How to anchor embeds in slab prior to pour?
Finally getting close to the pour, unfortunately we are hitting some of the hottest parts of the year.
A new question arose that I hope I could get some help with. We have about 14 weld plates which need to be secured prior to the pour. How do we do that, my builder is only familiar with “wet-setting” weld plates after the pour.
We considered attaching the plates to the beam steel but that has some degree of mobility and will for sure not be very precise. We are also thinking of driving rebar into the pad and securing the rebar to the nelson studs in the weld plates but I am afraid that exposes those studs to rust.
Any help from people with experience working on this issue would be greatly appreciated. Thank you.
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I'm hoping that a GBA reader who has faced this problem will post a suggestion.
Here is an article with some insight on embeds. It is geared to commercial work, and emphasizes the design aspect, but the last half of the article provides some insights on placement and securing techniques. I hope it helps you.
https://www.cecoconcrete.com/wp-content/uploads/2018/10/Constructability-of-Embedded-Steel-Plates-in-CIP-Concrete.pdf
Jim
On larger steel frames - it is common to pour a pad footing below the slab elevation. The anchor bolts are set it the pad footing and extended above the finished floor. Then the finished floor is poured on a different day. Usually the pad footing is needed for the high loads the steel frame can support.
You could pour small pad footings to set the location of the embed plates, setting the location fixture rebar into that pad. It would give you time to get the plates in the correct locations.
As Tim said, I've never seen anchors directly set into a slab. His suggestion of a pre-pouring a pad is all I can think of too.
For setting antenna towers (the only time I’ve been involved with things like this), L shaped bolts are set in the concrete, usually using a wooden frame that holds the anchors in position during the pour. Other times the anchors are tied into the rebar cage.
Are you working with a structural engineer? If you are, you should have details covering any embedded anchors. It’s very important to get this right so that you don’t have weak anchors or problems with stress fractures in the concrete.
Bill