cast in anchor bolts

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Had a lift operator run over a few anchor bolts and broke 2 off the other day, We have core drilled down as far as we can around the bolts but they are longer than our drill. The thought was brought up to try and burn them off down about 8" so new ones can be epoxied in. Now Im pretty sure a torch is not the right tool for the job here as concrete and torches tend to end up with concrete going snap crackle pop. Would a carbon rod or even 6010 work you think? The holes are about 12" deep and we only need 8 or so. This is a 3/4" anchor bolt
Reply:Hello ironmangq, an oxygen lance might be the thing to use. I believe that Arc Air refers to theirs as a "Slice". You would still likely need to spend a bit of time doing some clean-up before epoxying your new studs in though. Depending upon the depth of the pour under these, you might be able to "drill" the holes afterwards with a slightly oversize roto-hammer bit to clean up the slag residue and force extra materials out the bottom of the holes. Good luck and best regards, Allanaevald
Reply:just be aware, concrete can explode when heated.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Simplest thing to do would be to see if you can shift the anchor bolts and redrill your base plate. Then all you would have to do is drill and epoxy after cutting off the old ones flush with the ground. This is some times possible if there is enough room on the base plate of a column for example. If this is a stamped project, they may want an extra one or two blots, or heavier reinforcing put over the base because you had to shift the original holes. We've done this on occasion.My other thought is what Allan suggested which would be an exothermic torch or oxygen lance. Note they are not cheap, and I'm not to sure where you would easily rent one. Most commercial dive companies use these for underwater cutting, so that might be an avenue to pursue.Last thought would be to hire a coring specialist to drill deeper holes for you..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I'd use a rotary hammer with a carbide concrete bit for the job, assuming there's no code against it. Put multiple close, small holes around the circumference and  then use a chisel to cut the web away if needed. Quicker, cheaper, less danger and less damage to surrounding concrete than heat, I'd bet.
Reply:Oldiron2 has got the right answer here.The other thing you might have been able to do was cut new threads on the anchor bolt in place (after removing some concrete) and put a threaded coupling (not pipe coupling) on it.
Reply:Just a reminder: Put a dog leg in the bolts before your epoxy them in. When you tighten the nut they will not rotate.
Reply:If possible cut the anchors off flush with the slab with a grinder and build a base plate for what is to be mounted so the new mounting holes are somewhere the damaged anchors are not. Then weld this to whatever is to be mounted. Use expansion type concrete anchors for this new mount.
Reply:In the past we have just rotorhammered far enough down to put a coupling nut on them when they were truely unsaveable.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:From what i've seen i'd recommend strongly against using an air arc.  I watched a couple guys do this once this summer and the sparks were spactuclar!  but it shot out right into the operator's face.as other's have said, best bet is to shift the anchor bolts and drill a new hole.industry standard is for depth is 10 times the diameter of the bar in inches as a minimum for epoxied anchor bolts.  Expanding type anchors usually require special consideration by the engineer in charge, but you will likely need that for any type of construction change.I'd get the guy who designed it involved right away and see what the next best alternative is.  Surely this is not the first time this has happened.
Reply:Can you put a dog leg in them and weld another to them.
Reply:I'd try to modify your base plates first. That's by far the easiest option. If that's not possible...Weld it... Bevel the anchor bolt in the ground and the new one so they resemble the shape of a chisel but not so much of an angle approx 15* should be good. Open root 6010, clean and fill it with 7018. I've seen this procedure done on a homeland security site and was approved by the army corp of engineers.
Reply:Originally Posted by DSWSimplest thing to do would be to see if you can shift the anchor bolts and redrill your base plate. Then all you would have to do is drill and epoxy after cutting off the old ones flush with the ground. This is some times possible if there is enough room on the base plate of a column for example. If this is a stamped project, they may want an extra one or two blots, or heavier reinforcing put over the base because you had to shift the original holes. We've done this on occasion.My other thought is what Allan suggested which would be an exothermic torch or oxygen lance. Note they are not cheap, and I'm not to sure where you would easily rent one. Most commercial dive companies use these for underwater cutting, so that might be an avenue to pursue.Last thought would be to hire a coring specialist to drill deeper holes for you.
Reply:Modifying the base plate is the best plan, we are waiting for the columns to show up to see what kind of room we dealing with but my guess is that we will be drilling new holes and sinking new bolts in
Reply:those damaged bolts go that deep means they are hooked into the rebar. also if you have chopped out around the old bolts there is no concrete  to epoxy to..seems like youd have to replace the concrete and wait for it to come to strength, then drill for the epoxy ones..make sure the engineer will buy this..