I have that one. Too small. (1/3 cu ft batch) I use Imer workman 250. 9 cu ft drum. Will make 4.5 cuft of GFRC per batch.
I also have used the above mentioned Imer. Gotta be really patient with the mix, for the cement balls up for a long time before it starts to plasticize. Add fiber at the very end, but do it slowly so you don't get clumps of fiber in your mix.
I've been using a SPE Mixit 25 which is fantastic for GFRC, although only slightly more capacity than a large paddle mixer I guess. I usually mix up to around 40kg at a time. What I like is the tub rotates and you can feed your materials in really easily, scrape the sides clean and there's never any danger of dry material falling into mix when you pour it out.
Anyone familiar with the Imer mortarman 120. Says it can hold 3cu. ft. which probably translates into 1.5 cu. ft..
Jeff, I Haven't had luck with a drum mixer for GFRC.
The 120 PLUS is the mixer I use along with a hand mixer for small batches. We use to use a Stone 855PM but the 120 PLUS is smaller(yet still mixes a larger batch), more powerful and mixes batches much better. It is a great mixer for GFRC or any small aggregate mix! It mixes batches with up to 3/8" aggregate. We've sold many and everyone who has is in love with the mixer. Easy to use... plugs into 20amp 110 outlet, is very portable and has plenty of power. It can realistically mix around 2-3 cu ft. depending on the stiffness/fluidity of the mix. Think of it like a big bowl and to the rim it is 4 cu. ft. and with wetter mixes you can mix up to 3 cu. ft. I would also recommend a minimum batch size of 1 cu. ft. (For anything less than 1 cu. ft. we use a hand mixer).
The only issues we ran into is if you dose your AR fibers at the high end the paddles eventually create a snow plow effect with the heavy load of fibers in the mix. To fix just put the machine in reverse(yes it has a reverse) for a couple seconds and then back forward to clear. The other issue with the fibers is the discharge shoot. there is a safety grate that causes the mix to get clogged when there is a high load of fiber. Since it's not a good idea to remove the safety grate we mounted a small pneumatic vibrator to the shoot which causes the mix to flow out well.
All in all it is a giant leap into a quality mixer. If you need a larger mixer the 360 and the 720 are even better but have a larger minimum batch size. We've sold a lot of mixers over the years but the vertical shaft mixers are by far the best at thoroughly and quickly mixing mortar mixes(less than 3/8" agg). I would go as far as saying it's one of the better investments and a must have for most concrete countertop professionals.
Feel free to call if you have any questions/comments
I have the 120 plus, bought it from Tom. Works awesome on sand mixes and agg mixes as well. At first GFRC back mix was great, but lately it is a pain. Now we are blending all the Pozz again and modifying the way we load the mix into the mixer. Cement seems to clump easily now after having it for a good while.
Probably need to adjust the paddles as well. They have adjustments on them. All in all it is a great mixer and have been happy with the purchase. You just need to get comfortable with changing up your loading sequence.
Thanks for the input guys. 120 looks good. Just have to consider price/use. Tom, are you giving any away to nice customers? :)