scarifying and retreatment the second year will producea thicker and stronger surface.WARNINGBefore planning any road oiling work yoursupervisor should check with local authoritiesconcerning environmental protection restric-tions.Aggregate Surface TreatmentThe sprayed asphalt with aggregate cover surfacetreatments are applications of liquid asphalt, followedby an application of aggregate. This can be done in oneor more layers of construction. Two types of sprayedasphalt with covered aggregate surface treatments are inuse today: single- and multiple-surface treatments.SINGLE-SURFACE TREATMENT.— Single-surface treatments are thin, bituminous-aggregatetoppings, applied to existing bases or surfaces, such asconcrete or asphalt. Construction involves applying abituminous prime or tack coat to the base or surface.This coating is followed by an application of bitumenand small-sized aggregate. Single-surface treatmentsare sometimes called seal coats, because they seal thesurface of the road or runway.Sequence of Operations.— Figure 16-28 shows thesequence of operations for the application of asingle-surface treatment.The first steps, such assweeping, priming or tacking, and curing, are the sameas those used for applying a prime coat. The binder(bituminous material) is applied over the prime coatwith an asphalt distributor. The aggregate is then spreadover the binder by use of aggregate spreaders. Theaggregate cover is spread uniformly immediatelybehind the distributor.As soon as the aggregate isspread, it is pushed into the soft asphalt by rolling it witha pneumatic-tired roller.Binder Application.— When you are applying thebinder, it should be hot enough to spray properly andFigure 16-28.-Sequence of operations for the application of a single-surface treatment.16-24
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