Prime Coat
The major purpose of the prime coat is to protect the underlying layers from the wet weather by providing a temporary waterproofing layer. An additional benefit of the prime coat is to stabilize and bind the surface fines together and promote bonding to the hot mix asphalt layer. Prime coat increases the bond strength at the interface between a compacted base and an asphalt layer.
Tack coat
Tack coat is a brownish-black emulsion of asphalt that is applied to the prepared, existing asphalt or concrete surface prior the placing new hot mix asphalt. When it is placed, it bonds to the layer of emulsion, creating a monolithic pavement structure. Creating this bond also helps prevent water intrusion that can create potholes in asphalt work.