How can I create a mold for a large concrete pot ( greater than 1.5 by 1.5 metres) ?

I wanted to have series of pots next to a deck . Rather than just square,I wanted to have something like half a sphere drawn up; maybe a better way to describe it is a cone with the point cut off and inverted. I could make an internal mold with heaped wet sand , but how can I mold the walls for consistent thickness, reinforcerd with wire and asmooth exterior The problem is to create a pourable mold in an interesting shape.

What you are asking sounds like a job for "ferrocement", which is ideal for thin shells like you want to make. Ferrocement is placed by hand and smoothed with a float. Making a half sphere in damp sand is a good idea. Make simple depth gauge to measure the thickness as you make it by pushing a blunt dowel into the wet cement. has some stuff on the techniques and results.
jtp1398 years ago
you could cover one of those exercise balls then deflate it when the cement is cured.
lemonie8 years ago
That's very big. You could dig a big hole in the ground and line it with plastic sheet, but you'd have a job getting the things out again. A lot of work with wood and thin ply' may be the best practical answer if not the easiest.
See what Thinkenstein does with cement - might help.