light rolling and brooming. Excess prime, held in minor
depressions, should be corrected by an application of
clean, dry sand.
Any loose sand should be lightly
broomed from the primed surface before the wearing
surface is laid.
The primed base should be adequately cured before
the wearing surface is laid. In general, a minimum of
48 hours should be allowed for complete curing.
Ordinarily, proper surface condition is indicated by a
slight change in the shiny black appearance to a slightly
When a soil base is to be covered by a bituminous
wearing surface, the area should be barricaded to
prevent traffic from carrying dust or mud onto the
surface both before and after priming. If it is necessary
to open the primed base course to traffic before it has
completely cured, a fine sand may be used; when you
are ready to place the wearing surface, lightly broom the
sand from the primed base course.
To estimate the amount of bitumen required for the
prime coat, multiply the area to be treated by the rate of
NOTE: Under certain conditions, the estimate
should include sufficient bitumen for an additional
width of 1 foot on each side of the surface course to be
constructed on the primed base.
The formula for a prime coat estimate is as
10% at .10. This will depend on the
experience of the asphalt distributor
Example: the specification and other data for a
prime coat application are as follows:
For computing gallons:
length of treated section in feet
width of treated surface in feet
square feet per yard conversion factor
Waste factor of bitumen = 5% at .05 or
Always round your answer to the next higher
number. In this case, 7761.6 is rounded to 7762 gallons.
A tack coat is an application of asphalt to an existing
paved surface to provide bond between the existing
surface and the asphalt material to be placed on it. Two
essential requirements of a tack coat areas follows: (1)
it must be thin and (2) it must uniformly cover the entire
surface to be treated. A thin tack coat does no harm to
the pavement, and it will properly bond the course.
Some of the bituminous materials, used for tack
coats, are rapid-curing cutbacks, road tar cutbacks,
rapid-setting emulsions (may be used in warm weather),
and medium-asphalt cements. Because rapid-curing