No explanation needed at all, as We know the bitumen properties i.e water proofing.

Bituminous materials are commonly used in highway construction because of their good binding and water-proofing properties.

1. Binding properties:
Bituminous materials have excellent adhesion properties, which allow them to bind well with other materials used in highway construction. When bitumen is mixed with aggregate materials like gravel or crushed stone, it forms a strong and durable binder that holds the particles together. This binding property helps in preventing the disintegration and erosion of the road surface, especially under heavy traffic loads.

2. Water-proofing properties:
Bituminous materials have inherent water-repellent properties due to their hydrophobic nature. This makes them highly effective in preventing the penetration of water into the underlying layers of the road. Water can cause significant damage to the pavement structure by weakening the subgrade and subbase layers, leading to potholes, cracks, and rutting. By providing a waterproof layer on the road surface, bituminous materials help in preserving the integrity and longevity of the pavement.

3. Flexibility and elasticity:
Bituminous materials have the ability to deform and recover under loading, making them flexible and elastic. This property allows the pavement to withstand the repeated traffic loads without undergoing permanent deformation or cracking. The flexibility of bitumen helps in distributing the stress caused by moving vehicles over a larger area, preventing localized damage.

4. Rut resistance:
Rutting is a common pavement distress caused by the repetitive movement of vehicles in the same wheel tracks, leading to permanent deformation. Bituminous materials have good rut resistance due to their ability to flow and redistribute the stresses caused by traffic. This helps in maintaining a smooth and even surface, reducing the risk of accidents and improving driving comfort.

5. Skid resistance:
Bitumen surfaces offer good skid resistance, which is essential for ensuring the safety of vehicles and pedestrians. The rough texture of bituminous pavements provides better friction between the tires and the road surface, reducing the chances of skidding or slipping. This is particularly important in wet or icy conditions when the risk of accidents is higher.

Overall, the binding and water-proofing properties of bituminous materials make them an ideal choice for highway construction. They provide a strong and durable pavement structure that can withstand heavy traffic loads, prevent water ingress, and improve the safety and performance of the road.