Question

For a four layer flexible pavement, there is a surface course, base course, and ______________ constructed over a compacted, natural soil subgrade.

(a) sub-grade course

(b) sub-base course

(c) base course

(d) sub-ballast

Answer 1

Right answer is (b) sub-base course

Explanation: When building a three layer flexible pavement, the subbase layer is not used and the base course is placed directly on the natural subgrade.

A flexible pavement’s surface layer is constructed of hot-mix asphalt (HMA).Un stabilized aggregates are typically used for the base course; however, the base course could also be stabilized with asphalt, Foamed Bitumen, Portland cement, or another stabilizing agent. The sub base is generally constructed from local aggregate material, while the top of the subgrade is often stabilized with cement or lime.