What is the minimum concrete cover required for #5 rebar in a concrete footing that will be in direct contact with soil?
Correct Answer
B) 3 inches
For concrete cast against and permanently exposed to earth, the minimum cover is 3 inches for reinforcing bars. This protects the steel from corrosion due to moisture and chemicals in the soil.
Why This Is the Correct Answer
According to ACI 318 building code requirements, concrete cast against and permanently exposed to earth requires a minimum cover of 3 inches for reinforcing bars. This specification applies to footings in direct contact with soil. The 3-inch cover provides adequate protection against corrosion from moisture, chemicals, and other aggressive elements present in soil that could compromise the steel reinforcement over time.
Why the Other Options Are Wrong
Option A: 2 inches
2 inches is insufficient cover for concrete in direct contact with soil. This reduced cover would not provide adequate protection against moisture infiltration and soil chemicals that cause corrosion of the reinforcing steel, leading to structural deterioration over time.
Option C: 4 inches
4 inches exceeds the minimum requirement and would be unnecessarily conservative for this application. While not technically wrong from a safety standpoint, it's not the code-specified minimum and would result in increased concrete costs and footing dimensions.
Option D: 1 inch
1 inch is severely inadequate for soil contact conditions. This minimal cover would provide virtually no protection against corrosion, allowing moisture and soil chemicals to quickly reach the reinforcing steel and cause rapid deterioration of the structural integrity.
Memory Technique
Remember 'Soil = 3' - when concrete touches soil directly, think 3 inches minimum cover to protect the steel from earth's corrosive elements.
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