Ferro Cement Construction – An Overview

Ferro cement, commonly known as Ferro-cement, is a construction method that employs a metal mesh “armature” of woven, expanded metal, or metal-fibers, as well as closely spaced thin steel rods such as rebar to reinforce mortar or plaster (lime or cement, sand, and water).

Ferro Cement Construction, also known as thin-shell concrete structures or ferroconcrete, is a reinforced concrete system made of sand, cement, and water placed over layers of metal such as bird mesh, chicken wire, woven or expanded metal (iron) mesh, or fibers linked to a frame of bigger diameter bars. It’s utilized to make thin, robust forms in a variety of shapes for things like boat hulls, shell roofs, dome-shaped structures, water features, garden planters, and water tanks, as well as a variety of other spectacular Ferro-cement constructions.

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Ferrocement’s Applications

It is employed in residential constructions because it saves cement and steel in the construction of structures. Ferrocement is used in the construction of home overhead water tanks. The tank is small and light, making it easy to move.

Properties of Ferrocement construction 

  • Ferrocement members are a long-lasting and adaptable material.
  • Ferrocement has a low water-to-cement ratio, resulting in impermeable constructions.
  • It is lighter and shrinks less.
  • Ferrocement constructions are stiff, rigid, and have high tensile strength.
  • They are more resistant to impact and punching shear.
  • Ferro Construction recommends a ferro-cement mix ratio of sand/cement ratio of 1.5 to 2.5 and a water/cement ratio of 0.35 to 0.5, with all values measured by weight.
  • Ferrocement uses a lot less cement and steel, and it performs better, therefore it’s better for the environment. As a result, Ferro cement is a multi-sustainable material with financial benefits as well as the potential to save lives in the event of an earthquake with a Richter scale of 8 or higher.
  • Ferrocement is a thin building element with a thickness of 10–25 mm (3/8–1 in.) that is made with rich cement mortar, no coarse aggregate, and one or more layers of continuous/small diameter steel wire/weldmesh netting as reinforcement.

Factors Affecting FerroCement Construction

Ferrocement houses may be manufactured to survive for many years, although this is dependent on a number of factors, including mortar composition, aggregate quality, water-cement ratio, degree of compaction, mortar cover thickness over reinforcement, curing, and reinforcement corrosion. Only after 30 years of existence can a building demonstrate its longevity, and Ferro cement structures passed this test.

A Ferro cement element can withstand all types of aggressive factors if a few design and technical standards are followed. To improve the long-term durability of Ferro cement structures, proper surface coating to prevent moisture and air penetration, as well as regular inspection and maintenance, are required.

The use of galvanized steel alone is insufficient for corrosion protection; instead, an appropriate cover is the best option. The surface treatment will also give the mortar and mesh the optimum protection.

Ferrocement Construction Methods

Casting can be done in four different ways:

  • Plastering by hand
  • Semi-automated procedure (using hand plastering)
  • centrifugation
  • Guniting

Forming Ferrocement Members: A Methodology

The mesh reinforcement for a Ferro cement structure is first built to the structure’s shape and size, then mortared and cured. The following is the procedure for making a Ferro cement element:

  1. Skeletal Steel Framework Welding: A skeleton of steel bars is welded to the structure’s exact geometrical shape and dimension. This creates a hard structure with the proper shape and size, as well as the proper line and level.
  2. Mesh Reinforcement Ties To Form the Cage, Place It Tightly Over It:
    This approach uses a stretching and tying technique to bind Weld mesh and fine wire chicken mesh over the welded skeleton. The secret to ferrocement construction is ‘tightly tying meshes.’
  1. Finishing and Curing the Mesh Cage after Impregnating it with Rich Cement Mortar:

The mesh layers are filled with hard cement mortar using the push fill method. The mortar must be forced inside the wire meshes from both sides when using the press fill method.
Essentially, all of these construction procedures must be completed in the order listed above. For large-scale Ferro cement structures, all three operations can be performed simultaneously.

Ferro Cement Construction vs Blast Load

An experiment was conducted on an Unreinforced U-shaped Ferro cement overlay brick masonry wall also known as Ferro cement wall construction. An unreinforced U-shaped Ferro cement overlay brick masonry wall was built utilizing the same proportions as an unreinforced masonry wall. 38 mm Screw and Rawal Plug @ 225 mm c/c were used to secure a 19 mm square steel wire (gauge 18) mesh to the external surface of the wall (staggered). Finally, the surface was coated using cement sand mortar (1:4).

Ferro Cement Construction
Ferro Cement Construction

The wall joints and middle-width of unreinforced masonry are subject to blast stresses. The maximum deflection is applied to the centerline. Furthermore, during the blast, the scaled distance is minimal for the geometrical center of each out-of-plane wall; it gets greater pressure than other parts of the wall. As a result, the damage is concentrated along the wall’s geometrical vertical center-line. Similarly, rotation of the out-of-plane wall caused the joint crack to form.

Ferro Cement Construction
Ferro Cement Wall Construction

Furthermore, during the blast, the scaled distance is minimal for the geometrical center of each out-of-plane wall; it gets greater pressure than other parts of the wall. As a result, the damage is concentrated along the wall’s geometrical vertical center-line. Similarly, rotation of the out-of-plane wall caused the joint crack to form.

As demonstrated in Figure, restricted and Ferro cemented overlay masonry walls revealed no cracks anywhere after event No.1, with a scaled distance of 4.353 (m/kg1/3) (a,b). As illustrated in Figure, an unreinforced masonry wall developed tiny vertical cracks in the center and at the joints of in-plane and out-of-plane walls, which expanded downward following mortar joints (c). The masonry was restrained against damage by the confining element in confined masonry and the Ferro cemented overlay.

Ferrocement’s Construction Benefits

  • When compared to R.C.C., it has a stronger tensile strength-to-weight ratio and better cracking behavior. They are less in weight since they are made up of thin elements and light structures.
  • The supplies are frequently available locally and are relatively inexpensive.
  • To construct the simplest constructions, only a few simple hand tools are required.
  • Repairs to Ferro cement structures are typically simple and affordable, implying that they have a minimal maintenance cost.
  • It is simple to use.
  • Ferrocement saves money and materials by 20%. Both cost efficiency and speed can be attained.
  • It has a lower thermal conductivity than RCC.
  • For a wide range of applications, it can be cast in any desired shape and size.
  • In residential buildings, it outperforms traditional materials like wood, adobe, and stone masonry in terms of fire, earthquake, and corrosion resistance.

Ferrocement’s disadvantages include

  • Excessive shrinkage occurs because of the greater cement content. To avoid shrinkage cracks, it must be continuously cured for a period of seven days.
  • Because the steel is not completely covered by masonry, the wire mesh is prone to corrosion.
  • Wire Mesh Corrosion in Ferrocement 03. Ferrocement is labor-intensive, so it’s not a viable solution in areas with high labour expenses.
  • Ferrocement structures can be perforated by a severe contact with pointed items.
  • They have limited ductility and shear strength.
  • Stress rupture failure is a risk with ferro cement.
  • Welding, drilling, nailing, screwing, and other ferrocement construction techniques are difficult to master.
  • According to ‘A. M. Neville’ (Author of Concrete Technology), the manufacturing process is labour intensive, hence ferrocement is rather expensive to manufacture.
  • Buckling is another factor to consider in ferrocement construction because the structures are typically thin.
  • They have weak impact resistance due to their thin ferrocement components.

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