The subgrade is the layer of natural soil beneath a concrete slab or pavement that ultimately carries its weight; when the subgrade weakens, washes out, or compresses, the concrete above it settles.
In depth
Every slab depends on the ground beneath it for support. If that soil was poorly compacted at construction, erodes from water, or shrinks and swells with moisture, it loses the ability to hold the slab level, and the concrete drops into the resulting space. Restoring a slab therefore means restoring the subgrade, not just the surface.
Polyurethane injection strengthens the subgrade as it works: the expanding foam compacts loose soil and fills voids, giving the slab uniform support from below rather than simply propping it up.
How Acme applies it. Acme’s polyurethane process is designed to provide maximum subgrade strength, compacting and stabilizing the soil while it lifts, so the repair addresses the root cause rather than the symptom.
Related terms: Subbase, Soil Compaction, Concrete Settlement, Under-Slab Void
Frequently asked questions
What is the difference between subgrade and subbase?
The subgrade is the native soil beneath everything; the subbase is an engineered layer of gravel or aggregate placed on top of the subgrade to spread load. Both must be stable for the slab to stay level.
Can a weak subgrade be fixed without digging?
Yes. Polyurethane injection densifies weak subgrade soil and fills voids through small ports, restoring support without excavation.