Dr. Diandra: The concrete facts about Nashville Superspeedway

Twenty-seven tracks host points-paying NASCAR Cup Series races in 2022. Only Nashville Superspeedway was designed with a concrete racing surface. Martinsville installed concrete in the turns 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 concrete-containing tracks. At 14 degrees of banking, it’s 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 accounts for 13% of NASCAR Cup Series surfaces. Dirt makes up 3.7%, leaving asphalt to account for the other 83.3%.

Concrete and asphalt are both composites: aggregate (also known as “small rocks”) bonded together by a glue-like material called a binder. Concrete dates to the Roman Empire, while the first asphalt roads weren’t constructed until 1848. The nature of the binders explains the difference in timelines.

Concrete usually uses a portland cement binder, a mix of limestone and clay. Asphalt uses bitumen, a tarry black substance derived from the heaviest components of crude oil, as a binder. The binders determine the application method. While concrete is poured and cured, asphalt must be heated to a high temperature before extruding and being allowed to cool.

Because asphalt is more flexible than concrete, asphalt can be laid in long, continuous swaths. Concrete must be poured in sections to prevent damage from weather-induced expansion and contraction. The lines between concrete sections also assist with water drainage. That’s needed because concrete is less porous than asphalt.

Asphalt’s flexibility means it doesn’t spread out