Reinforcing Ironwork: Bar Placement, Hooks, and Splices
What this domain tests
The Reinforcing Ironwork domain tests rebar identification, placement, tying, cover, hooks, lap splices, and support of reinforcement before concrete placement. It also checks whether you can read placing drawings and protect against impalement hazards.
Core rules
- Identify bars by number: #4 is 4/8 in. = 1/2 in. nominal diameter; #8 is 1 in. Know the bar size, grade, and coating on the placing drawing.
- Maintain specified concrete cover with chairs, bolsters, and spacers. Do not use concrete blocks or wood that can rot or crush unless approved.
- Tie bars securely enough to hold position during placement and vibration; don't over-tie epoxy-coated bars with damaged coating.
- Standard hooks: 90° hook extension = 12db; 135° hook = 6db (min. 3 in.); 180° hook = 4db (min. 2.5 in.). Minimum inside bend diameter is 6db for #3-#8, 8db for #9-#11, and 10db for #14-#18.
- Lap splice length depends on bar size, grade, concrete strength, coating, and splice class; use the placing drawing, not a rule of thumb.
- Protect exposed rebar ends against impalement; use approved caps or equivalent protection.
Worked example
A #6 Grade 60 bar needs a 90° standard hook. Nominal diameter = 6/8 = 0.75 in. Extension = 12db = 12 × 0.75 = 9 in. Minimum inside bend diameter = 6db = 4.5 in. So the hook is bent around a 4.5-in. inside diameter and extends 9 in. beyond the bend. A #8 bar would have a 12-in. extension and a 6-in. inside bend diameter.
Traps
Do not use the bar number as the diameter in inches. Do not shorten a hook because the form is tight. Do not substitute lap length by single-bar-diameter rules. Do not ignore coating damage on epoxy bars. Do not leave unguarded vertical rebar.