Hypertufa is an

anthropic rock Anthropic rock is rock that is made, modified and moved by humans. Concrete is the most widely known example of this. The new category has been proposed to recognise that man-made rocks are likely to last for long periods of Earth's future geolog ...

made from various aggregates bonded together using

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th c ...

. Hypertufa is intended as a manufactured substitute for natural

tufa Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertine. ...

, which is a slowly

precipitated In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

rock; being very porous, it is favorable for plant growth. Hypertufa is popular for making garden ornaments, pots and land forms. It is relatively light compared with

terracotta Terracotta, terra cotta, or terra-cotta (; ; ), in its material sense as an earthenware substrate, is a clay-based ceramic glaze, unglazed or glazed ceramic where the pottery firing, fired body is porous. In applied art, craft, construction, a ...

or traditional

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

and can withstand harsh winters, at least down to . Hypertufa was invented for use in

alpine gardens An alpine garden (or alpinarium, alpinum) is a domestic or botanical garden, or more often a part of a larger garden, specializing in the collection and cultivation of alpine plants growing naturally at high altitudes around the world, such as in ...

. Alpine gardeners formerly used antique animal watering troughs, which became rare and expensive.

Composition

Aggregates are generally '' Sphagnum'' (peat moss), sand, and perlite or

vermiculite Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and commercial furnaces can routinely produce this effect. Vermiculite forms by the wea ...

. Coconut coir is coming to take the place of sphagnum moss, as the latter is a very slowly renewing natural resource and the former is a ready byproduct of the coconut industry— it has all of the advantages of the moss but without the environmental costs. To increase structural strength and longevity, polymer fibers, liquid

acrylic Acrylic may refer to: Chemicals and materials * Acrylic acid, the simplest acrylic compound * Acrylate polymer, a group of polymers (plastics) noted for transparency and elasticity * Acrylic resin, a group of related thermoplastic or thermosett ...

, and

fiberglass Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...

may be incorporated into the mixture, along with various grades of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

, pebbles, and crushed rock which add to the final object's overall strength and stone-like appearance though they increase its weight. Powdered concrete dyes (in small amounts) also tint the hypertufa to resemble natural rock.

Example

An example of a hypertufa mortar mix (with classic proportions) is a 1:3 mix of cement-to-aggregate, given by a composition of: *Three parts type I

*Four parts sphagnum or coir *Five parts perlite Restated: Three parts cement to nine parts aggregate (by volume, not weight, very rough measure).

Manufacture

After water is added to the mixture, it is packed into a previously constructed mold, then sealed or covered in plastic and allowed to

cure A cure is a substance or procedure that ends a medical condition, such as a medication, a surgical operation, a change in lifestyle or even a philosophical mindset that helps end a person's sufferings; or the state of being healed, or cured. The ...

. The object may be carefully removed from its wrapping after 2–3 days for trimming and/or distressing, after which it is re-wrapped for another 3–5 days at which time it is no longer considered "green" and can be handled & worked without danger of breakage. It is then re-wrapped, moistened if necessary & left to cure for a month. The longer the cure, the stronger the hypertufa. After the hypertufa object is completely cured, it is removed from the plastic, rinsed thoroughly, and allowed to sit exposed to the elements for several more weeks to reduce its otherwise-toxic surface alkalinity. It can then be used to hold plants.

References

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External links

Video and text instructionsGardenweb forum discussing Hypertufa techniques
What to plant in your finished project. Garden features Concrete

Composition

Example

Manufacture

See also

References

External links