How Can You Pour a Concerte Drag Strip in a Continuous Pour

BRAINERD, Minn. -- The drag strip at Brainerd International Raceway has been silent since late October, when construction equipment shut down for the season without completing the $750,000-plus reconstruction of our quarter-mile drag strip. But beneath the 100 protective thermal tarps covering the track for the winter is 700 feet of concrete that is unique among drag strips. And when the construction project is completed next spring, BIR will have one of the fastest and flattest drag strips in the country, bar none.

A number of innovative design components and a construction material not found in the surface of any other racetrack was used to produce a more durable surface and, potentially, much faster speeds. This could include some world drag racing records. Several companies were interviewed to produce a world-class drag strip, but C.R. Meyer & Sons, a Rhinelander, Wis.-based company known for world-class concrete construction and technology, was selected as the general contractor. On-site Project Manager Ed Shaughnessy, of C.R. Meyer & Sons, provided the day-to-day direction.

The key to the new track is the concrete slab that extends from the burnout box to half-track, 700 feet away. Common to concrete slab construction, laser equipment was used throughout the process to create an ultra flat surface, and the track's design eliminates traverse joints, which run perpendicular to the track. After the concrete was adequately cured, the flatness was measured and found to have an average flatness factor of 98. In other words, the difference between any two spots on the track is less than the thickness of a piece of paper. To the best of our knowledge, the only drag strip flatter than BIR is NHRA's Pomona Raceway in Pomona Calif., which has a flatness factor of 104.

Although Pomona Raceway is slightly flatter than BIR, Pomona also has a transverse joint between the previous 300 feet of concrete and the current expansion of concrete extending to half-track. And as racers will attest, expansion joints create a rough ride at accelerated speeds of over 200 mph. Our new track will have no transverse joints; instead, the slab will be deeply anchored in the ground at half-track but will be allowed to expand at the starting line end with the help of an expansion joint. This means the entire slab was constructed as one continuous concrete pour and will slide toward and away from the starting line as the concrete expands and contracts.

When racers reach half-track and run out of concrete, the transition to asphalt will be much less dramatic because of a unique material used in the asphalt. Instead of mixing common rock aggregate to the asphalt, taconite tailings are being used as the substrate because they're more durable and dense than rock aggregate, making the asphalt's density more similar to concrete. Tailings provide greater tire traction and allow the surface to better withstand the punishing weather extremes that central Minnesota experiences.

The tailings come from taconite mines in northeast Minnesota. During the mining process, taconite is extracted, leaving jagged rock-like waste material called tailings. These tailings are being used as asphalt substrate in an increasing number of highway construction projects in Minnesota with great success, but no racetracks are known to use them.

The tailings are inexpensive, about 95 cents per ton, because huge piles of them are prevalent throughout the northeast iron-mining region of Minnesota. But because of their density, tailings are expensive to transport, which makes them less appealing for most applications. Our construction will involve 600 tons.

In addition to extending concrete farther down the track, BIR's new track has less slope from the middle of the track to the outside edges. After reconstruction, the middle of the track, or crown, will only be about 2 inches higher than the outside edges, which is more in line with the design of most major drag strips. On the old drag strip, the middle of the track varied from 4-6 inches higher than the outside edges, requiring race crews to make special adjustments to their high-powered race cars.

Our plans called for construction to be completed last fall, but the weather wouldn't cooperate. Prior to shutting down the construction equipment at the end of October for the winter, the major concrete portion of the track was completed, which was the most crucial part of the project.

The ultimate goal of this project is to upgrade our race facility by producing a world-class drag strip. Brainerd International Raceway will enter its 34th year as a nationally recognized multi-use motorsports facility. Drag racing has been a part of our annual program since 1976.

Next spring, we'll lay the taconite asphalt, install the new timing system and put the final touches on the project. When the first cars make the inaugural run next May, it'll be on the premier drag strip in North America and a model that others will use when constructing new tracks or rebuilding existing ones.

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Source: https://www.dragracecentral.com/drcstory.asp?ID=30477

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