Concrete Roads Multiple Choice Question
(A) Subgrade
(B) Base course
(C) Base coat
(D) Wearing course
Explanation
In road construction, the layers of a pavement vary depending on whether it is a flexible pavement (e.g., bituminous) or a rigid pavement (e.g., concrete). In concrete roads, the base coat (also known as prime coat in flexible pavements) is not required because no asphalt layers are placed above the concrete slab. The concrete slab itself serves as both the structural layer and the wearing surface.
Key Layers in Pavement Construction
| Layer | Description | Flexible Pavement | Rigid Pavement |
|---|---|---|---|
| Subgrade | The prepared soil layer that forms the foundation of the pavement. | Required | Required |
| Sub-base Course | An optional layer for drainage and load distribution. | Optional | Optional |
| Base Course | The main load-distribution layer (e.g., WBM, WMM in flexible pavements). | Required | Optional |
| Base Coat (Prime Coat) | A thin layer of bituminous material to prepare for asphalt layers. | Required | Not Required |
| Wearing Course | The top layer providing the driving surface (asphalt in flexible pavements, concrete slab in rigid pavements). | Required | Included in Concrete Slab |
| Concrete Slab | The main structural and wearing surface in rigid pavements. | Not Applicable | Required |
Key Notes
- The base coat is specific to flexible pavements to bond asphalt layers to the base course, making it unnecessary in concrete roads.
- The concrete slab in rigid pavements serves as both the structural and wearing surface, eliminating the need for a separate wearing course.
- The subgrade is essential in both pavement types as it provides the foundation.
- The base course may be omitted in rigid pavements if the concrete slab and subgrade provide sufficient strength.
Note: Understanding the differences between flexible and rigid pavement layers is crucial for efficient road design and construction in civil engineering.
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