Two structures of asphalt pavement layers

2023-12-08 17:02:05 ENUO

Asphalt pavement is one of the most common road paving materials. It is durable and cost-effective, making it an excellent choice for road construction. Focusing on the asphalt pavement surface layer, there are two commonly used structural types: single-layer and double-layer. In this article, we will introduce both these types of structures.

Single-layer Structure

The single-layer structure is a simple and straightforward construction method. It consists of a single layer of asphalt concrete mixture that is composed of asphalt binder and aggregate. Here are the construction steps:

1. Base preparation

A solid and stable base is crucial to ensuring the integrity of the asphalt pavement. The base preparation includes grading, compacting the soil, adding a sub-base layer, and compacting again until it reaches the required level.

2. Applying tack coat

To ensure the asphalt mixture adheres to the base surface, a tack coat is applied before laying the asphalt layer. This creates a bond between the base and asphalt layer.

3. Laying the asphalt mixture

Hot-mix asphalt is used in the single-layer structure, and it is laid using a paving machine. The asphalt is then compacted with a roller, ensuring uniform thickness and smooth surface.

Double-layer Structure

The double-layer structure has an extra layer of asphalt, which makes it more durable than the single-layer structure. The two layers are different in composition, with the lower layer being more rigid for better load distribution and the upper layer being more resistant to deformation. Here are the construction steps:

1. Base preparation and tack coat

Similar to the single-layer structure, the base preparation and tack coat are also needed for the double-layer structure.

2. Lower layer asphalt mixture

The lower layer is composed of a dense-graded asphalt concrete mixture with a larger aggregate size. The mixture is laid and compacted to the desired thickness.

3. Upper layer asphalt mixture

The upper layer is composed of an open-graded asphalt concrete mixture with a smaller aggregate size and higher asphalt content. This layer provides a skid-resistant and durable surface for vehicles.

4. Sealing coat

A sealing coat is applied to the surface of the upper layer to prevent water intrusion and oxidation.


Both single-layer and double-layer structures have their unique advantages and disadvantages. The single-layer structure is more cost-effective and easier to maintain, while the double-layer structure provides better durability and performance. When choosing which structure to use, various factors, such as traffic volume, climate, and project budget, should be considered. With proper construction and maintenance, the asphalt pavement can last for many years, providing a smooth and safe driving experience.