Kim. The short answer is no you cant reuse it. You may be able to patch it back together.

The reason you cant reuse it is because once the hydration process (curing) begins there is no going back.

Like Rockhewer said, no you can't reuse your tufa. However, if you want to recycle to some extent, crumble up that broken piece and let it fully harden. Then you can use the 'crumbs' as one part of your aggregate. I've done that lots of times with the tufa I carve off. I don't like to waste stuff if I can help it.

Marly

Hi Kim
I used partly cure still damp tufa without any problems at all.
I have a trick I use to make Pots O Many Colors.
I make several colored lumps of tufa let them sit until they harden (half a day in this heat) then break them up into chunks of all sizes, add them to fresh Portland and water and make my pot. It's an interesting look once cured and wire brushed.
My pots seem to cure strong.

Dont be discouraged by this first attempt. Many years back I tried to make a planter out of tufa and the whole thing just crumbled. I am sure I wasnt patient enough. I tried again with the same results. But many years later I found this forum and decided to try again. After many successful projects I am having a lot of fun doing this. Patience and the right recipe works wonders. I took the pieces that were left from my disaster and shaped them into small stones and used them in my gardens.

I won't get discouraged, just have to find more patience. I wanted to do some carving on this before it set up too much. I'm using a small plastic dishpan type container that's narrower at the bottom than at the top, so do I need to line it with plastic or oil it? The plastic bag left wrinkles I didn't like. About how long should I let it sit before sliding it out of the mold?

Hi Kim
Curing time before unmolding is a tough one.
I would say for that recipe provided it was a fairly dry mix any where from 24-48 hours but there are always exceptions.
If it's too hard to mark with your fingernail it should be Ok to unmold but it still needs careful handling.
If you make a small brick along with your project and keep it with the work you can test hardness on that.
Carving can jar the work and break it so I try to do my early shaping with a very course rasp and wire brushes that don't subject the work to hard knocks. Moving to knives and other shaping tools after the pot has had more time to set up.
If you keep your pot in a plastic bag and completely wet you will get several days before it's becomes too hard to carve.

But with more practice you will get the a feel for the tufa and find you can unmold safely earlier.

A release film like oil is a good idea even on plastic but remember that the wet tufa creates suction, so often what feels like sticking is just vacuum. Putting a few holes in your plastic mold will help eliminate suction.

Kim, Is it just the pic or does this trough also have dye in the recipe. You can usually see the perlite and on my monitor this has a mauvey color. Not like your regular gray mixes. Were there drain holes?
I've used those small dishpans for classes and just spray them with PAM, a vegetable baking spray. We unmold that size in 24 hours, carve or clean up then spray with water and put back in the plastic bag. Billie

I didn't put any dye in the mix, it's regular gray color. Also, I didn't make any drain holes but will for the next try, and will spray with Pam. What is the fiberglass mesh called? I asked at a building supply center and they don't carry anything like it, said I needed to go to a cement operation that's many miles away. Maybe I can order it online?
Can someone explain the process of unmolding? If I turn the dishpan upside down, it will "plunk" out on the tabletop and probably crack. Maybe I should put more mix in, to the top of the dishpan so there's no extra space (does that make sense?).