Minimum Concrete Cover Tolerance
Minimum Concrete Cover Tolerance
(OP)
Per ACI 381-05, Section 7.5.2.1, the tolerance on minimum cover reads -3/8" for d<=8" and -1/2" for d>8". For tilt-up wall panels, the delegated engineer on my project has specified a minimum clear cover of 3/4". We have found locations where the reinforcing is very close (<=1/2") to the face of panel, with even some locations the rebar showing.
The way I am reading this tolerance is subtract the tolerance value from the minimum clear cover. So for 3/4" minimum clear and a d<=8", this would allow the minimum clear cover to be as small as 3/8". This to me seems unreasonably close. Shouldn't these tolerances be (+) instead of (-)???
The way I am reading this tolerance is subtract the tolerance value from the minimum clear cover. So for 3/4" minimum clear and a d<=8", this would allow the minimum clear cover to be as small as 3/8". This to me seems unreasonably close. Shouldn't these tolerances be (+) instead of (-)???
Nick Deal, P.E.
Michael Brady Inc.
http://www.michaelbradyinc.com






RE: Minimum Concrete Cover Tolerance
Greg
RE: Minimum Concrete Cover Tolerance
The tolerance for d and the tolerance on allowable clear cover are seperate items. In typical construction, they are at adds, but both must be satisfied.
It appears in your case, the cover tolerances have been violated in construction and a means of remediation must be determined.
With 3/4" minimum cover, reducing that by 1/3 would give a minimum allowable cover of 1/2". If you are able to see bars at the surface and tell that bars are 1/2" below the surface, you have additional issues as noted by Greg.
The revised 117-06 does a pretty good job of giving more detailed explanations of tolerances noted. Take a look.
Daniel Toon