Ferrocement
Encyclopedia
The term ferrocement is most commonly applied to a mixture of Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

 and sand reinforced with layers of woven or expanded steel mesh and closely spaced small-diameter steel rods rebar
Rebar
A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...

. It can be used to form relatively thin, compound 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 terms describing their actual contents.

The term "ferrocement" was given to this product by its inventor in France, Joseph Monier
Joseph Monier
-Overview:Joseph Monier was a French gardener and one of the principal inventors of reinforced concrete....

. At the time, (1850's) he wanted to create urns, planters, and cisterns without the expense of kiln firing. In 1875 he created the first steel and concrete bridge. The outer layer was sculpted in its wet state to mimic rustic logs, thereby also introducing Faux Bois
Faux Bois
Faux bois refers to the artistic imitation of wood or wood grains in various media. The craft has roots in the Renaissance with trompe-l'œil. It was probably first crafted with concrete using a steel armature by the inventor of ferrocement, Joseph Monier. In 1875, Monier created the first bridge...

 concrete into practice. (Recent trends have "ferrocement" being referred to as ferro concrete or reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

 to better describe the end product instead of its components. By understanding that aggregate
Construction Aggregate
Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world...

s mixed with Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

 form concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, but many things can be called cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

, it is hoped this may avoid the confusion of many compounds or techniques that are not ferro concrete.)

Ferro concrete 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 labor. In the 1930s through 1950's, it became popular in the United States as a construction and sculpting method for novelty architecture
Novelty architecture
Novelty architecture is a type of architecture in which buildings and other structures are given unusual shapes as a novelty, such as advertising, notoriety as a landmark, or simple eccentricity of the owner or architect. Many examples of novelty architecture take the form of buildings that...

, examples of which created "dinosaurs in the desert", or a "giant pair of cowboy boots and hat" for a service station.

Construction

The desired shape may be built from a multi-layered construction of mesh, supported by an armature, or grid, built with rebar
Rebar
A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...

 and tied with wire. For optimum performance, steel should be rust-treated, (galvanized) or stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....

. (In early practice, in the desert, or for exterior scenery construction, "sound building practice" was not considered, or perhaps unknown as it grew in some cases, from a folk craft tradition of masons collaborating with blacksmiths.) Over this finished framework, an appropriate mixture (grout
Grout
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints . Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel...

 or mortar
Mortar (masonry)
Mortar is a workable paste used to bind construction blocks together and fill the gaps between them. The blocks may be stone, brick, cinder blocks, etc. Mortar becomes hard when it sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a mixture of sand, a binder...

) of Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

, sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

 and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 and/or admixtures is applied to penetrate the mesh. During hardening, the assembly may be kept moist, to ensure that the concrete is able to set and harden slowly and to avoid developing cracks that can weaken the system. Steps should be taken to avoid trapped air in the internal structure during the wet stage of construction as this can also create cracks that will form as it dries. Trapped air will leave voids that allow water to collect and degrade (rust) the steel. Modern practice often includes spraying the mixture at pressure, (a technique called shotcrete
Shotcrete
Shotcrete is concrete conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique....

,) or some other method of driving out trapped air.

Older stuctures that have failed offer clues to better practices. In addition to eliminating air where it contacts steel, modern concrete additives may include acrylic liquid "admixtures" to slow moisture absortion and increase shock resistance to the hardened product or to alter curing rates. These technologies, borrowed from the commercial tile installation trade, have greatly aided in the restoration of these structures. Chopped glass or poly fiber can be added to reduce crack development in the outer skin. (It should be noted that chopped fiber could inhibit good penetration of the grout to steel mesh constructions. This should be taken into consideration and mitigated, or limited to use on outer subsequent layers. Chopped fibers may also alter or limit some wet sculpting techniques.)

Economics

The economic advantage of ferro concrete structures is that they are stronger and more durable than some traditional building methods. Depending on the quality of construction and the climate of its location, houses may pay for themselves with almost zero maintenance and lower insurance requirements. Water tanks could pay for themselves by not needing periodic replacement, if properly constructed of reinforced concrete
Reinforced concrete
Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

.

Ferro concrete structures can 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
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, ferro concrete 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 concrete.

In the 1970s, designers adapted their yacht
Yacht
A yacht is a recreational boat or ship. The term originated from the Dutch Jacht meaning "hunt". It was originally defined as a light fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries...

 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
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 hull. New methods of laminating layers of cement and steel mesh in a mold may bring new life to ferrocement boat-building. A thorough examination of reinforced concrete and current practice would benefit the boat builder.

Advantages

The advantages of a well built ferro concrete construction are the low weight, maintenance costs and long lifetime in comparison with purely steel constructions. However, meticulous building precision is considered crucial here. Especially with respect to the cementitious composition and the way in which it is applied in and on the framework, and how or if the framework has been treated to resist corrosion.

When a ferro concrete sheet is mechanically overloaded, it will tend to fold instead of break or crumble like stone or pottery. So it is not brittle. As a container, it may fail and leak but possibly hold together. Much depends on techniques used in the construction.

Please note: Much more information for projects of reinforced concrete has been updated regularly, than for products that we call ferrocement or ferro concrete.

Disadvantages

The disadvantage of ferro concrete construction is the labor intensive nature of it, which makes it expensive for industrial application in the western world. In addition, threats to degradation (rust) of the steel components is a possibility if air voids are left in the original construction, due to too dry a mixture of the concrete being applied, or not forcing the air out of the structure while it is in its wet stage of construction, through vibration, pressurized spraying techniques, or other means. These air voids can turn to pools of water as the cured material absorbs moisture. If the voids occur where there is untreated steel, the steel will rust and expand, causing the system to fail.

In modern practice, the advent of liquid acrylic additives and other advances to the grout mixture, create slower moisture absorption over the older formulas, and also increase bonding strength to mitigate these failures. Restoration steps should include treatment to the steel to arrest rust, using practices for treating old steel common in auto body repair.

See also

  • Types of concrete
    Types of concrete
    There are many types of concrete, variations of installation, composition, finish and performance characteristics.-Mix design:Modern concrete mix designs can be complex...

  • Joseph Monier
    Joseph Monier
    -Overview:Joseph Monier was a French gardener and one of the principal inventors of reinforced concrete....

  • Faux Bois
    Faux Bois
    Faux bois refers to the artistic imitation of wood or wood grains in various media. The craft has roots in the Renaissance with trompe-l'œil. It was probably first crafted with concrete using a steel armature by the inventor of ferrocement, Joseph Monier. In 1875, Monier created the first bridge...

  • Ferro concrete
  • Reinforced concrete
    Reinforced concrete
    Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

  • Ferro concrete restoration
  • Scenery construction

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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