Sub-Base Course of Flexible Pavement
Sub-Base course is the layer (or layers) under the base layer. A sub-base is not always needed. A proper sub-base consists of various sizes of crushed stone aggregate, commonly known as crusher run. Depending on the sub soils on your site you may need 8-12 inches of various sizes of sub-base.
With well drained sub soils, without movement, added sub-base materials may be sufficient, along with proper pitch & grade.
If the sub-base is knowingly sufficient, grading & compaction with vibratory roller or plate compactor in small areas, may be all that is necessary.
Function of Sub-base course of flexible pavement
It functions primarily as structural support but it can also help:
- Minimize the intrusion of fines from the sub-grade into the pavement structure.
- Improve drainage.
- Minimize frost action damage.
- Provide a working platform for construction.
- The subbase generally consists of lower quality materials than the base course but better than the sub-grade soils.