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Cement and perlite vs. cement and sand

April 2, 2008

I've been toying with the idea of using perlite instead of sand with cement. Ie. 1 part cement and 2 to 3 parts perlite to make a lighter mix and curing it as one does with the cement/sand mix. My objection to using a hypertufa recipe with peat is the cure time. I'm hoping I could cut down the cure time with the perlite. Has anyone tried this? What do you think?

Comments (20)

  • valolson1

    For a light mix I often use this recipe...one part portland cement, two parts peat moss and three parts perlite. The texture is wonderful, the cure time is no different and it's light, light, light. It's no good for birdbaths but wonderful for plant containers.

  • tehuti

    fleur I posted this opinion before but since you asked:)
    My 2 cents:
    I have stopped using peat moss in my projects. By definition my projects are not hypertufa and that is okay. Most of what I have read on various forums and message boards verifies my experiences with "tufa"; a very high failure rate, long unnecessary curing times, eventual collapse, and the addition of various additives necessary to strengthen the structure, although many additives (aggregates) do little to increase the strength when peat moss ia part of the mix.
    My research and hands on experiences suggest peat moss is a part of the hypertufa mixes for two main reasons: weight, peat by volume reduces project weight by at least 50% depending on the mix and surface appearance, peat will eventually dissolve, or decompose leaving a pock-marked surface simulating volcanic rock. However, tufa is not volcanic rock.
    "(Tufa is the name for an unusual geological form of calcite rock. Tufa is a rough, thick, rock-like calcium carbonate deposit that forms by precipitation from bodies of water with a high dissolved calcium content. Tufa is not to be confused with tuff, which is volcanic.
    Tuff (from the Italian "tufo") is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption.
    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.
    The basic recipe for hypertufa uses 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
    or 3 parts cement: 9 parts aggregate
    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. ------ From Wikipedia, the free encyclopedia)"
    My mixes are variations of Portland cement, sand, perlite, and vermiculite. Sometime I use all ingredients. Usually I use sand only in projects I do not intend to carve or manipulate the shape after or during construction. The sand will eventual destroy most files and blades.
    Here are a few references I use:
    Sculpting with Cement by Lynn Olson uses cement and steel wool to create "fiber" cement and a mix of sand/cement for sculpting.
    Sculpture as Experience by Judith Peck covers the use of Portland cement and vermiculite (two parts vermiculite one part cement) as a sculpting medium.
    Sculpture in Concrete by John Mills states "the sculptor usually achieves the tensile strength so important to him, by making freestanding forms hollow, working on the principle that, by its very nature, a hollow sphere has a greater strength than a solid sphere, and a tube has a greater tensile strength than a solid rod."
    Creating with Concrete by Sherri Warner Hunter has 13 different mixes for cement sculpture use and three slurries to use in connecting concrete pieces.

  • billie_ann

    fleur, There is no difference in the cure time for any of the hypertufa, concrete, mortar recipes that do not use an excelerator. Some sand should be used in most recipes.

    r_murray, Hypertufa planters and troughs lasts a long time with proper care just as a concrete planter. I haven't read anything about a high failure rate, there is no long cure time, I've got planters that are 20 years old and there is no need for additives-many people start experimenting then start posting that you have to use fibers or excelerators or superplastizers. It's not true.
    The original hypertufa recipe came from England and was equal parts cement, sand and peat moss. And the real tufa rock is porous with a pockmark look. When the peat moss is washed or aged out of the hypertufa planters/troughs you get that same porous, pockmarked look. Google a picture of tufa rock. Billie

  • tehuti

    billie_ann I won't argue with success: good for you.
    BTW, did you make those 20 year old planters?

    I was not as successful with peat moss so I don't use it. What else can I say?

    Not to beat a dead horse, but as far as complaints and failures etc, well - I guess we don't read the same post.

    amaretto Sat, Dec 9, 06 at 17:07

    OK, first of all, I want to thank Billie_Ann for cheering me on. Had it not been for the support, I would have given up and never taken on this project. After my last project failure,

    My google search:
    "Trying to get advice from experts on safe curing times for concrete can be frustrating. An authoritative (British) textbook on building science says that trench foundations, for example, should be left for a week before wall-building begins. Having read this, I asked the Rhodes University Architect whether he agreed with it. Perhaps not a week, he said, but a minimum of three days, certainly. A little later I asked a local building contractor whether he left trench foundations for three days before building on them. Perhaps not as long as that, he answered, but 24 hours, certainly. You must leave them for 24 hours."

    Two questions:
    1.Can you handle a hypertufa pot in 24 hours?
    2.Did you really have frozen leaves in the freezer? No food in the freezer just leaves!


  • Fleur

    Thank you all for your advice. In the interest of science, a phrase I use for my "experiments", I believe I'll use 1 portland to 1 1/2 each sand and perlite.

    By the way, several years ago I cast a lovely rhubarb leaf from a leaf I had in the freezer for a few weeks.

  • elephantear

    Robert....In regards to what you posted above:(Most of what I have read on various forums and message boards verifies my experiences with "tufa"; a very high failure rate, long unnecessary curing times)

    Robert, Sound's like you don't believe in what we are doing here-HYPERTUFA and you appear to know all there is plus more than there is to know about this subject. This form is called the HYPERTUFA form where we enjoy hearing and sharing about HYPERTUFA - in most cases it's just a hobby, something that is fun to create, which many can tell you, they've had much success. After a time if something crumble and breaks it breaks-we are having such fun playing in the mud we throw away the pieces and build another! We like to hear of the many 'joyful' success stories here and to build confidence and to possible help our 'fellow tufa' artists and newbies wih new ideas or who's tufa and or cement projects may have failed.
    my 2 cents worth -Wendy

  • tehuti

    Elephant ear,
    I am interested in creative ideas - both old and new and continue to try new things discarding any that do not fit my requirements. I think it's wonderful you have found your niche.

    Yes, certainly it is a hypertufa forum and there are many people that are involved in, as you put it, "playing in the mud". However, there is no forum for "cement" artist and a search on the Gardenweb for cement brings one inevitably to the Hypertufa forum where one can logically presume all cement related topics can be found. And it appears there are also many people working in cement-based mixes other than those containing peat moss. I regret there is nothing, well nothing I have found yet, that reduces the weight of cement based pieces as much as peat but that is just the way things are.

    This situation is quickly getting out of control.
    There was a question on the hypertufa forum (Cement and perlite vs. cement and sand),
    "My objection to using a hypertufa recipe with peat is the cure time. I'm hoping I could cut down the cure time with the perlite. Has anyone tried this?"

    I offered my OPINION. Thats it - my OPINION. It is not my intention to step on anyones toes I have made several successful hypertufa pieces and still have them in my garden one of my favorite pieces is a solar-powered, hypertufa lantern.
    but I have made many other projects quicker and more successfully without peat moss.

    Whether you use peat moss or not I wish you all the success possible with your choice.


  • elephantear

    Robert I do agree this form is for people who work with cement, I'm one of them. The way I read your first lengthy post above could possible appear to 'newer' people who come here for advice on hypertufa as "it don't work, it don't last - so why would anyone want to bother with any part of making Hypertufa". I'm no pro' but I know there are still some here who could answer the question above in simpler terms, so if any of you are reading this please jump in. Wendy

  • valolson1

    I've been doing "hard core" hypertufa for over four years and I've never experienced a high failure rate. In fact, most projects get more stone-like with time. I've discovered that for best results, I simply use one part portland cement to two parts perlite and two parts peat moss. To be honest, I don't even put my projects into a plastic bag and cure slowly. Once they go through the first cure (a day or so), I wire brush, carve and enjoy them immediately. But, I like to keep things simple.

  • Fleur

    I think I'll have time to mull over everyone's thoughts before I start any projects. We got 3 more inches of snow last night.

  • fredw10

    I have experience making and teaching hypertufa for about six years, and I believe from some of what I read here that part of the problem many folks have is that their expections are different from reality.
    I don't quite understand complaints about "excessive and unnecessary cure time".
    If I experience a long or short cure time, it is always my fault for having the mix too wet or not keeping the piece covered and damp while cureing or ignoring the fact that the temperature may be 50 degrees or 90 degrees.
    I don't really know if adding strengthening fibers is necessary or not. I always use them, and never have a strength or cracking problem, so why not use them. I read the comments about the extra work fibers require and am ammused. When adding a small handful to a wheelbarrow of mix it takes perhaps two minutes to break up and add the fibers. Sure you need to burn off protruding fibers later--again another two minute job, and if you miss some, no one will ever know.
    For those complaining about excessive weight: As far as I'm concerned it is all pretty heavy, and the ingredients I use are to give the desired appearance- not lighter or heavier pieces.
    Peatmoss: I almost always use it without problems.
    Sand: Good for strength as in stepping stones, but it does make for a heavy piece. I also use perlite, vermiculite, and have even tried potting soil and ground bark.
    If I encounter a "heavy" piece it is again usually my fault. In troughs and planters I aim for a wall thickness of 1 1/2 inches, but I don't worry about being exact. If I make two identical pieces and end up with a wall thickness of 1 3/8 on one and 1 7/8 on the other, the thicker one will weigh one third more than the other.
    Sure I have had pieces "fall apart", but that is always my fault for being impatient and trying to remove the mold too soon or not being careful about the way I grab the fresh piece when turning it over.
    These ar just a fwe thoughts. Keep experimenting and learn from failures as well as from your successes.

  • valolson1

    fredw is right. Most mistakes don't come from the cure time but the handling right after you make the project. I've had my share of "fall aparts" but it's usually due to my impatience. The only time I've had cracking is when I made pieces in the desert dryness and every once in a while you'll get a crack. I've had this happen on projects I've bagged and misted for a few weeks, and projects I've enjoyed immediately. It really doesn't matter. I've never had a project crack when I've made projects up north. It has more to do with the desert dryness, then the mixture. So, I learn to live with a crack every once in awhile.

  • billie_ann

    Regarding the name of this forum. We use to post about hypertufa and cement items in the Accoutrements and Garden Junk forums. There were a lot of us then and we asked "Spike", the owner of this forum at that time for our own spot. It's call Hypertufa but it's about anything with cement. If you read back through old threads this discussion comes up from time to time.
    1) I made the 20 year old planters.
    2) The quote from an old thread "amaretto Sat, Dec 9, 06 at 17:07
    OK, first of all, I want to thank Billie_Ann for cheering me on. Had it not been for the support, I would have given up and never taken on this project. After my last project failure,"
    If you had look at his posts about his two previous projects that fell apart he made them with cement and sand, no peat moss. And I think, but I'm not postive that he used too much water.
    3) Your "google search" results are from Science in Africa and refer to the footings of a garage that was being built and the need to wait 24 hours before building on the footers. Don't quite know why you referenced that BUT leaf castings can be unmolded in as little as a couple hours. Small to medium planters can be unmolded in 24 hours, gently! Wax milk cartons filled with a cement/vermiculite mix for carving can be unmolded in 45 minutes to an hour.
    4) If you've been on this forum and looked at old threads I've stated repeated that you can GENTLY clean or carve in 24 hours most size planters that people on this forum make.
    5) I think the person with the leaves in the freezer and no food was Marly. I think I may have commented on it. I think fleur had some leaves in her freezer at one time.

    This is a fun forum and a great place to exchange information. Billie

  • garden-smitty

    I love working with hypertufa. I have had a couple of failures but only when I did not add sand. Sand does make the trough a little heavier but it also makes it stronger. I left mine out this winter with sedums in them and they came through great. We had lots of snow and minus temps and they look really good. I have purchased some of the additives but have not used them. I like casting leaves also but do not use the hypertufa for them. My recipe is: 1 part Portland cement,one part peatmoss,one part perlite,one part sand. For the leaves I use:one part cement to 3 parts sand. Its fun to try other peoples ideas also. But this is what works well for me.

  • Fleur

    To all. I don't want to make hypertufa. I just want to replace the sand in the regular mix with perlite. No sand, no peat. I think I'll try that as soon as the weather warms up...July maybe. It's just an experiment, after all. I might also try it with just cement and vermiculite although I think that might crumble due to the layers vermiculite has where cement couldn't "penetrate"...(cover). I'm just curious as to how it will turn out. If it fails, it fails and I'll have learned something. I'll keep you posted.

  • eva1429

    Hi, Fleur ~

    A few summers ago, I cast this large cone-shaped torch holder using a mix of 1 part cement to 3 parts perlite. I love how lightweight it turned out.

    But my problem was my impatience. I couldn't wait to put the cone on a pipe in the ground. The cone was too green and developed a stress line.

    Fleur, when I try this mix again, I'll throw in some fibers and use bonding agent/admix in the water. I can see this mix being very durable when allowed to cure properly.

    Please let us know your experience with it.


  • tamahlee

    Wow .. you guys do beautiful work! I love the leaf bricks! What a cool ideas... I was wondering about your home made playdough impressions .. do you use the air dry kind or you bake dry..and how do you get it to not stick to concrete when demolding? I have used the drywall compound by Lepage called Poly Instafill..in the same way but more expensive lol. Silly me! You are inspiring! Thanks for posting your pictures!

  • spat72

    fleur do not be discouraged by failures of peat. more on that in a moment.

    I will start by stating I have no exp with hypertufa. That is what led me here. However as most things I do, I try to think of all things untried from a start on the foundation of physics (career habit). I think your suggested mix will be ok with 1 additional additive, a plasticizer. My first thought is with such a large percentage of perlite your mold will have a sever case of crumbling due to the excessive expanding and contracting of the perlite material. This type of activity is only 1 of many cuases for cement base products to crack but probably the most common. I would try starting with very small batches for something simple like maybe some coasters for the coffee table. Just add some felt or cork to the bottom for protection of the table.

    In my search on the web I have found tons of various lightweight cement ideas but the Hypertufa seems to be the most practical for home use. There are a lot of other lightweights out there but they employ special manufacturing technics that are not possible/practical for small scale use.

    On your problems with the peat. I have read that the best way to prepare the peat is to completely break it up and soak it in water for a few minutes then squeeze the excess water out before adding to the mix. Not sure how peat is sold in your area but for me it is sold in compressed blocks and if I took a small clump and tossed it in water it would simply float for hours. I have to literally pulverize it before use. I recall the first time I used peat was for a mulch and the water just flowed right off the bed. So I had to go thru the whole bed and rake it all out. I learned it wasn't good for mulch so I mixed it in the compost pile, it did wonders there.

    I don't mean to be harsh but I find it difficult to think you have done it all correctly when so many people have succeeded. Keep in mind curing is critical and curing all depends on both ambient temp and humidity plus the moister content of the mix. In my area the only successful crack free cement projects I have seen is when the project is continuously kept moist for several days. The real tragedy in that is I rarely see that done. I work in the construction field and most houses I go to have cracks in the driveways and often in the foundation yet the contractors seem to just consider it normal. I personally would never buy a home with foundation cracks when it is only a few days old.

  • Fleur

    I'm not using peat and the one hypertufa I made was/is just fine. Now I'm thinking of trying perlite, admix and quikwall, perhaps in equal parts. The quikwall has lots of good stuff in it...fibers and some waterproofing ingredient. I can't wait for wrm weather so I can try some of these ideas. Not hypertufa though. I use all my peat in the flower beds.

  • wannadanc

    Back when I was doing this all the time, I bought a freezer just so that I could freeze leaves - honest to Pete, I did that. The one leaf type that let me down was rhubarb - and, of course, it was the one leaf I had in HUGE supply. The problem was that the freezing released the oxalic acid in the leaves (that is the part of rhubarb that makes it sour) ....and that acid did not allow crete to set up. I was making portland cement/sand/admix leaves. This was the ONLY time I had set up failure. I am impressed that someone here posted that they were able to cast a thawed out rhubarb.

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