What is the standard size designation for #4 rebar?
Correct Answer
C) 1/2 inch diameter
#4 rebar has a nominal diameter of 1/2 inch (0.5 inches). The numbering system for rebar corresponds to eighths of an inch, so #4 = 4/8 = 1/2 inch diameter.
Why This Is the Correct Answer
Option C is correct because #4 rebar has a nominal diameter of 1/2 inch (0.5 inches). The rebar numbering system is based on eighths of an inch, where the number indicates how many eighths of an inch the diameter measures. Therefore, #4 rebar equals 4/8 inch, which simplifies to 1/2 inch diameter.
Why the Other Options Are Wrong
Option A: 4/8 inch diameter
Option A shows 4/8 inch diameter, which is mathematically correct (4/8 = 1/2) but is not the standard way to express this measurement. The industry standard is to express #4 rebar diameter as 1/2 inch in its simplified fractional form.
Option B: 4/10 inch diameter
Option B is incorrect because 4/10 inch diameter (0.4 inches) does not correspond to any standard rebar size designation. This fraction also doesn't follow the rebar sizing system which is based on eighths of an inch, not tenths.
Option D: 4 mm diameter
Option D is incorrect because rebar sizes in the United States are measured in inches, not millimeters. Additionally, 4 mm would be approximately 0.157 inches, which is much smaller than the actual #4 rebar diameter of 0.5 inches.
Memory Technique
Use the phrase 'Rebar Eights Rule' - the rebar number tells you how many eighths of an inch the diameter is. #4 = 4 eighths = 4/8 = 1/2 inch.
Reference Hint
ACI 318 Building Code Requirements for Structural Concrete, Chapter 20 (Reinforcement Details) or Florida Building Code, Structural section covering reinforcing steel specifications
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