Describe the function of prime coat, tack coat and seal coat in bituminous construction

Prime Coat

The objectives of the priming the granular surface are to

1. Penetrate deep into the surface and plug or seal the voids on the surface
2. Coat and bond the loose particles on the surface.
3. Render the surface of the base course water-resistant and
4. Permit the tack coat to be applied over the primed surface to provide proper adhesion between the base and the bituminous pavement layer constructed above the treated granular base.

Tack Coat

To provide an adequate interface bond between the receiving pavement surface and the new bituminous layer being overlaid. The binder of the tack is not expected to penetrate into the pavement surface and plug the voids.

Seal Coat

To prevent the entry of water into open graded premix carpet seal coat is laid.