Livnlife,
I can only imagine what went wrong.....too cold, not enough water...bad portland ?? I hope someone here can answer for you.
But I do want to tell you I have been succesful at taking a hammer, and beating my 'mistakes' back to almost powder - no chunks-, adding portland and getting a nice result. If yours is only crumbling, then you won't have to work too hard.
Marcia

If I were to guess it may be not enough water. Or you did not give them proper time to cure. Or maybe you did not mix the water completely with the ingredients. If you have some dry spots in the mix it will not bond well. Every particle of portland should get wet.
It is a trial and error process - I have made many mistakes - some resulted in great containers and others end up as landfill. So continue to make tufa until you get it the way you like.

My no brain formula - I use a 1 gal container to measure.
1 portland, 1 peat 1 perlite 1 water. Add water slowly until you get a moist mix. You should be able to make a ball of tufa and squeeze a drop or two of water out. You may not use all of your water or you may need a little more. This will depend on the temp outside and how moist your peat moss is already.

LOL - Mike

Here is a link that might be useful: my blog

Thank you so much for your responses!
I think your right about the water...that one is the tricky part for me...too little...too much...but I kept trying and have had some success!
I even played around with some other recipes and tried some papercrete, too.
I think I have become addicted! I work in our garage which also houses my washer and dryer so during the winter months I keep it around 60 degrees (it is very well insulated)...can I still do my concrete projects without any ill effects? I am up here in Montana so we definetly have freezing temps outside.

Here is a link that might be useful: {{gwi:74545}}

I think I read somewhere that the peat should be moistened first so I guess I'd use some of the water to do that and then add the other ingredients amd mix thouroughly, then adding enough remaining water to have it "pack" when you grab a fistful. Also pack tightly when putting it in your mold. Just a thought.

My guess is that your mixture was too dry. Peat and vermiculite both absorb water. This absorption reduces the available water of the mixture and can really foul up the chemical reaction of the concrete.
Don't get in a hurry to cast your 'tufa mix, give the ingredients time to absorb water. Also, be willing to add SMALL amounts of water while you're working with the 'tufa. If it feels dry or crumbly it's probably too dry.
Keep in mind the age of your ingredients too. Fresh peat tends to absorb water more quickly than old. Prewetting the peat helps speed this process but be mindful of the amount of water you then add to your 'tufa mixture. Too much water can be harder to remedy than too little.
Good luck!