equipment shall be permitted within 8 meters 25 feet of heating,
distributing, and transferring operations of bituminous material other than
bituminous emulsions. [If tar is used, a full-face organic vapor-type
respirator and protective creams shall be used by personnel exposed to
fumes. Protective creams shall not be used as a substitute for cover
clothing.]
3.2.4
Aggregate Application Rate
The aggregate shall be spread in the quantities shown in TABLE III. The
exact quantities within the range specified, which may be varied to suit
field conditions, will be determined by the Contractor, and approved by the
Contracting Officer prior to use. The aggregate weights shown in this
table are those of aggregate having a specific gravity of 2.65. If the
specific gravity of the aggregate to be used is less than 2.55 or greater
than 2.75, adjustments shall be made in the number of pounds of aggregate
required per square yard to insure a constant volume of aggregate per
square yard of treatment.
3.2.5
Application of Aggregate
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NOTE: When using cutback asphalt, the asphalt cools
to the temperature of the surface to which it is
applied in approximately 1 1/2 minutes. In the case
of emulsified asphalt, breaking of the emulsion
occurs in 3 to 4 minutes. No bituminous material
should be down more than the following number of
minutes before it is covered with aggregate:
1 - 1 1/2 Minutes for cutback asphalt
3-4
Minutes for emulsified asphalt
1
Minute for asphalt cement
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The specified quantity of cover aggregate shall be spread uniformly over
the bituminous material. Before the bituminous material is applied,
sufficient aggregate to cover the distributor load of bituminous material
shall be on trucks at the site of the work. No bituminous material shall
be down more than 3 minutes before it is covered with aggregate. Spreading
shall be done uniformly with aggregate-spreading equipment. Trucks
spreading aggregate shall be operated backwards, covering the bituminous
material ahead of the truck wheels. Areas having insufficient cover shall
be lightly recovered with additional aggregate by hand during the
operations whenever necessary.
3.2.6
Rolling and Brooming
Immediately following the application of cover aggregate, rolling
operations shall begin. Rolling shall be accomplished with pneumatic-tired
rollers. The rollers shall be operated at a speed that will not displace
the aggregate. Rolling shall continue until the aggregate is uniformly
distributed and keyed into the bituminous material. All surplus aggregate
shall be swept off the surface and removed not less than 24 hours nor more
than 4 days after rolling is completed.
SECTION 02785
Page 17
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