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Bolt issue with concrete and securing Auto Lift

H

haanzel

Active member
Joined
Dec 14, 2014
Messages
44
Location
Texas
I bought a 2 post lift and got it mostly installed. The last hole on one of the columns I had to drill through rebar, but made it through. When I put the anchor in the concrete and I started to tighten it eventually just kept spinning. I am thinking it's unable to securely fasten due to the rebar.

How do I secure this last one? I was thinking about using some concrete filler- good product recommendations welcomed- and filling it about 1-2" so that it would cover the rebar. Once dried, then put the last bolt in. It would stick out a little more but I do not think it should be a big deal since the other 9 are good between the two posts. There are 5 per side.

I could try to get a longer bolt too, but unsure where to get these, they are different and unlike anything I have seen before. So finding one could be very difficult.

Thoughts?
 
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matt_i

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Imo there's a little more to it than that...if you epoxy you should prep the hole properly, which means some combination of bottle brush and compressed air blast, ideally a long pipe or tube-end that can reach the bottom of the hole to remove *all* the dust. Do it over and over until no dust can be found. You should use a dust mask as the 'crete dust is really not good for you.

Epoxy works well at higher temps (lets say 70F and above).

Imo you want to epoxy in a stud (meaning a threaded rod or "allthread"). I wouldn't trust the el cheapo Grade 2 stuff. I would source B7 threaded rod which approximates the tensile strength of a Grade 5 bolt. McMaster Carr is one source. Saw to length, put a Higby end on the lead thread. I like to work the epoxy into the threads with a gloved hand, then apply some to the walls of the hole, use many twists of the rod while inserting it to spread the epoxy as thoroughly as possible onto the walls of the hole (in otherwords don't just gun some into the bottom and expect it to fully squish upwards filling all voids) there's no way to know for sure if the 'poxy got spread fully, so do the best job you can do.

Let it cure 24 hrs at 70F, longer at lower temps, and then you can apply final torque then. Now you have an anchor that you can trust!
 
T

topp64

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Jan 29, 2013
Messages
126
Location
Des Moines, Iowa
matt_i said:
Imo there's a little more to it than that...if you epoxy you should prep the hole properly, which means some combination of bottle brush and compressed air blast, ideally a long pipe or tube-end that can reach the bottom of the hole to remove *all* the dust. Do it over and over until no dust can be found. You should use a dust mask as the 'crete dust is really not good for you.

Epoxy works well at higher temps (lets say 70F and above).

Imo you want to epoxy in a stud (meaning a threaded rod or "allthread"). I wouldn't trust the el cheapo Grade 2 stuff. I would source B7 threaded rod which approximates the tensile strength of a Grade 5 bolt. McMaster Carr is one source. Saw to length, put a Higby end on the lead thread. I like to work the epoxy into the threads with a gloved hand, then apply some to the walls of the hole, use many twists of the rod while inserting it to spread the epoxy as thoroughly as possible onto the walls of the hole (in otherwords don't just gun some into the bottom and expect it to fully squish upwards filling all voids) there's no way to know for sure if the 'poxy got spread fully, so do the best job you can do.

Let it cure 24 hrs at 70F, longer at lower temps, and then you can apply final torque then. Now you have an anchor that you can trust!
Click to expand...

I'm guessing the OP is in a heated shop or garage. If not, epoxy designed for cold weather is available. I just looked at a cartridge of fast cure epoxy that reads "Application Temperature: 15°F through -95°F.

I work for a paving contractor, on a crew that does hand work (cul-de-sacs, intersections etc), so we use epoxy almost every day. We change to cold weather epoxy when the temps drop into the 40's.

I agree that the hole needs to be cleaned out good. Compressed air works but it's not actually OSHA compliant these days. You're supposed to drill using a drill equipped with a dust extractor running to a HEPA filtered vac. If you could rig up a hose or tube to a shop vac, so that it reaches to the bottom of the hole, that should work for 1 hole.

Follow the epoxy manufacturer instructions for installation of your anchor bolt. Usually you fill the hole 2/3 with epoxy then insert the anchor using a slow turning motion until it's fully inserted. It'll probably try to push back out until you get all the air pockets out. You'll know when the air is out because you'll feel the anchor being sucked in. If it's done correctly you'll have a little extra epoxy come out of the hole.

I suggested the Sika brand because it's easily available and the OP could use a standard caulking gun. If you want to go with a type of epoxy that comes in a dual cartridge system that mixes in the tip, you will need a gun designed for that system. There might be places that rent stuff like that, IDK.
 
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Wamsutta

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Jan 8, 2014
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Amarillo, Texas
matt_i said:
Imo there's a little more to it than that...if you epoxy you should prep the hole properly, which means some combination of bottle brush and compressed air blast, ideally a long pipe or tube-end that can reach the bottom of the hole to remove *all* the dust. Do it over and over until no dust can be found. You should use a dust mask as the 'crete dust is really not good for you.

Epoxy works well at higher temps (lets say 70F and above).

Imo you want to epoxy in a stud (meaning a threaded rod or "allthread"). I wouldn't trust the el cheapo Grade 2 stuff. I would source B7 threaded rod which approximates the tensile strength of a Grade 5 bolt. McMaster Carr is one source. Saw to length, put a Higby end on the lead thread. I like to work the epoxy into the threads with a gloved hand, then apply some to the walls of the hole, use many twists of the rod while inserting it to spread the epoxy as thoroughly as possible onto the walls of the hole (in otherwords don't just gun some into the bottom and expect it to fully squish upwards filling all voids) there's no way to know for sure if the 'poxy got spread fully, so do the best job you can do.

Let it cure 24 hrs at 70F, longer at lower temps, and then you can apply final torque then. Now you have an anchor that you can trust!
Click to expand...

Are you saying you drop the bolt in first and then pour the epoxy in around it? Or do you mean filling the hole up with epoxy and then re-drill the hole through the epoxy?
 
K

KnurledNut

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topp64 said:
You fill the hole with epoxy, then push the bolt in. The diameter of the hole should be 1/8" bigger than the bolt.
Click to expand...

This is not true in every case.
Sometimes the specs only call for 1/16" bigger.
For example, 1/2 threaded rod might call for 9/16 drill.
While 1/2 rebar might call for 5/8.
But 1/2 rebar is not actually 1/2.

Always best to check, not guess, especially if structural.
 
OP
H

haanzel

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Joined
Dec 14, 2014
Messages
44
Location
Texas
Thanks for the replies.

Currently the shop is not insulated but it's on the radar for this year. Being in TX, I don't deal with extreme cold but we do have heat.

I cannot drill the hole larger, the post is already placed and the foot has a certain size for the anchor. I can clean it out well, no issue there. The hole is probably about 7-8" deep.

If I understood this, I fill in the hole with concrete epoxy filler a few inches, then insert the anchor turning it so that it coats the anchor going down. Let set a couple of days then tighten. Correct?

I do have a standard caulk gun a well as a dual cartridge 3M dispenser. The simpson looks like it would work.
 
L

lakeroadster

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Jan 19, 2015
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Location
Central Colorado
This thread is indeed scary.

OP, contact your local Hilti representative. They are experts in regard to epoxy anchors.

Tell them the specifics, follow their advice.
 
M

matt_i

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Messages
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Location
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I don't regard the smaller hole as a problem. The epoxy develops pullout strength in shear, so typically a thinner layer aids this. However in "construction site conditions" nobody wants to take the time to make sure its well-coated, the expectation is that its a wham bam process since we have 758 of these things to put in today, and that's where a slightly larger diameter hole makes it easier to spread the epoxy to get the contact area up, its a more reliable result in the field while still giving you adequate strength.

Trying to get to the point that if you take pains to get the stuff coated all around the ID of the hole (can always heat the tube itself with a space heater or an incandescent lamp prior to gunning the adhesive so it spreads more easily...my preference is the Sika Anchorfix 2 - buy @ home depot) and get the walls of the hole coated by many many twists of the anchor stud, use the rotation to bring it upwards, no reason you can't pull it out halfway thru and add some more just to enhance the coating, other than its hard to do and time consuming but the epoxy is not damaged...it hardens on the order of an hour....its not super-glue.
 
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