Double Bituminous Surface Treatment (DBST) is a common method used for constructing road surfaces. It involves two layers of bitumen and aggregate. Here’s a breakdown of the typical road structure for a DBST road:
1. Subgrade: This is the natural soil that has been compacted to support the loads transmitted from the road structure. Proper compaction and stabilization of the subgrade are crucial.
2. Sub-base: This layer is made of granular material such as gravel or crushed stone. It provides additional load distribution and drainage. The thickness of the sub-base depends on the expected traffic load and subgrade conditions.
3. Base Course: Similar to the sub-base, the base course is made of higher quality granular material. It provides structural support and helps in load distribution. In some cases, a cement or lime-stabilized base might be used for added strength.
4. Prime Coat: This is a low-viscosity bitumen layer applied to the base course to promote adhesion between the base course and the first bituminous layer. It also helps seal the base course to prevent water infiltration.
5. First Bituminous Layer: A layer of bitumen is sprayed, followed by an application of aggregate. This layer is then compacted to ensure proper adhesion and a uniform surface.
6. Second Bituminous Layer: Another layer of bitumen is sprayed on top of the first bituminous layer, followed by another layer of aggregate. This is also compacted to form the final surface.
7. Surface Dressing: This final layer consists of a bitumen emulsion and fine aggregate, providing a smooth and durable surface.
### Summary of DBST Road Structure
1. Subgrade
2. Sub-base
3. Base Course
4. Prime Coat
5. First Bituminous Layer
6. Second Bituminous Layer
7. Surface Dressing
Each layer has a specific function to ensure the road can handle traffic loads, provide a smooth driving surface, and maintain durability over time. Proper design and construction practices are essential to ensure the longevity and performance of a DBST road.
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