Ferro Cement - Applications and Benefits
Ferro cement is a comparatively new material that is formed with wire meshes and cement mortar. It includes tightly spanned wire meshes which are permeated with strong cement mortar mix. When the mortar produces the mass, the wire mesh passes on tensile strength and ductility to the material. The ferro cement has strong resistance capacity against cracking as well as extreme fatigue resistance, toughness and greater impenetrability.
Material applied for ferrocement
Cement Mortar Mix
Generally, portland cement and fine aggregate matrix are the main ingredients of ferrocement. The matrix comprises of approx 95% of the ferrocement and controls the behavior of the final product. The cement-sand ratio 1:2 to 1:3 with water cement ratio 0.4 to 0.45 remains in cement mortar.
The fine aggregate adheres to grading zone II and zone III with particles exceeding 2.36 mm and lesser than um (micro meter) are ideal for ferrocement. The fine sand should not be utilized in ferrocement.
Plasticizers and other admixtures are included to enhance the functionality, stability and strength as well as decrease permeability. Pozzolanas like fly ash can also be included up to 30% as substitute of cement to improve the stability.
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Two types of reinforcements alias skeleton steel and wire mesh are applied in ferrocement.
Skeleton steel - It includes considerably large-diameter (approx 3 to 8 mm) bars spanned at 75 mm to 100 mm. It comes as tied-reinforcement or welded wire fabric. The skeleton frame is created with adherence to the geometry and shape of structure and useful for retaining the wire meshes in exact location and shape of the structure.
Wire mesh - The wire mesh comprises of galvanized wire of 0.5 to 1.5 mm diameter and 6 to 20 mm center to center gapping is provided. The wire meshes are created with the help of welding, twisting or weaving. The welded wire mesh may come in the shape of square or hexagonal openings. The mesh having square openings is better as compared to hexagonal wire mesh but it is expensive. Normally, the square woven meshes with 1.0 or 1.5 mm diameter wire spanned at 12 mm are recommended.
The construction process is divided into the following 4 phases :-
- Fabrication of skeleton frame
- Setting of bars and mesh
- Use of mortar
The necessary number of layer of wire mesh are secured on both sides of the skeleton frame. A gapping of minimum 1 to 3 mm should be provide among two mesh layers. Mortar is used by hand or shotcreting. There is no formwork necessary for ferro-cement construction.
The Advantages of ferro cement
- The construction process is very easy
- It can be transformed into almost any shape for a wide range of uses
- Because of their small thickness, lesser dead weight is created on the element
- Near about 20% savings can be obtained on materials cost.
- Very effective for pre casting
- Flexibility in cutting, drilling and jointing
- It has high tensile strength
- Crack widths are also less with regard to traditional concrete
- It has good resistance capacity against fire
- It has strong waterproof capacity
- Maintenance cost is low