Asphalt distributors are the most common piece of equipment to apply bond coat to pavements. All distributors consist of several basic components including the material holding tank, a tank heating device, the distributor bar with nozzles, a network of pumps and valves to control material flow, and a computer to maintain constant shot rates. To achieve a uniform distribution of bond coat several factors must be controlled: speed of the distributor in feet per minute (ft/min or FPM), the flow rate from the pump in gallons per minute (gal/min or GPM), the spray width in feet and the nozzle type. All of these work together to achieve the desired application rate. Fortunately, most modern distributors have an integrated flow rate computer that manages all of this information and maintains the proper application rate even if the speed of the distributor changes.
Technical Drawing of a Vogele Spray Paver
Spray pavers have been used in Europe for a number of years. They are the most common piece of equipment used in hot mix paving. These pavers have tank for emulsions built into the paver. A spray bar is installed on the paver immediately in front of the screed. A specially designed high strength emulsion is applied to the pavement surface immediately before the mix is placed. This design prevents anything from driving in the bond coat before the hot mix is placed and allows for the use of a very aggressive bond coat emulsion.
Asphalt Transport Trailer used as on-site storage
Asphalt Storage Tank
The asphalt tank holds bond coat material until it is ready to be applied. The tank may be insulated and typically has a capacity of 6,000 gallons: most often asphalt transport trailers are used. Sometimes frac tanks or dedicated on-site storage tanks may be used. Asphalt transport trailers normally contain a series of baffle plates to minimize splashing of the bond coat while the truck is moving. Storage and handling best practices for asphalt emulsions are included below.
Store emulsion in vertical tanks. for long-term storage.
Store at a temperature between 50°F and 180°F (10°C and 83°C).
Don’t let the emulsion freeze.
Don’t allow emulsion temperatures to exceed 212°F (100°C) or water boiling point.
Don’t allow emulsion to free-fall into vessel from loading line or recirculation line.
Do bottom load.
Circulate material every two weeks.
Protect pump, valves and lines from freezing.
Don’t mix anionic and cationic emulsions.
Don’t load elevated temperature material above 212°F (100°C) on top of asphalt emulsion.
Circulate vessel while heating with direct fire tubes. (Low fire on heating tubes).
Dilute emulsion by adding warm water to the emulsion.
Check with the emulsion manufacturer for guidance on dilution of emulsion.
Wear proper personal protective equipment (PPE) to safely handle the emulsion.