There has to be 20 feet or more of 1/2" rebar. The pieces can be fastened with the regular rebar ties. I think one is done once the 20 minimum is reached. No need to fasten all the rebar. Rules are tougher for livestock buildings. I would think the concrete crew could handle that part. The bad thing would be waiting for an inspector. We don't have inspection for what I do in Nebraska so I can't speak from personal experience. I've been told they do want to actually see the rebar before the pour. This is from the 2008 U.S. Code:
2008 NEC?250.52 Grounding Electrodes.(A) Electrodes Permitted for Grounding.
(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 f.t) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, or consisting of at least 6. 0 m (20 ft.) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. Where multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.
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