Help forming 2-inch-thick concrete walls

[Bill Gebhardt]

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 a 24" by 2” void. Suspect keeping the mud loose and a lot of tamping and knocking. Any suggestions?
Bill

[jim sauterer]

I filled an 8x10x15 inch high box my wife wanted and used a sander to vibrate the box to get out the air.worked fairly well had to make a little slurry to fill a couple small holes.

[Peter Kelly]

Why is the form hollow in the center? Seems like it’d be a massive PIA to fill small spaces and not end up with a ton of voids. Could it not be just the outsides of the form with a solid middle?

[Bruce Wrenn]

I filled an 8x10x15 inch high box my wife wanted and used a sander to vibrate the box to get out the air.worked fairly well had to make a little slurry to fill a couple small holes.

That's how we do it. Cheaper the sander, the worse it vibrates, which in this case is a good thing. When pouring a concrete counter top, attach a block of wood to sander, and use as a vibrating screed. Wrap the whole shebang up in a plastic bag. No clean up problems, just throw the bag away

[Matt Day]

Needle scaler on the form would be a pretty good vibration.

[Bill Gebhardt]

How about a Palm nailer?

[Frank Pratt]

Wouldn't a palm nailer be too harsh?

[Tom M King]

Don't vibrate too long, or all the aggregate will settle to the bottom. How long is always the question. When using a vibrator that's made for the job, for something like that it would only be a couple of seconds. Anything else is guesswork.

Plasticizer helps a whole lot. You can even get small quantities off Amazon.

The only similar job that I've done has been casting replacement window sills in place. I just tap all around the form with a hammer, and use a paint roller designed for weathered wood texture on the top-also available on Amazon.

[Adam Herman]

i would use the plastizier and the fiberglass with the rapid set "morter mix" i think. i used this without the fiber glass, and with some welded wire grid for a concrete countertop and it worked great. you could make the inside a square tube, so that it gets thicker at the bottom and just taper the outside.

recipercating saw with no blade works as a vibrator also.

[Bill Gebhardt]

Too much of a hassle so forget the thin wall idea and fill the mold and go easy with the vibrations. Thanks all for your contributions.
Bill

[Mike Kees]

Listen to Tom on the plasticiser. I do ICF basements (styrafoam forms) and use plasticiser in them all the time. Amazing stuff.