Is there a downside to this?

[bluedog225]

I’m thinking of using some corrugated pipe as the form for a little concrete job I’ve got to do.

The task is to put a cap on some 12 inch concrete piers. And embed the welding plates in them. These will formed the base for columns going up to a balcony. Engineer said I could do what I wanted with the cap as long as it was stout enough. And wide enough for the welding plate (rebar etc).

I was thinking a frustum but I’m getting lazy. Pretty sure I can form it up right. And then replicated it three times. But it just stretches the job out. And I’m sure I’ll get one of them wrong somehow so it won’t match the others. And it’s just gonna piss me off in general. Life is short.

A 24” or so piece of corrugated 12” high would do the job nicely. And I think I can live the aesthetics. If not, I can always pile river rocks or similar around it.

What do you guys think. Is there any downside to this?

And is there any reason they have the spiral joined with the “straight” rings on top? Or just for looks?

Thanks

 

[rlitman]

I always understood the reason for smooth sided forms (like Sonotube on a concrete pier in contact with undisturbed earth), was to reduce side friction with the soil around the tube, to eliminate frost heave. If you're in a place where frost heave isn't a thing, then I don't see the ridges being a problem, but maybe someone here who knows more about the subject (I certainly don't, and am here to find out too) can chime in.

 

[cvairwerks]

You can use Sonotube and it will cost way less...24" galvanized culvert runs about $45 a foot and Sonotube and similar run less than $15 a foot.

 

[CraigStu]

That is the way some culvert pipe comes. The straight ridges are at the end so a clamp can join two pieces of pipe together w/ minimal leakage. See the pic on the left
https://www.drainagesupply.com/uploads/3/2/0/6/32063939/capture_10.png

 

[bluedog225]

No frost heave here. But I guess clay “heave“ is similar.

The piers are poured to 12’. Since the cap will be larger than the tube, I’ll put a sand layer under the cap and wash it out after the pour. And put some barriers in to keep the soil out. That will leave a few inches clear of the clay or surface expansion similar to the way the main building slab is poured.

 

[bluedog225]

You can use Sonotube and it will cost way less...24" galvanized culvert runs about $45 a foot and Sonotube and similar run less than $15 a foot.

Agreed. But plain sonotube concrete would be a little bit of an eyesore if I don’t cover it. I almost like the look of the corrugated.

I imagine I can find some on Craigslist.

 

[rlitman]

Agreed. But plain sonotube concrete would be a little bit of an eyesore if I don’t cover it...

Or you just rip it off after the pour cures.

 

[cvairwerks]

Rip the forms off after curing and paint the concrete to look like minions....

 

[jack stand]

So the existing 12' deep piers need to be extended about 2'?

 

[bluedog225]

So the existing 12' deep piers need to be extended about 2'?

There is plenty of vertical room. They need to be widened to support welding plates for 6”x6” columns. I think I have some flexibility on how high to bring them.

 

[yatg]

stainless steel drums or kegs? usually cheap used.

 

[jack stand]

There is plenty of vertical room. They need to be widened to support welding plates for 6”x6” columns. I think I have some flexibility on how high to bring them.

My thoughts are bonding the new "cap" to the old concrete and some pinning between the two will be necessary.

 

[bluedog225]

My thoughts are bonding the new "cap" to the old concrete and some pinning between the two will be necessary.

Agreed. I’ve got 3 sticks of #7 rebar embedded in the piers that will run up to the top of the cap and tie into the embedments for the welding plates.

 

[egdede]

No frost heave here. But I guess clay “heave“ is similar.

I have expansive clay soil. That's what I thought. In my area when the soil expands it is also less dense and things sink a bit (as opposed to being lifted by the expansion). A super-big problem when your houise is so old the foundation was poured without rebar....