Frost heave is the upward movement of a concrete slab caused by water in the soil freezing and expanding, forming ice lenses that push the ground, and anything resting on it, upward.
In depth
When moist soil freezes, the water within it expands and forms ice lenses that lift the soil surface. Slabs, sidewalks, and steps riding on that soil are pushed up with it. As the ground thaws, the slab drops again, and repeated freeze-thaw cycles work the concrete up and down until it cracks or ends up uneven. Fine-grained soils like clay and silt, which hold water, are the most heave-prone.
Frost heave is essentially the inverse of settlement, and both plague Northern Illinois because of its moisture and severe seasonal cold. Managing water in the soil and maintaining stable, well-drained support are the keys to controlling it.
How Acme applies it. Acme notes that Northern Illinois soils endure frequent freeze and thaw cycles along with moisture-driven shrinking and swelling, which is why the ground is always moving and settling and wreaking havoc on the concrete it supports.
Related terms: Freeze-Thaw Cycle, Expansive Soil, Concrete Settlement, Concrete Cracking
Frequently asked questions
What causes frost heave?
Water in the soil freezes and expands into ice lenses that push the ground and the concrete on it upward. Clay and silt soils that retain moisture are especially susceptible.
How is heaved or unstable concrete addressed?
Because heave is driven by water and freeze-thaw movement, controlling drainage and restoring stable, uniform support beneath the slab are essential. Polyurethane can re-level slabs disturbed by seasonal movement.