Fog Seal Road Treatment Best Practices

ASTM D-2995 can be used to estimate emulsion application rate and residual application rate.

To ensure success, a site visit should be arranged to document the texture and condition of the existing road surface, as well as the traffic type and level.

Typically a fog seal would require an emulsion application rate of 0.23 – 0.68 liters per square meter (0.05 – 0.15 gallons per square yard).  These rates will depend upon the residue content of the fog seal emulsion being applied.

If required, a test strip should be placed in conditions similar to those that are expected to occur during the project.

• Dilution may be improved by pre-warming the dilution liquid to 25 to 90° C (77 to 194° F).
• Never add emulsion to water, always add water or other diluent to emulsion.
• Diluted emulsions are normally not stored, unless bad weather necessitates temporary storage.
• Water for dilution should be clean, potable water, free from detectable solids or incompatible soluble salts.
• Test for dilution incompatibility, whenever in doubt, by diluting the emulsion in the severest conditions anticipated (e.g., high dilution, cold water, hard water, high shear pumps). 

In residential areas, place a cone at the end of each driveway until the Fog Seal has cured adequately to carry traffic, and explain the reason for these cones in the public notifications.

In extreme hot, dry conditions, it may be advantageous to lightly dampen the surface by spraying water to prevent premature break of the emulsion.

Emulsion applied by a pressure distributor shall be applied at a uniform rate, without splattering or drilling from the spray bar, by using low pressure. Nozzle angle and spray bar height must be adjusted to insure correct spray pattern.

ASTM D-2995 can be used to estimate emulsion application rate and residual application rate.