MTVs for DOTs

Case Studies
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Nearly 18 months ago, Terex Roadbuilding unveiled its latest paving innovation—the Terex CR662RM RoadMix material transfer vehicle (MTV)—to thousands of road-building contractors at ConExpo-Con/Agg 2005. This machine represented a new generation of MTV, designed to deliver both continuous paving and asphalt-remixing capabilities.

“The RoadMix was built from the ground-up to offer continuous paving capabilities as well as combat material and thermal segregation,” said Mark Hunt, general manager of Terex Roadbuilding’s Asphalt Group. “It is the only MTV on the market to aggressively reblend 100% of the material.”

The CR662RM features the next generation of Remix Anti-Segregation System, in which asphalt is aggressively remixed by four counter-rotating augers. Paired in sets of two, the interleafing augers channel and reblend the asphalt in a figure-eight motion, uniformly pulling material from all areas of the hopper to combat segregation.

The machine’s low, 53,000-lb operating weight solves application and transportation challenges common with other MTV designs. With its 18-in.-wide rubber track, the RoadMix has an incredibly low 11.5-lb psi ground-contact pressure, compared with other MTV designs at more than 100-lb psi. This allows the RoadMix to be used on base, binder and surface courses, whereas other MTVs can only be used on the surface course.

Terex Roadbuilding is working with several state departments of transportation (DOT) to get the CR662RM approved as an MTV for state paving projects. The most rigorous RoadMix testing to date has been with the Georgia DOT. Currently, the state of Georgia requires the use of an MTV on most state asphalt paving projects.

“The DOT really challenged the RoadMix, testing five different applications in six weeks,” said Tom Webb, district manager for Terex Roadbuilding. “At each site, we had to train a different crew on how to operate the machine, which is not ideal for testing the machine’s capabilities.”

The Georgia DOT ran a variety of mixes through the CR662RM . In Macon and Cochran, two different base designs were tested. On State Highway 252 in Dublin, the RoadMix MTV helped to lay a polymer-modified binder mix before being shipped back to Macon to help lay the topping mix.

The toughest challenge, however, was on S.R. 21 outside of Statesboro. The Georgia DOT used the MTV to help pave with a base material consisting of a 22-mm nominal maximum aggregate size. The crews paved at 18 ft wide and 5 in. deep with paving speeds of 25 and 11 ft per minute.

In addition to establishing continuous paving, preliminary tests showed that the RoadMix MTV beat the state’s thermal spec of no more than 20°F temperature variance across the width of the mat. The CR662RM has received approval by the Georgia DOT to be used as an MTV on state paving projects. Recently, Louisiana and Mississippi have followed suit and approved the Terex RoadMix MTV to be used on state paving projects. Terex Roadbuilding is continuing to work with other DOTs to get the CR662RM approved as an MTV on state paving projects.

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