Tack coat: Very light application of asphalt (emulsion) to ensure a bond between the surface being paved and the overlying course.More economical design, since binder course generally consist of larger aggregates and less asphalt and doesn’t require high quality.HMA is too thick to be compacted in one layer (if the binder course is more than 3” it is placed in two layers).Binder course (known also as Asphalt base course) is the asphalt layer beneath the surface course.

If the above requirements can not be met, the use of seal coat is recommended.

Water proof to protect the entire pavement from the weakening effects of water.

Provide smooth and skid resistant riding surface.Tuff to resist and withstand wear & abrasive effects of moving traffic & stable to prevent permanent deformation.

Is the top course of asphalt pavement (Wearing course).

Single Surface treatment = single application of bituminous material that is covered by a light spreading of fine aggregate or sand (spread mechanically) then compacted with pneumatic tired rollers.

Rejuvenate or revitalize old bituminous wearing surfaces.

Seal coat: Thin asphalt surface treatment used to:.

The use of various courses is based on either necessity or economy, and some of the courses may be omitted.

It is assumed to posses considerable flexural strength that will permit it to act as a beam and allow it to bridge minor irregularities in base and subgrade.

Pavement constructed of Portland cement concrete.

A structure that maintains intimate contact with subgrade and distribute loads to it, and depends on aggregate interlock, particle friction, and cohesion for stability.

Pavement constructed of bituminous & granular materials.

Flexible pavement design aashto example