Going Through the Paces

Familiar design

The new MTV’s design is based on the Terex/Cedarapids patented Remix Anti-Segregation System, which explains LL Pelling’s improvement in mat uniformity. In-hopper augers reblend asphalt from the truck to provide a more homogeneous mix to the screed. The two sets of two counter-rotating auger design is field proven to reduce both thermal and material segregation.

The RoadMix’s reblending system differs slightly from the Remix paver’s auger design. Auger diameter on the RoadMix has been increased to 12 inches, delivering an additional 42 percent auger face area and material carrying capacity.

“Increasing the diameter allows the augers to turn slower while still carrying the same amount of material as with the Remix design, which helps to reduce wear,“ explains Hunt.

The chromium carbide hardened augers are dropped further into the hopper frame, so the tops are at or below wing level. The auger troughs are completely filled by the auger sets to reduce material slippage.

A 3-inch, front-to-rear slope design - a 4-inch inset at the hopper’s front and 7-inch inset at the rear-hardened steel feed tunnel - increases channeling capabilities of the auger sets. The 7-inch recess at rear increases the volume of area to reduce material build-up. “All the design changes result in less wear and increased throughput,“ adds Hunt.

Another design change from Remix to RoadMix puts the auger drives at the front of the hopper. A single hydraulic motor powers each set of counter-rotating augers. This design ensures the auger sets rotate in-synch.

This drive change was necessary to accommodate the MTV’s conveyors. A short fixed-position conveyor accepts asphalt from the augers and delivers it to a long swiveling conveyor, which rotates 55 degrees left or right of center to allow for offset paving. The delivery conveyor’s height can be adjusted from 72 to 116 inches.

Continuous savings

Even though this was LL Pelling’s first experience with the CR662RM and the MTV’s inaugural field test, the contractor was quickly able to establish a continuous paving process. Designed similar to and capable of converting to a paver (see “MTV double duty“), the MTV required minimal time for the operator to learn the control panel layout and machine operation.

Since the MTV is not connected to the paver, it delivers non-contact paving. This allowed the paving crew to eliminate any “bumping“ of the paver during truck exchanges and any potential mat marking.

LL Pelling significantly reduced the number of trucks required for the 13,000-ton Benton County application. For the 40-minute haul, the contractor required only 14 trucks to ensure a continuous flow of material to the MTV. “If we would have delivered directly to the paver, we would have needed approximately 20 trucks,” says Finnegan.

At peak paving production, the contractor set daily goals of 2,200 to 2,400 tons per day. At this rate, the paving crew laid more than four miles of asphalt at the 1.5-inch depth. This also allowed the contractor enough room to produce additional asphalt mixes from the J Street plant for local commercial paving applications. “With traffic flow concerns on a county highway, paving at 250 tons per hour is a good clip,“ says Finnegan.

Mat quality was just as important as establishing a continuous paving speed matched to plant production on the Benton County Highway project. Uniformly-spaced aggregate and uniform mat temperatures allow the rollers to more easily achieve spec densities.

The CR662RM helped LL Pelling to achieve this as well. “Mat uniformity was great,“ says Finnegan. “The RoadMix helped us to lay one beautiful mat.“