Non-Shrink grout and leveling nuts

[Deadblow]

Hello All,

How do you all specify the application of non-shrink grout under steel column base plates when the steel was erected utilizing leveling nuts? I observed the contractor "packing" the grout in with a mason's trowel. I am questioning how big of a void is under the base plates (18"x18" plates). The access to these base plates is also severely hindered by the surrounding slab-on-grade. The only access for the dude installing the grout was pretty much from the vertical direction with only a couple inches of horizontal movement for his trowel. When I brought my concerns to the attention of my superior, the E.O.R., they said that it should have been a "flowable" non-shrink grout installed with a pencil vibrator. They also told me to include in my report that the grout shall be removed and new "flowable" grout installed. I feel bad and I think it will be next to impossible to remove the existing grout.

FYI, the vertical forces are in the neighborhood of 110 kips service load.

1. I have never seen or heard of a "flowable" non-shrink grout or a pencil vibrator for that matter. Have you?

2. How do you make sure that the plate gets solid bearing on grout? I used to work as a carpenter and we always used leveling plates on a thick bed of grout. Then we tapped the plate down until it was at the correct elevation and level. The firm I work for always calls out leveling nuts.

Thanks for your thoughts


EIT

 

[SwinnyGG]

I have heard (and used) the term 'flowable non-shrink grout'- Sika 212 is the grout product with which I am most familiar. It is useable as dry pack or becomes less viscous through the addition of water, and can be made wet enough to be poured or pumped without a problem.

A pencil vibrator is also a standard tool, although with your description of the install space, it seems that to properly place the grout in a flowable condition and then properly bed it with a vibrator would be, at best, difficult.

 

[topsisu]

Five Star has a free download PDF Guide about grouting that discusses various methods.
The link can be found here:

http://www.fivestarproducts.com/resource-center/literature-downloads.html

 

[Lomarandil]

We've used the five star products with good results. It can definitely be made flowable.

Can you selectively drill a few access ports to install the flowable grout in addition to (rather than removing) the dry pack?

 

[Deadblow]

Thank you all for your responses and personal experiences. I learned something new! topsisu, thank you for the resource, I appreciate it!

EIT

 

[Tmoose]

"steel column base plates" -

Are the columns light poles, or structures that will hold up buildings or even machines?

 

[hokie66]

Tmoose,
I think it is evident from his first post that they are not light poles. 110 kips would be a big light pole, one which would require a lot bigger base than 18" x 18".

 

[BUGGAR]

Doesn't anybody dry-pack anymore?

 

[dik]

For large heavily loaded industrial columns, I still use thin 'leveling plates' that can be removed to verify that the grout is fully under the base plate. For other applications I use dry pack and flowable depending on requirments. You have to watch for the dry pack because many grout suppliers require a minimum/maximum thickness. Same with flowable. I've not encountered any issues with actual installation.

Dik

 

[Tmoose]

I'd say dry-pack used on/under "structural" base plates is best only used when expectations are aesthetic and a modicum of sealing. That is due to the difficulties in achieving
proper placement. Dry-packing requires an almost unobstructed space and must be installed by skilled workers. The American Concrete Institute even reports dry-packing operations require nearly constant inspection to ensure that the proper layer thickness and compactive effort are being used.

Structural base plates, and especially rotating machinery base plates and bed plates require 100% filling and support. That requires flowable grout, plus millwrights with experience and integrity, and base plates designed to facilitate complete filling. And hard shimming in place of the under-plate leveling nuts. If the under plate nuts are left in place, when the top nuts are tightened they do not clamp the base against the grout.

The expansion curve of many "non-shrink" grouts includes a some pretty severe early expansion (up to at least 4% , or over 1/16" for a 2" inch thick space) followed by shrinking to close to original size.
The frequently mentioned ASTM C827 says this about itself - "However, the specimen used in this test method is not completely unrestrained so that the measurements are primarily useful for comparative purposes rather than as absolute values."

https://www.astm.org/Standards/C827.htm

I envision that especially if the base plate is stout, and the equipment is heavy, The vertical expansion is restrained during the expansion phase and the grout will plastically "upset" outward. Then when later the subsequent shrinkage to original volume may actually result in height shrinkage. So much for "permanently and completely" filling a space.

 

[SwinnyGG]

"I envision that especially if the base plate is stout, and the equipment is heavy, The vertical expansion is restrained during the expansion phase and the grout will plastically "upset" outward. Then when later the subsequent shrinkage to original volume may actually result in height shrinkage. So much for "permanently and completely" filling a space."

This is exactly what *can* happen when materials are not spec'd or installed correctly- I have had to force a contractor to re-set a machine when it was pulled out of position due to the grout not being mixed correctly.