Ferrocement

Last updated
Mulberry harbour remains at Arromanches Arromanches-les-Bains port artificiel Mulberry.jpg
Mulberry harbour remains at Arromanches
Lambot's original 1848 bateau in the Brignoles Museum in France. Bateau en ciment arme de Lambot.jpg
Lambot's original 1848 bateau in the Brignoles Museum in France.
Ferrocement hull under construction Barco de ferrocemento.JPG
Ferrocement hull under construction
A particularly fair ferrocement vessel, the staysail schooner "Rich Harvest" Staysail schooner "Rich Harvest".jpg
A particularly fair ferrocement vessel, the staysail schooner "Rich Harvest"

Ferrocement or ferro-cement [1] is a system of construction using reinforced mortar [2] or plaster (lime or cement, sand, and water) applied over an "armature" of metal mesh, woven, expanded metal, or metal-fibers, and closely spaced thin steel rods such as rebar. The metal commonly used is iron or some type of steel, and the mesh is made with wire with a diameter between 0.5 mm and 1 mm. The cement is typically a very rich mix of sand and cement in a 3:1 ratio; when used for making boards, no gravel is used, so that the material is not concrete.

Contents

Ferrocement is used to construct relatively thin, hard, strong surfaces and structures in many shapes such as hulls for boats, shell roofs, and water tanks. Ferrocement originated in the 1840s in France and the Netherlands and is the precursor to reinforced concrete. It has a wide range of other uses, including sculpture and prefabricated building components. The term "ferrocement" has been applied by extension to other composite materials, including some containing no cement and no ferrous material.[ citation needed ]

The "Mulberry harbours" used in the D-Day landings were made of ferrocement, and their remains may still be seen at resorts like Arromanches.

Definitions

Cement and concrete are used interchangeably but there are technical distinctions and the meaning of cement has changed since the mid-nineteenth century when ferrocement originated. Ferro- means iron although metal commonly used in ferro-cement is the iron alloy steel. Cement in the nineteenth century and earlier meant mortar [3] or broken stone or tile mixed with lime and water to form a strong mortar. [4] Today cement usually means Portland cement, [5] Mortar is a paste of a binder (usually Portland cement), sand and water; and concrete is a fluid mixture of Portland cement, sand, water and crushed stone aggregate which is poured into formwork (shuttering). Ferro-concrete is the original name of reinforced concrete (armored concrete) known at least since the 1890s and in 1903 it was well described in London's Society of Engineer's Journal [6] but is now widely confused with ferrocement.

History

The inventors of ferrocement are Frenchmen Joseph Monier who dubbed it "ciment armé" (armored cement) and Joseph-Louis Lambot who constructed a boat with the system in 1848. [7] Lambot exhibited the vessel at the Exposition Universelle in 1855 and his name for the material "ferciment" stuck. Lambot patented his boat in 1855 but the patent was granted in Belgium and only applied to that country. At the time of Monier's first patent, July 1867, he planned to use his material to create urns, planters, and cisterns. These implements were traditionally made from ceramics, but large-scale, kiln-fired projects were expensive and prone to failure. In 1875, Monier expanded his patents to include bridges and designed his first steel-and-concrete bridge. The outer layer was sculpted to mimic rustic logs and timbers, thereby also ushering faux bois (fake wood) concrete. In the first half of the twentieth century Italian Pier Luigi Nervi was noted for his use of ferro-cement, in Italian called ferro-cemento.

Ferroconcrete 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 1950s, it became popular in the United States as a construction and sculpting method for novelty architecture, examples of which are the Cabazon Dinosaurs and the works of Albert Vrana.

Construction formwork

The desired shape may be built from a multi-layered construction of mesh, supported by an armature, or grid, built with rebar and tied with wire. For optimum performance, steel should be rust-treated, (galvanized) or stainless steel. Over this finished framework, an appropriate mixture (grout or mortar) of Portland cement, sand and water 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) or some other method of driving out trapped air.

Older structures 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 absorption 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. [8] Chopped glass or poly fiber can be added to reduce crack development in the outer skin. (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.[ citation needed ] Ferro concrete structures can be built quickly, which can have economic advantages. [9]

In India, ferro concrete is used often because the constructions made from it are more resistant to earthquakes.[ citation needed ] Earthquake resistance is dependent on good construction technique.

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 ferro-cement hull can prove to be of similar or lower weight than a fiber reinforced plastic (fiberglass), aluminium, or steel hull.[ citation needed ]

There are basically three types of methods of ferrocement. They are following

  1. Armature system: In this method the skeleton steel is welded to the desired shape on either of sides of which are tied several layers of stretched meshes. This is strong enough, so that mortar can be filled in by pressing for one side and temporarily supporting from the other side. Filling in of mortar can also be administered by pressing in the mortar from both the sides. In this method the skeletal steel (bars) are at centre of the section and as such they add to the dead weight of without any contribution to strength.
  2. Closed mould systems: Several layers of meshes are tied together against the surface of the mould which holds them in position while mortar is being filled in. The mould may be removed after curing or may remain in position as a permanent part of a finished structure. If the mould is to be removed for reuse, releasing agent must be used.
  3. Integrated mould system: Using minimum reinforcement any integral mould is first to be considered to act as a framework. On this mould layers of meshes are fixed on either side and plastering is done onto them from both sides. As the name suggests, the mould remains permanently as an integral part of the finished structure. (e.g. double T-sections for flooring, roofing, etc.) Precaution should be taken to have firm connection between the mould and the layers filled in later, so that finished product as a whole integral structural unit.

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. [10] However, meticulous building precision is considered crucial, 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. As a container, it may fail and leak but possibly hold together. Much depends on the techniques used in the construction.

Using the example of the Mulberry Harbours, pre-fabricated units could be made for ports (such as Jamestown on St Helena) where conventional civil engineering is difficult.

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.

Insurance issues

During the 1960s in Australia, New Zealand and the UK, home boatbuilders realised that, for a given budget, ferrocement enabled a much larger hull than otherwise possible. However, some builders failed to realise that the hull forms only a minor part of the overall cost because a larger boat would have very much higher fitting-out costs. Consequently, several homebuilt ferrocement boats became unfinished projects, or if finished, then badly executed, overweight, lumpy "horrors". Realising that their boats were not merely disappointing but also unsaleable, some builders insured their boats and fraudulently scuppered them for compensation. Insurance companies have long memories of such frauds, and today, even for well-built ferrocement boats, it has become difficult to get insurance coverage for third-party risks, while comprehensive cover is virtually unattainable.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Boat</span> Vessel for transport by water

A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size or capacity, its shape, or its ability to carry boats.

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.

<span class="mw-page-title-main">Cement</span> Hydraulic binder used in the composition of mortar and concrete

A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.

<span class="mw-page-title-main">Reinforced concrete</span> Concrete with rebar

Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars (rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.

<span class="mw-page-title-main">Grout</span> Building material

Grout is a dense fluid that hardens used to fill gaps or as reinforcement in existing structures. Grout is generally a mixture of water, cement, and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sections of precast concrete, filling voids, and sealing joints such as those between tiles. Common uses for grout in the household include filling in tiles of shower floors and kitchen tiles. It is often color tinted when it has to be kept visible and sometimes includes fine gravel when being used to fill large spaces. Unlike other structural pastes such as plaster or joint compound, correctly mixed and applied grout forms a water-resistant seal.

<span class="mw-page-title-main">Building material</span> Material which is used for construction purposes

Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings and other structures, like bridges. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.

<span class="mw-page-title-main">Boat building</span> Design and construction of floating vessels

Boat building is the design and construction of boats — and their on-board systems. This includes at minimum the construction of a hull, with any necessary propulsion, mechanical, navigation, safety and other service systems as the craft requires.

<span class="mw-page-title-main">Stucco</span> Construction material made of aggregates, a binder, and water

Stucco or render is a construction material made of aggregates, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as a decorative coating for walls and ceilings, exterior walls, and as a sculptural and artistic material in architecture. Stucco can be applied on construction materials such as metal, expanded metal lath, concrete, cinder block, or clay brick and adobe for decorative and structural purposes.

Concrete ships are built primarily with ferrocement hulls, reinforced with steel bars. This contrasts against more traditional materials, such as pure steel or wood. The advantage of ferrocement construction is that materials are cheap and readily available, while the disadvantages are that construction labor costs are high, as are operating costs. During the late 19th century, there were concrete river barges in Europe, and during both World War I and World War II, steel shortages led the US military to order the construction of small fleets of ocean-going concrete ships, the largest of which was the SS Selma. United States Maritime Administration (MARAD) designation for concrete ships-barges was Type B ship. Few concrete ships were completed in time to see wartime service during World War I, but during 1944 and 1945, concrete ships and barges were used to support U.S. and British invasions in Europe and the Pacific. Since the late 1930s, there have also been ferrocement pleasure boats.

This page is a list of construction topics.

<span class="mw-page-title-main">Efflorescence</span> Migration of a salt to the surface of a porous material

In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water or occasionally, in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.

<span class="mw-page-title-main">Shotcrete</span> Concrete or mortar building material

Shotcrete, gunite, or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface. This construction technique was invented by Carl Akeley and first used in 1907. The concrete is typically reinforced by conventional steel rods, steel mesh, or fibers.

<span class="mw-page-title-main">Formwork</span> Molds for cast

Formwork is molds into which concrete or similar materials are either precast or cast-in-place. In the context of concrete construction, the falsework supports the shuttering molds. In specialty applications formwork may be permanently incorporated into the final structure, adding insulation or helping reinforce the finished structure.

<span class="mw-page-title-main">Joseph-Louis Lambot</span>

Joseph-Louis Lambot, is the inventor of ferro-cement, which led to the development of what is now known as reinforced concrete. He studied in Paris, where his uncle Baron Lambot was aide-de-camp to the Duke of Bourbon.

<i>Faux bois</i>

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 an iron armature by garden craftsmen in France called "rocailleurs" using common iron materials: rods, barrel bands, and chicken wire.

<span class="mw-page-title-main">History of structural engineering</span>

The history of structural engineering dates back to at least 2700 BC when the step pyramid for Pharaoh Djoser was built by Imhotep, the first architect in history known by name. Pyramids were the most common major structures built by ancient civilizations because it is a structural form which is inherently stable and can be almost infinitely scaled.

<span class="mw-page-title-main">Structural material</span>

Structural engineering depends on the knowledge of materials and their properties, in order to understand how different materials resist and support loads.

<span class="mw-page-title-main">Textile-reinforced concrete</span> Type of reinforced concrete

Textile-reinforced concrete is a type of reinforced concrete in which the usual steel reinforcing bars are replaced by textile materials. Instead of using a metal cage inside the concrete, this technique uses a fabric cage inside the same.

<span class="mw-page-title-main">Types of concrete</span> Building material consisting of aggregates cemented by a binder

Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.

The reinforcement of 3D printed concrete is a mechanism where the ductility and tensile strength of printed concrete are improved using various reinforcing techniques, including reinforcing bars, meshes, fibers, or cables. The reinforcement of 3D printed concrete is important for the large-scale use of the new technology, like in the case of ordinary concrete. With a multitude of additive manufacturing application in the concrete construction industry—specifically the use of additively constructed concrete in the manufacture of structural concrete elements—the reinforcement and anchorage technologies vary significantly. Even for non-structural elements, the use of non-structural reinforcement such as fiber reinforcement is not uncommon. The lack of formwork in most 3D printed concrete makes the installation of reinforcement complicated. Early phases of research in concrete 3D printing primarily focused on developing the material technologies of the cementitious/concrete mixes. These causes combined with the non-existence of codal provisions on reinforcement and anchorage for printed elements speak for the limited awareness and the usage of the various reinforcement techniques in additive manufacturing. The material extrusion-based printing of concrete is currently favorable both in terms of availability of technology and of the cost-effectiveness. Therefore, most of the reinforcement techniques developed or currently under development are suitable to the extrusion-based 3D printing technology.

References

  1. Sometimes erroneously called thin-shell concrete or ferro-concrete
  2. Gani, M. S. J. Cement and Concrete. London: Chapman & Hall, 1997. 8. Print.
  3. Chambers, William, and James Donald, eds. "cement", Chambers's Etymological Dictionary of the English Language. London, Edinburgh: W. & R. Chambers, 1873. 66. Print.
  4. "cement, n." Oxford English Dictionary. 2nd. ed. 2009. CD-Rom.
  5. Ward-Harvey, K. Fundamental Building Materials. 4th ed. Boca Raton, Fla: Universal-Publishers, 2009. Print.
  6. Augustus de Rohan Galbraith, "The Hennebique System of Ferro-Concrete Construction". Journal, P. F. Nursey, ed. Society of Engineers. London. E & F. N.Spon. 1903. 177-208. Print.
  7. Nedwell, P. J.. Ferrocement: Proceedings of the Fifth International Symposium on Ferrocement. UMIST, Manchester, 6–9 September 1994. London: E & FN Spon, 1994. 28-30. Print.
  8. fauxboisconcrete.info
  9. Naderpour, Hosein; Rezazadeh Eidgahee, Danial; Fakharian, Pouyan; Rafiean, Amir Hossein; Kalantari, Seyed Meisam (April 2020). "A new proposed approach for moment capacity estimation of ferrocement members using Group Method of Data Handling". Engineering Science and Technology. 23 (2): 382–391. doi: 10.1016/j.jestch.2019.05.013 . S2CID   192644241.
  10. Jackson, G and Sutherland, W. Concrete Boatbuilding. George Allen and Unwin Ltd, 1969, p43