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In tack coat, bitumen is used at the rate of
Kgm2
1 kg/m┬▓
o.5 Kgm2
0.5 kg/m┬▓
Kgm2
5 kg/m┬▓
10 Kgm2
10 kg/m┬▓
o.5 Kgm2
0.5 kg/m┬▓
A tack coat is a very light application of bituminous material applied to an existing pavement surface to ensure a strong bond between the old surface and the new overlying asphalt course. It is applied at a low rate, typically ranging from 0.2 to 0.5 kg/m┬▓, depending on the surface texture and porosity.
A tack coat is a very light application of bituminous material applied to an existing pavement surface to ensure a strong bond between the old surface and the new overlying asphalt course. It is applied at a low rate, typically ranging from 0.2 to 0.5 kg/m┬▓, depending on the surface texture and porosity.
R=AWтАЛ тАФ where R is the application rate (kg/m2), W is the weight of bitumen applied, and A is the surface area.
The tack coat functions as an adhesive agent to prevent slippage or delamination between the structural layers of the road. By filling surface voids and creating a tacky film, it improves the shear strength at the interface of the existing and new layers, ensuring the pavement acts as a unified monolithic structure.
Used primarily on non-absorptive surfaces like existing asphalt or concrete.
Ensures bonding to prevent internal sliding of pavement layers.
Excessive application can lead to a 'slippery' surface or 'bleeding'.
Commonly uses Bitumen Emulsion (SS-1 or CSS-1 grade) or low viscosity cutback bitumen.
Increases structural stability of multilayer pavements.
Prevents lateral sliding between old and new layers.
Reduces maintenance costs by preventing surface fatigue.
Requires careful control to avoid over-application.
Sensitive to weather conditions during application.
Pavement overlays (bituminous concrete over existing surface).
Widening of roads (bonding new pavement to existing lanes).
Application over milled/scraped surfaces.
IRC (Indian Roads Congress) standards typically specify 0.2 to 0.5 kg/m┬▓ depending on the surface condition.
Option A (1 kg/m┬▓) is generally too high and causes slippage; options C and D are excessive and uneconomical, leading to potential pavement failure.
B is correct тАФ The standard application rate for a tack coat is approximately 0.5 kg/m┬▓ to ensure effective bonding without causing slippage.
Always remember: Tack coat is for bonding layers (low rate), while Prime coat is for porous granular surfaces (higher rate, typically 0.6тАУ0.9 kg/m┬▓) to plug voids and penetrate the base layer.