Polymers%20in%20Civil%20Engineering

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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.

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Polymerization

• the use of heat, pressure or a chemical catalyst
  to link monomer material into polymer chains.

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Plastic Types

• Thermosetting plastic
• a polymer material that cannot be reformed after
  manufacturing
• cross linked chain networks
• less creep, isotropic
• good structural properties
• injection molded

• Thermo plastic
• a polymer that can be remolded after
  manufacturing.
• softens upon reheating
• substantial creep, isotropic properties
• extrusion (PVC pipe) or molding (PET soda bottles)

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Natural Polymers

• wood
• leather
• cotton
• rubber
• wool
• asphalt

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Manufactured Polymers

• Epoxy (thermosetting)
• Polyesters (thermoplastic or thermoset)
• Sulfur Concrete (thermoplastic)
• Methyl Methacrylate (MMA)
• Polyurethane
• Polystyrene (thermoplastic)
• Polyvinyl chloride, PVC (thermoplastic)
• Polyethylene (thermoplastic)

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Epoxy (thermosetting)

• Physical Properties
• 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

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Epoxy

• Disadvantages and limitations
• 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

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Epoxy

• Applications
• Adhesive (old concrete to new concrete, welding
  cracked concrete, bonding diverse materials)
• Patching voids
• Durable overlays and coatings

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Polyesters

• Thermoplastic or Thermoset
• Physical Properties
• Strength and Moduli vary with temperature and
  formulation
• Thermal coefficient greater than concrete

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Polyesters

• Advantages
• Good Chemical Resistance
• Easy to use
• Good strength
• Good ductility
• Inexpensive

• Disadvantages and Limitations
• Some have marginal bond quality
• More expansion and shrinkage than concrete

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Applications of Polyester

• 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

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Sulfur Concrete (thermoplastic)

• Physical Properties
• Modulus of Elasticity similar to concrete
• Thermal expansion greater than concrete
• Advantages
• Exceptional chemical resistance
• Cold joints preventable
• Rapid Strength gain (80_at_ 2 h 100_at_ 24 h)
• High strength (7000 psi)
• Will set below freezing

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Sulfur Concrete

• Disadvantages
• Requires special equipment
• Special handling required - high temperature
  (280F)
• Will melt at 246F
• Few applicators

• Applications
• High chemical resistance floors, etc.
• Rapid pavement repair or construction

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Methyl Methacrylate (MMA)

• Thermoset
• Physical Properties
• clear or any color
• thermal expansion higher than concrete
• low viscosity (lt water)
• high strength

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MMA

• Advantages
• Rapid Strength
• Good bond to dry surfaces
• Easy to mix
• Pre-packaged mixes
• Impermeable to water
• resistance to acids
• excellent abrasion resistance

• Disadvantages
• expensive
• hazardous (fire)
• odor
• more shrinkage than concrete

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MMA

• Applications
• Plexiglas
• Pavement of bridge decks
• Thin Overlays (3/16")
• Impregnation
• precast elements

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Polystyrene (thermoplastic)

• Advantages
• water resistant
• dimensional stability
• inexpensive

• Disadvantages
• low tensile strength
• low modulus
• poor heat resistance
• poor weather resistance
• brittle, low toughness

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Polyvinyl chloride, PVC

• Thermoplastic
• Physical Properties
• 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)

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PVC

• Advantages
• excellent insulator
• diverse applications
• chemical resistance
• long-term stability
• flame resistant
• weather resistant
• Adhesion to glass
• resistance to oil

• Disadvantages
• low modulus
• Moisture sensitivity in production

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PVC

• Applications
• pipe
• raincoats
• window frames and moldings
• electrical cables
• floor tiles
• siding

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Polyethylene (thermoplastic)

• Physical Properties
• E .13 GPa (.19 x 105 psi)
• ?t 1.0 x10-4/F
• tensile strength 13.8 MPa (2 ksi)
• Advantages
• tough, durable, weather resistant
• chemical and moisture resistance
• excellent electrical properties

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Polyethylene

• Applications
• sheet plastic, membranes, liners
• pipe, electrical conduit
• tanks, bottles

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Polyurethane

• Physical Properties
• Sensitive to temperature and RH
• low elastic moduli 4- 400 ksi
• Advantages
• Resistant to Chemicals
• lightweight and resistant to wear
• Closed Cell material when used with foams
• Cryogenic performance

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Polymer Composites

• An Overview

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Composites with Thermoplastics

• Glass Fiber Composites (20-40 wt)
• Monofilament
• Braided Strand
• Chop Fiber
• Polymer
• Polypropylene (PP), Polycarbonate (PC),
  Polyethylene Terephthalate (PET), Polybutylene
  Terephthalate (PBT), Nylon

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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 -
Steel 200 400 0.002
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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

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Materials Used in FRP

• Fiber Types
• Glass
• Poly-Vinyl Alcohol (PVA)
• Carbon
• Aramid (Kevlar)

• Resin Types
• Epoxy
• Polyester
• Resins are thermosetting

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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

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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

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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

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Advantages of FRP

• Will Not Corrode In Field Conditions
• Lightweight
• Strong in Tension
• Methods of Construction Same as Steel
  Reinforcement

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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

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Conclusion

• FRP Reinforcement is an Engineered Material that
  Shows Great Promise In the Future of Civil
  Engineering