Expansive soil is soil, usually clay, that swells when it absorbs moisture and shrinks when it dries, and this repeated movement pushes concrete up and lets it drop, causing cracks and uneven surfaces.
In depth
Clay-rich soils change volume dramatically with moisture. A wet season swells the soil and lifts the slab; a dry spell shrinks it and the slab settles. Because the wetting and drying is rarely uniform across a slab, the movement is uneven, producing cracks, tilts, and trip hazards over time.
Expansive soils are one of the reasons a repair must stabilize the ground, not just re-level the surface. Polyurethane can stabilize the soil and fill the voids that shrink-swell movement leaves behind.
How Acme applies it. Acme identifies expansive soils such as clay, which expand and contract with moisture, as a common cause of cracked and unlevel slabs, and uses foam to stabilize the soil and limit further movement.
Related terms: Frost Heave, Concrete Settlement, Subgrade, Concrete Cracking
Frequently asked questions
How does expansive soil damage concrete?
It swells when wet and shrinks when dry, moving the slab up and down unevenly until the concrete cracks or becomes unlevel.
Can concrete on expansive soil be repaired?
Yes. Polyurethane injection stabilizes the soil, fills the voids left by shrinkage, and re-levels the slab, though managing moisture around the slab remains important.