What is the typical 28-day strength used for design in many residential slabs?

• A. Approximately 3000 psi
• B. 2000 psi
• C. 4000 psi
• D. 5000 psi

Answer: (B)

The number to focus on is the design strength chosen for typical residential slabs. This strength is the target compressive capacity the concrete should achieve at 28 days, used to size the slab and determine performance under service loads.

For many residential slabs, 2000 psi is used. This reflects the relatively light live loads and the common practice of keeping material costs down while still ensuring adequate support if the slab is properly placed, cured, and the subgrade is well prepared. Higher strengths like 3000 psi or more are reserved for heavier structural elements or floors with larger loads, where extra strength is needed. So 2000 psi is the standard choice for the usual residential slab scenario.