Attaching strong-point to concrete base. Rawlbolt?

[james01]

I suspect that my concrete base is not very deep and degenerates into tightly-packed hardcore an inch or two below the surface. I'm concerned that the expanding Rawlbolt is designed mainly for standard building-quality masonry bricks or blocks, and may not have sufficient expansion to grab tightly into hardcore/rubble. Does anyone know of an expander-bolt which offers more lateral expansion? Or is there some liquid product which could be poured down the drilled hole to make a secure fitting?

[thirdcrank]

I suspect that my concrete base is not very deep ...

I think that that's going to make a definitive answer difficult. There are all sorts of different "Rawlbolt" type things, from various manufacturers, each intended to be suitable for a specific location eg masonry, cavity-blocks, plasterboard, w.h.y. Go to a genuine hardware/ ironmongers and they'll have boxes full of many different types and people able to identify which you need for your particular use. (I'll give a plug to George Spence's, Wellington Road Leeds, who have been really helpful to me for around 50 years, even though I'm very obviously not a tradesman.) I fancy that there's likely to be a problem if you can't say with some certainty what you are drilling into. If you have doubts about the construction of your base, then nobody can be certain what to recommend and, perhaps more to the point, your doubts may linger after installation.

If you own the concrete base, it may be worth doing a bit of exploratory drilling, with a view to digging through the base if it turns out to be too thin, fitting a solid ground anchor of some sort, then refilling the hole.

http://www.geospence.co.uk/

[AlaninWales]

Or is there some liquid product which could be poured down the drilled hole to make a secure fitting?

Post-crete (other makes of rapid-set cement mix are also available). It's a powder to which you add water after pouring the powder down the hole (it's designed as the name suggests for setting posts in rather larger holes), which then rapidly sets (circa 5 - 10 minutes) into very hard concrete.

[Mick F]

I second the idea of drilling exploratory holes.

I suspect you're asking this with respect to bicycle security?
You could fix a large metal plate to the (possibly) thin concrete to spread the load and torque. Instead of one large fixing point, you could have many smaller/shallower fixing points with one anchorage in the centre. Maybe a plate a yard square?

If that's impossible, dig out a large hole and use Postcrete as suggested. Fit a suitable anchor point in the hole, pour in the Postcrete and top up with water. It goes off like ................. concrete.

[wirral_cyclist]

I'd test drill a hole and hoover/blow out debris then pour some water in and see how (if) it runs away, if it doesn't run away then you're good to go, if it drains fast you need to consider other options. Styrene resin is used in walls with threaded rod (so a threaded eye bolt would work) and so might be an option. (though now the concrete is wet!)
Something like this:-
http://www.toolstation.com/shop/Screws+ ... sin/p10001

When fixing stuff 'securely' into grass/soil then multiple rods are driven into the ground at angles to form something like a pyramid with their eyes together at the apex (IYSWIM) and then a vertical pull is resisted by the multiple legs - might work if you can fan out into your sub base at varying angle through one access hole.

[tim-b]

Hi
Something like a bucket with a plastic pipe through and fill the bucket with concrete, or an old car tyre again filled with concrete? Feed a chain through the hole and you should put many thieves off. A bigger bucket would probably discourage the rest
Regards
tim-b

[Vmlopes]

Chemical Anchors is your solution

[Brucey]

if the concrete is thin it won't matter how you secure the studding, it'll pull out if someone gives it a good tug.

cheers

[Psamathe]

Also, assuming it is for locking a bike to, consider the security of the entire lock system. No point in taking lots of trouble installing an attachment in concrete that would withstand the efforts of the entire East Anglian Tractor Pull Team, when the bike is going to have a chain that can be fairly easily cut using a hacksaw that is stored in the same garage. Assuming the bike is going to lean up against e.g. a wall, is it easier to install something of equal strength into the wall ?

Another consideration with many of the "Rawlbolt" things is that use a traditional hex topped bolt which is then left exposed - meaning the bike thief only needs a spanner/adjustable wrench/etc. and all the other expensive locks are useless.

Ian

[Tangled Metal]

If you get the secure base right (gunk you pour into the hole or special fixings) then you can get sold secure gold rated anchors. The issue witht he exposed bolt heads would be sorted. IIRC some have the bolt or fixing covered by the lock or chain once it is being used.

How secure is a brick wall likely to be for a secure bike anchor? Also what about the other aspects of the shed/garage. I heard about a £2-4k bike getting nicked by the thieves getting in through the roof then taking their time to get through the SS gold rated lock. The owner got stung by their house insurers because it was not a SS gold rated anchor and there was no evidence of purchase (they often need receipts of the lock and the anchor to show they are SS gold rated.

Do check your insurance find print and even ask them directly what is their requirement for security before paying out. Just something to consider to all those bucket of concrete with pipe in it for a chain types on here. Might stop your bike being nicked but if that fails insurers can use it as a loophole since it is not rated. I do not know if there is a minimum standard for the substrate the SS gold anchor is put into or the handiwork of the installer. Think that is not covered and a weak point / possible get out of paying up card for insurers.

[pwa]

Sounds like you need to grind / chisel out a hole in the concrete crust, then dig out the chippings / hardcore beneath. Then fill the void with nice new concrete, with your fixing system embedded in it.

[NATURAL ANKLING]

Hi,
Bear in mind that if the anchor fixing into a hole that is all metal it will crack bricks (clay) and in a thin concrete layer be useless.

Dig hole through concrete size of bucket and fix a piece of steel rod formed in to a hair grip with ends turned over, say diameter 15 MM diameter, and you could place some smaller diameter rings in the loop for a smaller padlock etc.
Leaves no fixings and wont get out easy.

Stainless steel might not seem that hard but its a ******** to cut with anything other than a angle grinder so consider st stl rod

[PBA]

I'd buy an expanding anchor bolt and try it to see how strong it was!

Either try it somewhere remote where you can leave it in place or buy an anchor bolt smaller that you plan on using and then re-drill the hole after you remove it. Don't re-use holes for expanding anchors.

If the floor concrte is really thin so that you are fixing into rubble below the concrete, then an expanding anchor isn't the way to go. You would then need to dig a bigger hole and fill it with concrete - then use a steel hairgrip bar or eye bolt cast into the concrete. You would get the best result by making sure the new plug of concrete was of a larger diameter at depth than the hole through the concrete slab.

[ukdodger]

I suspect that my concrete base is not very deep and degenerates into tightly-packed hardcore an inch or two below the surface. I'm concerned that the expanding Rawlbolt is designed mainly for standard building-quality masonry bricks or blocks, and may not have sufficient expansion to grab tightly into hardcore/rubble. Does anyone know of an expander-bolt which offers more lateral expansion? Or is there some liquid product which could be poured down the drilled hole to make a secure fitting?

Rawlbolt make a glue for fixing metal to concrete. I've used it to secure reinforcing bars in concrete and it works perfectly. It even works under water. I forget the name. I asked Rawlbolt technical help and they gave it to me. It comes in a glass tube that goes into the hole. You then smash the glass with the metal whatever and leave it. They wernt cheap though. But as Brucey says if the concrete isnt thick enough nothing will work except more concrete.