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Re: Grounding rebar

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Fellow engineers,

        In northern climates, bridges (which are not buildings), and parking structures, (which are buildings and which may be part of very large high-rise buildings) have a problem with corrosion of reinforcing steel due to salt exposure. One method of protecting structures against such corrosion, cathodic protection, is accomplished by electrically connecting the rebar together and using a sacrificial zinc anode OR electric generating equipment, either of witch causes the reinforcing to act as a cathode thus protecting it against corrosion.

        I am not an expert in cathodic protection, however, engineering logic tells me that deliberately grounding the structural reinforcing for the convenience of the electrical contractors, or others could be a very bad thing to do if cathodic protection of the reinforcing is required.  It should, therefore, follow that any code requirements specifying electrical grounding of the structural reinforcing would have to have some exceptions or alternative provisions.

        I hope this does not cause rain to fall on anyone's parade.


H. Daryl Richardson

"Scott, William N" wrote:

NEC 250(A)(3) Concrete-Encased Electrode requires grounding of reinforcing. on new construction.
NEC 250.50 has an exception for existing concrete-encased (reinforcing) electrodes. Grounding of existing reinforcing is now required if the reinforcing can only be exposed by disturbing the concrete.

Bill Scott, SE
Structural Engineer
North Slope Operations
ConocoPhillips Alaska, Inc.
P.O. Box 100360
Anchorage, AK 99510-0360

From: Greene, Al [PTS] [mailto:AGFO(--nospam--at)]
Sent: Thursday, August 23, 2007 8:44 AM
To: seaint(--nospam--at)
Subject: Grounding rebar

Is there a code requirement that says that rebar in a slab or footing has to be grounded?  I have an electrical engineer telling me NEC says so.

Al Greene, PE, SECB
Chevron Richmond Refinery
841 Chevron Way, 244/Tech Center
Richmond, CA 94802
Phone: (510) 242-1788
Fax: (510) 242-2509
Cell: (510) 507-5080