Self-Reliance Handbook/Ferrocement Construction
The term ferrocement is most commonly applied to a mixture of Portland cement and sand reinforced with layers of woven steel mesh and closely-spaced small-diameter steel rods. It is normally used in the form of thin curved sheets to make hulls for boats, shell roofs, water tanks, etc. It has been used in a wide range of other applications including sculpture and prefabricated building components. The term has been applied by extension to other composite materials including some containing no cement and no ferrous material. These are better referred to by available terms describing their actual contents.
Ferrocement has relatively good strength and resistance to impact. When used in house construction in developing countries, it can provide better resistance to fire, earthquake, and corrosion than traditional materials, such as wood, adobe and stone masonry. It has been popular in developed countries for yacht building because the technique can be learned relatively quickly, allowing people to cut costs by supplying their own labour.
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 that the cement is able to set and harden.
The wall thickness of ferrocement constructions is in general between 10 and 30 mm (3/8 to 1-1/8 inch). Like other applications of cement, about 28 days is necessary for the material to fully cure and reach its final strength, unless chemical accelerators or steam curing are used. As the cement hydrates, it becomes increasingly strong. Depending on the span of the building element or structure, and the load to be applied, it may be possible to put it into service prior to full curing.
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 only 10 to 25% of the weight of a comparable construction made of bricks
The economic advantage of ferrocement structures is that 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 more resistant to 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 to be of similar or lower weight 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. Template:Ferrocement