Contact US

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!

*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

Gap Between New Column and Existing Beam

Gap Between New Column and Existing Beam

Gap Between New Column and Existing Beam

I'm working on a project where we are increasing the size of existing structural columns which fall within walls on multiple floors.  The face of the existing column we are increasing was scarified and we dowelled into the top and bottom of the beams which would sit above and below the new columns.  A cage was then installed and we also dowelled into the face of the existing column to create a bond between the two.  

In order to pour the new section we did a letterbox form so that we could pour above the botton of the existing beam and vibrated well to try and get concrete right up to the underside of the beam.  Now that we have removed the formwork we see that there are a number of gaps between the poured column and the existing beam and I'm trying to deterine the best way to repair this.  

The gap needs to be filled completely to allow load transfer between the existing beams and the new columns.  I am thinking of cleaning out the gap and using a very fluid non-shrink grout to patch these gaps.  Any suggestions would be helpful.

RE: Gap Between New Column and Existing Beam

Clean the area carefully, install a steel plate over the gap on all sides where gap exists, then pressure inject epoxy.  The area is too small to flow grout into the cavity and the grout will shrink a little as well.

After the epoxy sets, you can remove the steel plates or leave in place.  If you remove them, you can use neat cement grout to patch the holes and provide similar surface to surrounding concrete.

RE: Gap Between New Column and Existing Beam

Agree with Ron - epoxy injection is the way to go.

If the gap is great enough, pre-placed aggregate (3/8" nominal diameter) pre-placed by-hand prior to installing the steel backer-plate works very well in minimizing the volume of epoxy required, and also acting as a heat-sink for the exothermic reaction that occurs with mass epoxy.

In your case, the volume of epoxy is rather small, and you have a lot of surrounding concrete-mass, however, in instances of large resin volume a low-exothermic resin can be used, where the cure time is measured over several days, as compared to the usual initial cure of a few hours.

RE: Gap Between New Column and Existing Beam

Thanks guys.  I think this will work well.  Is the idea that you leave a small gap at the top of the plate to allow the injection of the epoxy?  Thanks again.

RE: Gap Between New Column and Existing Beam

BE...no, you drill a hole in the plate where you want to inject.  That way you can develop the injection pressure.

RE: Gap Between New Column and Existing Beam

...and depending on the viscosity of the resin used, usually the perimeter of the steel plate/concrete surface will be "sealed" with a paste epoxy to avoid leakage.

Also, best to have 2+ injection ports - allows the operator to gauge when the void is full, and after it is capped off (injection port usually), you can increase the injection pressure slightly to ensure that you have indeed filled the void by maintaining the supplied pressure.

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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close