Shims & Sika 212 Non-shrink grout

[sedonas]

1. Sika 212 non-shrink grout were poured under the base plates with shims at the sides supporting the plates. The shims were small strips cut from flat bar.. Would you think the sika 212 can take the load away from the shims?

2. 12 hours after the grout is put.. what is your estimate of the compressive strength of the Sika 212?

3. Would you really trust the non-shrink grout won't shrink over time and your shims wouldn't retake the load?

4. Does the sika 212 supposed to expand under the base plate so all voids are automatically filled? I read it expand 120%.

 

[KootK]

Yeah, I hate shim stacks. That's how it's done in my neighborhood too though. The only difference is we put the shims under the centre of the columns most times.

1. Sika 212 non-shrink grout were poured under the base plates with shims at the sides supporting the plates. The shims were small strips cut from flat bar.. Would you think the sika 212 can take the load away from the shims?

Nope. By my reckoning, the still shims will always be the stiffest part of that assembly and will always be loaded. The only mitigating factor might be base-plate flexibility.

2. 12 hours after the grout is put.. what is your estimate of the compressive strength of the Sika 212?

I don't know off of the top of my head. Call Sika. They're technical reps are very helpful.

3. Would you really trust the non-shrink grout won't shrink over time and your shims wouldn't retake the load?

You ought to be okay here. I believe that Sika 212 is actually slightly expansive.

4. Does the sika 212 supposed to expand under the base plate so all voids are automatically filled? I read it expand 120%.

It is slightly expansive but I would have no expectations of it actually filling voids.

There are at least two members here that would be really well suited to answering this question: Ron & CELinOttawa. Let's hope that they surface.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sedonas]

Yeah, I hate shim stacks. That's how it's done in my neighborhood too though. The only difference is we put the shims under the centre of the columns most times.

The shims is put under the center of the base plate so it is free to rotate from moments against the grout? I put the shim at each edge and plan to cut and remove them when the grout has set. Can you see any problems with this?

Nope. By my reckoning, the still shims will always be the stiffest part of that assembly and will always be loaded. The only mitigating factor might be base-plate flexibility.

If shims and non-shrink grout would be avoided.. can you level or finish the top of the concrete foundation pedestal surface to such accuracy that when you put the base plate, all the surfaces would bear? How did you do it?

 

[KootK]

The shims is put under the center of the base plate so it is free to rotate from moments against the grout

No, not to my knowledge.

I put the shim at each edge and plan to cut and remove them when the grout has set. Can you see any problems with this?

Only that it sounds like quite a lot of work for your contractor.

If shims and non-shrink grout would be avoided.. can you level or finish the top of the concrete foundation pedestal surface to such accuracy that when you put the base plate, all the surfaces would bear? How did you do it?

To my knowledge, that is not a practical solution except possibly in cantilevered systems where the final location of the cantilever tip is not critical (lamp posts etc). Avenues for tolerance adjustment should always be provided. You could design your base plate to bear on nuts instead of grout I suppose.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sedonas]

No, not to my knowledge.

All I was saying was the shims was at the center so it can be adjusted and later when grout was put, it is the grout that bears on the plate and any moments can bear on the concrete at its side. The center of the shims become the center of gravity like center of a wheel for instance so there is no inbalance bearing on the sides.

If there is a 10mm gap and you can somehow remove the column/base plate with a crane, and put direct cement/sand mortar on the 10mm gap.. would this direct cement/sand mortal addition still become 3000 psi if it is mixed as 3000 psi.. like is there a minimum size before a cement/sand or concrete can reach its compressive strength?

 

[KootK]

If there is a 10mm gap and you can somehow remove the column/base plate with a crane, and put direct cement/sand mortar on the 10mm gap.. would this direct cement/sand mortal addition still become 3000 psi if it is mixed as 3000 psi.. like is there a minimum size before a cement/sand or concrete can reach its compressive strength?

I would think so but it would be best to check with the grout manufacturer. I've never attempted a grout bed less than 3/4".

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sedonas]

I would think so but it would be best to check with the grout manufacturer. I've never attempted a grout bed less than 3/4".

How small should the shims at center be to avoid moment restrain from the center. Imagine a shim that is 6x6 inches under a 12x12 inch base plate. Is there a recommended percentage of shims area to be used at center?

 

[sedonas]

To my knowledge, that is not a practical solution except possibly in cantilevered systems where the final location of the cantilever tip is not critical (lamp posts etc). Avenues for tolerance adjustment should always be provided. You could design your base plate to bear on nuts instead of grout I suppose.

Important question. So non-shrink grout purpose is more of levelling the column and not because the concrete mortar can't be put and polished at the surface of the pedestal with full contact accuracy with base plate? We have a chance to remove the base plate and steel tomorrow to remove the bad grout that can't be removed by sticking pointed object thru the 10mm gap. So if I'll have concrete mortar directly applied to the surface of the pedestal with a 10mm formwork elevation. I'm not sure if the surface can be polished or finished with levelling bar for full base plate contact.. theoretically is this possible? or is there always micro curvature in the surface that makes it not possible.. something that only non-shrink grout can do.. that is complete contact at the molecular level?

 

[KootK]

Grout is indeed for the twin purposes of levelling and uniform bearing. If reasonably uniform bearing can be achieved without grout, localized concrete crushing and base plate deformation can probably iron out the remainder. What is the expected stress beneath the base plate?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[oldrunner]

I like expansive grout (has iron filings). In the past to insure transfer of load bearing to a new concrete column we used Embeco.

 

[sedonas]

Grout is indeed for the twin purposes of levelling and uniform bearing. If reasonably uniform bearing can be achieved without grout, localized concrete crushing and base plate deformation can probably iron out the remainder. What is the expected stress beneath the base plate?

Axial load is below 2kN.
Moment is below 5kN.
Shear is below 6kN.

Tomorrow I can remove the base plate for last time (to remove bad grout that was unsuccessfully applied and possibly to put shims at center should filling in gap method be necessary )... what is your experience in using grout bed and putting the plate on top of it? Is it possible to put it on the grout bed after 10 minutes of putting the grout? So it can compress the grout with uniform bearing? Or must the base plate be really put first and the gap filled with the grout for more guaranteed uniform bearing? I'm worried if the plate has micro curvature and the grout bed flat.. they may not bear.. is plate (15mm thickness) usually perfectly flat?

For adjustments. How big a shims (in inch or mm) in percentage do you usually use beneath base plate? I understand though that if I'd put plate directly on grout bed.. no shims is necessary. Your help so much appreciated and others.

 

[KootK]

I have no experience with placing the grout ahead of the base plate I'm afraid. I see that Ron an others have advised you well on this issue in other threads however. Your loads are very light. I think that your only concern here should be ensuring that the final product is durable. Again, q chat with your Sika rep is probably the way to go.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sedonas]

Yes. I'll ask assistance from Sika and BASF later.. because not only must it done with surgical precision.. the tolerance has to be military spec with contact of grout and metal plate at the molecular level to transfer the load per square inch at least above 90%...