Non-Shrink grout and leveling nuts
Non-Shrink grout and leveling nuts
(OP)
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
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






RE: Non-Shrink grout and leveling nuts
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.
RE: Non-Shrink grout and leveling nuts
The link can be found here: http://www.fivestarproducts.com/resource-center/li...
RE: Non-Shrink grout and leveling nuts
Can you selectively drill a few access ports to install the flowable grout in addition to (rather than removing) the dry pack?
RE: Non-Shrink grout and leveling nuts
EIT
RE: Non-Shrink grout and leveling nuts
Are the columns light poles, or structures that will hold up buildings or even machines?
RE: Non-Shrink grout and leveling nuts
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".
RE: Non-Shrink grout and leveling nuts
RE: Non-Shrink grout and leveling nuts
Dik
RE: Non-Shrink grout and leveling nuts
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.
RE: Non-Shrink grout and leveling nuts
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.