Ferrocement

Ferrocement is a composite material which is used in building or sculpture with cement, sand, water and wire or mesh material—often called a thin shell in North America.

Ferrocement has great strength and economy. It is fireproof, earthquake safe and does not rust, rot or blow down in storms. It has a broad range of applications which include home building, creating sculptures, repair of existing artifacts and building boats and ships.

Construction

The desired shape may be built from a multi-layered construction of chicken wire or other steel mesh, and if needed reinforced with steel wire or steel bars. Over this finished framework, an appropriate mixture of cement, sand and water is spread out. During hardening, the ferrocement is kept moist, to ensure the cement is able to set and harden.

The wall thickness of ferrocement constructions lies in general between 10 and 30 mm (3/8 to 1-1/8 inch). Like other applications of cement, a considerable amount of time may be necessary for the material to fully cure and reach its final strength. Curing time is dependent upon the span or application load, and ferrocement can take a month before it is ready for use. As the cement hydrates, it becomes increasingly strong.

Economics

The economic advantage of ferrocement structures is they are stronger and more durable than other traditional building methods. Houses pay for themselves with almost zero maintenance and lower insurance requirements. Water tanks pay for themselves by not needing periodic replacement.

Cement structures can also be built quickly, which can have economic advantages. In inclement weather conditions, the ability to quickly erect and enclose the building allows workers to shelter within and continue interior finishing.

In India, ferrocement is used often because the constructions made from it are better resistant against earthquakes. Earthquake-resistance is dependent on good construction technique and additional reinforcement of the cement.

In the 1970s, designers adapted their yacht designs to the then very popular backyard building scheme of building a boat using ferrocement. Its big attraction was that, for minimum outlay and costs, a reasonable application of skill, an amateur could construct a smooth, strong and substantial yacht hull. A ferrocement hull can prove similar to or less weighty than a fiber reinforced plastic (fiberglass), aluminum, or steel hull. New methods of laminating layers of cement and steel mesh in a mold may bring new life to ferrocement boat-building.

Advantages

The advantages of a well built ferrocement construction are the low weight, maintenance costs and long lifetime in comparison with steel constructions. However, meticulous building precision is considered crucial here. Especially with respect to the cement composition and the way in which it is applied in and on the framework.

When a ferrocement sheet is mechanically overloaded, it will tend to fold instead of crack or rupture. The wire framework will hold the pieces together, which in some applications (boat hull, ceiling, roof) is an advantage.

A ferrocement construction has 10 to 25% of the weight of a comparable construction made of bricks.

Disadvantages

The disadvantage of ferrocement constructions is the labor intensive nature of it, which makes it expensive for industrial application in the western world.

External links

• FerroBoats.com
• Ferrocement.com (multi-lingual)
  • How to build a water tank
  • How to build a ferrocement house
• Ferrocement Educational Network
• Flying Concrete Steve Kornher's light weight concrete structural & sculptural forms
• CRS Ferrocement Water Tank Construction Manual. An in-depth and user friendly manual for designing and constructing low cost ferrocement water tanks.
• Water Storage book by Art Ludwig, includes Ferrocement Tanks & Excel Water Tank Calculator
• Monolithic Dome Institute Ferrocement dome structures
• Mother Earth News: How To Build A Ferrocement Boatca:Ferrociment