"If the jobsite requires 4,000 psi concrete and the contractor places ... basement floors and other small, flat slabs. They're also handy on large flatwork pours for handwork and getting into ...

The concrete compressive strength at this early age is often comparable to that of slab-on-ground at 28 days (3,500 to 4,500 psi). Polishing of suspended slabs usually takes place much longer ...