Tack Coat
The application of a tack coat is an integral part of any Hot Mix Asphalt (HMA) operation, whether the HMA is placed over compacted gravel bases, existing HMA surfaces, or over Portland Cement Concrete (PCC).
A tack coat is a very light spray application of an asphalt emulsion to create a bond between asphalt overlay and the existing surface. Tack coat applications ensure a proper bond and enhance the shear strength between asphalt layers, as well as aiding in overall HMA compaction. Adjacent vertical surfaces, such as HMA cold joints and where HMA meets PCC, should also be tacked to help mitigate cracking and de-bonding.
Features & Benefits
Prevents the separation of HMA layers
Prevents mat slippage and reduces cracking from the surface down
Allows additional layers to bond as one, boosting the roadway's overall strength
Helps increase mat density during rolling by reducing slippage and forward movement of the HMA
Extends pavement life and reduces lifecycle costs.
Low cost with high benefits
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Trackless Tack
Trackless tack coats serve the same functions as regular tack coat application, only it has an added benefit of a non-tacky residual binder being left on the surface. This added benefit prevents tracking by construction vehicles and the general public, keeping a sufficient amount of tack on the base and allowing for proper bonding and shear strength to be achieved with an overlay. This is an excellent choice for busy urban areas to eliminate unsightly tracking of tack coat.
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Conventional Tack
The most common tack coats used are asphalt emulsions, such as: SS-1, SS-1H, CSS-1, CSS-1H and RS-1. Certain emulsions are capable of being diluted to suit specific field applications and equipment requirements. Application rates depend on several factors, including existing pavement conditions, surface type, temperature, and dilution rates.
