Forms are being stripped from an exterior site wall reinforced with No. 4 horizontal bars. The wall face remains exposed to weather; what minimum concrete cover applies to those bars?
Correct Answer
B) 1-1/2 in. for No. 5 and smaller bars in formed weather exposure
For formed concrete exposed to earth or weather, ACI 318-19 Table 20.6.1.3.1 lists 1-1/2 in. minimum cover for No. 5 bars and smaller. Other choices: 3/4 in. fits interior slabs or walls not exposed to weather, 2 in. fits No. 6 through No. 18 bars in this exposure, and 3 in. is for concrete cast against earth rather than formed wall faces.
Why This Is the Correct Answer
For formed concrete exposed to earth or weather, ACI 318-19 Table 20.6.1.3.1 lists 1-1/2 in. minimum cover for No. 5 bars and smaller.
Why the Other Options Are Wrong
Option A: 3/4 in. for interior slab or wall bars
In concrete work, 3/4 in. for interior slab or wall bars is the wrong selection for Concrete cover: 3/4 in. for interior slab or wall bars is a concrete-cover value for a different exposure/member case; ACI 318-19 Table 20.6.1.3.1 keys this item to 1-1/2 in.
Option C: 2 in. for No. 6 and larger bars in formed weather exposure
Choice C gives 2 in. for No. 6 and larger bars in formed weather exposure. Its specific error: 2 in. for No. 6 and larger bars in formed weather exposure is a concrete-cover value for a different exposure/member case; ACI 318-19 Table 20.6.1.3.1 keys this item to 1-1/2 in.
Option D: 3 in. for concrete cast directly against earth
Choice D (3 in. for concrete cast directly against earth) is rejected because 3 in. for concrete cast directly against earth is a concrete-cover value for a different exposure/member case; ACI 318-19 Table 20.6.1.3.1 keys this item to 1-1/2 in.
Memory Technique
Use a stormwater map memory cue for concrete cover: the stem's condition unlocks 1-1/2 in. for No. 5 and smaller bars in formed weather exposure.
Reference Hint
Open ACI 318-19, Building Code Requirements for Structural Concrete; use ACI 318-19 Table 20.6.1.3.1 to confirm that For formed concrete exposed to earth or weather, ACI 318-19 Table 20.6.1.3.1 lists 1-1/2 in.
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