Going Through the Paces

Temperatures soaring into the upper 90s with dew points reaching the oppressive 70-degree range mean it is just another typical Midwest day during the height of paving season. While the corn that stretches as far as the eye can see relishes the thick, moist air, the conditions are barely fit for the crew or beastly paving equipment. And it’s certainly not the conditions that a company would purposely select for a new material transfer vehicle’s (MTV) first field test.

But this was just the application that Terex/Cedarapids chose for field testing conditions of its CR662RM RoadMix MTV (now marketed by Bomag, March 26, 2013).

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“We want to make sure it performs in all conditions, so why not start with extreme heat?“ comments Mark Hunt, general manager of Terex Roadbuilding’s Asphalt Mobile Equipment Group. During this first field test, the RoadMix kept its cool and a consistent pace on a county highway project in Eastern Iowa.

Feel the heat

The Benton County Highway W26 application coincided with a heat wave that saw record temperatures in Iowa. Six-and-a-half miles of roadway were milled at 1/2-inch depths at the headers and 1 1/2-inch depths at the ends. The road’s poor conditions also required two-inch thick milling depths in certain sections.

“The surface was in pretty rough shape from years of patching,“ says Jack Robinson paving foreman for North Liberty, IA-based LL Pelling Co., the contractor on the Highway W26 project. “Parts of the road were patched over the years, which forced us to go a little deeper in those areas.“

Surface milling took place over three days and the millings were recycled and used to strengthen the shoulders. The highway’s new surface was laid in two 1 1/2-inch-thick lifts. Both the leveling and surface courses consisted of a half-inch minus aggregate with a PG64-22 asphalt binder. LL Pelling’s J Street plant, located nearly 20 miles from and an average 40-minute one-way haul time to the site, supplied the 13,000 tons of mix for the job.

This mix was laid at approximately 290 degrees Fahrenheit with the breakdown roller immediately compacting the mat after being laid. “We tarp our loads to reduce temperature loss during transit,“ says Brett Finnegan, vice president of LL Pelling.

The CR662RM RoadMix MTV led the paving train and consistently channeled material to a Terex/Cedarapids CR561R paver with Stretch 20 diesel screed, which laid the mat and delivered initial densities. Following the paver were the I-R tandem vibratory breakdown and finish rollers and a Dynapac rubber-tire roller.

The MTV’s primary objective was to establish a continuous paving process that matched the plant’s target production capacities for the job. According to Finnegan, the RoadMix “did its job.“ Beyond continuous, non-contact paving, the MTV’s in-hopper reblending augers helped to improve mat uniformity and quality.

“When working on other projects without the MTV, we would occasionally see little chunks of asphalt slip through the paver and into the mat,“ says Robinson. “The RoadMix breaks up those chunks and gives us a more consistent mat.“