overhead epoxy application

is it practical in the field to use epoxy adhisive for doweling rebars out of the soffit of a concrete beam or a slab?
how efficient it is?
and is there a reduction factor that need to be applied to the pull out capacity of the rebar?

again, is it a common practice in the field and does the performance of the epoxy get compromised by overhead application?

thank you

 

[Taro]

Overhead epoxy installation is possible. However, consideration should be given to thermal effects. Most epoxies lose considerable strength at elevated temperatures. Therefore, restrictions are often placed on overhead use.

 

[CottageGuy]

The use of epoxy to dowel rebar is quite common practice, you just have to ensure that the application is okay for the enviroment. I agree with Taro that epoxies lose considerable (all) strength under extreme heat (ie fires), so alternate methods of fire protection must be provided.

Contact Hilti North America for advise or other options at 1-800-363-4459, or hilti.com.

I wouldn't recommend using expandable anchors on the soffit of a slab/beam. As the slab deflects, local cracks in the concrete around the anchor may widen and reduce the strength of the bolt. (undercut bolts do not have this problem)

 

[Ginger]

I agree with both of the above, however, using wedge anchors in the soffit of a beam or slab is not a problem provided that you use the appropriate reduction factors for the capacity of the bolt in cracked concrete.

Even though you may not be able to see the cracks it must be assumed that they are there due to the strains induced under bending of the section.

Each type of bolt will have its own reduction factor listed in the manufacturer's specification data. Ths reduction tends to be around 40% on the bolt's tensile safe load capacity.

As for epoxy fixings, not a problem provided you use a suitable resin with a fairly quick initial set time to prevent gravity causing the epoxy to drip out of the hole.

Regards Andy Machon

 

[dougantholz]

Another thing that you might look into is using capsulated epoxy, where you can "drop" the glass pack in and then mix in the hole. Simpson still makes glass packs for this app.