Lesson 2/Learning Event 1
Learning Event 1
IDENTIFICATION AND ESTIMATION OF MATERIALS
Many different combinations of materials are used on bituminous surfaces. This part of the
lesson will cover the materials used in treatments and pavements:
Hot plant mix
Before a bituminous surface is placed, the surface to be covered generally requires the placing of
a preliminary treatment, a primer or a tack coat.
Prime coats are placed on a dirt or gravel surface. The purpose of priming is to waterproof and
dust proof the surface, plug capillary voids, and coat and bond loose particles. It also hardens or
toughens the surface, promotes adhesion between the existing surface and the new surface, and
penetrates the surface to 1/4".
The priming material may be:
a low viscosity tar, such as RT-2, RT-3, or RT-4;
a low viscosity asphalt such as MC-30, -70, -250, or SC-70, -250, -800; or
a diluted asphalt emulsion. Bituminous materials for the prime coat should be applied in
quantities of not less than 0.2 gallon or more than 0.5 gallon per square yard. The exact
quantities can be determined by a test strip. Apply enough to perform the objectives listed above
and let cure.
Estimation for a Prime Coat
To estimate the amount of bitumen required for the prime coat, multiply the area to be treated by
the rate of application. The estimate must 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 formulas for a prime coat estimate are: