×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Minimum Concrete Cover Tolerance

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 (-)???

Nick Deal, P.E.
Michael Brady Inc.
http://www.michaelbradyinc.com
 

RE: Minimum Concrete Cover Tolerance

I'm sure you are meaning ACI 318-05.  You must also read the text, not just the table, where the text provides a tolerance for "cover shall not exceed minus 1/3 the minimum concrete cover required in the design drawings and specifications."  Reiterated in ACI 117 where  "Reduction in cover shall not exceed 1/3 the specified concrete cover."  This seems reasonable to me.  It seems to me if you are missing cover concrete, you may also have an issue with consolidation.    

Greg

RE: Minimum Concrete Cover Tolerance

The tolerances given in 318 are in reference to the design capacity of the member and as such, locate the tension steel such that a reduction in d is minimized, but an increase in d is allowed, such that cover is not compromised. As noted above, an increased d does not relieve the requirement for cover and ACI 117 provides a more in depth review of the requirements.

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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources