Hypertufa

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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).

Hypertufa was invented for use in alpine gardens. Alpine gardeners formerly used antique animal watering troughs, which became rare and expensive.

[edit] 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

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.