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Expanding foam vs Concrete for securing pier

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#1 Noobulosity

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Posted 08 September 2020 - 06:17 PM

As I started researching the best method for securing a pier into the ground, I ran across the use of expanding closed-cell foam for fence posts and such.  Does anyone have experience with this stuff for securing a pier?  I'm curious if it has vibration-dampening properties and how rigid it is compared to concrete.  I'm also curious how well it may hold up over time.  If this stuff really does work, my back will surely thank me.  grin.gif



#2 photoracer18

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Posted 08 September 2020 - 07:16 PM

Way too lightweight for anything of substance. Type of fence posts you might use this with are plastic fences. Reason you use concrete for a pier is its heavy and you need heavy in the ground to hold something only a little lighter on top. Not counting the effect of the frost layer which the concrete needs to go down far enough to get under.



#3 Noobulosity

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Posted 08 September 2020 - 07:21 PM

Way too lightweight for anything of substance. Type of fence posts you might use this with are plastic fences. Reason you use concrete for a pier is its heavy and you need heavy in the ground to hold something only a little lighter on top. Not counting the effect of the frost layer which the concrete needs to go down far enough to get under.


Do you have experience with the expanding foam? Maybe used it on a project? There are types of foam heavier, harder, and more rigid than many common materials. Way stronger than concrete. I think many compare to things like Great Stuff expanding foam, but that's not the same stuff. I just don't know what this type of foam is and how well it works for this application.

This video is what got me curious how viable this stuff is...

https://youtu.be/2_FyfJLeGN0

#4 Galaxyhunter

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Posted 08 September 2020 - 08:44 PM

Go for it.  You can be our official Ginnie pig.  question.gif.   Could be interesting. 


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#5 descott12

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Posted 08 September 2020 - 08:47 PM

Concrete is cheap, incredibly easy to work with and proven. I wouldn't "fix what ain't broke" as the saying goes.



#6 Noobulosity

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Posted 08 September 2020 - 08:51 PM

Go for it. You can be our official Ginnie pig. question.gif. Could be interesting.


Honestly, I'm tempted. But I'll probably try calling contractors or manufacturers before I jump into using it.

Concrete is cheap, incredibly easy to work with and proven. I wouldn't "fix what ain't broke" as the saying goes.


But that line of thinking also ignores other, possibly-better solutions that may pop up. That's why I'm asking. I just want to know if this is something worth considering. It's entirely possible it's worthless for this purpose. But if no one actually knows, why simply ignore it?

#7 speedster

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Posted 09 September 2020 - 01:13 AM

Foams like Secure Set are 4 lb/cf closed cell PU foams.  Twice the cost of concrete and literally thousands of times more elastic. 

 

5.6 lb foam E = .134 ksi

concrete E = 2,000 to 10,000 ksi

steel E = 29,000 ksi

 

Will it stick a post?  Absolutely.  Will it provide arc-sec deflection?  Not even close.


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#8 Noobulosity

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Posted 09 September 2020 - 01:21 AM

Foams like Secure Set are 4 lb/cf closed cell PU foams. Twice the cost of concrete and literally thousands of times more elastic.

5.6 lb foam E = .134 ksi
concrete E = 2,000 to 10,000 ksi
steel E = 29,000 ksi

Will it stick a post? Absolutely. Will it provide arc-sec deflection? Not even close.


This is what I'm looking for. Thanks! It makes sense, knowing more about the material properties. Seems like it works for less critical stuff, but not this.

Though,I did just run across another potential partial solution in the Diamond Pier...

#9 Noobulosity

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Posted 09 September 2020 - 11:49 AM

I just heard back from Sika on their Post Fix product.  They wouldn't even estimate on the longevity of their product, as there are lots of variables involved.  However, they stated it would not be recommended for a pier-mounted telescope application.

 

Post Fix and similar products are out of the question.


Edited by Noobulosity, 09 September 2020 - 11:49 AM.


#10 Tfer

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Posted 14 September 2020 - 02:14 PM

I used it on a fence installation.  4' in the ground, and 6' above.

 

2 years later, I was mixing concrete...  You couldn't even lean on the fence without it giving a couple of inches.

 

There is absolutely no way that I'd mount a pier with it.  None.  If it can't hold a 4"X4" fencepost securely, it hasn't got a chance with a pier.  Add a scope sitting on top worth thousands...?

 

Nope...


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#11 iwannabswiss

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Posted 14 September 2020 - 04:11 PM

Honestly, I'm tempted. But I'll probably try calling contractors or manufacturers before I jump into using it.

Wait, you reached out to people who know astronomy and have built piers, but now you're considering reaching out to a contractor who builds things? Good luck. Hopefully, you can find one into astronomy and understands what you're trying to accomplish and how vitally secure it is. Otherwise, that will be an interesting conversation, explaining about moving parts swinging around a central axis. ​ wink.gif



#12 Noobulosity

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Posted 14 September 2020 - 05:36 PM

Wait, you reached out to people who know astronomy and have built piers, but now you're considering reaching out to a contractor who builds things? Good luck. Hopefully, you can find one into astronomy and understands what you're trying to accomplish and how vitally secure it is. Otherwise, that will be an interesting conversation, explaining about moving parts swinging around a central axis. ​ wink.gif

Did you not read the rest of the thread before replying?

 

I reached out to the company that actually makes the product.  I told them I needed a product that's rigid with minimal flexure, and I was planning to set a telescope on the post.  Sika told me it wasn't fit for this application.  See post #9 above.  Considering they make the actual product, I figure it helps to ask them as subject matter experts.

 

And how is reaching out to contractors and/or fabricators who build things a bad idea?  Are you implying they couldn't possibly understand that I need a rigid post with minimal flexure?  Honestly, that's pretty insulting to tradespeople.  Building stuff is what they do for a living.  Lots of contractors are smart and could easily understand what we'd need for a simple pier.  They don't need to be into astronomy for that.

 

Besides, what if there's a better material out there?  What if I don't feel like digging a huge hole, maybe there's an alternative?  What if I there's an easier product with less mess and faster set-up time?  We won't know unless we ask.  That's all I was doing.  I'm just trying to do adequate research before I just do what internet randos tell me to do because that's what everyone else does.



#13 speedster

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Posted 14 September 2020 - 06:58 PM

Sadly, iwannabswiss is right.  Having designed everything from fences to international airport hotels for 35 years, I see workmanship getting worse.  Many tradesmen are insulting to their trade.  There are still plenty of talented people but most handymen are far from that crowd.  They won't understand what we want when we tell them "rigid post".  For example, how many concrete contractors would put gravel in the bottom of a pier hole?  Half of them?  "Well, I saw someone put gravel down on YouTube and the presenter looked like he know what he was doing."  Gravel in a pier works against you every time yet people still do it.  A tradesman would know his materials and know better than to spend more to make the assembly work less.



#14 Noobulosity

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Posted 14 September 2020 - 07:23 PM

Sadly, iwannabswiss is right.  Having designed everything from fences to international airport hotels for 35 years, I see workmanship getting worse.  Many tradesmen are insulting to their trade.  There are still plenty of talented people but most handymen are far from that crowd.  They won't understand what we want when we tell them "rigid post".  For example, how many concrete contractors would put gravel in the bottom of a pier hole?  Half of them?  "Well, I saw someone put gravel down on YouTube and the presenter looked like he know what he was doing."  Gravel in a pier works against you every time yet people still do it.  A tradesman would know his materials and know better than to spend more to make the assembly work less.

Aside from a bit of settling, how does gravel hurt a pier?  If the base of the pier is below the frost line anyway, I wouldn't expect it to make a huge difference.  But, maybe I'm totally mistaken, and you've piqued my interest.

 

Also, this is exactly why you get multiple opinions.  The same goes for any job or home improvement project.  And, yes, preferably you get opinions from people who have done similar work before.  I think everyone just assumed I'd go to a random Joe with no experience.  Instead, when I mentioned contractors, I was planning to reach out to a friend of mine in the construction business to see if he could recommend someone up to the task.  I also have connections at a local non-profit observatory, so I'd ask around there for some advice and assistance.



#15 iwannabswiss

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Posted 14 September 2020 - 08:02 PM

Did you not read the rest of the thread before replying?

 

I reached out to the company that actually makes the product.  I told them I needed a product that's rigid with minimal flexure, and I was planning to set a telescope on the post.  Sika told me it wasn't fit for this application.  See post #9 above.  Considering they make the actual product, I figure it helps to ask them as subject matter experts.

 

And how is reaching out to contractors and/or fabricators who build things a bad idea?  Are you implying they couldn't possibly understand that I need a rigid post with minimal flexure?  Honestly, that's pretty insulting to tradespeople.  Building stuff is what they do for a living.  Lots of contractors are smart and could easily understand what we'd need for a simple pier.  They don't need to be into astronomy for that.

 

Besides, what if there's a better material out there?  What if I don't feel like digging a huge hole, maybe there's an alternative?  What if I there's an easier product with less mess and faster set-up time?  We won't know unless we ask.  That's all I was doing.  I'm just trying to do adequate research before I just do what internet randos tell me to do because that's what everyone else does.

 

I did read the posts above. Obviously, you didn't see the wink face, which meant my comment was meant to be more of a joke. Merely looking from the outside, I thought it was funny because it appeared that you asked for opinions, were given responses, and yet seemed to brush them off.

 

I never said it was a bad idea to reach out or insulted anyone's abilities, experiences, or ability to comprehend. I merely said I hope you can find a company or person who understands our hobby; most people aren't as invested in this hobby as we are. You are right; it is best to reach out to those who make the products. I'm sure that any company or person knows the concept of needing something rigid, but how what exactly rigid means different things to everyone. I'm equally confident to say that unless they are in this hobby, they don't realize how vital arcseconds of precision are or what arcseconds mean to us and how they affect us.

 

There may be better materials out there, and it's fair to ask questions because times and products do change. You're also right that some internet randos out there will give bad advice, and it's unfortunate that people out there are either ill-informed or have malice intent. However, I believe you should also consider that most of our hobby only thrives because of other astronomers' innovation and experiences; random companies aren't designing or testing their products with astronomy, or its precision in mind.  And while you should always take internet advice with a grain of salt, I'm also sure we aren't the forum most people are clamoring to join, just to troll.

 

I agree with the advice given by descott12, "Concrete is cheap, incredibly easy to work with and proven. I wouldn't "fix what ain't broke" as the saying goes." I will be moving my observatory soon, and when I do, I'll be digging another one cubic yard hole in the ground to fill with Concrete.

 

I think everyone just assumed I'd go to a random Joe with no experience.

No, just people who aren't familiar with our equipment.



#16 Noobulosity

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Posted 14 September 2020 - 09:36 PM

Merely looking from the outside, I thought it was funny because it appeared that you asked for opinions, were given responses, and yet seemed to brush them off.

Fair enough.  But the responses to that point were mostly just guessing (correctly, as it turns out) as to the viability, or lack thereof, of the foam.  Fortunately, we did get someone else with some experience with it chiming in after that.  And hearing back from Sika directly put the matter to rest.  It's definitely not a good choice here.

 

Honestly, Tfer's experience of only lasting a couple years is pretty abysmal.  I don't think I'll use it even for light loads.  It might do best only as a temporary hold for something until a more-permanent solution can be put in place.


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#17 iwannabswiss

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Posted 14 September 2020 - 10:51 PM

It would be nice to find something lighter to work with. It took 31 80-pound bags for my pier foundation; luckily, we had a mixer, but still had to do most work by hand. I'm not looking forward to doing it again, lol.



#18 Noobulosity

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Posted 14 September 2020 - 11:07 PM

It would be nice to find something lighter to work with. It took 31 80-pound bags for my pier foundation; luckily, we had a mixer, but still had to do most work by hand. I'm not looking forward to doing it again, lol.

Yeah, my back won't have any of that.  I'd probably pay someone to pour it for me, if I wanted such a large mass of concrete.


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#19 speedster

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Posted 15 September 2020 - 06:07 PM

Gravel in a pier hole:  "Aside from a bit of settling, how does gravel hurt a pier?"  A bit of settling may be something we are trying to avoid.  This is definitely not a deal breaker and the concrete would hopefully fill the gravel voids.  I don't say it may be "harmful" because it probably won't matter in the end but why do things that can work against us?  Gravel is intended to be a drainage layer but in a hole there is nowhere for anything to drain so there is no point in making a void.



#20 t-ara-fan

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Posted 23 September 2020 - 12:39 PM

It would be nice to find something lighter to work with. It took 31 80-pound bags for my pier foundation; luckily, we had a mixer, but still had to do most work by hand. I'm not looking forward to doing it again, lol.

One truck with a few cubic yards of concrete is another way to go.  Leaves time to hit the gym because you missed lugging 2,480 pounds of cement sacks across your property.

 

 


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