Detailed information about the application of tack coat (type of material, weather limitations and quantity of tack coat per square metre)
Detailed information about the application of tack coat -
Scope: The work shall be consist of the application of a single coat of low viscosity liquid bituminous material to existing bituminous, cement concrete or primed granular surface preparatory to the superimposition of a bituminous mix, when specified in the contract.
Material: The binder used for tack coat shall be either cationic bitumen emulsion (RS 1) complying with IS:8887 or suitable low viscosity paving bitumen of VG 10 grade conforming to IS:73. The use of cutback bitumen RC:70 as per IS:217 shall be registered only for sites at sub-zero temperatures or for emergency applications as directed by the engineer.
Weather and seasonal limitations: Bituminous material shall not be applied during a dust storm or when the weather is foggy, rainy or windy or when the temperature in the shade is less than 10°C. Where the tack coat consists of emulsion, the surface shall be slightly damp, but not wet. Where the tack coat is of cutback bitumen, the surface shall be dry.
Application of Tack coat: The application of tack coat shall be at the rate specified in table below. No dilution or heating at the site of RS1 bitumen emulsion shall be permitted. Paving bitumen if used for tack coat shall be heated to appropriate temperature in bitumen boilers to achieve viscosity less than 2 poise. The normal range of spraying temperature for a bituminous emulsion shall be 20°C to70°C and for cutback 50°C to 80°C .
Curing of Tack coat:Tack coat shall be left to cure until all the volatiles have evaporated before any subsequent construction is started .
Gyan of engineering (Mukesh Kumar)