33 04 N Road Construction Bitumen pavement

Summary

This guide details the process of constructing flexible bituminous pavements, commonly known as bitumen roads, which have been used for over a century. It covers material selection, mix design, and construction layers such as prime coat, binder course, and surface course. The guide emphasizes the importance of proper temperature control, compaction, and quality assurance throughout the process. Key steps include laying a prime coat, applying binder and surface courses, using hot mix plants for material preparation, and ensuring proper sealing with a seal coat. The final pavement should be durable, water-resistant, and capable of handling traffic loads for up to five years.

Takeaways

• 😀 Bituminous roads, also known as flexible pavements, have been in use for over 100 years and are designed to distribute loads point-to-point within a small area.
• 😀 Before constructing a bituminous road, it is crucial to determine the appropriate bitumen proportion and test the properties of locally available aggregates and filler materials.
• 😀 A proper bitumen mix design is essential, ensuring factors like aggregate gradation, bitumen percentage, mixing method, and temperature control are optimized for road construction.
• 😀 The construction of a bituminous road involves several layers: prime coat, binder course, surface course, and seal coat, which should be applied in sequence for optimal performance.
• 😀 The prime coat is applied to create a water-resistant surface, plugging capillary voids and binding loose materials. It must be sprayed evenly and allowed to dry for at least 24 hours before proceeding with other layers.
• 😀 The binder course, an intermediate layer between the base and surface course, is made from graded aggregates coated with bitumen and compacted to form a dense, impervious layer.
• 😀 The hot mix plant is used to prepare the bitumen mix, where aggregates are heated and mixed with bitumen at specific temperatures (150-160°C), ensuring the proper consistency before laying it on the road.
• 😀 Proper handling and transportation of the mix are vital. Trucks used for hauling asphalt should be clean and covered to protect the material from weather elements.
• 😀 Compaction of the bituminous pavement is critical for achieving a dense surface. This is done in stages using heavy, vibratory, and light rollers to ensure adequate stability and durability.
• 😀 The final surface is sealed with a seal coat to waterproof the pavement and enhance its performance. The seal coat is typically applied using a mechanical spray or rubber mop, ensuring even coverage.

Q & A

What is a bituminous road, and how long has it been used?

A bituminous road, also known as a flexible pavement, uses bitumen as a binding material. These roads have been in use for over 100 years due to their flexibility and ability to distribute loads efficiently.

Why is it important to determine the proportion of bitumen used in road construction?

Determining the right proportion of bitumen ensures the proper mix for durability, flexibility, and load distribution. It also helps in achieving a balance between water resistance and the strength of the pavement.

What materials need to be tested before beginning bituminous road construction?

Locally available aggregates (coarse and filler) need to be tested to determine their suitability for use in the road. The quality of these materials directly impacts the pavement's performance.

What are the key layers involved in constructing a bituminous road?

The main layers include the prime coat, binder course, surface course, and seal coat. These layers are constructed sequentially, with each serving a specific purpose to ensure the road's durability and performance.

What is the purpose of the prime coat in road construction?

The prime coat is applied to the base course to seal capillary voids and bind loose material. It also helps in making the surface water-resistant, ensuring a stable foundation for subsequent layers.

What is the recommended bitumen grade for prime coat application, and what is the typical application rate?

The recommended bitumen grade for the prime coat is VG-44, with an application rate of 0.7 to 1.0 kg per square meter.

What is the purpose of the binder course, and how is it applied?

The binder course serves as an intermediate layer between the base and surface courses. It is made from well-graded aggregates mixed with bitumen, laid hot, and compacted to form a dense, impervious layer.

What is a common practice regarding the thickness of the binder course?

The common practice is to have the binder course thickness between 75 mm and 40 mm, depending on the road design requirements.

How should the surface course be prepared and laid?

The surface course should be manufactured in a hot mix plant. The aggregates should be heated before adding bitumen, ensuring thorough mixing. After the temperature reaches above 160°C, bitumen at 150°C is added, and the mix is applied to the surface.

What role does the seal coat play in bituminous road construction?

The seal coat serves to waterproof the pavement, preventing water penetration and protecting the underlying layers from damage. It is applied with a VG-10 bitumen at 0.5 kg per square meter.