Hypertufa – A Hybrid

Hypertufa is a hybrid concrete that is very light and very strong, much lighter than regular concrete, and is perfect for making sculptures, waterfalls, reptile landscapes, planters, pots, fake rocks & trees, cliffs, and other things typically made from poly-resins or concrete, etc..

The sand has been replaced by Sphagnum Moss (peat moss) a very light moss

The gravel has been replaced by Perlite, a weightless volcanic glass. the mixture is reinforced with fiberglass strands

Tufa is a type of naturally porous rock with holes in it, and Hypertufa is designed to look like real tufa rocks by having the peat moss decompose away after a short time, leaving openings and holes in the structure once the peat moss is gone. Thus, it is very important to sift the peat moss to have smaller pieces only, especially where holding water is important, as any big pieces in the peat moss mix will leave holes which drain water too fast, and are too large for naturally looking tufa.

The basic procedure is as follows:

  • mix the dry ingredients together in a plastic bucket
  • add water little by little, slowly
  • mix with your hands while wearing rubber gloves
  • when it forms a ball and just a few drops of water come out, let it rest 10 minutes
  • mix it up again, add more water if its too dry, or more cement and peat moss if its too wet

Recipe 1:

  • 2 parts Portland Cement (波特兰水泥 borelan shuini)
  • 3 parts sifted Peat Moss (泥煤苔 nimei tai) (Sphagnum Moss) available in garden shops, you need to sift out big sticks, etc, yourself.
  • 3 parts Perlite (珍珠岩 zhenzhu yan) or Vermiculite (蛭石 zhishi), also available in garden shops
  • Fiberglass strands, as reinforcing fibers, about a handful (found at hardware stores, or maybe some concrete stores, and maybe some auto body or boat repair shops), you may have to cut them yourself to be 2-4 cm in length

Recipe 2:

  • 1 part pre-mixed Portland cement/sand mix
  • 1 part peat moss
  • 1 part perlite or vermiculite
  • water to make mud pie consistency

too much water will make the final product crumble and fall apart, add water little by little until it sticks together

Recipe 3:

  • 1 part portland cement
  • 1 part builders sand
  • 2 parts peat moss
  • Acrylic fortifying additive
  • Enough water to make a mud-pie consistency

Recipe 4:

  • Basic Hypertufa Recipe A
  • 1 part Portland cement
  • 1-1/2 parts peat
  • 1-1/2 parts perlite

This recipe is suggested if you want the ability to carve a pattern or design into the ‘tufa. It is workable while still quite damp. This would also be a good basic “granite look” recipe. (Use white Portland cement.)

Recipe 5:

  • Basic Hypertufa Recipe B
  • 1 part Portland cement
  • 1-1/2 parts peat
  • 1-1/2 parts vermiculite

Vermiculite, instead of perlite, will add a little extra weight to your object. There is also a little sparkle to the vermiculite, which can be a nice touch. This recipe is also carvable as the one above.

Recipe 6:

  • Hypertufa Recipe For Added Strength
  • 1 part Portland cement
  • 1 part sand
  • 1 part peat
  • 1 part perlite or vermiculite

Note this is using an equal ratio of all ingredients. This mixture will give you a stronger ‘tufa. It will be a bit heavier than the previous 2 recipes. Your choice of sand (textures vary here, too) will affect the final coloration of your object.

Recipe 7:
Hypertufa Recipe With Fiber Mesh For Added Strength

  • 2 parts Portland cement
  • 2 parts perlite
  • 1-1/2 parts peat moss
  • 1/2 part coarse sand
  • 1 large handful nylon fiber mesh

Note: The amount of mesh you need for a hypertufa project is very small in relation to the other ingredients. Ratio example: For each 1 cup measure of your dry mixed ‘tufa’ ingredients, the fiber mesh needed would be no more than a tablespoon.

Other fibers you can use are steel fibers such as Carbon etc., or synthetic fibers such as Polypropylene fibers etc.

White wood glue can also be added to the mix in place of some water to strengthen the mixture.

You can also add powdered concrete dyes before adding the water, or liquid concrete dyes at the same time as the water or after the water is mixed in. If adding any color, be sure to use white Portland cement so the color will show up nicely. Mix colors less for marbling effects

For example, 3 buckets of sifted Peat Moss, 3 buckets of Perlite, 2 buckets of Portland Cement, 1 or 2 rice bowls of loosely packed reinforcing glass fibers, and water.

Measure the peat moss, perlite, Portland cement, and reinforcing fibers into a plastic container. Using gloved hands, mix the dry ingredients.

Add water slowly, mixing with your hands until the material is about the consistency of cottage cheese, or slightly drier than regular concrete. The total amount of water needed will depend on the dryness of the peat moss and the humidity in the air. The mixture shouldn’t be runny – too much water and you’ll get a weak container. A free-form container needs a drier mixture so that it will hold its shape.

To test the concrete, grab a handful of the mixture, and squeeze it; it should hold together and only a little water should come out

Because its light, you can make molds to shape and form it from cardboard boxes, or Styrofoam panels. you can create the molds my cutting the Styrofoam and pinning the pieces together with bamboo cooking skewers, then cover the entire thing with plastic bags. The Hypertufa wont stick to cardboard, plastic, or Styrofoam, but it will stick to wood, metal, and other things, so whatever you use, its a good idea to cover it
with plastic first, and cover the plastic with a release agent

Release Agents: (to be used on top of the plastic coating over the mold)

  • Vaseline / Petroleum Jelly
  • Motor oil (new or used)
  • Cooking spray (i.e. PAM is one brand)
  • Vegetable oil
  • Mineral oil
  • A blend of equal parts mineral oil and corn oil
  • WD-40

If you are using something made from terra cotta as a mold, first soak the item all night long, then cover it with a mixture of mineral oil & corn oil, or it will not release.

You can form it into any shape you want, around anything at all, even a pile of clothes covered in a plastic bag could be a mold for a bowl or small pond

You just mold it like you would mold plain mud, just set the Hypertufa onto the plastic-covered mold in the shape you want with your hands and pack it down firmly

Be sure to include any drainage pipes, supports, compartments, or other characteristics you want built into your final product.

After setting the shape, you can use a knife or other tool to carve designs or other things into the product

Curing Hypertufa:

The initial curing stage takes from 14 to 48 hours, the longer the better, so during this stage you need to cover your project with plastic and keep it wet. The plastic makes it cure more slowly, and slower curing produces a strong product. Put it in a large heavy-duty plastic bag and seal it up completely tight, after misting your product with water.

After a day and a half, test the hardness of the mixture with your fingernail. If you can scratch the surface, the mixture is still too soft and should be left for a few more hours and then retested. When it requires a screwdriver to scratch the surface, the mold may be removed,

After the first stage of curing, the product has hardened enough that you can begin to smooth the corners and tops with a wire brush, and adding other textures if you like. be careful, its still, not dry and can easily be broken. Be sure to wear gloves, as the hypertufa is still wet.

It is now ready for the second stage of curing. The second stage of curing takes about three or four weeks, so leave the product wrapped in plastic for about four weeks, being sure to wet it down daily, or set up a few misters inside the bag, until it finishes curing in 4 weeks

After four weeks, your product will be a lighter color and will weigh less, and when you tap on it, it should sound hollow. but you still need to wear your gloves, as its still alkali. which brings us to the final step:

Leaching Lime Out:

  • The last step is to leach out the strong alkali or free lime contained in the Portland cement, because a heavy concentration of lime will kill plants, reptiles, fish, and other animals.
  • You can leach away the lime by the following methods:
    • Filling the product with water. Over the next ten days, refill the product whenever it’s empty.
    • Submerge the product in water, and change the water every day for 3-5 days
    • Hose the product down (rinse it well) 2 times a day for 3-5 days
    • Turn on the waterfall pump and let it run all day, changing all the water out every day for 3-5 days
  • After leaching, test the Ph Level with a test kit form the fish store., when it reads acceptable, drain the water one last time, and refill it
  • Otherwise, you should spray the product with water every day for the next 10 days, and keep it covered in plastic
  • You can also combine steps 2 & 3 to add water continually while its covered in plastic for about 1 month to 6 weeks, the water makes it cure more slowly, and produces a stronger product

Finishing Touches:

The finished product will be naturally porous, but if you want additional drainage, or need to add holes for any reason, drill holes using a masonry bit.

You can also air brush the product, or use spray paint cans, or paint brushes. If adding color, use White Portland Cement in the mixing process.

Below is color chart for concretes: Concrete Color PDF

Waterproofing:

Because Hypertufa is naturally porous, it will drain water out naturally over time. So if your structure needs to hold water as a watering hole for lizards, snakes, birds, or other pet creatures, or if it is part of a pool at the top or bottom of a waterfall, or is going to be used to hold goldfish or Koi, or will be used as a bird bath, or as a stream bed etc, etc, it needs to be waterproofed. The waterproofing only needs to be applied on the area which will hold the water.

Here are some ideas for waterproofing. most good cement shops carry good waterproofers:

  • Use a brush-on liquid latex liner
  • Use a spray-on waterproofer
  • Use liquid fiber-glass resin (from auto / boat supply & repair shops) mix with hardener, brush inside surface, let it cure for 12 hours, apply a 2nd coat, and repeat cure.
  • 1 part cement & 3 parts sand, and add water, to brush on a coat of waterproofing
  • Hot liquid Paraffin
  • Use Thoroseal Cement-based waterproofing, may paint it with latex paint
  • Some water-proofing agents may be found at Home Improvement Stores
  • Use 3-5 coats of waterproof concrete sealant (not “water-resistant”)
  • Use pure poly-modified cement, with (polymer added)
  • Use pure Portland cement and water only
  • Use roofing sealant
  • If your finished product will be used to hold fish, be sure it is non-toxic before you buy it.

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