Tack Coat and Bond Coat Application

Tack coat and bond coat are bitumen-based liquids sprayed onto road surfaces to promote adhesion between layers.
The application temperature for cationic emulsion tack coats is typically 40–70°C — lower than hot bitumen.
Polymer-modified bond coats for bridge decks and high-stress areas may be applied at higher temperatures.
Spray application from a tanker-mounted lance distributes the binder evenly across the prepared surface.
Bitumen emulsion contact with skin causes irritation and potential burns at elevated temperatures.
Overspray can coat vehicles, structures, and workers if wind direction and spray pattern are not controlled.
Traffic management must be in place before application on public highways.
The sprayed surface is slippery until the emulsion breaks and the water evaporates.
Application rate must be controlled — too little causes delamination; too much creates a slip surface.
COSHH assessment is required for all bitumen emulsion products used during the application.

Skin burns	Hot bitumen emulsion causes skin burns on contact, and prolonged exposure to fumes irritates the respiratory system.
Slip hazard	Freshly applied tack coat is extremely slippery — workers and vehicles can lose traction on the coated surface.
Layer bonding	Incorrect application rate or contamination of the tack coat causes layer delamination and premature pavement failure.

Do

Don't

Complete a COSHH assessment for the specific tack or bond coat product being used
Wear chemical-resistant gloves, eye protection, and coveralls during spray application
Control the spray pattern and direction to prevent overspray onto workers and structures
Apply at the rate specified by the engineer — check coverage with calibration checks
Install traffic management before applying tack or bond coat on any public highway
Warn workers and drivers that the freshly coated surface is extremely slippery
Allow the emulsion to break and become tacky before vehicles or paving plant cross it
Clean any bitumen emulsion from skin immediately using appropriate bitumen remover
Maintain the spray equipment including nozzles and pumps to ensure even application
Brief the surfacing team on the application plan, wind direction, and slip hazard

DON'T apply tack coat without the COSHH assessment and correct PPE in place
DON'T spray into the wind where overspray will coat workers, vehicles, or structures
DON'T allow vehicles or pedestrians onto the freshly sprayed surface before it has broken
DON'T clean bitumen emulsion from skin using diesel, white spirit, or solvents
DON'T apply tack coat on wet, frozen, or contaminated road surfaces
DON'T exceed the specified application rate — excess creates a dangerous slip surface
DON'T apply bond coat in rain — water prevents proper adhesion to the substrate
DON'T walk on fresh tack coat without non-slip overshoes or waiting for it to break
DON'T allow spray equipment to operate with blocked or damaged nozzles
DON'T spray tack coat without traffic management on public highways

See also: Asphalt Laying Safety | Road Construction Safety Awareness

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