In summer 2012 the emphasis was on high-performance asphalt mixes and placement as crews of Austin Industries — under terrific deadline pressure — laid three courses of critical pavement at the new Circuit of The Americas (COTA) Formula 1 track just southeast of Austin, TX.
Executed in the midst of crews working to erect administration buildings, grandstands, an amphitheater, an observation tower, fences and landscaping, the paving at COTA took a little over four months. Each lift of asphalt was specifically designed to meet the standards of the sanctioning body, the FIA or Fédération Internationale de l’Automobile, and the rigors of the central Texas climate. Specifications demanded that the two top courses be placed in echelon, that is, by multiple pavers at the same time, to eliminate cold joints.
Compaction at the paver was required in advance of the rolling train. For this critical, high-visibility application Austin selected four Super 2100-2 asphalt pavers from Vgele with AB 600-2 TP2 screeds, and a host of Hamm vibratory and pneumatic compactors, including HD+ 90 VV-S rollers with split drums, and the new GRW 280 rubber-tired rollers.
The base course was designed to support the vertical forces of the cars. The binder or intermediate course was designed to support the horizontal forces of the cars during acceleration and breaking, and the wearing course was designed to provide grip at high speeds.
“The overall design of the asphalt mix for the track is crucial to the performance of the car,” said Oscar Rodriguez, Rodriguez Engineering, one of the subcontractors working on the project. ”We worked with Tilke Engineers & Architects, and our asphalt expert, Dr. Rainer Hart, to produce a mix that met their specifications.”
Ground was broken in January 2011. Circuit of The Americas sits on nearly 1,000 acres; 350 of which are the track itself. When construction was completed, COTA will represent a private investment of approximately $400 million.
The 3.4-mile track features 20 turns – some extremely sharp – plus inclines and a straightaway. Width varies from 32 to 52.5 feet and it’s designed to accommodate speeds approaching 200 mph. The maximum change in elevation is nearly 133 ft.
In mid-October 2012, in advance of the first race the weekend of Nov. 16-18, crews were putting the finishing touches on the track, with fresh coats of bright red paint to the edges of the margin. The track’s run-off areas will feature red white and blue stripes to commemorate the American heritage of the circuit.
But all this was possible due to the hard work of Austin crews using high-performance asphalt construction equipment to place bituminous lifts to exacting specifications, under blazing-hot environmental conditions that pushed or exceeded 100° F week after week.
Strict smoothness specs
The combination of strict smoothness specs, a tight schedule, rigorous mix designs, and having to work in the public eye meant a challenging project that would tax the best contractors.
By race day, approximately 700,000 cu. yd. of material will have been used to precisely construct the 3.4-mile track alone. During construction of the entire project, some 3.25 million cu. yd. of earth were moved, enough to fill a 1/3-mile-deep hole the size of a football field.
For the track, the project crew excavated approximately 10 ft. of Texas clay the entire length of the track. A black 30 mil polyethylene liner was then placed along the length of the grade as a separation layer. Then, 7 ft. of sandy, clayey loam select fill, 1.5 ft. of pit-run clayey sand, and 6 in. of crushed recycled concrete aggregate (RCA) was placed with conventional equipment.
This was followed by 6 in. of crushed limestone flex base and 3.1 in. of HMA base course, these layers placed by a single Super 2100-2 paver. The subsequent 2-in. binder course and 1.6-in. wearing course were placed by multiple Super 2100-2 pavers in echelon, resulting in a total asphalt pavement depth of 6.7 in.