Compressive strength is the amount of load a material can bear before it deforms, measured in pounds per square inch (PSI); for lifting foams it indicates how much weight the cured foam can support.
In depth
A slab-lifting foam must both raise the concrete and hold it up permanently, so compressive strength is a defining spec. Typical lifting foams provide around 100 PSI, which is more than enough for residential and most commercial slabs, while specialty infrastructure foams reach far higher. Notably, hydrophobic polyurethane keeps essentially all of its compressive strength even when saturated with water.
Compressive strength rises with foam density, so heavier loads are matched to denser, stronger formulations.
How Acme applies it. Acme’s common foam delivers about 100 PSI at 4 lb/ft3; its RR-601 reaches about 292 PSI for high-load DOT work, and its stabilization foams meet Illinois Tollway compressive-strength standards.
Related terms: Foam Density, High-Density Foam, Polyurethane Foam, Undersealing
Frequently asked questions
How much weight can lifting foam hold?
Common lifting foam offers about 100 PSI of compressive strength, ample for driveways, floors, and commercial slabs, while high-density infrastructure foams provide several times that.
Does foam lose strength when wet?
No. Hydrophobic closed-cell polyurethane retains virtually all of its compressive strength even when fully saturated.