The subbase is the engineered layer of compacted gravel or aggregate placed between the natural subgrade soil and a concrete slab to spread load and provide a stable, well-draining foundation.
In depth
A properly built slab sits on a compacted subbase that distributes weight evenly onto the soil below. When that layer is thin, poorly compacted, or eroded by water moving through it, support becomes uneven and the slab begins to settle or crack. This is one of the most common construction-related causes of sinking concrete.
Acme’s website describes concrete sinking when it is built over stone or soil that was not properly compacted, which leads to quicker sinking and cracking. Injection restores the missing support by filling the gap and stabilizing the material beneath the slab.
How Acme applies it. Acme’s foams will not shrink or wash out like the aggregate-based slurries used by mudjacking companies, so the restored base stays stable through the region’s freeze-thaw and moisture swings.
Related terms: Subgrade, Soil Compaction, Soil Washout, Under-Slab Void
Frequently asked questions
What causes a subbase to fail?
Poor compaction during construction and water eroding the aggregate are the main causes. Both leave the slab without continuous support, leading to settlement and cracking.
How is a failed subbase repaired?
Polyurethane is injected to fill the voids and stabilize the base material, re-establishing uniform support without removing the slab.