Thursday, December 1, 2011

RE: Post Installed Anchors in Young Concrete

Your concern is warranted. 
What the contractor wants puts you squarely in the cross hairs.  The first thing is to look at the ACI 318 Appendix D which will direct you to the ACI 355.4 for qualifying epoxy anchors.  You will also need to look at the ICC ESR for the specific anchor you are going to consider. 
But getting back to the ACI 355.4, you should reference section 4.3 for the caveates on the concrete.  If the anchor is to be qualified, the concrete must be at least 21 days old per section 4.3.5, or the concrete is considered "non-standard".  If anything bad happens, you will be left twisting in the wind.  An independent lab would have to develop the research for this because it violates the established concrete premise for qualification. 
If your contractor wants a non standard solution, I would suggest the following.  Use an undercut mechanical anchor, install the pump, apply a tension load to the anchor in excess of the service load by a margin of at least 30%, use a certified hydraulic tensioner to develop the applied load, and re-tension the anchor after it has matured to 28 days.  If the interstitial space between the mechanical anchor and the hole is of concern, drill a port at an angle into the shaft and inject epoxy into the space to seal it up after the anchor is set. 

Regards, Harold Sprague
From: Paul Blomberg <>
To: seaint <>
Sent: Wednesday, November 30, 2011 9:12 AM
Subject: Post Installed Anchors in Young Concrete

I have a contractor that is casting a small pump pad and five days later wants to drill and epoxy anchor bolts into the pad for the small pump and motor.  Does anyone know of any guidance on how much strength or how old the concrete should be before drilling and epoxying? 
I don't need the anchors to actually hold their load until later when the rest of the piping is hooked up and by then the concrete will reach it's design strength.  I'm more worried about damage to the concrete pad or integrity of the installed anchor when it is installed in green concrete.
I appreciate your thoughts and comments!
Phoenix, AZ