A flat base course will also allow the slab to slide easily as it shrinks reducing restraint and the risk of cracks as the concrete contracts after placement drying shrinkage.
Sub base for concrete slab.
For instance it is harder to obtain a proper grade and an optimal flat structure without a thoroughly prepared sub base.
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.
The entire subbase and base system should be at least 4 inches thick thicker if the engineer feels it is needed for proper support.
Both subgrade and subbase shall be constructed.
Subgrade and subbase are the foundation of a concrete slab and play critical role in its performance.
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.
Then once the subbase is ready protect it until the concrete slab is placed see sidebar maintaining the slab support system.
The recommended gravel base for a concrete driveway.
Other articles related to preparing the soil support system for a.