Expansion screw - installation

[62_an]

I'm going to attach a steel beam to a concrete slab and thought of using expansion bolts, so I bought Biltema's 10x120mm in hot-dip galvanized finish. But I have never used expansion bolts myself before, so I'm not very sure how they work. The screws didn't fall directly into the holes; I had to hit them quite hard. But when I try to tighten the nuts, the screws don't seem to grip properly in the holes. The worst are the holes where I had to hit the screws in hardest. I'm wondering if the concrete is too porous... the slab is 50 years old, and I know it has varying quality. Or is it poor screw quality?

One screw came up about 20mm, so I loosened the nut and tapped it down again. It might grip slightly better after that. But no screw is gripping completely tight. I assume the screw should grip so that you can tighten "very" hard and not be "spongy."

- How tight should you be able to tighten a 10mm screw?
- How far should the screw come up out of the hole before it "grabs hold"?

Help is greatly appreciated

 

[anaitis]

Do not drill too deep!
The lower part of the screw must reach the bottom of the hole.
To get the screw to grip the hole, you must hit it HARD so that it expands and sticks.

 

[62_an]

Ahhh... I drilled a couple of cm deeper than the screw...
So you mean that it's the actual end of the screw that should expand first by being pressed/struck against the bottom of the hole?

I thought it was the loose ring at the end of the screw that locks the screw in place by grabbing the hole and flaring out over the conical end when you start screwing.
Wrong, then?

So what do you do now?
Try to unscrew the screws completely (if possible) and insert chemical anchors before you put them back?

 

[Mr_XXX]

62_an, you have done exactly right. But you should also drive them down deep enough so that you just barely have a few threads left (keep the nut on so they don't disappear).

Then "many bolts slip up a few mm or, if you're unlucky, a cm. If they never stop, you get the whole bolt up and can then start over.

The holes should be clean so that you can get the bolt down. You can also try lubricating the cone slightly so that the bolt slides in more easily and wedges in the sleeve.

 

[anaitis]

Chemical anchors work well
But if the screws are stuck, that's enough, right?

 

[62_an]

62_an, you have done exactly right. But you should also knock them down deep enough so that you just have a thread left (keep the nut on so they don't disappear).

So you mean that you can drill deeper than you need to?

Then "many bolts slip up a few mm or if you are unlucky, a cm. If they never stop, you can pull up the whole bolt and start over.

The holes should be clean so that you can insert the bolt. You can also try to lightly lubricate the cone so that the bolt slides in more easily and wedges into the socket.

If you start over, isn't there a risk that the hole will "wear out" so the fastening becomes even worse? Or if it works, maybe you can do as I tried, i.e., if they go too far, loosen the nut, knock it down again, and start over? But lubricating, doesn't that also reduce the friction against the hole wall?

Chemical anchors work fine. But if the screws are fixed, isn't that enough?

Fixed... That's exactly what I'm wondering about... Heco states that their 120x10 should be tightened to 30Nm. How much Biltema's should be tightened isn't stated. But my screws come up with significantly less torque/force. So I assume they're not fixed.

 

[Amatörbyggaren]

I have used Biltema's expansion screws for sills and they worked well, I might have discarded some, can't remember why. It was completely new concrete, maybe the concrete is too porous as you mention (where is Tyresö?). I tightened "just right" and there were no problems.

 

[62_an]

(where is Tyresö?)

Uhh??

 

[Mellanbarn]

So you mean that you can drill deeper than you need?



.

A trick is to drill through the concrete slab. Then you can knock down the screw so it disappears the day you no longer need it. Some consideration may need to be taken for what is under the slab.

 

[62_an]

But what should I do if it's a fact that it doesn't really hold?
And there's no room for more holes in the beam.
Trying to pull the whole thing out might be troublesome, maybe not even possible...

How fluid is chemical anchor - is it possible to get the chemical anchor to creep down into the gap around the screw when it's in place?

Other ideas?

 

[Mr_XXX]

But what should I do if it is a fact that it doesn't really grip? And there is no room for more holes in the beam. Trying to pull out the whole thing might be difficult, maybe not even possible...

How fluid is the chemical anchor - is it possible to get the chemical anchor to seep into the gap around the screw when it's in place?

Other ideas?

I would continue tightening the nuts until it either catches or comes up; if it comes up, you can redo the procedure with a light lubrication on the cone and possibly pry up the sleeve a bit so that it grips in the hole more and has a slight gap against the bolt. If they still don't catch, you can buy chemical anchor capsules that you drop into the hole before driving down the expander (with or without sleeve) (or threaded rod), or just use epoxy/chemical metal that you apply in the hole and then press down the expander or threaded rod. Let it cure and then tighten the nuts.

Is the beam just supposed to rest against a concrete slab? Loadings?

 

[Maveric77]

Öhh??

"Tyresö" was an active member until last week when he was banned from the forum by the moderators. He knew "everything" about concrete and casting and was happy to answer questions of this kind!

 

[62_an]

"Tyresö" was an active member until last week when he was banned from the forum by the moderators. He knew "everything" about concrete and casting and happily answered questions of this type!

Ahh..I understand...

As I said, Heco says 30Nm (http://www.heco.se/trycksaker/PDFer/Pdf_katalog/Heco_kat_betonginf.pdf) and one can probably assume at least that Biltema's is something similar.
I thought 30Nm sounded much more than I can tighten the screws with. True, I have managed to get a little better grip a bit higher up in the holes, but not so that it becomes solid directly.
So I tested with a simple torque wrench from Biltema and you have to tighten about 5-6kgm, which corresponds to 50-60Nm before the nut turns.
So then it seems like everything's fine then?! I didn't think it tightened at all! :blushing:
Or perhaps it's time to get a new torque wrench??

 

[csam11]

You must not drill too deep!
The lower part of the screw must touch the bottom of the hole.
To get the screw to anchor in the hole, you have to hit it HARD so that it expands and sticks.

I always drill deep enough so that I can knock in the entire expander if I'm not going to leave it. You shouldn't do it the way mentioned above. The expander expands when you tighten the nut and not by hammering it down. Next time you need to fasten something in concrete, I suggest you try concrete screws that are coarsely threaded. You need to drill a smaller hole and not hammer in any bolt.

 

[isolde]

Drill and screw. Stays put like a rock.
http://www.hilti.se/holse/page/modu...36FA3983AB424401C.node2?lang=sv&nodeId=-45443