Residential Building Inspector B1Building Planning and Life SafetyHard
A residential building inspector is reviewing plans for a new single-family dwelling that includes a concrete foundation wall. If the concrete is specified to have a minimum compressive strength of 2,500 psi at 28 days, what is the maximum water-cementitious materials ratio (w/cm) allowed for this concrete when exposed to severe weathering?
- A0.40
- B0.50
- C0.45
- D0.55
Show answer & explanationAnswer & explanation
Correct answer: C. 0.45
According to IRC Table R402.2(1) for Minimum Specified Compressive Strength of Concrete, for concrete exposed to severe weathering (as indicated in Footnote f), the maximum water-cementitious materials ratio for 2,500 psi concrete is 0.45. This ensures durability against freeze-thaw cycles and other weathering effects.
Why the other options are wrong
- A. This ratio is lower than required and would result in stronger, but potentially less workable, concrete; it's not the maximum.
- B. This ratio is too high for concrete exposed to severe weathering with a 2,500 psi strength requirement.
- D. This ratio is too high for concrete exposed to severe weathering with a 2,500 psi strength requirement.
Concrete Water-Cement Ratio
The ratio of the weight of water to the weight of cementitious materials in a concrete mix, critical for strength and durability.
- Lower ratio generally means higher strength.
- Higher ratio increases workability but reduces durability.
- Impacts resistance to weathering.
Memory trick: Severe weather and 2500 PSI, a 0.45 w/cm ratio keeps the foundation dry.