Help forming 2-inch-thick concrete walls

[GEB]

I need to build/create a 24” pedestal to support some yard art. Currently looking at a square column with a 12” square base, 2” thick walls narrowing to an 8” top. I have mixed my share of concrete for slabs, post holes etc. But no experience filling 24’ of a 2” void. Suspect keeping the mud loose and a lot of tamping and knocking. Any suggestions?

Bill

[Snipe Hunter]

Any reason it can't be solid?

[GEB]

Any reason it can't be solid?

No reason other than to do so would almost double the weight.. But I am prepared to do that if I can not do the thin walls.
Bill

[Splinter Puller]

No reason other than to do so would almost double the weight.. But I am prepared to do that if I can not do the thin walls.
Bill

Put a plug of styrofoam in the middle

[Robert Adams]

Funny I need to do something like that to cover up the ugly wellhead. Probably end up with a birdbath on top. I have done stuff like it before and it just takes a little looser mix with peagravel tapping and rodding it into place. If you can get a handful of fiberglass it wouldn't need any steel. If you have voids in the surface just pix up a slurry to fill them. You can sand it smooth as well.

[frule]

I need to build/create a 24” pedestal to support some yard art. Currently looking at a square column with a 12” square base, 2” thick walls narrowing to an 8” top. I have mixed my share of concrete for slabs, post holes etc. But no experience filling 24’ of a 2” void. Suspect keeping the mud loose and a lot of tamping and knocking. Any suggestions?

Bill

Add perlite to mix?  https://www.google.com/search?q=light+we...eXvoCYBw36

[brianwelch]

Assuming the top would be integral with the walls, the traditional way would be to build it upside down, build the tapered exterior form, and an interior void form, tapered, as well as well oiled, for ease of removal. You will need to anchor the void form as it will want to float, depending on the slump of the concrete. You will also want to install some spacers between the 2 forms to maintain uniform wall thicknesses. Fiberglass reinforcing would be a great idea as well...

[Snipe Hunter]

The reason I asked is because 2" would be hard to tamp/remove voids etc. Could lighten it up with a piece PVC pipe or a hollow wood form inside.

[tomsteve]

i think ya need to vibrate more than tamp.

[crokett™]

No reason other than to do so would almost double the weight.. But I am prepared to do that if I can not do the thin walls.
Bill

Put a partial void in the middle.  Build your outside form, then your inside form is  a square box, or a piece of 4" PVC as a form.   You have thicker walls at the bottom, but it is still lighter weight.