GREEN LAND General Construction

Kaka-Mecha Lot 1 Project Under Construction (Adiyo Woreda)

Road Pavement Layers.
(Composition, Function & Construction – Practical & Technical)

1. What are road pavement layers?
The different structural layers constructed above the subgrade to distribute traffic loads and provide a durable riding surface.

2. Why are pavement layers provided in roads?
To spread wheel loads safely to the subgrade, improve riding quality, and protect the road from environmental damage.

3. What are the main layers of a flexible pavement?
Subgrade, sub-base, base course, binder course, and surface (wearing) course.

4. What is the subgrade layer?
The natural soil or prepared earth surface that supports the entire pavement structure.

5. Why is subgrade strength important?
Weak subgrade leads to settlement, rutting, and premature pavement failure.

6. What is the sub-base layer?
A layer of granular material placed above the subgrade to improve load distribution and drainage.

7. What materials are used for sub-base?
Laterite, crushed stone, gravel, sand-clay mix, or stabilized soil.

8. What is the function of the sub-base layer?
Load distribution, drainage improvement, frost protection, and working platform for construction.

9. What is the base course?
The main load-bearing layer of the pavement placed above the sub-base.

10. What materials are used for base course?
Crushed stone, wet mix macadam (WMM), cement-treated base, or asphalt base.

11. What is the binder course?
An intermediate bituminous layer between the base course and surface course.

12. What is the function of the binder course?
To provide strength and distribute loads while bonding the surface course to the base.

13. What is the surface (wearing) course?
The top layer of pavement that comes in direct contact with traffic.

14. What are common surface course materials?
Asphalt concrete, bituminous concrete, surface dressing, or concrete (for rigid pavements).

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