Asphalt Recycling Section
Better Roads Staff
But now Bergkamp Inc., Salina, KS, has introduced the Mobile Stockpile, a fully-mobile material transfer trailer that increases the time pavers spend on paving instead of hauling. The unit reduces costs, simplifies job management and minimizes overweight truck citation risks. It eliminates the need to find off-site stockpiles — one of the biggest challenges that pavement preservation contractors face.
Standard trucks bring aggregate and emulsion directly from the supplier and load the Mobile Stockpile, which is located on the jobsite. Then, truck-mounted slurry seal or microsurfacing pavers can easily connect to it and be fully replenished with material on-site in less than 10 minutes.
Because this static stockpile is on site, multiple long-distance trips are eliminated. That way, fewer pavers can do more work in less time. The results: better allocation of workers, fewer pavers per job, less paver idle time and reduced fuel costs.
By using standard dump trucks to load the Mobile Stockpile with aggregate, and tankers for emulsion, contractors avoid the risk of receiving overweight citations due to overloaded pavers driving to the jobsite from an off-site stockpile location. Water is replenished via a tanker or hydrant through the Mobile Stockpile’s 50-foot hose reel transfer. The unit is designed to use a minimal footprint, taking just one lane-width of roadway for an entire static stockpile operation. The Mobile Stockpile is compatible with most equipment manufacturers’ slurry seal and microsurfacing pavers.
Aggregate and emulsion are delivered through an efficient process. Aggregate is dumped into the inlet hopper located at the rear of the unit. The material is then transferred to the 21.5-cu. yd. main hopper on an enclosed 32-inch inlet conveyor at a speed of up to six tons per minute. The main hopper can either store the material or simultaneously transfer it during filling via a 24-inch discharge conveyor. The discharge conveyor moves the aggregate up a 28-degree angle before leveling out horizontally toward the discharge end to make a smooth aggregate transition to the slinger conveyor. The conveyor extends and throws the material into the truck-mounted paver at a rate of three tons per minute, retracting and slowing down as the truck evenly fills up to avoid over filling or spilling of the aggregate. Asphalt emulsion is loaded from a tanker evenly into four separate tanks on the Mobile Stockpile that together hold 6,000 gallons of asphalt emulsion. It is then pumped into the truck-mounted paver’s asphalt emulsion tank.
The Mobile Stockpile weighs 40,650 pounds empty and 147,900 pounds when fully loaded. A semi-truck or truck-mounted paver, capable of towing 42,000 pounds with a 6,000-pound vertical load, can pull the unit to the desired location by attaching to a pintle hitch on the end of a sliding tow bar.
New Modified Slurry Seal Making Inroads
TRMSS Scores a Hit in Southern California
Tire Rubber Modified Slurry Seal (TRMSS), a new type of slurry seal, is catching on in Southern California. Last year, contractors placed some 16,000 tons of Type I, II, and III TRMSS in the greater Los Angeles area. More is expected to go down this year, says Lance Allan, Manager of Roy Allan Slurry Seal, a contractor based in Santa Fe Springs, Calif.
To make TRMSS, tire rubber is first digested into liquid asphalt at the terminal in amounts of 5-, 10- or 15 percent rubber. Then that rubberized asphalt is emulsified to make the emulsion used in the slurry seal. It is relatively easy to emulsify the 5 percent rubberized asphalt, and more difficult to emulsify the 10 or 15 percent material, Allan says. But recently, Pacific Emulsions Inc., a Roy Allan affiliate, has been able to emulsify 15 percent rubberized asphalt.
“Rubber products have two benefits,” says Nelson Nelson, assistant director of public works for the City of Corona, Calif. “One is that it stays black longer than a conventional slurry seal. Secondly, it is more flexible under traffic. The conventional seal is more brittle, flakes off, and doesn’t last as long. I have been very happy with TRMSS.”
What’s more, Allan says, TRMSS can be applied with the same slurry machines as conventional slurry requires. Other rubberized slurry seals require modified machinery to place, he says. Typically a slurry machine, such as a Bergkamp, fits onto the rear of a tandem axle truck.
TRMSS differs from other rubberized slurry seals because it is based upon a cationic quick set emulsion. Cationic, (positively charged) emulsions cure chemically, not through evaporation like anionic (negatively charged) emulsions. That fact allows cationic emulsions to be used in cooler temperatures and still cure successfully. By their nature, cationic emulsions set quickly and create a natural bond to negatively charged aggregates.
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