How long does mortor have to be cured before it can be drilled and an expanding bolt put in it. I am putting some decking along side a raised pond. Sods law when drilling a hole to take a bolt it was too close to the edge of concrete block and the edge broke away. I repaired it but how long before I can safely drill it?
Kevin
Zen83237 wibbled on Monday 22 March 2010 17:25
Couple of weeks at least - preferably longer, for the mortar to get to any sort of decent hardness. IME a strong mix will take plugs after a couple of days, but no way for metal expanding bolts.
Given you've broken it once, now the repair is likely weaker, have you considered using some chemical bolts (resin + stud) instead? There will be no expansion forces so if you are confident of any pull or lateral forces being OK on that bit, it will be a much stronger fixing and I think you could safely proceed after a few days depending on how strong your mortar mix was.
Expanding bolts near the edge of any substrate usually spells disaster :(
If you want to be cheap but still effective, Screwfix no-nonsense chemical mortar/resin is OK (but needs the larger mastic gun, not the normal DIY size). You might be able to get small volume tubs if you look around, or even one shot capsules. A2 stainless rod from Toolstation or anywhere else in 10 or 12mm would generally work out cheaper than a box of the "proper" studs, and certainly much cheaper than the proper studs in stainless. A2 is bendier than zinc passivated studs but in 10 or 12mm it is unlikely to be a problem. I've used this technique to fix up bog cisterns and basins to crappy thermalite block walls with much success.
All you need is to blow the hole out thoroughly and a bit of tube taped to a car or bike pump which will work fine, or use your mouth if needs be on said tube (it's only to blow the dust out from the back of the hole).
Half fill the hole with resin, ram stud in, clean up excess gunk (cut it off with a screwdriver when it hits the plastic phase that lasts a few mins), hold stud in place for 5 mins, leave for an hour or two then fit whatever to it. Best to leave for a few hours before finally tightening everything up fully (check the instructions).
indeed, my fave (for more than the odd one) is a kids drink straw and a vaccuum (sp) cleaner:- insert straw to end of hole, hold vac nozzle as tightly around hole with fingers to form as much seal as you can *leaving outer end of straw open to air* , switch on - air sucked thru straw to deep end of hole and then back out with all dust etc into vac - simples!
Cheers JimK
An alternative is the multi monti/thunderbolt type fixing, my weapon of choice for attatching joists to walls when decking.
Tim Watts wibbled on Monday 22 March 2010 17:42
^^^^
Threaded stud
Around 6 weeks to get almost full strength, but varies with temp, water, additives, etc. For most purposes, full strength isn't required, but an expanding bolt is probably a case where it is. To be honest, an expanding bolt in mortar is probably not a good idea in any case.
Indeed, even if it holds unless the bolt is stainless over time it will corrode and fracture the mortar layer. Even without this, expanding bolts are not particularly strong fixings compared to alternatives.
Resin joint, Multi-monti, Fischer SX8/SX10 extra length.
This one hole is only one of 5 on the piece of wood that I am bolting to the side of the pond. I could just as easily redrill the timber then put the bolt a couple of inches to the left or right but then to a pefectionist like me I would have one fixing not equally spaced even though you wont see it as it will be underneath the decking.
It is a 12 mm bolt and not taking a huge load so I think it will suffice in this instance.
this time of year, two to three days AT LEAST.
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