Tack Coat and Prime Coat Applications with Asphalt Emulsions

Back to Asphalt Emulsion FAQs

What is tack coat?

Tack coat (also known as bond coat) is a light application of asphalt emulsion between hot mix asphalt layers designed to create a strong adhesive bond without slippage. Heavier applications may be used under porous layers or around patches where it also functions as a seal coat.

Why use tack coat?

Without tack coat the asphalt layers in a road way may separate which reduces the structural integrity of the road and may also allow water to penetrate the structure.

What type of emulsion should be used for tack coats?

The type of emulsion used for tack coats varies from country to country. Normal practice in the USA is to use a slow-setting emulsion that is diluted with water before application. In many European countries cationic rapid setting or specially designated low viscosity medium setting emulsions are used, which are applied undiluted.

Why use prime coat?

Prime coats protect the integrity of the granular base during construction and help reduce dust. In the case of a base which is to be covered with a thin hot mix layer or a chip seal for a low volume roadway, priming ensures a good bond between the seal and the underlying surface which otherwise would have a tendency to delaminate.

Why use asphalt emulsion prime?

Compared to cut back asphalt primes, emulsion primes are environmentally friendlier.

What type of emulsion is most suitable for emulsion prime?

Slow-setting grades of asphalt emulsions (diluted with water before application) are suitable. With dense granular bases, or stabilized bases the surface may need to be broken up by scarifying before application, to ensure good penetration.

Where can I learn more about asphalt emulsion tack coats and prime coats?

You can order AEMA’s Basic Asphalt Emulsion CD-Rom right here on this website – just click here.