413.4 Bituminous Fog Sealing

Material Inspection for Sec 413.10

Asphalt Binder for use in fog sealing shall be inspected in accordance with 1015 Bituminous Material.

District procedures are identical to those in micro-surfacing.

Laboratory Procedures

No additional laboratory procedures in this section of the Engineering Policy Guide.

Maintenance Fog Sealing

A fog seal is a light application of diluted slow-setting emulsion sprayed on an existing asphalt surface without an aggregate cover. The emulsion can be diluted up to one part emulsion to five parts water (1:5) but in most cases, a one to one dilution is used. The asphalt emulsion normally used is a SS-1, SS-1h, CSS-1, and CSS-1h.

Fog seals are used to renew old asphalt surfaces that have become dry and brittle with age and to seal very small cracks and surface voids. It also coats aggregate particles at the surface.

The surface condition or texture, dryness and degree of cracking of the pavement will determine the quantity required, but the normal application rate of a 50/50 diluted material is 0.10 to 0.15 gal/sq. yd. The fog seal should be allowed to completely cure before traffic is permitted on the surface to prevent pickup by vehicle tires. The surface must be porous enough to absorb the emulsion. Sand can be used to blot wet spots.

Fog seals may be used on asphalt shoulders and on cold-mix roadways only. Because of the time required for the slow-setting emulsion to break, and because of the potential for reduced surface friction immediately after seal application fog seals are not recommended for high-speed roadway pavements constructed with dense braded mixes. A for seal may be used to add additional asphalt to a chip seal and as a dust control agent on a chip seal. The best conditions under which to apply a fog seal is a warm sunny day with low humidity.