A few restrict its use in wearing courses even fewer (one or two) prohibit its use completely. Almost all state highway departments now allow the use of RAP. The specifying agency or owner will set the limit for RAP content. RAP has a history of positive performance. The Asphalt Institute strongly endorses the use of RAP in asphalt mixtures. If either of these cautions is violated, there is a good chance that upper layer will not bond to the under layer and a slip plane will develop. The emulsion will break, but the water and emulsifying agents will freeze and remain in the layer that has been tack coated. Caution #2: Never apply an emulsion tack coat to a cold pavement (below the freezing point).

In marginal weather it may take several minutes. In good paving weather, it will take only a few minutes. The length of time required for this to happen will depend on the weather.

Caution #1: Once the tack coat is applied, time must be allowed for emulsion to break (turn from brown to black) prior to placing hot mix on it.

Therefore, an application rate of 0.10 to 0.15 gals/sy of the diluted material will give you the 0.03 to 0.05 gals/sy. Slow-setting emulsions generally have a residual asphalt content of about 2/3. You want to accomplish a very uniform application of about 0.03 to 0.05 gal/sy of residual asphalt on the layer to be tacked (a paint job, so to speak). Then relay the mixed material and compact. Apply about 0.20 gal/sy 2 of straight emulsion (undiluted) and blade mix it with the scarified material.

Complete placement of the base course material, then scarify up about 3/4 inch.

Use a dilution and application rate which will provide 0.1 to 0.3 gallon per square yard (3:1 dilution 4 applications 0.15 gal/sy rate).

Incorporate an emulsion into the compaction water while placing the last 2 to 3 inches of the base course.

By applying several (4 or 5) light applications (0.10 gal/sy), a waterproof surface can be obtained on the base course.

If the granular base material has a gradation that is somewhat porous, placing a prime coat can often be affected by placing a slow-setting emulsion (SS-1, SS-1 h, CSS-1, CSS-1 h) diluted 5 parts water to 1 part emulsion.

Most emulsion manufacturers make proprietary products, one of which is an emulsion specifically designed for use in prime coats.

There are several ways to accomplish a prime when using an emulsion: In such areas the use of an emulsified asphalt is necessary. However, in a lot of areas air quality is of concern and the EPA has restricted or eliminated the use of cutbacks. Usually a light grade of medium curing cutback such as an MC-30 will work well. For a prime coat to be effective it must be able to penetrate into the base course.

Yards drift asphalt 9