Cost Efficient Construction
(COTM 5271)
Ermias Adane (MSc, PCM)
Material Selection in Design
Key Principles:
• Minimize the use of non-renewable construction materials and
other resources such as energy and water through efficient
engineering, design, planning and construction and effective
recycling of construction debris.
• Maximize the use of recycled content materials, modern
resource efficient engineered materials, and resource efficient
composite type structural systems wherever possible.
• Maximize the use of re-usable, renewable, sustainably
managed, bio-based materials.
• Remember that human creativity and our abundant labor
force is perhaps our most valuable renewable resource.
Alternative walling materials
• Precast/factory-made walling units using light weight cellular
concrete
• Concrete hollow blocks
• Timber/bamboo
• Ferro-cement
• Mud (Wattle & Daub)
• Sun-dried bricks
• Rammed earth
• Stabilized soil blocks
• Kiln-burnt bricks
• Stone block masonry
The various alternative materials
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Clay/micro-concrete tiled roofing
Stone roofing with distributors
Corrugated sheet: galvanized iron (GI) and asphaltic
Prefabricated brick panel
'L'panel roofing
Plank and Joist system
Clay tile - RCC batten root
Precast cellular concrete roofing unit
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RCC channel units
Precast joist and hollow block construction
Precast RCC solid planks/joists
Funicular shells over edge beams
Precast plate floors
Ferrocement roofing elements
Filler slab roofing with various filler material
FERRO CEMENT
‘Ferro cement is a type of thin wall
reinforced concrete commonly
constructed of hydraulic cement
mortar reinforced with closely
spaced layers of continuous and
relatively small size wire mesh.’
ACI Committee 549 definition
Materials used
• Portland Cement mortar mix
• Skeleton steel
• Steel mesh reinforcement or Fiberreinforced polymeric meshes
• Admixtures, and coatings.
.Cont. ..
The construction of ferrocement can be divided into four phases:
1. fabricating the steel rods to form a skeletal framing system;
2. tying or fastening rods and mesh to the skeletal framing;
3. plastering; and
4. curing.
• Formwork is usually not required, in contrast to conventionally
reinforced concrete construction,
• Ferrocement is especially suitable for curved surfaces, such as
• shells and
• free-form shapes
➢Mortar provides the mass and wire mesh imparts tensile strength
and ductility.
➢Ferro cement is a super reinforced concrete. It differs from
conventional concrete in that there is a higher ratio of steel to cement
mortar.
Mix ratios
▪ Ordinary Portland cement and fine aggregate matrix is used
▪ The matrix constitutes 95% cement mortar & 5% or more wire mesh.
▪ FA (sand), occupies 60 to 75% of the volume of the mortar
▪ Water-cement ratios in ferrocement production vary between 0.30 and 0.55, by weight (mass).
▪ Water-reducing admixtures may be used to enhance mix plasticity and reduce water.
Reinforcement concentration should be at least 440 to 500 kg/m3 (or 5.1 to 6.3 percent of the total
volume),
Average spacing between reinforcing elements should be of the order of 5 mm to 10 mm
MIX PROPORTIONS
➢Sand: cement ratio (by mass) 1.5 to 2.5
➢Water: cement ratio (by mass) 0.35 to 0.60
STEEL WIRE MESH REINFORCEMENT
▪ The reinforcing mesh Consists of galvanized steel wires of
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diameter 0.5 to 1.5 mm, spaced at 6 to 20mm center to
center
It may be of different kind, the main requirement being
flexibility.
It should be clean and free from dust, grease, paint, loose
rust and other substances.
Addition of short and discrete fibers of different types
favorably affects the control of cracking and the capacity
of the matrix to resist tensile loads.
Relatively short and slender (l/d = 100) steel fibers may be
randomly distributed in hydraulic cement mortars for
effective production of ferrocement, to increase tensile
strength and improve the shear resistance of these
mortars.
.Cont. ..
Fig. Samples of woven wire mesh
Fig. Sample of expanded metal lath
Meshes materials
• Metallic mesh,
• Non Metallic Meshes, Such as
• woven alkali resistant glass,
• organic woven fabrics (i.e. polypropylene),
• organic natural fabrics made with jute, burlap, or bamboo fibers.
▪ woven or interlocking mesh (such as chicken wire cloth),
▪ woven cloth mesh in which filaments are interwoven and
their intersections are not rigidly connected,
▪ welded mesh in which a rectangular pattern is formed by
perpendicular intersecting wires welded together at their
intersections
Fig. Samples of hexagonal
and welded wire mesh
SKELETON STEEL
➢It support the steel wire mesh
➢Thickness varies from 6-20mm according to loading condition
• Generally mild steel or Fe 415 or Fe 500 bars are used
• Spacing 7.5cm to 12m
➢Used to impart structural strength in case of boats, barges etc.
➢Reinforcement should be free from dust, rust and other impurities.
TECHNIQUES OF
MANUFACTURES
➢ Hand plastering
➢ semi-mechanised
process
➢ Centrifuging and
Guniting (Shotcrete
APPLICATIONS OF FERRO CEMENT
1. Marine Applications
➢ Boats, fishing vessels, barges, cargo tugs, flotation buoys
➢ Key criteria for marine applications: light weight, impact resistance, thickness and water tightness
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
.Cont. ..
4. Residential Buildings
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Houses, community centers, precast housing elements, corrugated roofing sheets, wall panels etc.
5. Rural Energy
➢ Biogas digesters, biogas holders, incinerators, panels for solar energy collectors etc.
6. Miscellaneous uses
➢ Mobile homes
➢ Kiosks
➢ Wind tunnel
➢ Silos and bins
Ferrocement
water tank
Construction Method – Example
Construction Method – Example
Candela’s L’Oceanografic (2002), Valencia, Spain
Nervi’s exhibition hall (1949), Turin, Italy,
Rib trusses & ferrocement panels
Kenya Ferrocement Technology
PROPERTIES OF FERRO CEMENT
➢It is very durable, cheap and versatile material
➢Less shrinkage, and low weight
➢High tensile strength and stiffness
➢Better impact and punching shear resistance
➢Undergo large deformation (deflection) before cracking or high
deflection
ADVANTAGES OF FERRO-CEMENT
➢ It is highly versatile and can be formed into almost any shape for a wide range of uses
➢ 20% savings on materials and cost
➢ Suitability for pre-casting
➢ Flexibility in cutting, drilling and jointing
➢ Very appropriate for developing countries; labor intensive
➢ Good fire resistance
➢ Good impermeability
➢ Low maintenance costs
➢Thin elements and light structures, reduction in self weight & Its simple
techniques require a minimum of skilled labor
➢Reduction in expensive form work so economy & speed can be achieved
➢Only a few simple hand tools are needed to build any structures
➢Structures are highly waterproof & Higher strength to weight ratio than R.C.C.
DISADVANTAGES OF FERRO-CEMENT
➢Low shear strength
➢It can be punctured by collision with pointed objects.
➢Corrosion of the reinforcing material due to the incomplete coverage
of metal by mortar.
➢It is difficult to fasten to ferrocement with bolt, screw, welding and
nail etc.