Ferro cement - materials, techniques of manufacture, properties and application

1. FERRO CEMENT
Dr. Vinay Kumar B M

2. Definition
“Ferro cement is a type of thin wall reinforced
composite, commonly constructed of cement
mortar, reinforced with closely spaced layers of
continuous and relatively small size wire mesh. The
mesh may be made of metallic or other suitable
materials”
-ACI Committee 549, 1980
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3. • Cement mortar is reinforced with layers of
continuous and small diameter wire meshes
• Mortar provides the mass and wire mesh imparts
tensile strength and ductility
• Italian engineer P.L Nervi is credited with
inventing ferro cement in the 1940’s
Ferro cement
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4. Materials used in Ferro cement
• Cement mortar mix
• Skeleton steel
• Steel mesh reinforcement or Fibre-reinforced
polymeric meshes
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5. 5
Typical section of Ferro cement

6. Cement mortar mix
• OPC and fine aggregate matrix is used
• The matrix constitutes 95% of the composite and
governs its behavior
• FA (sand), occupies 60 to 75% of the volume of
the mortar
• Plasticizers and other admixtures are used
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7. Mix Proportions
• cement: Sand ratio (by mass) 1:2 to 1:3
• Water: cement ratio (by mass) 0.35 to 0.60
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8. Skeleton steel
• Forms the skeleton of the structure
• 3 to 8 mm steel rods are used
• Used in the form of tied reinforcement or welded
wire fabric
• Used to impart structural strength in case of boats,
barges etc
• Reinforcement should be free from dust, rust and
other impurities
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9. Steel mesh reinforcement
• Consists of galvanized steel wires of diameter 0.5
to 1.5 mm, spaced at 6 to 20mm centre to centre
• Available as woven/interlocking mesh and welded
mesh
• Welded wire mesh has hexagonal or rectangular
openings
• Expanded-metal lath is also used
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10. 10
Types of Wire Meshes

11. 11
Chicken wire mesh

12. 12
Expanded Metal Lath

13. 13
Typical cross-sections of Ferro cement(Source: Naaman 1999)

14. Constructions Methods
• Does not require skilled labour nor heavy capital
investment on equipment.
• There are four steps in ferrocement construction:
1. Placing of reinforcement
2. mixing of mortar
3. placing mortar
4. curing
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15. • As the reinforcement content is very high(upto 8 %
by volume) and is the uniformly distributed
throughout the thickness of the element.
• The essential requirement is that Continous mesh
reinforcement has to be completely impregnated and
covered with reinforcement.
• A number of techniques are being used for placing
the mortar into the framework of the mesh.
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16. Casting techniques includes:
1. Hand Plastering
2. Semi-Mechanised process(using hand plastering)
3. Centrifuging
4. Guniting
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17. Hand Plastering
• One stage technique:
single application of mortar from outside to
inside of mesh and subsequently finishing it off to a
smooth surface before initial set takes place.
• Two stage technique:
Mortar is plastered from one side without fully
penetrating through all the mesh layers. later the
remaining portion is plastered with mortar.
• Sectional plastering:
• While undertaking plastering of large ferrocement
structures, it is preferable to plaster in sections using
one stage technique, necessitating the need for
construction joints.
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18. Semi-Mechanised process(using hand
plastering)
• Developed for casting thin ferrocement of cylindrical
units.
• In this system an inner cylindrical mould is provided
over which one layer of wire mesh is wound.
• Over this layer,4mm wire is tied at a spacing of 15cm
in both directions.
• Over this one more layer of chicken wire mesh is
wound. This forms the complete wire mesh system of
reinforcement.
• The cement plastering is then done layer by layer.
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19. Centrifuging
• Commonly adopted for the fabrication of concrete
cylindrical units.
• In this process,the mild steel cage is replaced by wire
mesh layer cage.
• Because of good compaction, the ferrocement pipe
cast by centrifuging can be used as pressure pipes.
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20. Guniting
• Guniting can be adopted for applying the mortar to
the wire mesh system.
• This process, applied properly with experienced
gunman can give good compact and uniform surface.
• This appears to be suitable process for mass
production of ferrocement prefabricated units.
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21. Advantages of Ferro cement
• High ductility
• High resistance to cracking width
• Ability to undergo large deflection
• Improved impact resistance and toughness
• Good fire resistance
• Good impermeability
• Low maintenance costs
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22. Applications of Ferro cement
• Marine applications
• Water supply and sanitation
• Agricultural
• Residential buildings
• Rural energy
• Other structures
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23. 1. Marine Applications
• Boats, fishing vessels, barges, cargo tugs, and
flotation buoys.
• Key criteria for marine applications: light weight,
impact resistance, thickness and water tightness
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24. 24
Boat with Ferro-cement hull

25. 2. Water supply and sanitation
Water tanks, sedimentation tanks, swimming pool
linings, well casings, septic tanks etc.
3. Agricultural
Grain storage bins, silos, canal linings, pipes, shells
for fish and poultry farms
4. Residential Buildings
Houses, community centers, precast housing
elements, corrugated roofing sheets, wall panels etc.25

26. 26
Ferro cement structure for roofing

27. 5. Rural Energy
Biogas digesters, biogas holders, incinerators,
panels for solar energy collectors etc.
6. Other structures
Bus shelters, industrial shelters, pedestrian
bridges, skateboard rings, sculptures etc.
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