Non shrink grout and steel columns

[DeanAlan]

It is tough sitting between trades as an inexperienced self-builder, main contractor, principle designer.

 

My steel fabricator is installing columns this week and says bricklayer needs to grout them with a non-shrink grout.

 

Brick layer says "sure, that is a specialist item and you need to order the non shrink grout and we can do the work"

 

Steel fabricator says "typically  sand cement mix with a c-bex non shrink additive"

 

Brick layer says, yep I understand.

 

I say "Do I need to order anything special then or can you obtain this with the other materials"

 

Brick layer says "normally something which is a special order"

 

So now I'm thinking c-bex additive, something else?

 

Any clarifying thoughts?

 

cheers,

- Dean

[Mr Punter]

I have used this stuff before:

 

https://www.tradebuildingproducts.co.uk/products/sikagrout-111-gp-cementitious-general-purpose-grout?variant=41399952539801&currency=GBP&

 

Do a frame of 2 x 2 around the base plate held in place with a couple of bricks.

[LA3222]

1 hour ago, DeanAlan said:

It is tough sitting between trades as an inexperienced self-builder, main contractor, principle designer.

This made me laugh, indeed it is.

 

This is one of those jobs that when you know, you know!

 

It's a piece of piss and you can do it yourself. Get the sika grout 111, mix up in a bucket and with a drill, paddle mixed and some watter, and then pour away. It flows really well and will fill the void nicely. 

 

I built a wooden former around the base, silicone the outside edge for good measure. Let it go off for an hour or so, remove tue former and tidy up the edges. Job is a fish.

Edited November 8, 2021 by LA3222

[DeanAlan]

4 minutes ago, LA3222 said:

It's a piece of piss and you can do it yourself. Get the sika grout 111, mix up in a bucket and with a drill, paddle mixed and some watter, and then pour away. It flows really well and will fill the void nicely. 

 

Oh my god - now I'm in a real panic. Where the f do I get "watter" from and what is that? ?

 

Thanks all - sounds simple. Just confused why my brick layer says I need to order something special. If I google non-shrink grout there are loads of products.

 

cheers,

-Dean

[markc]

Watter the stuff that comes out of taps.

[markc]

Non shrink tile adhesive (thick bed) or grout also works really well and no problem for the amount you will be needing.

or if access is ok just ram dry mix under the column bases

[Conor]

I used Larsen multi grout 60. Flows like hot oil. Just make sure you have it well shuttered or else it will flow out.

[tonyshouse]

Ram in strong dry mix if decent gap and flaunch edges 

[tonyshouse]

Ram in strong dry mix if decent gap and flaunch edges 

 

i would not use tile adhesive 

[Adam2]

I understand one of the roles of the grout under columns is to ensure good support hence the non shrink nature of the grout. I also did research sent SE product spec etc. Sika product above easy to get and easy to use but can be tricky to pour in depending on your site etc. We had some horizontal beams which were a bit awkward.

[Gus Potter]

Hope this helps.

 

Say you have some concrete pads to support columns. When the pads are cast they may vary in level, say + / 15mm. Often columns need to carry two basic forces, axial load and shear load. Sometimes they need to transmit a bending force to the concrete pad.

 

There are three common ways to connect the column base plate to the pad.

 

1/ Cast in holding down bolts in cones. Usually waxed paper or polystrene. The cones are narrow at the bottom an wide at the top and this lets you wobble the bolts a bit to get them through the holes in the base plate.

2/ Cast in bolts with no cones.. need to be very accurate when doing this so avoid if you can.

3/ Place the column, drill out the concrete and use resin to fix the bolts. Works well with lowish forces.

 

To get the column base plates level you often aim to set the top of the pad 20 -25mm below the intended level of the bottom of the base plate. The steel erector then uses shims under the centre of the base plate to get that plate level in the centre, then adjusts the bolts to pull the column plumb. It rocks about on the shim in the middle. Sometimes they use steel wedges round the edge of the plate to get it level and the column plumb.

 

Now the grout. If you have cones then if they are not fully filled then the column can move sideways.. as the bolts still wobble about in the cone holes..not good! You can't get the cones filled using ordinary mortar as it does not flow enough to get under the plate and down the cone holes, and you can't compact the mortar in the cone holes.

 

We know ordinary mortar etc shrinks when it cures.. and when it does so the nuts on the holding down bolts can come slack say after a month. The specialist grouts you buy are what we call compensated grouts. The grout contains an additive that expands as the grout cures and this is balanced against the shrinkage of the cement component. Hence the terms you see such as "non shrink grout. The grout sets up pretty quick. Once you get most of the steel up nip back and just give the nuts a check to see they are still tight.

 

To keep life simple and for the cost I would just buy a bag of say the Sika 111 or a similar one part grout. all you need to do is add water as per the instructions and mix. If you start using a separate additive you'll only use a little and have to get the mix spot on. Make life easy and use the thinking time on the other exciting parts of your project.

 

 

 

Edited November 11, 2021 by Gus Potter

[saveasteading]

OK I do really know about this. Must have specified/supervised for tens of thousands of these, on mostly very big, but some small, columns.

 

Gus and others are mostly right, but my opinions are based on the difference between theory and practice. 

 

You perhaps don't need the theory so here is my suggestion.

 

For a small column, as this is,  pour the concrete base solid with no bolts, to 20mm below the base plate level.

Make sure the Engineer and/or steel fabricator have not already allowed for this with a shorter column. (That would be clever of them but a nuisance if you do it too).

Check the column length on site too, as fabricators have been known to cut the measured length then add the plate.

 

Then you can mark the bolt positions absolutely precisely and drill/ stud/ epoxy. (quality important, see the instructions, and supervise the work)

 

For shims use square fence washers, 3mm thick so you are never more than 1mm out. They will squeeze down a bit when the nuts are tightened.

OR (my choice) set spare nuts on the stud to the plate level. Then there is nothing in the way of the grout.

 

Grout up using a stiff dryish mortar mix. Use small size ballast if you can get it, otherwise sharp sand. 

push under and ram it hard to refusal, so you need a back stop board.

Flaunch to vertical or 45 degrees.

 

Why not use expanding grout? Because they tend to assume it is magic and leave it well short of the plate and with gaps in it. 

Use it if you like but still supervise.

 

[DeanAlan]

Thanks all.

 

Our columns have just gone up (400mm base plates with resin bolts and level around 15mm in some cases with steel shims put in before being bolted down).

I have just received some Silka 111G (seems 1 bag will make about 13L of grout and at a 20mm gap I would need about 3.6L per column - we have 8 cols so I've got 3 bags just delivered).

 

I'll let you know how we get on. 

 

Thanks for all the comments. I now understand this much more.

 

cheers,

Dean

[Gus Potter]

On 12/11/2021 at 11:18, saveasteading said:

OK I do really know about this. Must have specified/supervised for tens of thousands of these, on mostly very big, but some small, columns.

 

Gus and others are mostly right, but my opinions are based on the difference between theory and practice. 

 

You perhaps don't need the theory so here is my suggestion.

 

For a small column, as this is,  pour the concrete base solid with no bolts, to 20mm below the base plate level.

Make sure the Engineer and/or steel fabricator have not already allowed for this with a shorter column. (That would be clever of them but a nuisance if you do it too).

Check the column length on site too, as fabricators have been known to cut the measured length then add the plate.

 

Then you can mark the bolt positions absolutely precisely and drill/ stud/ epoxy. (quality important, see the instructions, and supervise the work)

 

For shims use square fence washers, 3mm thick so you are never more than 1mm out. They will squeeze down a bit when the nuts are tightened.

OR (my choice) set spare nuts on the stud to the plate level. Then there is nothing in the way of the grout.

 

Grout up using a stiff dryish mortar mix. Use small size ballast if you can get it, otherwise sharp sand. 

push under and ram it hard to refusal, so you need a back stop board.

Flaunch to vertical or 45 degrees.

 

Why not use expanding grout? Because they tend to assume it is magic and leave it well short of the plate and with gaps in it. 

Use it if you like but still supervise.

 

@saveasteading"OK I do really know about this. Must have specified/supervised for tens of thousands of these, on mostly very big, but some small, columns. "

and "Gus and others are mostly right, but my opinions are based on the difference between theory and practice."

 

I have speced a few bases over the years, worn a different hat on occasion and erected a bit of steel too and mucked about with the grout.. packing of base plates and so on.

 

Better to be mostly right than mostly wrong so thanks for the general agreement saveasteading. Good points you make.. the fence washers are a bit great of practical cost effective advice.

 

For all you can see that there are a number of different approaches.

 

To be on the safe side always check with your SE / designer as to how they have designed the base. If the bases are required to carry a horizontal load as well as a vertical (up / down load) then the bolts may be designed to carry horizontal shear load. If the bolts are in cones and you don't fill the cones fully then the shear force transfer to the found can be compromised particularly when you have an upward (uplift) force in a column. On a self build with steel work have a look to see if you have diagonal bracing to stabalise the structure. You may also have a big roof that acts like a kite and wants to lift off.. and this effect is needs to be dealt with.

 

If you do have something like the above then you will probably have horizontal load transfer between the steel and the found.. you don't want movement taking place here.

 

"Why not use expanding grout? Because they tend to assume it is magic and leave it well short of the plate and with gaps in it. 

Use it if you like but still supervise."

 

Good advice here too. Ask your SE / designer and put forward you proposals..once you understand what the bases are required to do then follow through with good supervision. If you set yourself up right then it can be a good rewarding experience putting up the steels.. you really feel like you are making progress.

 

 

[SteamyTea]

On 08/11/2021 at 15:38, DeanAlan said:

Where the f do I get "watter" from and what is that

 

They speak funny in Lincolnshire, just so they are not confused with people from Norfolk.

 

[eandg]

This is a job I'm going to need to grapple with shortly. If in doubt, get the brickie out to do it? For a baseplate that's 240x240 what dimensions should the grout be? Thanks. 

[markc]

8 minutes ago, eandg said:

This is a job I'm going to need to grapple with shortly. If in doubt, get the brickie out to do it? For a baseplate that's 240x240 what dimensions should the grout be? Thanks. 

Grout just has to fill the void under the plate. Use sand or mud to build a dam around the plate with an inch or so extra then when you pour the grout it can fully fill the void without trapping air , fill up to top of plate and the extra reservoir will account for any settling.

[eandg]

6 minutes ago, markc said:

Grout just has to fill the void under the plate. Use sand or mud to build a dam around the plate with an inch or so extra then when you pour the grout it can fully fill the void without trapping air , fill up to top of plate and the extra reservoir will account for any settling.

Thanks - so dimensions/positions need to be bang on?

[markc]

2 minutes ago, eandg said:

Thanks - so dimensions/positions need to be bang on?

No, unless it’s going to be on show then you batter the edges etc to make it neat

[markc]

[markc]

If not seen then size and shape of the dam/shutter can be anything

[eandg]

4 minutes ago, markc said:

If not seen then size and shape of the dam/shutter can be anything

Won't be seen as screeding over the top. Only issue would be potential impact on the sole plate around it if it's oversized? Will need to speak with kit company to see if that causes a problem. 

[Mr Punter]

38 minutes ago, eandg said:

For a baseplate that's 240x240 what dimensions should the grout be? Thanks. 

 

Make a frame using 2"x2".  Cut 2 lengths at 290mm and 2 at 360mm.  Fix the longer pieces to the ends of the shorter ones with 80mm screws.  Offset the frame with a couple of blocks and pour the grout slowly into the offset bit until you can see it coming out all round.  Take the frame off the next day.  Should look like this:

 

[saveasteading]

On 08/11/2021 at 16:56, tonyshouse said:

Ram in strong dry mix if decent gap and flaunch edges 

Agreed. I can understand why people specify fancy non-shrink grout (actually expanding is better), because it is easy, pretty good, and moderately idiot proof.

 

The trouble is you have no idea whether it is in contact with the steel or not, unless you drill holes in the plate. I have seen removed columns where there was only 50% contact.

 

Having been responsible for say 5,000 columns I prefer as Tonyshouse says. It is lo-tech, easily done by any builder whether experienced or not as long as they do as told.

Dryish mix* with small aggregate, pushed into place and then banged in with a stick against a timber on the opposite face. The flaunching gives a little more pressure into place and prevents any suggestion of edge displacement. 

 

This isn't possible though if the column is recessed and doesn't allow access....then the specialist grout is the way.

 

* manageable and doesn't shrink.

 

Then tighten the bolts again.