Twenty-seven tracks host point-awarding NASCAR Cup Series races in 2022. Only the Nashville Superspeedway was designed with a concrete racing surface. Martinsville installed concrete around the corners in 1976, while Bristol and Dover transitioned 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 tracks that contain concrete. At 14 degrees of cant, it is slightly more banked than Martinsville (12 degrees), but much less banked than Dover (24 degrees) or Bristol (24-28 degrees). If we count half of Martinsville, concrete makes up 13% of NASCAR. Cup series surfaces. Earth represents 3.7%, leaving the remaining 83.3% to asphalt.
concrete vs asphalt
Both concrete and asphalt are composites: aggregates (also known as “little rocks”) held together by a glue-like material called a binder. Concrete dates back to the Roman Empire, while the first paved roads were not built until 1848. The nature of the binders explains the difference in time lines.
Concrete typically uses a Portland cement binder, a mixture of limestone and clay. Asphalt uses bitumen, a black tarry substance derived from the heavier components of crude oil, as a binder. Binders determine the method of application. While the concrete is being poured and cured, 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 laid in long, continuous strips. Concrete should be poured in sections to prevent damage from weather-induced expansion and contraction. The lines between the concrete sections also help with water drainage. That’s necessary because concrete is less porous than asphalt.
The flexibility of asphalt means that it does not distribute loads. Asphalt experiences larger and more concentrated stresses than concrete. The following figure shows typical stress distributions (in red) for asphalt and concrete.
As you might guess from this graph or your own personal experience with potholes, asphalt is more easily damaged than concrete. Asphalt simply cannot withstand the high forces of racing cars taking sharp turns at high speed.
Transportation engineer Van Walling compiled the fascinating compendium (not yet published) oval track almanac. The three volumes document 45 years of extensive investigation of more than 1,000 leads in the United States and abroad.
Martinsville, Walling explained, turned to concrete because race cars damaged the asphalt in the turns. Trucks can damage asphalt on freeway exit ramps in the same way.
“Between the high temperature and the force of the vehicles,” Walling said, “the asphalt can move, creating a washboard-like texture.”
While “push,” as the phenomenon is called, is annoying for an off-ramp, those potholes create a real problem for race cars. Road operators have no choice but to frequently resurface or rebuild, or switch to concrete.
That is not to say that concrete tracks are waterproof. In 2004, Jeff Gordon lost a race at Martinsville due to concrete dislodging from the track. In 2018, a piece of Dover’s concrete surface came loose and damaged Jaime McMurray’s car. Debris from the impact shattered windows in a crosswalk above the racing surface. That episode led Dale Earnhardt Jr. to cheep that “Asphalt is for competition. Concrete is for sidewalks.”
Walling, who has studied the original plans for Daytona International Speedway, said NASCAR founder Bill France Sr. wouldn’t necessarily agree.
“I intended the corners at Daytona to be concrete,” Walling said. “The problem was the cost.”
Concrete requires a much higher initial investment, and France was already struggling to find financing.
“He initially planned a 60-foot racing surface,” Walling said, “but ended up settling for 40 feet.”
If France hadn’t found the money, Walling says, Daytona could have ended up a much flatter track. The initial cost is the reason almost all new tracks are built with asphalt, even though maintenance is more expensive in the long run.
How concrete changes careers
The main gripping mechanism on any race track is the deformation of the tire around the aggregate. Concrete, by its nature, is softer 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 in the tire. Although Goodyear designs its tires to deposit rubber on concrete tracks, the rubber doesn’t sit still.
“At speed,” said Greg Stucker, Goodyear racing director, “the track will turn progressively black as the cars deposit rubber on the concrete surface and then turn white again under the caution flag as the tires remove much of that rubber. Keeping pace with that transition is an important element of race strategy.”
A driver loses traction on a concrete track much faster than on asphalt. Drivers have already turned more in 2022 with the Next Gen car than in all of 2021. The accident rate has also increased.
Nashville’s concrete surface can present a real challenge. Dover, the only race of 2022 on an all-concrete track so far, had 13 cautions. That’s nearly double the number of cautions in each of the previous two races, and triple the number of each of the previous two.
One positive aspect is that concrete does not wear down as quickly as asphalt. Although the car is new, the surface will not have changed much since last year. The tires are also familiar. Teams used Nashville’s left-side tire three times (including at Dover) and right-side six times this year. They’ve even run the same left-right configuration twice: at Charlotte and in the Texas All-Star Race.
In black and white
Follow up on color issues.
The sun emits a spectrum of electromagnetic waves. The small band that we can see is what we call light. But the sun also provides infrared waves, like the heat lamps restaurants use to keep food warm. Its ultraviolet waves are why you should wear plenty of sunscreen on the track.
Surfaces of different colors interact differently with waves from the sun.
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. This is 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 no light is reflected, you see black. The same is true of infrared waves, which cause black surfaces to heat up faster than white surfaces.
White tracks also reflect more light into drivers’ eyes. Drivers will need tinted sunglasses for the 4 pm local (5 pm ET) start, which will air on NBC.
The heat causes the bitumen in the asphalt to release oils that make the runway more slippery. That doesn’t happen with concrete.
The bottom line is that a concrete track doesn’t change as much over the course of a race as an asphalt track. Nashville Superspeedway should be easier for crew chiefs to follow because changes in temperature won’t change the racing surface as much.
On the downside, if a team misses the set-up, there’s a much lesser chance of the track getting to them during the race.