Application of Polymer Concrete APPLICATION OF POLYMER MODIFIED CONCRETE 1. INTRODUCTION Despite being thought of as a modern material, concrete has been in use for hundreds of years. The word concrete comes from the Latin concretus, which means “mixed together” or compounded. Concrete is an extremely popular structural material due to its low cost and easy fabrication. Concrete is made up of sand or stone, known as aggregate, combined with cement paste to bind it. Aggregate can be of various sizes. It is broadly categorized as fine (commonly sand) and coarse (typically crushed stone or gravel). The greater proportion of concrete is aggregate which is bulky and relatively cheaper than the cement. As much of the constituents of concrete come from stone, it is often thought that concrete has the same qualities and will last forever. Concrete has been called artificial stone, cast stone, reconstructed stone and reconstituted stone. However, concrete must be thought of as a distinct material to stone. It has its own characteristics in terms of durability, weathering and repair. Concrete is a relatively durable and robust building material, but it can be severely weakened by poor manufacture or a very aggressive environment. A number of historic Department of Civil Engineering, JNNCE Shivamogga Page 1
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Application of Polymer Concrete
APPLICATION OF POLYMER MODIFIED CONCRETE
1. INTRODUCTION
Despite being thought of as a modern material, concrete has been in use
for hundreds of years. The word concrete comes from the Latin concretus,
which means “mixed together” or compounded. Concrete is an extremely
popular structural material due to its low cost and easy fabrication.
Concrete is made up of sand or stone, known as aggregate, combined
with cement paste to bind it. Aggregate can be of various sizes. It is
broadly categorized as fine (commonly sand) and coarse (typically crushed
stone or gravel). The greater proportion of concrete is aggregate which is
bulky and relatively cheaper than the cement.
As much of the constituents of concrete come from stone, it is often
thought that concrete has the same qualities and will last forever.
Concrete has been called artificial stone, cast stone, reconstructed stone
and reconstituted stone. However, concrete must be thought of as a
distinct material to stone. It has its own characteristics in terms of
durability, weathering and repair.
Concrete is a relatively durable and robust building material, but it can be
severely weakened by poor manufacture or a very aggressive
environment. A number of historic concrete structures exhibit problems
that are related to their date of origin. These problems can be solved by
application of polymer in concrete construction.
A polymer is a large molecule containing hundreds or thousands of atoms
formed by combining one, two or occasionally more kinds of small
molecule (monomers) into chain or network structures. The main polymer
material used in concrete construction are polymer modified concrete and
polymer concrete.
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Application of Polymer Concrete
Polymer modified concrete may be divided into two classes: polymer
impregnated concrete and polymer cement concrete. The first is produced
by impregnation of pre-cast hardened
Portland cement concrete with a monomer that is subsequently converted
to solid polymer. To
produce the second, part of the cement binder of the concrete mix is
replaced by polymer (often in latex form). Both have higher strength,
lower water permeability, better resistance to chemicals, and greater
freeze-thaw stability than conventional concrete.
Polymer concrete (PC), or resin concrete, consists of a polymer binder
which may be a thermoplastic but more frequently is a thermosetting
polymer, and a mineral filler such as aggregate, gravel and crushed stone.
PC has higher strength, greater resistance to chemicals and corrosive
agents, lower water absorption and higher freeze-thaw stability than
conventional Portland cement concrete.
2. AIM
The main aims of this research are to identify and present the application
of polymer in concrete construction
3. OBJECTIVES
The objectives of this work are:
i) To study the application of polymer in concrete construction.
ii) To determine the advantage and disadvantage of polymer.
iii) To investigate the problems in the use of the polymer as repair
materials in concrete construction
4. INTRODUCTION TO POLYMERS
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Application of Polymer Concrete
Polymers are a large class of materials consisting of many small molecules
(called monomers) that can be linked together to form long chains, thus
they are known as macromolecules. A typical polymer may include tens of
thousands of monomers. Because of their large size, polymers are
classified as macromolecules. Humans have taken advantage of the
versatility of polymers for centuries in the form of oils, tars, resins, and
gums.
However, it was not until the industrial revolution that the modern polymer
industry began to
develop. In the late 1830s, Charles Goodyear succeeded in producing a
useful form of natural
rubber through a process known as "vulcanization." Some 40 years later,
Celluloid (a hard plastic formed from nitrocellulose) was successfully
commercialized. Despite these advances, progress in polymer science was
slow until the 1930s, when materials such as vinyl, neoprene, polystyrene,
and nylon were developed. The introduction of these revolutionary
materials began an explosion in polymer research that is still going on
today Unmatched in the diversity of their properties, polymers such as
cotton, wool, rubber and all plastics are used in nearly every industry.
Natural and synthetic polymers can be produced with a wide range of
stiffness, strength, heat resistance, density, and even price. With
continued research into the science and applications of polymers, they are
playing an ever increasing role in society
5. POLYMER MODIFIED CONCRETE
Although its physical properties and relatively low cost make it the most
widely used construction material, conventional Portland cement concrete
has a number of limitations, such as low flexural strength, low failure
strain, susceptibility to frost damage and low resistance to chemicals.
These drawbacks are well recognized by the engineer and can usually be
allowed for in most applications. In certain situations, these problems can
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Application of Polymer Concrete
be solved by using materials which contain an organic polymer or resin
(commercial polymer) instead of Portland cement. These relatively new
materials offer the advantages of higher strength, improved durability,
good resistance to corrosion and reduced water permeability.
There are three principal classes of composite materials containing
polymers:
1. Polymer impregnated concrete
2. Polymer cement concrete
3. Polymer concrete.
The distinction between these three classes is important to the design
engineer in the selection of the appropriate material for a given
application.
5.1 Polymer Impregnated Concrete
Polymer impregnated concrete is made by impregnation of pre-cast
hardened Portland cement concrete with low viscosity monomers (in either
liquid or gaseous form) that are converted to solid polymer under the
influence of physical agents (ultraviolet radiation or heat) or chemical
agents (catalysts). It is produced by drying conventional concrete;
displacing the air from the
open pores (by vacuum or monomer displacement and pressure);
saturating the open pore structure by diffusion of low viscosity monomers
or a pre-polymer-monomer mixture (viscosity 10 cps; 1 x 10-2 Pa·s); and in-
situ polymerization of the monomer or pre-polymer-monomer mixture,
using the most economical and convenient method (radiation, heat or
chemical initiation). The important feature of this material is that a large
proportion of the void volume is filled with polymer, which forms a
continuous reinforcing network. The concrete structure may be
impregnated to varying depths or in the surface layer only, depending on
whether increased strength and/or durability is sought. The main
disadvantages of polymer impregnated concrete products are their
relatively high cost, as the monomers used in impregnation are expensive
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Application of Polymer Concrete
and the fabrication process is more complicated than for unmodified
concrete.
Impregnation of concrete results in a remarkable improvement in tensile,
compressive and impact strength, enhanced durability and reduced
permeability to water and aqueous salt solutions such as sulfates and
chlorides. The compressive strength can be increased from 35 MPa to 140
MPa, the water absorption can be reduced significantly. And the freeze-
thaw resistance is considerably enhanced. The greatest strength can be
achieved by impregnation of auto-claved concrete. This material can have
a compressive-strength-to-density ratio nearly three times that of steel.
Although its modulus of elasticity is only moderately greater than that of
non-autoclaved polymer impregnated concrete, the maximum strain at
break is significantly higher.
The monomers most widely used in the impregnation of concrete are, such
as
1. Methyl methacrylate (MMA)
2. Styrene
3. Acrylonitrile
4. T-butyl styrene
5. Vinyl acetate
Acrylic monomer systems such as methyl methacrylate or its mixtures
with acrylonitrile are the preferred impregnating materials, because they
have low viscosity, good wetting properties, high reactivity, relatively low
cost and result in products with superior properties. By using appropriate
bifunctional or polyfunctional monomers (cross-linking agents) in
conjunction with MMA, a cross-linked network is formed within the pores,
resulting in products with greatly increased mechanical strength and
higher thermal and chemical
resistance. Improvement of these properties will depend on the degree of
cross-linking. A cross-linking agent commonly used with vinyl monomers
such as MMA and styrene is trimethylolpropane trimethacrylate.
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Application of Polymer Concrete
Thermosetting monomers and pre-polymers are also used to produce
polymer impregnated concrete with greatly increased thermal stability
(i.e. resistance to deterioration by heat). These include epoxy pre-
polymers and unsaturated polyester-styrene. These monomers and pre-
polymers are relatively viscous and, therefore, their use results in reduced
impregnation. Their viscosity can be reduced by mixing them with low-
viscosity monomers such as MMA.
Applications of concrete impregnated in depth in building and construction
include structural floors, high performance structures, food processing
buildings, sewer pipes, storage tanks for seawater, desalination plants and
distilled water plants. Marine structures, wall panels, tunnel liners,
prefabricated tunnel sections and swimming pools. Partially impregnated
concrete is used for the protection of bridges and concrete structures
against deterioration and repair of deteriorated building structures, such
as ceiling slabs, underground garage decks and bridge decks.
Table no: 5.1 General Characteristics and Applications of Polymer-
Modified Concretes
Polymer Impregnated Concrete
General
Characteristics
Consists generally of a pre-cast concrete, which has
been dried then impregnated with a low viscosity
monomer that polymerizes to form a network within
the pores. Impregnation results in markedly improved
strength and durability in comparison with conventional
concrete.
Principal
Applications
Principal applications include use in structural steel