What is Ferrocement
Ferrocement is a material used in the Construction industry and is a composite of Ferro (iron) and cement (cement mortar). Ferrocement offers a wide range of uses in construction due to its low self-weight, minimal skilled labour needs, and low structural requirements.
P.L.Nervi, an Italian architect, designed it in 1940. Since the pieces are mounted on a piece of machinery setup, the quality of the ferrocement works is assured, and the execution time on the job site is reduced. Maintenance is very inexpensive. Only in the last two decades has this substance been widely used in architecture.
It’s a composite of closely woven wire mesh, tightly wound skeletal steel, and a rich cement mortar impregnated with it.
Since mortar can be sprayed, this method is very effective when it is delivered by hand. As a result, it is commonly used in developed countries with low labour costs. The main market for ferrocement in the West has been for the construction of boats. It’s also used for architectural systems and roofing shells. In Asia and areas of the Pacific, ferrocement is commonly used.
Joseph Monier, a French architect, invented the word “ferrocement.” He decided to construct urns, planters, and walls without having to pay for firefighting at the time (the 1850s). He designed the first steel and concrete bridge in 1875.
Faux Bois (false timber or wood grain from different sources) concrete works were introduced as the outer layer was carved in its wet condition to resemble rustic wood.
The new styles use a “ferrocement” called ferroconcrete or reinforced concrete, which is a better term for the finished product than “ferrocement.” Since the mortar bonded with Portland cement is called concrete, certain items may be referred to as cement.
Ferrocement has a more than 170-year tradition. The Kood style of the old way of the wall is analogous to the idea of impregnating tightly spaced steel wires with rich cement. Bamboo and reeds are closely connected in the Kood structure, which is packed with mud and cow dung as a matrix. It is widely utilised in India’s rural areas. As a result, Ferrocement may be thought of as a modified version of Kood’s materials, construction techniques, and structures.
Instead of bamboo and reeds, the mesh is used, and cement mortar is used instead of clay.
Forming Ferrocement Members: A Basic Methodology
A ferrocement frame is constructed by first constructing mesh reinforcement to the structure’s form and size, then mortaring and curing it. The following is the procedure for creating a ferrocement element:
1) Structural steel welding
The metal bars’ skeleton is welded in a realistic geometric and scale way. This results in a sturdy foundation of the same form and scale as the bottom surface, as well as a straight and flat bottom surface.
2) Form a cage by tying mesh reinforcement securely around it.
Weldmesh and fine wire chicken mesh are bonded to the welded skeleton using stretching and binding techniques. ‘Tightly tying meshes’ is the key to ferrocement building.
3) Impregnating the mesh cage with rich cement mortar, finishing and curing.
A pressing technique is used to fill the mesh layers with firm cement mortar. In a pressure-filling operation, the mortar is pressed within the mesh from both sides.
Both of these building phases must be finished in the order specified. All three operations can be completed at the same time with a larger build.
Advantages of Ferrocement
Ferrocement has the following primary advantages over RCC.
1) Increase in bond strength
The relation between the two allows for load transfer from metal to concrete and vice versa. The concrete’s pressure and the area of interaction between the metal and the concrete decide the bond’s strength.
M 15 concrete has a weight per cm2 of just 6 kg. The bond can be significantly strengthened by increasing the surface area between the metal and the mortar. Ferrocement accomplishes this by using small-diameter cables.
2) Bond area increase:
The additional surface of the bond provides more adhesion between the metal and the mortar, allowing it to act as if it were a single material with a very high bond extension.
3) Dispersion of steel wires
Ferrocement is made up of many layers of interconnected steel wires. The proportion of steel in volume is very high, as high as 8%. Furthermore, the mortar that covers the meshes is 3 to 5 mm thick. As a result, the cable insulation is uniformly spread across the joint.
As a result, ferrocement and cement become very close. Collisions, flexibility, impact tolerance and crack resistance are used to build Ferrocement structures.
4) Crack control
Meshes are fully affixed to the mortar and are spaced widely near the wall.
Ferrocement is a cement form. The fragile strings are separated by a large distance and are very close to the face.
Ferrocement works as a crack preventative.
5) Strength in all directions is equal
Due to the constant positioning of equilibrium reinforcement in both directions, Ferrocement achieves equal strength in both directions and efficiently counteracts horizontal stress caused by cutting.
6) Mortar matrix containment in mesh layers
In Ferrocement, layers of welded wires are fused together and immersed in cement mortar. The matrix is preserved and contained in the middle play.
7) Construction of no specified forms
They will trap wet cement mortar pressing against the sides of the ferrocement. Cement and cement have a tight consistency and contain a small volume of water. It’s not easy to get it out of meshes. As a result, no formwork or shuttering is needed when broadcasting Ferrocement. Another benefit is that when the intoxication is performed in front of the eyes, no bee stings can occur during the filling of the pressure.
8) Form as a source of strength
Ferrocrete structures have thin walls that range in thickness from 25 to 50 mm. As a result, Ferrocement is constructed in a variety of ways in order to improve its performance while minimizing softness and tightness.
9) Material that is lightweight, homogeneous, and flexible
The ferrocement systems are similarly high in both directions. It can be moulded into almost any form or scale. Ferrocement is a lightweight, simple-to-work-with fibre that can be sliced into small pieces.
10) High strength to weight ratio
Since ferrocement has thin, high-strength walls, its strength-to-weight ratios in congestion and pressure are extremely high. As a result, smaller components can handle greater loads.
Materials used in the construction of ferrocement structures
a) Skeletal steel includes angles, steel bars, welded wire materials, and tubing.
b) Steel wire meshes that form cages.
c) A rich cement mortar micro-concrete matrix
The three raw materials are widely used in traditional framework construction.
a. In the form of steel bars
As the names suggest, skeletal steel, in the form of steel bars, is utilised to give structures their foundational shape and size. As being used for frame construction, steel rods can be divided by 500 mm. They are often used as gaps between mesh layers where structural strengthening is not needed. The outline of the frame of the most strained systems, where the skeletal metal also serves as a reinforcement, will assess the fragmentation of the skeletal muscle. Steel rods from 4 to 10 mm in diameter are widely used. To reinforce the arrangement, the Angle system is used.
b. Fabric in the shape of welded bar
For big Ferrocement bars, welded bar fabric may be used as Skeletal steel. Welded bar fabric comes in widths varying from 4 to 10 mm, with spacing between bars ranging from 50 X 50 mm square to 300 X 300 mm rectangular.
Practical hints in selecting the skeletal steel
- The metal surface, especially in the short-cut bar, should not account for more than half of the Ferro-cement short-cut area. Thermal fractures in the steel line have been discovered where high-diameter or angle steel bars are used.
- 6 or 8 mm thick bars may be used with narrower frames. The edge bars can be up to 8mm dia. tor-steel, and certain bars can be 6mm dia. soft metal to preserve the frame’s resilience.
Steel wire meshes
As seen in the figure, rectangular-patterned wire is formed by aligning the wires differently and connecting them to the crossroads of their tracks. Weldmesh is a wire-tied skeleton that acts as the foundation for linking fine wire meshes.
Its surface area is taken into account when measuring the composite’s unique surface. The opening size of the weldmesh is defined, followed by a wire gauge with longitudinal and transverse directions. For long and non-breaking points, weldmesh with an opening diameter of 100 mm x 100 mm and 12 gauge steel gauges are 100 mm x 100 mm x 12 g x 12 g.
In ferrocement systems, welding meshes with opening sizes of 25 x 25, 50 x 50, 75 x 75, 100 x 100, and 150 x 150 are often used. Wire gauges can be anywhere between ten and sixteen.
Welding mesh is available in rolls with widths of 900, 1200, and 1500 mm and lengths of 15 to 30 metres.
Crimped woven wires mesh (Watson mesh)
Watson devised a three-dimensional mesh designed especially for boat building. Three alternating layers of straight wires are frictionally locked together by a crimped creeper wire. It produces a mesh with a complete thickness of five wires.
The ferrocement matrix is mostly composed of mud or thin concrete, with packed cement as a binder, a significant amount of sand, and water as the water. The heart is usually made of well-drained sand with a thickness of more than IS 2.36 mm per filter. If the match size and distance between mesh layers allow, the small combined size will be used in the sand.
The mortar matrix typically accounts for more than 90% of the discovery volume and has a substantial effect on the final product’s actions. As a result, considerable care must be taken in selecting the materials to be used, as well as correctly assembling and storing them.
New, high-quality cement should be free of lumps and foreign matter. It should be kept as dry as possible for the shortest amount of time. Fast-acting cement, sulfate-resistant cement, white and coloured cement, and pozzolana cement are some of the types of Portland cement available. The conditions in the workplace specify the form of cement to be used. Ferrocement is usually used in Ordinary Portland Cement grades 43 and 53.
In marine areas or structures exposed to seawater or acid-toxic waste, sulphate-resistant cement is recommended. If the sulphate or admixture resistance of the cement is inadequate, a rich cement mortar should be added first, followed by a building cover.
The cement content of ferrocement is greater than that of typical reinforced concrete. Ordinary Portland Cement should be manufactured according to DO 8112: 2015 and IS 12269: 2015.
When flowing through a 2.36mm IS filter, a decent range of ferrocement is always well mixed with river sand. The mesh opening size and the distance between the mesh layers decide the total size. A successful 13 mm opening should have a maximal value of 1/4 of the opening distance, or less than 3.25 mm.
To get the correct width, the sand fineness modulus should be between 2.4 and 2.5 with a maximum grain size of 1.18 mm and 2.9 to 3.0 with a maximum grain size of 2.36 mm. Proper grain size and effective modulus control will result in the necessary amount of water, as well as improved efficiency and strength. Sand laying with grade 43 cement and crushed sand compaction in line with IS 383-1970.
Sand (Crushed or manufactured)
Crushed sand should be used in place of natural sand. It’s made of pointed rock with particle sizes ranging from 4.75 to 150 microns. Crushed sand is not the same as rock grit, which is a waste product from stone crushers. Crushed sand measurement and particle size of crushed sand are two significant considerations to consider. Split sands have been successfully used in concrete ranges ranging from M15 to M40.
Water that is fresh, clean, and safe to drink is needed. Organic matter, mud, oil, sugar, chlorides, and acidic products can all be removed from the environment. The pH of the water should be about 7.0. While drinking saline water is not recommended, drinking chlorinated water is.
Chemical admixtures serve four purposes in ferrocement:
a) Water removal increases resistance while lowering permeability. This may be accomplished by the use of superplasticizers.
b) To keep buildings watertight, waterproofing additives may be used.
c) Air entraining agents help to prevent freezing and thawing.
d) Water mixed with about 300 parts per million of chromium trioxide suppresses galvanic activity between galvanised steel and cement.
Proportioning of cement mortar
Rich cement mortars with varying concentrations (1: 1.5) to (1: 4) are often used in maturation. The amount of water used to sustain the same efficiency increases as the sand content increases. The test mix should be made to produce a solid, compacted mortar with a consistency that allows layers of meshes to be easily penetrated.
Calculate and apply the rate of soil erosion, the rate of water-cement, and the rate of sand cement for mixing. Since the wires are distributed across the ferrocement body, shrinkage is not an issue. Based on how the mortar is used, plasticity is important.
The sheet that can be cast should have a thickness of at least 2 cm. The intensity obtained by this method would be smaller than that of other methods. However, this approach can be used to construct units in situations where no other superior methods are available.
Semi Mechanized Process
● Since the mould can be rotated to facilitate mortar dashing, this method is referred to as semi-automated.
● In terms of compaction, this method outperforms the previous one.
● The uniformity of this scheme is even better than the previous one.
● This system has the benefit of not needing any sophisticated machines or instruments.
For the construction of cylindrical concrete units, the centrifugation method is widely used.
The centrifuging ferrocement pipe can be used as a pressure pipe due to its strong compression.
The gunite process can be used to apply mortar to the wire mesh system; it is performed by professional gunmen who can create a lightweight and uniform surface, and it tends to be a reliable technique for mass manufacturing of ferrocement prefabricated units.
Sustainability Values of Ferrocement
- Ferrocement is environmentally friendly and has low carbon. The carbon footprint of this construction material is about 70% less than that of conventional reinforced concrete construction.
- 70 percent less material = 70 percent of construction profit as carbon credit
- Metal and cement products are 100% recycled (95% of currently renewable metal content)
- There are no organisms or construction waste, so there is a low impact on the environment.
- Environmental damage is minimized because there is less disruption to the site.
- Travel costs are reduced: 70% of the time Consumption of mineral oil is reduced as material demand is reduced.
- Longevity increases the life cycle of shell construction, reducing the cost of the unit cycle.
Construction Methods for Ferro Cement
Skeletal Armature Method
- This procedure involves welding the skeleton steel to the correct form and tying numerous layers of stretched meshes on each side.
- This is strong enough to fill in the mortar by pushing on one side while supporting the other momentarily.
- Filling in the mortar may also be done by pulling from both sides.
- Because the skeleton steel (bars) are in the centre of the section in this configuration, they contribute to the section’s dead weight rather than its strength.
Integral Mould Method
- Every integral mould should be seen first and foremost as a form that needs the least amount of reinforcing possible.
- On both sides of this mould, layers of meshes are fixed, and plastering is completed.
- As the name implies, the mould is firmly attached to the finished structure. (Double T-sections, for example, are used in flooring, roofing, and other applications.)
- Care is taken to maintain a solid relationship between the mould and the layers filled in later to ensure that the finished product as a whole is an integrated structural device.
Close Mould Method
● Several layers are tied together against the mould’s surface to keep the meshes in place as the mortar is being filled in.
● Аfter drying, the mold may be discarded or kept in place as a permanent part of the finished structure.
● Before the mould can be reused, it must be removed using a releasing agent.
Open Mould Method
● Closely related to the closed mould technique is the open mould technique.
● On one hand, the mortar is poured into the open mould, passing through the mesh layers and rods.
● The mould is made of a wooden lattice with a wooden lining. The type is either completely wrapped in polyethene sheeting or treated with a release agent
● As a result, a mould will be produced that is identical but not as rigid and transparent. This makes it easier to remove mould and identify and fix any defects that might occur during the mortar application process.
Market survey and Labour component
This demonstrated that ferrocement is a revolutionary material that is suitable for homes, water, and food storage systems due to its readily available material and simple construction methods. It can be a good investment if provided proper workforce. Ferrocement has been discovered to be a good material for restoring and improving the efficiency of faulty RCC structural components. Since the efficiency of ferrocement is determined by the properties of the reinforcement mesh, an optimal set of mesh properties must be defined. Due to its distinct characteristics, ferrocement will be an effective RCC and repair material in the future.