Chapter No 2 Introduction To Ferrocement
Chapter No 2 Introduction To Ferrocement
Chapter No 2 Introduction To Ferrocement
INTRODUCTION
TO FERROCEMENT
Chapter 2
INTRODUCTION TO FERROCEMENT
Introduction
[3]
The initial definition of ferrocement can be drawn from a patent application submitted
by Joseph-Louis Lambot of France, in 1852. The patent for iron-cement, contained
the following description:
My invention shows a new product which helps to replace timber where it is
endangered by wetness, as in wood flooring, water containers, and plant pots etc.
The new substance consists of a metal net of wire or sticks which are connected or
formed like a flexible woven mat. I give this net a form which looks in the best
possible way, similar to the articles I want to create. Then I put in hydraulic cement or
similar bitumen tar or mix, to fill up the joints.
Lambot built two rowboats in 1848 and 1849, in length respectively about 3.6 m and
3 m (12 and 9 foot), 1.3 m (4 ft) wide and 38 mm (1.5 in.) thick, and disclosed his
patent at the Paris exhibition in 1855 by showing one of the boats. The first boat is
now at the Brignoles museum in France (Figure 1.2). A typical modern version of a
ferrocement canoe is shown in Fig 1.3.
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Joseph Louis Lambot was born May 22, 1814, in MinFort-sur-Argens and died
August
2, 1887, in Brignoles, France
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In 1887 a Dutch man, Mr. Boon, built a small craft of ferrocement, the Zeemeuw (or
seagull) and several barges of reinforced mortar to carry ashes and refuse on water
canals. The Zeemeuw was reported to be still operating at the Amsterdam zoo in
1968. It is currently displayed in the lounge of the Vereeniging Nederlands Cement
Industries office in Amsterdam.
During the First World War, ships and barges were built with reinforced concrete, and
this was again attempted during the Second World War due to shortages of materials,
particularly steel. In effect, ferrocement was forgotten and replaced by reinforced and
pre stressed concrete
Ferrocement finally achieved wide acceptance in the early 1960s for boat building in
the United Kingdom, New Zealand, Canada and Australia. In 1968, the Fisheries
Department of the Food and Agriculture Organization (FAO) of the United Nations
started ferrocement boat building projects in Asia, Africa, and Latin America. Other
countries followed, including the Soviet Union, China, and several countries in SouthEast Asia. In 1972, the US National Academy of science formed a panel to report on
the application of ferrocement in developing countries. One of the recommendations
of the panel was to establish a worldwide center to collect, process, and disseminate
information on ferrocement. Subsequently, in 1976, the International Ferrocement
Information Center was established at the Asian Institute of Technology (AIT) in
STRENGTHENING OF REINFORCEMENT CONCRETE BEAM USING FERROCEMENT
CAST INSITU LAMINATES
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Bangkok, Thailand. In 1975, the American concrete Institute formed Committee 549,
Ferrocement. In 1991, the International Ferrocement Society was established (under
the leadership of R. Parma) with headquarters at AIT in Bangkok.
2.1.2
The following definition of ferrocement was given by ACI Committee 549 in a stateof-the-art report on ferrocement (ACI 549R) first published in 1980 and still enforced
at time of this writing.
Ferrocement 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. The mesh may be made of metallic or other suitable
materials.[4]
2.1.3
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Based on past experience and advances in ferrocement, the author suggests the
following definition, which is an extension of that of ACI Committee 549:
Ferrocement 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. The mesh may be made of metallic or other suitable
materials. The fineness of the mortar matrix and its composition should be compatible
with the mesh and armature system it is meant to encapsulate. The matrix may contain
discontinuous fibers.
2.1
APPLICATIONS OF FERROCEMENT
In its role as a thin reinforced concrete product and as a laminated cement-based
composite, ferrocement can be used in numerous applications, including new
structures and the repair and rehabilitation of existing structures. [5]
2.1.1
Marine Applications
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[6] Initially ferrocement was defined as being made of a cement-based matrix and
steel mesh reinforcement. A broader definition of ferrocement would include the use
of skeletal steel in addition to the mesh system, and a cementitious matrix with and
without short discontinuous fibers. Typical reinforcement armatures for ferrocement
with and without skeletal steel are shown in Fig 1.12. An overview of ferrocement
composition, reinforcing parameters and properties is given in Table 1.1
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2.2.1
Cement Mortar Matrix: Composition and
Compressive Strength
The hydraulic cement matrix for ferrocement should be designed according standard
mix design procedures for mortar and concrete. Its components generally include
Portland cement, fine aggregates (sand), water, and various admixtures. The materials
should satisfy standards similar to those used for quality reinforced concrete
construction, with particular attention paid to the type of application.
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2.2.2
Skeletal Steel
In ferrocement construction skeletal steel is often used in the form of welded wire
fabric, or simply as a grid of steel wires, rods, or strands. Such skeletal reinforcement
is needed to form the skeletal of the shape of the structure to be built, around which
the mesh layers are later attached. The use of skeletal steel, when the thickness of
ferrocement allows it, can be very cost affective. It acts as a spacer, leading to savings
in mesh layers. It also adds significantly to the tensile and punching shear resistance
of ferrocement.
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2.4 Physical
Compared to reinforced concrete, ferrocement
2.4.2
Is a thinner material.
Has distributed reinforcement throughout its thickness.
Is reinforced in two directions (transverse and longitudinal).
Has a matrix made of fine mortar or paste instead of concrete which contains
larger size aggregates (the maximum size of the particles in ferrocement is
controlled by the average opening of the stack of mesh system to be
encapsulated).
Mechanical
Ferrocement can have homogenous-isotropic properties in two directions; twoway action and a high level of redundancy in indeterminate systems are
expected.
Ferrocement generally has a high tensile strength and a high modulus of
rupture. Its tensile strength can be of the same order as its compressive
strength.
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2.4.3
Processing / Manufacturing / Maintenance /
Repair
2.4
SIMILARTIES BETWEEN FERROCEMENT AND
REINFORCED CONCRETE
There are numerous similarities between ferrocement and reinforced concrete. In
addition to the fact that both use similar matrix and reinforcement materials, they obey
the same principles of mechanics and can be modeled according to the same theories;
they can be analyzed using similar techniques; and they can be designed according to
the same philosophy, such as the limit state design philosophy to satisfy both ultimate
and serviceability limit states. One must keep in mind, however, that ferrocement can
be considered an extreme boundary of reinforced concrete and, as such, scale effects
may be significant enough to differentiate them.[8]
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2.5
2.5.1
When the same square or rectangular wire mesh is used throughout the depth of a
ferrocement element, the volume fraction of reinforcement can be calculated from
the
following equation. [9]
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2.6.1
FRP Meshes
The diameter of a yarn of a fiber reinforced plastic or polymeric (FRP) mesh (as of a
textile yarn) is generally given in a unit called denier. A denier is defined as the
weight in grams of 9000 meters of yarn. Hence a 9000 m long yarn of 200 denier
would weigh 200g. For yarns or bundles of filaments of any cross section, round or
not, it is often desirable to determine the equivalent diameter. [9]
Let us consider a fiber or yarn with a denier value Df. Define:
Wf = weigh of yarn material in grams per meter
Yf
= Specific gravity of yarn material, in grams per cm3.
Assuming a round fiber of diameter Df, or a non-round yarn of equivalent diameter,
Df, it can be shown that:
For a mesh of wire diameter (or equivalent wire diameter) dw, the following relation
can be easily derived.
4 Vr
2 dw
In the special case of a tensile prism with longitudinal reinforcement only, Eq. 1.12
becomes
Sr
SrL
4 VrL
dw
Where Ac is the cross sectional area of the composite and p is the sum of perimeters of
all the wires crossing Ac.
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Sr can be divided into two parts one associated with the longitudinal and the other with
the transverse direction, thus:
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2.8.2
2.8.1
Numerous and lengthy debates have taken place among specialists as to how to define
first cracking in ferrocement, and more generally fiber reinforced cementitious
STRENGTHENING OF REINFORCEMENT CONCRETE BEAM USING FERROCEMENT
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composites. Indeed it can be shown that cement matrices develop micro cracks (penny
shaped two-and three-dimensional surface cracks) as soon as they are subjected to
tensile loading.
Numerous experimental studies have observed that, everything else being equal, the
tensile stress at first cracking in ferrocement is directly related to the specific surface
of reinforcement
2.8.2
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2.8.3
Testing a layer of bare mesh in tension may give a substantially smaller elastic
modulus than testing a single wire taken from that mesh. Moreover, a layer of mesh
cut in the longitudinal (warp) direction may have a different modulus and tensile
strength than a mesh cut in the transverse (woof) direction. This is particularly true for
meshes that are not square welded.
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All the benefits that are attributed to the use of concrete and reinforced concrete in the
construction applications generally applied to ferrocement as well. However, there are
attributes that make ferrocement a preferred material when compared to wood, masonry,
reinforced concrete, steel, and fiber reinforced plastics. [13]
1. Ferrocement is made of materials that are readily available in most countries; should
steel meshes be in short supply, other ingenious reinforcing systems made of jute,
sisal, bamboo, and the like can be used.
2. Ferrocement is suitable for a wide range of construction techniques, ranging from
self-help construction for housing and agricultural structures, to highly prefabricated
industrial processes, including precast panels for housing, pipes, channels, and curtain
walls.
3. At the low end, ferrocement requires a low level of technology and common labor
skills; because it is relatively light weight, it does not require heavy construction
equipment or plants.
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4. At the high end, ferrocement is suited for industrialized construction and high levels
of prefabrication, where its relative light weight compared to conventional reinforced
concrete is also a benefit.
5. Ferrocement can be fabricated in any desired shape; it is particularly suitable for
shells and free form shapes and has been used for domes, boats, housing structures,
and sculptures.
6. Ferrocement, like concrete and masonry, is durable and resistant to the environment; it
is non-flammable; is less prone to corrosion than steel; is not sensitive to humidity
and, unlike wood, does not rot; and has a significantly longer service life than fiber
reinforced plastics.
7. Ferrocement can be easily maintained and repaired after damage.
8. Ferrocement is cost effective.
9. According to a definition adopted by the United Nations Conference on Environment
and Development, ferrocement can be considered an environmentally sound
technology. Environmentally sound technologies protect the environment, are less
polluting, use all resources in a more sustainable manner recycle more of their wastes
and products and handle residual wastes in a more acceptable manner than
technologies for which they substitute. Ferrocement qualifies in terms of using fewer
resources and less energy, in being less polluting, and in generating less waste.