Cracks in grout under baseplate 2

[met33]

Are the cracks in the grout under this baseplate a concern?

It's a 10" x 10" x 1/2" steel baseplate. The column has a design load of 10 kips. This is residential construction.

I don't know what type of grout was used.

 

[jerseyshore]

How thick is the grout there? If that's a 1/2" base plate we can barely see any of it so I'm assuming it's basically completely sunk in. The cracks at the edges look like spalling of the grout against the side of the base plate.

 

[met33]

The total grout thickness is around 1" to 1.5", depending on the baseplate.

Yes, I believe it's a 1/2" thick baseplate, and it's basically sunk in to the grout (top of baseplate is almost flush with top of grout).

I would guess there's around 1/2" to 1" of grout below this baseplate.

Edit: Yes, the cracks are mostly on the side of the baseplate from what I can tell. I'm wondering if they might extend under it, but maybe it's just spalling on the top edges? This is my first time getting structural grout done. I wasn't expecting cracking, but maybe it's normal and expected when the base plate is sunk in like this?

 

[Tomfh]

Structural grout should look cleaner than that, however that being said it’s a fairly modest load.

It’d be worth bashing the grout with a hammer to get an idea of the strength.

 

[jerseyshore]

I think it's just the fluff around the side of the baseplate that is spalling because the baseplate is sunk down in. If that's nice high-strength non-shrink grout I agree with Tomfh it should like nicer than that, but typically you don't see the plate sunk down that much.

 

[met33]

Thank you both.

Maybe the installer didn't finish the edges well because the baseplates are getting buried under a concrete slab anyway?

Slab has been poured, so I would only change something at this point it's a structural concern.

 

[structSU10]

That grout appears to be placed in a manner that is generally not recommended. see page 36 of this document:

https://www.buildsite.com/pdf/fivestarproducts/Five-Star-59-Installation-Instructions-1095014.pdf

 

[met33]

That's a great reference. Page 36 shows the exact situation -- grout poured above the bottom of the baseplate and left unchamfered ("Unsatisfactory"). It says this configuration will lead to cracks in the shoulders of the grout, which is what occurred in my baseplates.

Pages 35-36 also explain that it's usually not a structural concern: "Do not allow grout to remain above the bottom edge of the baseplate or in an unchamfered shoulder. In those locations, grout is prone to cracking because of differential expansion when the temperature changes... Shoulder cracks rarely propagate under the baseplate, and do not affect the vertical load-carrying capacity of the grout. For a cosmetic repair, coat the crack with a paste made from the grout and a little water."

If the grout were left exposed, I can see how the cracks would be a serviceability concern, or freeze-thaw concern if outdoors.

Since my baseplates are covered with a concrete slab, perhaps it's not a concern in my situation.

 

[met33]

Here are some more figures illustrating cracks in improperly finished grout shoulders:

[URL unfurl="true"]https://www.uk.weber/technical-mortars/grouting-steel-baseplates[/url]