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Construction of asphalt concrete layers including Prime coat and Tack coat, Seal coat

This chapter is about Construction of asphalt concrete layers including Prime coat and tack coat, Seal coat and use of the Prime coat and tack coat, seal coat in the Bituminous pavement to strengthen the pavement layers.

Before laying any type of bituminous materials over a surface, it should be free from dust, dirt, or other organic materials, over the pressed surface, a thin layer of bituminous binder has to be provided by spraying, which is called as Interface treatment. Interface Treatment may be either a Prime coat and tack coat, or seal coat.

Prime coat

It’s similar to a primer in painting. A thin layer of low viscosity liquid bituminous material is first applied, using a mechanical sprayer @7.3 to 14.6 Kg/10 m2 are, over an existing porous surface. It’s mainly applied to plug in the capillary voids of the porous surface and to bind together all the loose minerals particles on the existing surface.

Prime coat
fig2 :Prime coat

Tack coat

Tack coat is the application of bituminous materials over an existing impervious pavement surface. It is applied by a mechanical sprayer of high viscous like hot bituminous @ 4.9 to 9.8 kg/10 cm2. depending upon the type of the surface.

Tack coat
Fig3.Tack coat

Seal coat

It’s used most often as a top coat over relatively pervious bituminous pavements. It’s thus a very thin surface treatment usually applied over an existing/worn out blacktopped surface.

The main functions of seal coat are :

  • To seal the surface against the ingress of water,
  • To develop a skid resistance surface,
  • To give a new life by patching the existing dry and weathered bituminous surface.
Seal coat
Fig 4 : Seal coat

Bituminous roads

They are flexible pavements made by laying a course of bituminous material over an existing/ prepared surface. It is strengthened by stagewise construction by laying one after the other in a certain period of time.

Followings are the some of methods available in use for the construction of the bituminous pavements.

  • Interface  Treatments,
  • Surface dressing,
  • Grouted or penetration type constructions,
  1. Penetration macadam,
  2. Built-up spray grout,
  3. Bituminous or asphalt concrete,
  4. Premix
  5. Bituminous bound macadam.
  6. Built-up spray grout
  7. Bituminous or asphalt concrete
  8. Sheet asphalt or Rolled asphalt
  9. Mastic Asphalt.

Some of these types are discussed here

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