Some times it's not the mix that causes the problem. Are the troughs sitting out empty in the Winter? Are they in direct contact with the ground? Do they have drainage holes that are plugged with roots and soil? Are there plants growing in them in the Winter? Any details regarding where they are in the Winter would help. Billie

billie ann
Both pieces that had big cracks had been stored on a wood deck under a 6' or more overhang. These pots were sheltered from rain or snow but could have had wind exposure. Each pot had potting soil. Neither pot was watered at all for months. One pot had the remains of annuals that grew in the summer. The other pot had succulants. I actually seemed to have less cracking on empty pots that layed out completely exposed in my yard all winter (I did find a few small cracks though). The cracked pots both have good drainage, 6 - 1/2" drain holes in the bottoms. Each pot had 4 or 5 cracks. Cracks are always through top going 6" inches down sides. Some cracks are hard to see but most are very obvious one is almost 1/32" inch wide. The cracks were big enough the lady was afraid to move the pot for fear it would break apart (unlikely). Soil was good commercial organic potting mix.
I don't suspect mis use or any type of harsh treatment.
I read in the FAQ that Calgary hypertufa left outside all winter didn't crack. I doubt these are freeze thaw cracks. What is a bummer is these cracks are happaning after months and months of looking perfect. I have doped up my new mixes with more and technically better fiber but when can I really be sure I fixed the problem? In concrete there is a shrinkage phenomenon that occurs and causes cracks. Not sure if that is equally true with hyperfufa. I have read other people anidotaly reporting ten+ years use out of their hypertufa.
steve

Ruegge...I appreciate your frustration, but I have never had cracking because of winter weather. I've only had cracking (months down the road) because of a dry, desert environment. I've been making hypertufa for four years and have over-wintered it in Idaho and now Oregon. I've never discovered any cracks. But, I have had a few cracks in on my projects in Yuma, Arizona. And, like you, only on large projects like birdbaths and garden bowls. Never on the smaller projects. I've cured and misted, and it never made a difference, so I don't bag my projects any longer. So, I guess what I'm saying, I don't know what to tell you, except that many of the fibers, curing, and other additives don't seem to help. So, just try using a straight mix of portland cement, perlite, and peat moss and keep it simple.

No cracking here, either - years of complete/total exposure year round - some with plants in - and some not. I hope you find the answer. My recipe is equal parts: peat, perlite, Portland cement.

If you chisel out the cracks and fill them with contrasting colored cement, the effect can be really good.

I had a problem with a large trough (36" in length x approximately 24" depth) cracking. That puppy was very heavy and cracked under the stress of its own weight. It has chicken wire in it, but still got a crack in the middle of the back where it separated about 1/4 of an inch. Perhaps the large vessels require a more sturdy reinforcement on the idea of the re-bar that's used to reinforce large concrete pieces to combat the stress. Never had anything else crack the way this large, rectangle did. The large bowls must have a different weight distribution as they don't pull themselves apart.

I've read that the inside walls should be slanted a little so that the soil/ice expands up and out the top as opposed to pushing straight out against the sides of the trough.
Cracks can come from not packing the mix very tightly. I leave my things out in the Northeast winters - on the ground, empty, full, off the ground, etc. -- any number of ways to see if they will break from ice, etc. and they have all held up -- except the first ones I made and didn't pack, pack, pack which allowed water and ice to get in and break them up.

On the larger pieces, I find that taking the time with the cure is more important than on small pieces that are not exposed to the weight of large amounts of soil, etc. Lately, I've been dumping things into a tub of water for two or three weeks and they seem to cure faster and better. Anyone else tried this and found a difference? I've always kept them moist and sealed up on plastic bags for a month or so, but this seems to be making a difference in the cure. Just my imagination?

Steve, The cracking was probably caused by leaving the soil in the pots. The soil will freeze and expand, breaking the pots. You can leave hypertufa pots outside as long as they are planted with trees, shrubs and some perennials. The roots and woody trunks/stems will take up some of the freeze expansion so the pot doesn't break. You treat these just as you'd treat a straight concrete planter. If no plant is growing empty the soil and either turn upside down or cover with plastic so no water gets inside. If planted and it's sitting on the soil, it doesn't hurt to shove a piece of wood (cedar shingle) under the planter to break contact with the ground. I'd bet on the soil cracking the pots. I'll try to remember to take a pic of a cracked pot from this past Winter. I forgot about it under the deck, no plants were growing in it and I left the potting soil in it. It's got three cracks, running from the top edge down a few inches. Billie

I have a different view point to think about. As you mentioned before, standard concrete has issues with cracking if not properly done. I am not referring to the mix but expansion joints. I have been toying with the idea of hypertuffa projects for a while but have not done any yet. Your problem is exactly why I haven't done any yet. All the projects I want to do are large scale. I don't see any reason hypertuffa would lack the issues of cracking that normal concrete and cement have. My question is what dimensions do you need to apply expansion joints. Does hypertuffa need expansion joints at closer intervals or larger? I considered do a few test pieces and compare dimensions with that of normal concrete. The problem is it can take months or even years for the end results! Surely someone has knowledge of this but who and where? Like normal concrete smaller projects, common among hypertuffa, don't need expansion joints. Even with add mixes normal concrete still needs expansion joints but the dimensions are increased relevant to the add mixes. I just wish I knew where to find some data useful to the laymen.

spat72, Not sure how to take your reply. Do you think we should put expansion joints in our planters? This person made a 5 gallon planter not a roadway, sidewalk or building. Have you ever seen a sidewalk that's pushed up by the soil underneath which is caused by the ground freezing and expanding. Same thing happens when you have soil that's frozen in a confined container. The soil expanse up and out causing cracking. That's why it's recommended to remove soil from planters that aren't planted in freeze-thaw zones. Billie

billie ann
Thanks for the suggestion. It is possible the soil freezes and pushes the walls so hard they crack. This would explain why I didn't see a problem with the empty pots in my yard. Next winter I will try to prove your hypothesis by leaving some exposed with soil in the pots. I would actually be very happy to know that was the only problem. The entire freeze thaw problem may not be hypertufa problem but an expansion problem with the soil. I was guessing the cracks were progressive cement shrinkage cracks. I hope you are right. It would be very difficult to trouble shoot shrinkage cracks. I read on the concrete tech sites that ultra rich portland cement mixtures are actually more shrinkage crack prone. I was running pretty rich mixtures.
Steve

Steve, Of course I'm right! LOL!
If you do a search online regarding Winter care of concrete planters (yes, I know we're working with all different recipes but it doesn't matter. our main ingredient is cement; the glue that holds everything together) you see that many of them tell you to remove the soil or cover them. I've been working with hypertufa and cement items for a long time. I've only lost a planter to Winter cracking due to forgetfulness (is that a word??). I was just reading the care instructions on one site and they give care instructions for an arid climate. What was interesting is that they don't recommend sealing the inside of planters. Seems the planter pulls moisture from the growing medium and that helps in the cure of the planter. Wasn't someone on this site having a cracking problem in an arid climate??!! All I can tell you, is I have planters in zones 3 to 7 and I tell the people the same thing. In Winter remove the soil if unplanted or cover with plastic. It would help if people on this forum went back to listing their zone information. What works for me in my zone isn't always going to work for you. Sorry to beat a dead horse. Have fun! Billie

Hi ruegge. Here is my opinion and cosequently here is where I evoke the wrath of the tufa gods and blaspheme against the holy peat.
My thoughts on hypertufa are well known and documented on this garden web forum.
Dare I suggest you try (try, says I) to construct your project without peat moss of course I do. If your projects negative space can be filled with more than one gallon of water try something else. For weed pots, herb planter or sedum pots hypertufa seems to work really well, beyond that I have my doubts and suspicions. I believe people who post about having cracked pots are truthful; I mean who would post a message admitting to a failing if there was none. On the other hand people who say, "IÂve never had a hypertufa pot crack" well whatever. For those that do they blame everything under the sun  except the holy peat.
I have been in some heated exchanges about tufa and the holy peat. My conclusion is: a bunch of folk who make hypertufa continue to promote their mantra; if it doesnÂt have peat moss, well, then, it just ainÂt hypertufa. (See Wikipedia definition at the end of this harangue.)
Accordingly it is a sacred ternate that, no matter what the ingredient list at the very least the mix must contain peat moss to be hypertufa.
Naturally I disagree but rather than continue a close-minded discussion I simply DONÂT make "hypertufa" I make concrete (look that up for laughs). My pieces are made using just about everything; vermiculite, perlite, sand (both fine and course), latex paint instead of water, metal filings, polystyrene beads (bean-bag beads), anything, BUT I DON"T USE PEAT MOSS! I still have failures but not near as many as I did with the holy peat. Mostly I just get too impatient and move ahead before I should.
Oh, keep in mind if you want to "work" or "tool" the finish, sand will wear away files and metal tools.
IMO use whatever you want to make your project a success and then call it hypertufa, hyperthreefer, or stretch it to be rueggetufa. Most importantly have fun and experiment.

Hypertufa From Wikipedia, the free encyclopedia
HYPERTUFA IS AN ANTHROPIC ROCK MADE FROM VARIOUS AGGREGATES BONDED TOGETHER USING PORTLAND CEMENT.
Hypertufa is intended as a manufactured substitute for natural tufa, which is a slowly precipitated limestone rock; being very porous, it is favorable for plant growth.
Hypertufa is popular for making garden ornaments, pots and land forms. Hypertufa is relatively light compared with terra cotta or concrete and can withstand harsh winters, at least down to -30 °C (-20 °F).
Basic recipe
Using the classic proportions for mortar (1 part cement: 3 parts aggregate) hypertufa is composed of
3 parts Portland cement - Type I
4 parts peat
5 parts perlite
(3 parts cement: 9 parts aggregate) Â 1:3 ratio
Other recipes may call for sand or gravel as aggregates, but they add unwanted weight without necessarily adding strength. To increase structural strength and longevity, synthetic reinforcing fibers (plastics, not fiberglass) and liquid acrylic may be incorporated into the mixture. Powdered mineral colors (in small amounts) tint the hypertufa to resemble natural rock.

Speaking of rocks - this rock (52"l X 32"w X 20"h and hollow) has been through two seasons without a crack.
{{gwi:68313}}

Ducking sniper fire and running for cover!

Robert
p.s. I'm really a nice guy.

Amen. I agree in general. What's in name anyway?
I have nothing against peat. I usually use it, both as purchased and screened. I've also used perlite, vermiculite, coarse sand, potting soil, chopped bark all in varying percentages, and always in combination with differing finishing techniques for a desired appearance while hoping for a piece that is somewhat lighter in weight than concrete.
I also use a small amount of reinforcing fibers in most thoughs "for crack prevention". I'll never really know if fibers help or not, but I have no cracking problem. Of course, I have had a few small cracks along the way after wintering full of soil, but in Alabama the soil never freezes enough to cause the cracks. My philosophy on cracks is--OK I'll just make another one if it falls apart, but no crack has ever been a problem and no one but me ever noticed them anyway.

billie ann - Sorry I didn't mean to imply that a typical planter made of hypertuffa or any simillar mix needs expansion joints. I only question the need of expansion joints in the case of larger projects. As with regular cement this is going to be effected differently based on local environment. Also dimensions, not just hight and width but also thickness, is taken into consideration with normal cements. What about with hypertuffa. Expansion joints don't necessarily need to be strait deep lines. I have seen many hypertuffa walls with varying surfaces such as carving to look like rocks or inlay texturing. I suspect that these designs are an aid to resist cracking on larger projects weather it was intentional or not. I would just like to know if someone has technical info or experience in that regard.

I am wanting to do a raised garden bed wall that is very long and low. 120 feet long x 16 inches high x 4 inches thick. That is a lot of work to later find out I should have done expansion joints. Or that if I did use expansion joints they where not close enough together.

But with small projects, no I don't see a need for expansion joints. Nor do small cement projects. See the relation? Thats my question. At what dimensions do expansion joints become needed.

I also wonder when ruegge mentioned(indirectly) his 5 gallon planter was 80lbs if he is making them very thick walled. Again that might have a relation to expansion issues. But I certainly value the input of those experienced. That I am not.

Take Care!
spat

Robert, Step off your soap box.....er, rock. I don't think anyone here has said you can't use whatever ingredients you want to add to your mix. I've told people that they are wasting their money when adding unnecessary ingredients like fibers for small planters. But that's their problem if they want to do that. I do correct people when they use the wrong terminolgy because it's confusing. We still have people that think their adding concrete to their recipes when it's cement. And how many times do you see on this forum people adding "quickcrete" to their recipes when it's the manufacturer "QUIKRETE". I enjoy working with hypertufa and mortar and lime fresco and want other people who try this to have fun and not be disappointed. By the way, the pot that cracked this past Winter was concrete (portland cement, sand and gravel), no peat moss! Nice legs!
Fred, "What's in a name anyway?" I posted about this once before. The forum got called "hypertufa" cause that's what most of us were making when this forum came into exsistence. But since that time, papercrete, mortar, quickwall, grout and other things have come on the forum. I don't think I've seen anyone told that they can't post here because of the recipe they use.
Spat, I sent you a private e-mail. Billie

Ruegge - Not sure if you're still on this forum, but I was wondering if you ever solved your hypertufa problem?