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Fog Seal

1. What It Is

A fog seal is a light spray of a diluted asphalt or rejuvenator emulsion applied by a distributor truck to renew surface asphalt. It delays further oxidation, weathering, and raveling, seals micro-cracks, and is a very low cost and effective pavement preservation treatment when applied correctly on pavements in good condition. Typical application rates are 0.05 to 0.15 gal/yd2. Rejuvenating fog seals are used to alter the chemistry of surface asphalt. Generally, they include oily fractions developed to restore the viscoelasticity of oxidized, hardened asphalt. Some commercial fog seal products do not need dilution, however, manufacturer recommendations should always be followed.

2. Where and When It is Used

Use fog seals on asphalt pavements that are structurally sound and in good condition before they exhibit signs of surface distress. Applying them to newly constructed chip seals can aid chip retention. Fog seals can also add 2 – 3 years to the life of an aging chip seal if applied before too much aggregate loss occurs. They can be used, as well to establish a black, aesthetically pleasing surface. A program that applies fog seals every 1 – 5 years (depending upon the road’s surface) can preserve a good road in good condition.

Fog seals are also very effective for shoulder preservation. But they should not be used on pavements with moderately or severely distressed surfaces, pavements with poor skid resistance or rutting, or roads that cannot be closed to traffic during the curing period. Only use rejuvenating seals where the surface asphalt has hardened; care should be taken to prevent loss of skid resistance.

3. Advantages

  • Very low cost
  • Easily applied
  • Can replace asphalt that has worn off surfaces
  • Reduces raveling
  • Waterproofs surfaces
  • Rejuvenates and protects asphalt surfaces from UV aging
  • Seals micro-cracks before they can widen
  • Protects pavement structure from moisture intrusion

4. Disadvantages

  • May initially reduce skid resistance, especially when applied too heavily. Fog seals may be sanded to reduce friction loss.
  • Lanes should be closed to traffic until the seal has completely cured, which can take several hours.
  • Shorter lifespan than some other surface treatments.
  • Fog seals should be applied in dry weather, when temperatures are warm enough to ensure a complete cure.

5. Estimated Life Extension

Pavement ConditionFog Seal Longevity
Good4 – 5 years
Fair1 – 4 years
PoorNot Recommended for Use

Pavement Preservation Knowledge Book:

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