Answer:

Introduction:
The petroleum product used for surfacing roads is called bitumen. Bitumen is a thick, black, viscous liquid or semi-solid form of petroleum. It is primarily used in road construction and maintenance due to its excellent adhesive and waterproofing properties.

Explanation:
Bitumen is derived from the fractional distillation of crude oil. During the refining process, bitumen is obtained when the heaviest components of crude oil are separated from the lighter fractions. It is composed mainly of hydrocarbons, which are organic compounds composed of hydrogen and carbon atoms.

Properties of Bitumen:
Bitumen possesses several properties that make it suitable for surfacing roads:

1. Adhesion: Bitumen has excellent adhesive properties, allowing it to bind aggregates together. This property helps to create a strong and durable road surface.

2. Waterproofing: Bitumen is highly impermeable to water, preventing water from seeping into the road structure. This helps in protecting the underlying layers from water damage, such as weakening of the base and subbase layers due to moisture.

3. Flexibility: Bitumen exhibits high elasticity, which helps the road surface to withstand heavy traffic loads and temperature variations. It can expand and contract without cracking, ensuring the road's longevity.

4. Viscosity: Bitumen has a high viscosity, meaning it is thick and sticky at normal temperatures. This property allows it to coat and adhere to aggregates during the road construction process.

5. Resistance to Oxidation: Bitumen has good resistance to oxidation, which helps in maintaining its properties over extended periods. It can withstand exposure to sunlight, air, and other environmental factors without significant degradation.

Application:
Bitumen is commonly used in road construction and maintenance in the following ways:

1. Asphalt Concrete: Bitumen is mixed with aggregates such as crushed stone, sand, and gravel to create asphalt concrete, which forms the topmost layer of roads. This mixture provides a smooth and durable road surface that can withstand heavy traffic.

2. Surface Dressing: Bitumen is applied as a thin layer onto existing road surfaces to improve their durability and skid resistance. This process is known as surface dressing or chip sealing.

3. Bituminous Emulsion: Bitumen can be emulsified with water to form a bituminous emulsion. This emulsion is used for surface treatments like slurry seals and micro-surfacing, which help in preserving and extending the life of roads.

Conclusion:
Bitumen is a crucial petroleum product used for surfacing roads. Its adhesive, waterproofing, and flexible properties make it an ideal choice for road construction and maintenance. By using bitumen, we can ensure the durability, safety, and longevity of road surfaces, providing a smooth and reliable transportation network.