On the banked parabolic return road, the paving crews faced additional challenges in placing a new asphalt surface. To place the MDOT 5E3 Superpave base course containing 30% reclaimed asphalt pavement, the leveling course containing 20% RAP, and the modified virgin wearing course, equipment and technique proved essential in the application on the 30-degree banked portion of the track. As with other banked track projects the paving contractor has delivered in the past, the Vogele paver and screed were secured with cable to another paver traveling in tandem on the above flat surface surrounding the curved track. The roller operators used outriggers to ensure compaction contact (and prevent the rollers from tipping over) as they maneuvered the banked portion of the track.
"This was the first parabolic project for the architects hired to design it and their original design called for a high-bank curve, but we worked with them from the beginning and assured them that the parabolic design was a better way to go, and that we could deliver the project," explains Clarence Jones, Ajax estimating manager. "The Vogele screed we used on the project is specially designed with 2-foot sections that can flex into the parabolic shape of the track. With the tamper compaction of the screed we were able to achieve 90% density of the mat before the roller operators took over."
To further guarantee the successful outcome of the complicated 30-degree banked parabolic design, Ajax performed the final grade of the limestone base and used GPS technology to make sure the geometric details were exactly where they needed to be before placing the first lift.
"We had to pay close attention to the transition areas going in and out of the banked area to make sure we were delivering a continuously smooth pavement," Marshall notes. "This was the third project of this type that the paving crew executed and they really did a great job."
Also worth noting, the Ajax paving crew relied on a Roadtec material transfer vehicle equipped with a 40-foot conveyor to feed the paver with a continuous supply of mix that would also ensure a smooth finish and transition to the VDA pad.
According to Marshall, Ajax's specialized track paving crew achieved an extremely smooth surface, exceeding the targeted smoothness specifications Bosch requested in the project design.
"We even achieved exceptional smoothness results across the longitudinal joints of the final lift," Marshall says.
Facility demands high standards
While ride smoothness was critical to the quality of the final surface, so was the friction coefficient that needed to be achieved. As a test facility designed to evaluate safety devices designed for motor vehicles, achieving the right surface friction was equally as critical for the paving contractor. For Bosch and other vehicle component suppliers, the friction coefficient of the testing facility is vital in evaluating the performance of many vehicle control/safety systems, such as anti-lock braking systems (ABS), traction control and 4WS systems.
Bosch's Automotive Proving Grounds provide the controlled environment necessary to develop and test technology that can improve the overall safety and performance of a vehicle. For example, before a technology like electronic stability program (ESP) can go into mass production, a long development and testing phase is required at a proving ground like Flat Rock to ensure the technology will perform as designed under any environmental situation.
The Flat Rock Test Facility not only serves Bosch's product development needs, but also those of automotive manufacturers and their suppliers, technical approval and control institutes, providers and engineering services, and educational institutions. From passenger cars, light trucks and SUVs to trailers and motorcycles, Flat Rock provides a controlled venue to evaluate vehicle performance in a variety of environmental situations.
"We're testing in wet and dry conditions to see how our products perform in different environments, so having optimal surface conditions is important to evaluate how those products perform," Champine says. "When you're developing products, you need to put those products through the same testing procedures to evaluate the performance of one design over another. That's what makes a testing facility like this so important, and this facility was designed and built with that in mind."