WHAT IS FERROCEMENT CONSTRUCTION - PROPERTIES, ADVANTAGE AND DISADVANTAGE

Ferrocement Construction

Ferro-cement construction is a type of construction in which reinforced mortar or plaster is applied over an "armature" of metal mesh,woven expanded-metal and closely spaced thin steel rods such as rebar.The metal commonly used is of iron or steel.The cement is typically a very rich mix of cement and sand in a ratio of 3:1. Ferro-cement is made with mesh of diameter 0.5 mm to 1 mm reinforced between cement mortar of ratio.

Materials Required for Ferrocement Construction

1.Cement Mortar Mix

The cement mortar is the mixture of cement,sand,admixture and water.Generally the mix used in the construction of ferrocement has cement-sand ratio of 1:2 to 1:3 with water cement ratio 0.4 to 0.45.

• Cement

In ferrocement construction Ordinary Portland Cement is used in mortar while in cold climate generally rapid hardening cement is used.The recommended quantity of cement is 500-600 kg/m3.

• Sand

In ferrocement, sand which we used should be clean and well graded.To attain a high grade impervious mortar ordinary river sand can be used.The maximum allowable grain size of the sand is 2.36mm and fineness modulus should lie within the range of 2.5 - 3.0.

• Admixture

Admixtures is used in ferrocement  to improve the workability of the mortar and can reduce the water cement ratio.A varities of admixtures are available in market.

2. Skeleton Steel

The skeleton steel forms the skeleton of the structure and consists of steel roads and staples and wire fabric.The basic function of the skeleton steel is to support the steel wire mesh that plays a major role in imparting structural strength especially in boats,bags etc.

The steel roads used are 3 to 8 mm thick and their thickness varies according to location from 6mm to 20mm.They are spaced at a distance of 7.5 cm to 12cm from each other.In skeleton steel mainly Fe-415 or Fe-500 bars are used.

3. Steel Mesh Reinforcement 

The steel mesh reinforcement is generally made of galvanized steel wires with diameter ranging from 0.5 mm to 1.5 mm and spaced out at a center to center distance of 6mm to 20 mm.The wires are either weaving or welded together to form a mesh. The woven mesh has a square opening,whereas the welded wire mesh has a rectangular or hexagonal openings.

Properties of Ferrocement

• It is very durable and versatile material.
• High tensile strength and stiffness.
• Less shrinkage and low weight.
• Better impact and punching shear resistance. 
• Undergo large deformation before cracking or high deflection.
• It is inexpensive.

Advantage of Ferrocement

• High resistance to cracking width.
• It has good impermeability.
• It has better resistance against earthquake.
• It has good fire resistance property.
• Suitable for pre-casting.
• Low maintenance cost.
• It is more suitable for structure like shells, roof, water tanks etc, because it can be fabricated in many desired shape.

Disadvantage of Ferrocement

• Corrosion of the reinforcing materials due to the incomplete coverage of metal by mortar.
• It has low shear strength.
• Much time consumed during tying rods and mesh.
• Large number of labours required.
• Low ductility.
• Susceptibility to stress rapture failure.
• It is difficult to fasten to ferrocement with bolts,screw,welding and nails etc.