete rails, the rubber doesn’t stick.

“At speed,” said Greg Stucker, Goodyear’s racing director, “the track will gradually turn black as cars put rubber over the concrete and then turn white under the traffic flag. caution as the wheels return most of that tire. Keeping up with that move is an important element of racing strategy. “

A driver loses traction on a concrete track faster than on asphalt. Drivers will drive more in 2022 with the Next Gen car than in the entire 2021. The accident rate is also rising.

The concrete surface of Nashville can pose a real challenge. Dover, the only 2022 race on a full concrete track so far, has 13 wards. That’s almost double the number of holds in each of the two races before, and tripled each of the two before that.

A positive, by concrete does not wear as fast as asphalt. Although the car is new, the surface hasn’t changed much since last year. Tires are also familiar. Teams have run the wheel on the left side of Nashville three times (including Dover) and the right side six times this year. They ran the same left-right configuration twice more: in Charlotte and in the Texas All-Star Race.

Black and white

The color of the track is important.

The sun emits a spectrum of electromagnetic waves. The little band we see is what we call light. But the sun also emits infrared waves, such as heat lamps used by restaurants to keep food warm. Its ultraviolet waves are why you should wear a lot of sunblock on the track.

Different colored surfaces interact with the sun’s waves.

We see things because they reflect, emit and/or transmit light. A red car absorbs all wavelengths of light except the red equivalents. 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.  That light reflects into our eyes.

White surfaces reflect most wavelengths of light. That’s why you see concrete as white – white light is the sum of all colors of light. Black surfaces, on the other hand, absorb a lot of light. Since there is no reflective light, you will see black. The same thing happens with infrared waves, which cause black surfaces to heat up faster than white surfaces.

A graphic that compares light hitting black and white surfaces

White tracks also reflect more light into the eyes of drivers. Drivers will need a tinted visor peel-off for the 4 pm local (5 pm Eastern) start, which will be broadcast on NBC.

The heat causes the bitumen in the asphalt to release oils making the track more slippery. That doesn’t happen in concrete.

The result is that a concrete track does not change the course of a race like an asphalt track. The Nashville Superspeedway should be easier for crew leaders to keep up because temperature changes won’t change much over the course of the race.

On the negative side, if a team misses the setup, the track is less likely to get to them during the race.

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