Experience using epoxy for high-strength anchoring?

[JimR1998]

I'm trying to put up a basketball pole. Every garage needs needs a spot to shoot some hoops, right?

Does anyone have experience with epoxy anchoring for something like this? I missed putting L-bolts into the wet pour because that would be too easy. Ugh!

My goal is to secure 5/8 threaded rod 20" deep into a concrete pier (24 round x 48 deep pier). I have a hammer drill for the hole but not sure which epoxy is appropriate. Or if anchoring cement is better. I need it to be safe for vibrations, not fatigue over time, and not crack apart in freezing weather. Some say "do not use for sustained loads" but don't elaborate on what that means.

Is the Quickrete stuff good for this? Sika AnchorFlex2? Hilti HY-200? I don't have the Hilti gun or any two-cartridge gun but I'll figure that out once I find the right product.

Thoughts from people who use this stuff a lot? Thanks.

 

[readhead]

I have used a lot of Simpson AT. For 5/8" rod you need to drill a 3/4" hole. Make sure the hole is very clean, fill it about a third full and work the rod down into the hole. Hardware store rod is grade 2 which is probably ok but if you want more B7 is grade 5. Be sure to clean the rod before putting it in the epoxy.

 

[Quick240]

My goal is to secure 5/8 threaded rod 20" deep into a concrete pier (24 round x 48 deep pier). I have a hammer drill for the hole...

If you're drilling holes that diameter, that deep, you'll probably want a rotary hammer.

 

[kwb]

Why on earth would you sink the rod 20"?
I have had 1T jib arm cranes installed with about 8" embed in a 10" slab.

Clean holes clean stud are critical.

 

[JimR1998]

I have a rotary hammer with a long 3/4 bit. The rod is black-oxide grade B7. I still have to de-oil it but will do. I planned on using a shop vac and water several times to clean out the hole.

The original L bolts were 16" long with a 4" L, supposedly to minimize vibration. I have the rod, figured deeper was better.

Will epoxy brand matter?

 

[egdede]

Simpson brand epoxy, but just the gun gets spendy.

I picked up some of these for $15 buck at lowes being cleared out. 1/2" and 5/8":

https://www.tools-plus.com/bosch-dx...MIpLmN2uKJ6QIV9_3jBx2mFAu1EAQYBCABEgK2GPD_BwE

But they just set up a display in another section of my store and are selling them at full price again

 

[wssix99]

Some say "do not use for sustained loads" but don't elaborate on what that means.

It means they are susceptible to epoxy creep: https://www.npr.org/templates/story/story.php?storyId=11854258

For a basketball post and backboard, I wouldn't worry about this. I expect it would be a bigger deal for something that has more significant sustained loads on it. If you are worried about it, you can look for an "overhead" epoxy, which would be creep resistant.

We install 10 ton car lifts with 4" deep wedge anchors. They are really simple and if they are good enough for a car lift, they are going to be just fine for a backboard!

 

[matt_i]

Shop vac is insufficient. Must blow with a pipette that can reach the bottom of the drilled hole. Blow and brush 3x alternating is typical industrial procedure.

I wouldn't drill more than 8" deep. At 5ksi (can depend on half of that so use 2.5ksi tensile.) The .625" dia hole has a circumference of .625*pi and a length of 8". So 15 sq-in roughly if you "unwrap" the epoxy sleeve and visualize it as a flat plane. 2500 lb/sq-in * 15 sq-in = 37,500 lbs holding power.

Back to the blow-brush-blow-brush-blow-brush procedure. Without it, the shop vac technique could get you 5% or less of the number above.

The pour should have been reinforced with rebar "hoops" or belts to keep it all together but I'm going to guess that got missed also.

Sika AnchorFix2 needs nothing more exotic than a caulking gun. A battery operated (cordless) one is really good for this but one can help themselves by warming the epoxy up to around 90-100F. I did this with a space heater aimed into a cardboard box.

You can mount the basketball post after an hour but I would strongly suggest clamping 2x framing timbers to the backboard to support the overhung load until the epoxy fully cures. Guideline is 24 hours at 70F and its likely colder than that overnight. So I'd give it a good 3 days to cure, then remove the timbers and you can level it up, tighten all of the nuts to full torque and play ball.

Its a very good idea to run the nuts by hand as soon as the rods are set to make sure epoxy didn't get into the threads. If so that's a perfect time to clean it up, if one waits until it cures it gets much harder.

I'm against using wedge anchors. I think a person would be disappointed. A basketball hoop is more of a jib crane with a tiny mounting plate (that nobody signing their name for liability would install with wedge anchors) than a vehicle lift with a relatively giant baseplate.

 

[JimR1998]

The pour should have been reinforced with rebar "hoops" or belts to keep it all together but I'm going to guess that got missed also.

No hoops but it does have 4-#4 rebars vertical. This is what was recommended for the wet L-bolt install too. Hole spacing is 9x9 square so they are not very close to the edge. Is this a big deal? CV19 messed up timing of the hoop delivery and the pour got done without the anchors. In retrospect I should have just waited and mixed the concrete myself.

Sika AnchorFix2 needs nothing more exotic than a caulking gun. A battery operated (cordless) one is really good for this but one can help themselves by warming the epoxy up to around 90-100F. I did this with a space heater aimed into a cardboard box.

Won't heat drastically reduce the working time? If anything I was going to chill it slightly so I have a few minutes to fill the hole and put in the rod. I'm slow.

I'd give it a good 3 days to cure, then remove the timbers and you can level it up, tighten all of the nuts to full torque and play ball.

I will definitely give it a good week before I put any load on it. Have to find some helpers for the backboard first. The whole thing probably weighs 5-600 lbs.

Just want it to be !!SAFE!! Thanks for the tips.

 

[Sureshot]

As already suggested I'd look at the wedge anchors.

 

[kald]

As already suggested I'd look at the wedge anchors.

I agree. Wedge anchors are more than enough.

 

[nadogail]

I have always had good results when I use Hilti products.

 

[matt_i]

Just want it to be !!SAFE!! Thanks for the tips.

I was curious about the loads so did some guesstimating.

Suppose assembly is 600 lbs and 1/2 is overhung, the other 300 lbs is in the vertical post.

Suppose a 300 lb person comes in for a jam and hangs on the rim (maybe youre neighbors with Zion Williamson or something )

I estimate impact loads at 10x of static.

I guessed at 3ft of overhang between rim and centerline of the post.

So we have (300 * 36") + (300 * 10 * 36") = 300 * 11 * 36" = 118,800 in-lbs of moment on the base. (equals 9900 ft-lbs).

Suppose its borne on bolts that are 9" from the front edge of the base, so the 118,800 in-lbs/9in = 13,200 lbs of uplift shared between 2 bolts.

To make matters worse many basketball post flanges are trapped between jam nuts to help level it out, Iow not sitting flat on the concrete due to leveling issues. Then the moment might be borne on bolt centers which are 7.5" apart, so the uplift potentially goes to 15,840 lbs shared between two bolts.

This is why I don't think the wedge anchors are appropriate.

Another way to look at it: suppose there's a fail, an easy fail where a wedge corrodes a bit and slips in the hole without fully pulling out and the hoop is 5 degrees off level. How to fix?

Suppose there's a dramatic fail with concrete cones breaking out of the surface of the monolith or the wedges pull completely out. Now 500-600 lbs is falling along with the person who just overloaded it and things are left to chance with the worst possibilities. I'd say a fatality is easily possible if the backboard hit you in the head. So then how do you fix that? Or even a serious injury where suddenly you have 5-6 figures of medical bills. Sue the company that made it? They would quickly figure out that the instructions weren't followed and substandard methods utilized.

I personally would err on the side of caution even though its about $100-200 more materials and labor and you have to wait 3 days.

As far as how i work with the epoxy, reread the blow + brush. Then degrease the threaded rod. I dispense some epoxy on the OD of the threaded rod with a nitrile gloved hand, working it into the threads. Then I put some into the hole. Then twist in a left-hand motion which pushes the epoxy downward. Twist twist twist which "mixes" within the void, the idea is to make sure everything is coated and its filled up.

The reaction doesn't start until it fills the tip, so there's enough time to make it work. Having some spare cardboard and a helper is greatly beneficial as the person using the glove is one-handed after that.

Good luck with your project.

 

[wssix99]

I agree. Wedge anchors are more than enough.

And they are safer for untrained non-professionals to install. (vacuuming out a hole properly is not as easy as it sounds)

Then the moment might be borne on bolt centers which are 7.5" apart, so the uplift potentially goes to 15,840 lbs shared between two bolts.

This is why I don't think the wedge anchors are appropriate.

Assuming your assumptions are accurate for this condition, wedge anchors can and are rated for this load. No problem. The nice thing is that they give instant feedback if they are holding.

If an epoxy anchor isn't bonded well at the bottom of the hole, then it could end up holding very little load before it pulls out of the hole.

 

[buildyourown]

You want the anchoring cement. The stuff that fit ins a chauk gun and has the mixing tip. You can just use all thread for the anchors. Works very well.
Just blow the hole out with an airgun and a shop vac. No way you need to go 20". You dont want to go into the gravel.