Building Materials, Third Edition

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matrix, high resistance to cracking is achieved.
Toughness, fatigue resistance, impermeability, etc. are
also improved. This material which is a special form of
reinforced concrete, exhibits a behavior so different from
conventional reinforced concrete in performance,
strength and potential application that it must be classed
as a separate material.
The reinforcement may be hexagonal wire mesh (0.5–
1.00 mm diameter at 5–25 mm spacing) welded wire
mesh (18–19 gauge), woven mesh, expanded metal sheet
and Watson mesh (Fig. 20.3). Generally characteristics
of different types of meshes are given in Table 20.3. The
skeletal steel may be placed 300 mm apart to serve as a
spacer rod to the mesh reinforcement. A rich mix of
Portland cement and sand usually 1:2 to 1:1.5 is used as
mortar. The thickness of the ferrocement element is kept 10–40 mm, with a clear cover of 1.5–
2 mm to reinforcement. No form work is required since the wire mesh and chicken mesh receive
the mortar wherein the mortar applied with pressure is held in position by mechanical interlocking.

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Steel bars, generally provided to make the formwork of the structure are known as skeletal
steel. The size of the rod varies from 4 to 10 mm and at a spacing of 300 mm apart. In highly
stressed structures like boats, barages and tubular sections this spacing is reduced to 75 mm.
For structures steel rods, along with wire mesh, are considered as a component of reinforcement
imparting structural strength and stiffness, whereas in most of the terrestrial structures wire
mesh is treated as the main reinforcement. The steel content in ferrocement various from 1–8%.
Portland cement, rapid hardening Portland cement, Sulphate resisting Portland cement or
Portland blast-furnace cement may be used.
Ferrocement which is specially advantageous in spatial structure has relatively better
mechanical properties and durability than ordinary reinforced concrete. Within certain loading
limits, it behaves as homogeneous. The high surface area to volume ratio (specific surface) of
the reinforcement results in better crack arrest mechanism, i.e., the propagation of cracks are
arrested resulting in high tensile strength of the material. Recent studies show that the inclusion
of short steel fibres in ferrocement increases further the first crack strength of the composite. Its
ultimate strength depends almost entirely upon the volume fraction of the wire mesh.

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