FDOT Earthwork Level 1 Practice Test

Subbase materials form the underlayment that distributes loads from the pavement to the subgrade and helps with drainage and frost protection. They are typically granular or stabilized materials placed on the subgrade to provide structural support for the layers above. Granular materials like crushed stone or gravel allow good compaction and drainage, while stabilization (with cement or lime) increases strength and reduces moisture effects. Asphalt overlays are surface layers placed on top of the base and subbase, not the subbase itself. Concrete blocks aren’t used as subbase material, and vegetation would not provide the required structural support.