Tack Coat

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Application Sequence

  1. The base surface is prepared by a throrough brooming: sometimes an older layer of asphalt may be removed by milling which can create a significant amount of debris. It is important that the base surface is clean and dry. 
  2. An asphalt distributor sprays a thin coat of bituminous liquid. It is critical that the correct rate of bond coat is applied and that it is uniformly applied across the entire base surface. 
  3. If the bond coat material is an emulsion it should have time to break before the hot mix is applied. 
  4. Hot mix is applied.  

Application Guidelines


Handling Asphalt Emulsions

  • Obtain, read, and follow the emulsion supplier’s Material Safety Data Sheet (MS DS) or Safety Data sheet (SDS) recommendations.
  • Provide adequate ventilation to avoid exposure to fumes, vapors, and mist.
  • Agitate gently when heating emulsion to minimize skin formation in the tank.
  • Do not let pumps, valves, and lines freeze in winter.
  • Clean out lines and leave drain plugs open when not in service.
  • Ensure that tanks and equipment contain accurate thermometers. Gradually warm up the pump to about 150°F to facilitate start up.
  • Dilution of the asphalt emulsion should only occur at the emulsion manufacturing facility. Dilution should not be done by the contractor in the distributor tank.
  • Avoid repeated pumping and recirculation of the emulsion to ensure storage stability.
  • Ensure that inlet pipes and return lines are at the bottom of the tank to prevent foaming.
  • Pump emulsion from the bottom of the tank to minimize contamination from skin formation on the surface.
  • Haul emulsion in truck transports with baffle plates to prevent sloshing.
  • Agitate emulsions slowly if they have been in prolonged storage.
  • Consult with emulsion supplier before mixing different emulsions of the same grade to ensure compatibility.
  • Do not mix different classes, types, and grades of emulsified asphalt in storage tanks, transports, and/or distributors.
  • Do not load emulsion into any tank containing remains of incompatible materials. A “heel” of liquid asphalt, cutbacks or any petroleum solvent in the tank will not only damage the emulsion but can create significant safety problems.
  • Do not apply severe heat to pumps or valves