Perlite won't hold as much water as vermiculite, but it holds a lot more air. It also won't hold nutrients. I use it for cacti and succulents. Vermiculite may be too soggy for a typical trough (ie. very sharp drainage), but maybe it will work with the plants you have.

OK, so I'm in the hypertufa forum and you're talking about concrete not soil. D'OH!!

I like vermiculite hypertufa more than the perlite but I guess that's just my opinion. Long-term stability of vermiculite concrete products is excellent, all the peat will be gone long before the vermiculite goes anywhere. It is heavier than perlite and seems to be stronger, but I use sand (or reinforcement) anyway for extra strength.

Here's some pictures of vermiculite hypertufa.

Smooth side, against mold:
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Rough side:
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And here is vermiculite concrete, no peat moss:
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Thanks for the info. Did you ever try replacing the peat moss with vermiculite and using portland, vermiculite and perlite?

I made a trough this week with portland and equal parts of vermiculte and perlite. Can't tell for sure about the weight yet because it is still wet (hope the wretched thing lightens up 'cause it's large and I can't lift it :)), but it certainly seems to be harder at that initial unmolding stage than my regular things, and also appeared to make the initial cure faster than my usual portland/peat moss, perlite mix.

Haven't decided if I like the texture, etc.; keep you posted.

In my experience adding vermiculite does speed up the curing process or at least the 'hardening' process.
I'm not sure why that is.
I'm not sure it leads to a strong project in the end but it does help speed up the uncasting process.

Vermiculite is in the sand and perlite category - aggregate. Vermiculite isn't a substitute for peatmoss as it isn't organic and it won't rot out or provide the rough "naturally aged" appearance that unsifted peat provides.

I find that vermiculite takes more liquid than sand - sand cement gets soupy fast compared to vermiculite. It is also much softer than sand which makes it carvable even months after curing. My vermiculite-cement castings have taken a lot longer than my sand-cement ones to harden and strengthen...maybe, probably, the extra liquid.

What I like best about vermiculite is the mica content - I like the gold flecks that appear when the surface is sponged or lightly sanded after setting or - even prettier - polished.

Be cautious about that initial hardening. I think it is only due to the vermiculite absorbing water and not due to a real improvement in curing speed. As such, you should continue to moist cure for the normal time.

Thanks for all of the input. The garden folks around here seem to like that old garden trough look and the peat moss helps with that, so I guess I'll continue with the peatmoss. Maybe make a vermiculite/perlite ratio and get some of the gold flecks -- have the best of both worlds!!

The vermiculte ones I made this week are still "cooking" in their plastic bags in the cellar until February, so I'll have to wait and see what happens.