The filler used in plastic bitumen, is

Definition: In plastic bitumen, a filler is a fine material added to the bitumen mix to improve its binding properties and performance.

Role of filler: It increases the viscosity of bitumen, fills the voids, and enhances the strength and durability of the paving material.

Specific filler used: Asbestos powder is commonly used as the filler in plastic bitumen due to its fine texture, high resistance to heat, and good binding compatibility with bitumen.

Reason: The addition of asbestos powder improves the stability, wear resistance, and lifespan of the bituminous layer.

Conclusion: For plastic bitumen, asbestos powder is the standard filler material used to achieve the desired strength and performance.