The recommended gravel base for a concrete driveway.
Sub base for concrete slab.
Even if a concrete slab is being placed on top of a granite subgrade the lack of uniformity in the absence of a sub base will pose several problems.
According to the aci code the subgrade is a compacted and improved natural soil or brought infill whereas subbase is a layer of gravel placed on the top of the subgrade.
Both subgrade and subbase shall be constructed.
Parts of this article were contributed by previous articles written by boyd ringo bruce suprenant ward malish ronald lech and joe nasvik.
The strength and durability of a concrete driveway are not only determined by the type of concrete mix but also by base or sub base over which.
Then once the subbase is ready protect it until the concrete slab is placed see sidebar maintaining the slab support system.
For instance it is harder to obtain a proper grade and an optimal flat structure without a thoroughly prepared sub base.
Subgrade and subbase are the foundation of a concrete slab and play critical role in its performance.
Dig the area deep enough to accommodate the sub base 100mm and damp proof membrane dpm as well as the thickness of the concrete slab itself.
The entire subbase and base system should be at least 4 inches thick thicker if the engineer feels it is needed for proper support.