Read more stockpiling tips from Schwartz.
Diesel or Propane Heating
Both types of hot boxes are built with triple walls, with an air space surrounding the holding box that enables heated air to heat the walls and the asphalt. Heat in the hot box reclaimer is generated either through propane or diesel. Manufacturers generally offer both types of heating systems (Ray-Tech offers only propane) and both work equally well.
"Typically if you're not used to working with propane and everything you have in your fleet is diesel, use diesel," Allen says. "Almost all infrared is propane fired so if you already have propane infrared then use propane."
Schwartz says there are some differences between the two fuels, which contractor should take into consideration.
"Diesel will reclaim a little quicker because it's a hotter heating system, but it's what works best for you," Schwartz says. "If all you have is diesel you might want to seriously consider diesel. If the propane filling station is 10 miles away you might want to consider diesel. But if you already have propane or have a propane tank in your yard then propane might be the best for you. Propane is cleaner and easier to work with."
But whichever fuel is used, cold mix must be heated slowly and steadily.
"Asphalt has to heat slowly or you'll scorch it," VanVelsor says. He says Ray-Tech units heat for 9 minutes and then shut down for 3 minutes, relying on a timer to turn the heat on and off.
"Once it reaches the right temperature a thermostat takes over and holds it at 280-300°F and during the whole operation of reclaiming it never exceeds 300°F," VanVelsor says.
The cycle is different for diesel-fueled reclaimers because diesel burns hotter than propane. "Whether it's a propane or a diesel heater what's important to realize is that a thermostat controls the burner and that control allows the asphalt to be warmed without overheating it," Schwartz says.
Manufacturers say the time it takes to heat cold mix to a workable temperature varies depending on a variety of factors including air temperature and moisture content of stockpiled mix.
Allen says 4 tons of cold mix can easily be heated to a workable condition overnight.
Trailer, Skid, or Truck
Hot box reclaimers are available in sizes ranging from 2 tons to 10 tons and in trailer, skid, and truck-mounted models.
Allen says KASI's most popular unit is the 4-ton propane-heated hot box reclaimer. "The reason for that is some days you need less than two tons and on the days you need more the trip back to the asphalt plant to get more is a killer," Allen says. "You only have to do that a few times to realize that the difference in price between a 2 and 4-ton unit is not that significant."
VanVelsor says Ray-Tech sells 15 reclaimers for every hot box, partly because the difference in price is not substantial. "A lot of the people we sell reclaimers to are contractors who work on parking lots and they can't get mix on the weekend so they use the reclaimer to make sure they have what they need," VanVelsor says.
Schwartz says KM International's biggest sellers are its 2-ton skid-mounted unit and its 4-ton trailer-mounted unit.
"We sell a lot of 2-ton trailers but usually if they move into trailer-mounted they go with the 4-ton," Schwartz says. "If they have an extra truck they often buy the skid-mounted."
But manufacturers are united in their support for both hot boxes and hot box reclaimers. "If a contractor is always going to have hot asphalt available to him he only needs a hot box," Allen says. "But if he operates in cold climates where asphalt plants close he's going to need a reclaimer. I'd recommend it to any contractor involved in asphalt repair."