Polymers in Civil Engineering
“Poly” “meros” = many parts
Monomer = non-linked “mer” material
Polymers = long continuous chain molecules
formed from repeated sequences of small
organic units (mers). molecular weight in
excess of 10,000.
Polymerization
the use of heat, pressure or a chemical
catalyst to link monomer material into
polymer chains.
Plastic Types
Thermosetting plastic
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a polymer material that
cannot be reformed after
manufacturing
cross linked chain
networks
less creep, isotropic
good structural
properties
injection molded
Thermo plastic
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a polymer that can
be remolded after
manufacturing.
softens upon
reheating
substantial creep,
isotropic properties
extrusion (PVC pipe)
or molding (PET
soda bottles)
Natural Polymers
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wood
leather
cotton
rubber
wool
asphalt
Manufactured Polymers
Epoxy (thermosetting)
Polyesters (thermoplastic or thermoset)
Sulfur Concrete (thermoplastic)
Methyl Methacrylate (MMA)
Polyurethane
Polystyrene (thermoplastic)
Polyvinyl chloride, PVC (thermoplastic)
Polyethylene (thermoplastic)
Epoxy (thermosetting)
Physical Properties
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Strength and Moduli vary with temperature and
formulation
Thermal coefficient greater than concrete
Brittle behavior (more brittle than concrete)
Excellent adhesion - tenacious bond
High tensile and compressive strength
Highly resistant to chemical attack and wear
Epoxy
Disadvantages and limitations
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Properties are very sensitive to mixing and
proportioning procedures
Some cannot be used in moist environments
Strong Allergenic, safety
Some have strong oder prior to polymerization
Physical properties are substantially different from
other materials
Epoxy
Applications
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Adhesive (old concrete to new concrete,
welding cracked concrete, bonding diverse
materials)
Patching voids
Durable overlays and coatings
Polyesters
• Thermoplastic or Thermoset
• Physical Properties
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Strength and Moduli vary with temperature
and formulation
Thermal coefficient greater than concrete
Polyesters
Advantages
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Good Chemical
Resistance
Easy to use
Good strength
Good ductility
Inexpensive
Disadvantages and
Limitations
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Some have marginal
bond quality
More expansion and
shrinkage than
concrete
Applications of Polyester
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Floor coatings
Protective coatings
Adhesive bonder or sealer
Binder for fiberglass or artificial wood
Sealer for Epoxy injection
Anchoring for drilled holes
Binder for polymer mortar
Sulfur Concrete (thermoplastic)
Physical Properties
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Modulus of Elasticity similar to concrete
Thermal expansion greater than concrete
Advantages
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Exceptional chemical resistance
Cold joints preventable
Rapid Strength gain (80%@ 2 h; 100%@ 24 h)
High strength (7000 psi)
Will set below freezing
Sulfur Concrete
Disadvantages
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Requires special
equipment
Special handling
required - high
temperature (280°F)
Will melt at 246°F
Few applicators
Applications
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High chemical
resistance floors, etc.
Rapid pavement
repair or construction
Methyl Methacrylate (MMA)
Thermoset
Physical Properties
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clear or any color
thermal expansion higher than concrete
low viscosity (< water)
high strength
MMA
Advantages
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Rapid Strength
Good bond to dry
surfaces
Easy to mix
Pre-packaged mixes
Impermeable to water
resistance to acids
excellent abrasion
resistance
Disadvantages
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expensive
hazardous (fire)
odor
more shrinkage than
concrete
MMA
Applications
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Plexiglas
Pavement of bridge decks
Thin Overlays (3/16"+)
Impregnation
precast elements
Polystyrene (thermoplastic)
Advantages
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water resistant
dimensional stability
inexpensive
Disadvantages
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low tensile strength
low modulus
poor heat resistance
poor weather
resistance
brittle, low
toughness
Polyvinyl chloride, PVC
Thermoplastic
Physical Properties
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Tensile 10-41 MPa (1500 - 6000 psi)
Compressive 55-110 MPa (8000 - 16000
psi)
200 - 15 % elongation
t = 75 x 10-6 in./in./°C
E = 3.6 Gpa (5 x 105 psi)
PVC
Advantages
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excellent insulator
diverse applications
chemical resistance
long-term stability
flame resistant
weather resistant
Adhesion to glass
resistance to oil
Disadvantages
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low modulus
Moisture sensitivity
in production
PVC
Applications
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pipe
raincoats
window frames and moldings
electrical cables
floor tiles
siding
Polyethylene (thermoplastic)
Physical Properties
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E = .13 GPa (.19 x 105 psi)
t = 1.0 x10-4/°F
tensile strength 13.8 MPa (2 ksi)
Advantages
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tough, durable, weather resistant
chemical and moisture resistance
excellent electrical properties
Polyethylene
Applications
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sheet plastic, membranes, liners
pipe, electrical conduit
tanks, bottles
Polyurethane
Physical Properties
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Sensitive to temperature and RH
low elastic moduli 4- 400 ksi
Advantages
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Resistant to Chemicals
lightweight and resistant to wear
Closed Cell material when used with foams
Cryogenic performance
Polymer Composites
An Overview
Composites with Thermoplastics
Glass Fiber Composites (20-40% wt)
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Monofilament
Braided Strand
Chop Fiber
Polymer
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Polypropylene (PP), Polycarbonate (PC),
Polyethylene Terephthalate (PET),
Polybutylene Terephthalate (PBT), Nylon
Typical Properties
E, GPa
Ft, MPa
ey
PP
5
70-90
0.02
PC & PBT
8
120
0.02
Aramid
80-170
3500
-
Carbon
34-800
5000
-
200
400
0.002
Steel
What is FRP?
FRP stands for Fiber Reinforced Plastic
FRP is used in structural shapes, repair
materials or as reinforcement for
concrete
FRP is a composite material consisting
of artificial fibers encased in a resin
matrix
Materials Used in FRP
Fiber Types
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Glass
Poly-Vinyl Alcohol
(PVA)
Carbon
Aramid (Kevlar)
Resin Types
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+
Epoxy
Polyester
Resins are
thermosetting
Manufacture of FRP Rods
Pultrusion
+
Enables a high percentage of fibers to be
included in the cross section
Braiding
+
Creates surface deformations which
enhance the FRP to concrete bond
Hybrid Rods
Engineering Properties of FRP
High Tensile Strength
 On average, the tensile strength of FRP is 10%
to 500% greater than steel
Low Moduli of Elasticity
 With the exception of Carbon rods, FRP has
only 1/10 to 1/2 the modulus of steel
Linear Stress-Strain Relationship
Applications of FRP
Reinforcement bars for Concrete
Prestressing Tendons for Concrete
Members
FRP sheets can be used to increase
flexural strength in weakened or
underdesigned members
Advantages of FRP
Will Not Corrode In Field Conditions
Lightweight
Strong in Tension
Methods of Construction Same as Steel
Reinforcement
Disadvantages of FRP
Low Moduli of Elasticity
Cannot be Shaped in the Field
More Expensive than Steel
Coefficients of Thermal Expansion are
Different than Those of Steel or
Concrete
Conclusion
FRP Reinforcement is an Engineered
Material that Shows Great Promise In
the Future of Civil Engineering