Polymers in Civil EngineeringPolymers 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 Polymerization

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

Plastic TypesPlastic 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)

Natural PolymersNatural Polymers

· wood· leather· cotton· rubber· wool· asphalt

Manufactured PolymersManufactured Polymers

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

Epoxy (thermosetting)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

EpoxyEpoxy

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

EpoxyEpoxy

Applications Adhesive (old concrete to new

concrete, welding cracked concrete, bonding diverse materials)

Patching voids Durable overlays and coatings

PolyestersPolyesters

• Thermoplastic or Thermoset• Physical Properties

Strength and Moduli vary with temperature and formulation

Thermal coefficient greater than concrete

PolyestersPolyesters

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

Applications of PolyesterApplications 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

Sulfur Concrete (thermoplastic)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%@ 2 h; 100%@ 24 h) High strength (7000 psi) Will set below freezing

Sulfur ConcreteSulfur Concrete

Disadvantages Requires special

equipment Special handling

required - high temperature (280°F)

Will melt at 246°F Few applicators

Applications High chemical

resistance floors, etc.

Rapid pavement repair or construction

Methyl Methacrylate (MMA)Methyl Methacrylate (MMA)

ThermosetPhysical Properties clear or any color thermal expansion higher than

concrete low viscosity (< water) high strength

MMAMMA

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

MMAMMA

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

Polystyrene (thermoplastic)Polystyrene (thermoplastic)

Advantages water resistant dimensional

stability inexpensive

Disadvantages low tensile

strength low modulus poor heat

resistance poor weather

resistance brittle, low

toughness

Polyvinyl chloride, PVCPolyvinyl chloride, PVC

ThermoplasticPhysical 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)

PVCPVC

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

PVCPVC

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

Polyethylene (thermoplastic)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

PolyethylenePolyethylene

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

PolyurethanePolyurethane

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

Polymer CompositesPolymer Composites

An Overview

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

Typical Properties

E, GPa Ft, MPa y

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

What is FRP?What is FRP?

FRP stands for Fiber Reinforced PlasticFRP is used in structural shapes, repair materials or as reinforcement for concreteFRP is a composite material consisting of artificial fibers encased in a resin matrix

Materials Used in FRPMaterials Used in FRP

Fiber Types+ Glass+ Poly-Vinyl Alcohol

(PVA)+ Carbon+ Aramid (Kevlar)

Resin Types+ Epoxy+ Polyester

Resins are thermosetting

Manufacture of FRP RodsManufacture 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 FRPEngineering 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 FRPApplications of FRP

Reinforcement bars for ConcretePrestressing Tendons for Concrete MembersFRP sheets can be used to increase flexural strength in weakened or underdesigned members

Advantages of FRPAdvantages of FRP

Will Not Corrode In Field ConditionsLightweightStrong in TensionMethods of Construction Same as Steel Reinforcement

Disadvantages of FRPDisadvantages of FRP

Low Moduli of ElasticityCannot be Shaped in the FieldMore Expensive than SteelCoefficients of Thermal Expansion are Different than Those of Steel or Concrete

ConclusionConclusion

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