By Tristar Concrete / August 3, 2022
What is the Base of a Concrete Slab?
The base in concrete construction is the layer between the sub-grade (existing soil) and the concrete slab. The base (usually a crushed stone material) acts as a support between the dirt and slab, and ultimately, reduces cracking of the slab.
Why is a Concrete Slab Base Necessary?
Imagine placing a pane of glass on a mattress. Now, imagine standing on that pane of glass. It’s going to crack and break, right? Essentially the same thing is going to happen to your concrete slab if it does not have a proper base to support it over its lifespan. The base provides a few important functions:
#1: Reduces Settlement
The dirt beneath your concrete slab is constantly moving. The base prevents the movement of the dirt from cracking the concrete slab by providing a layer that absorbs the differential movement often found in existing soil.
#2: Promotes Drainage
If a slab is poured on dirt, that dirt will be washed away, and the concrete will sink and crack. When a gravel base is applied, runoff washes through the gravel base keeping your slab well supported and crack free.
What Material is Used for a Slab Base?
The base in concrete construction is usually a form of crushed stone. Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage. Crusher run (a mix of crushed stone and stone dust) and #57 coarse aggregate are two of the best base materials for concrete slabs.
