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Concrete Repair: Bridges and Tunnels--Epoxies
- 1. Epoxy Applications Transportation Concrete Repair: Bridges and Tunnels ChemCo Systems
- 2. Epoxy Applications Transportation Civil uses Major roles: • Repair and Protection • Infrastructure Renovation – Bridges & Tunnels – Airports – Rail • Structural Rehabilitation – Commercial, Industrial & Residential – Public & Private Sectors ChemCo Systems
- 3. Epoxy Applications Transportation Corrosion = spalling Iron oxide (corrosion product commonly called rust) occupies about 7 times the volume of a similar mass of steel. The formation of rust generates high internal forces leading to spalling. Spalling is more common in applications with insufficient cover (depth of concrete over the steel reinforcement). ChemCo Systems
- 4. Epoxy Applications Transportation Salt: tough on steel and concrete ChemCo Systems
- 5. Epoxy Applications Transportation Monitor crack movement (strain gauge) ChemCo Systems
- 6. Epoxy Applications Transportation History of Epoxies 1936 First epoxy patents 1940s-50s Bakelight introduces commercial applications (electrical and jewelry) 1948 First use as construction adhesive (hardened-to-hardened concrete bonding) 1954 Caltrans uses bonding agent for traffic markers ChemCo Systems
- 7. Epoxy Applications Transportation History of Epoxies late 1950s Patching, bolt grouting, crack injection and overlays more common. 1959 U.S. Army Corp of Engineers issues specification 1959 PG&E dam successfully repaired using meter/mix pump and structural epoxy from Adhesive Engineering 1978 ASTM* C881 spec. published *American Society of Testing and Materials ChemCo Systems
- 8. Epoxy Applications Transportation Specification for civil engineering ASTM C881 Standard U.S. specification for epoxy bonding systems for concrete AASHTO* M-235 used by U.S. transportation design engineers as specification for epoxy bonding AASHTO M235 = ASTM C881 *American Association of State Highway and Transportation Officials ChemCo Systems
- 9. Epoxy Applications Transportation Properties: Viscosity measure of a material’s resistance to flow—common unit is centipoise (cps) Water = 1 cps Motor Oil = 100 - 500 cps (similar to some unfilled epoxies) Peanut Butter = 250,000 cps (similar to some epoxy pastes) ChemCo Systems
- 10. Epoxy Applications Transportation Properties: Modulus of Elasticity Ratio of stress to strain High modulus rigid or stiff • Structural uses – High creep resistance Low modulus flexible • Impact resistant, less brittle ChemCo Systems
- 11. Epoxy Applications Transportation Properties: Coefficient of Thermal Expansion (Thermal Compatibility {ASTM D648}) Materials change in size at Filled epoxies behave more like varying rates upon being heated concrete or steel or cooled • Aggregate gradation is key criteria Neat epoxies expand/contract at for filled epoxies (gap-grading is helpful) a higher rate than steel or concrete Important factor for thick layers and bulk applications EFFECT of BOND LINE STRESSES 50 45 NEAT EPOXY (SAND FREE) 40 35 30 25 MAXIMUM EPOXY SAND LOAD 20 AGGREGATE/BINDER RATIO EFFECT ON THE 15 THERMAL COEFFICIENT OF EXPANSION FOR AN EPOXY SYSTEM. 10 5 CONCRETE 10x6-6 0 1 2 3 4 5 6 7 8 9 ChemCo Systems
- 12. Epoxy Applications Transportation Properties: Heat deflection temperature (HDT) Temperature an adhesive polymer deflects under 3 point load 120ºF is minimum value for ASTM C881 load bearing structural use Cold temperature curing may undermine HDT performance Special adhesives available offering higher HDTs for high temperature use Creep is potential problem if use temp > HDT CONSTANT LOAD 264 psi Variable Hot Oil Bath EPOXY BEAM 1/2”x1/2”x5” ChemCo Systems
- 13. Epoxy Applications Transportation Properties: Reactions are exothermic Epoxies produce heat during cure Temperature dependent Mass dependent Can undermine product performance in bulk applications Exotherm may increase apparent shrinkage upon cure • Thick cross-sections and bulk uses should consider special low exotherm systems ChemCo Systems
- 14. Epoxy Applications Transportation Properties: Cure rate vs. temperature CURE RATE OF EPOXY ADHESIVES 160 140 120 Typical epoxy resin 100 Slower 80 Faster 60 40 20 0 30 40 50 60 70 80 90 100 Cure T e mpe ra ture D e g. F ChemCo Systems
- 15. Epoxy Applications Transportation Advantages Low shrinkage Tolerates moisture after cure Mechanical and chemical bond • Very high bond strength Cost effective repair vs. complete removal / replacement Chemically inert Long storage life of A and B components Repair is considered permanent ChemCo Systems
- 16. Epoxy Applications Transportation Limitations Thermal incompatibility • Minimal concern with thin glue line Creep • Minimal concern with thin glue line Vapor barrier Proper mixing and ratio is critical Short open time for some formulations Clean-up requires solvents Cure and viscosity is temperature sensitive ChemCo Systems
- 17. Epoxy Applications Transportation Surface Preparation Clean and free of contaminants (remove loose substrate, laitance, dirt, dust, grease, oils, chemical spills) Metal shot blasting machines, sand blasting, “dust-free” diamond grinding, hydroblast, scarifiers, scabblers Dry--no standing water • Some epoxies are designed for wet or underwater use Prepare surface profile for good mechanical / chemical bonding ChemCo Systems
- 18. Epoxy Applications Transportation Surface prep Shotblasting Hydroblasting ChemCo Systems
- 19. Epoxy Applications Transportation ASTM Bond Types: I, II, III, IV,V, VI, VII ASTM C-881 (or AASHTO M-235) Crack Repair – pressure injection or gravity feed (Types I & IV) Concrete Bonding (Types II & V) Low mod overlays and spall/joint repair (Type III) Segmental Bridge Adhesives (Types VI & VII) ChemCo Systems
- 20. Epoxy Applications Transportation Non-ASTM Specification Uses Miscellaneous Epoxy Products • Base plate grouts • Mortars for patching • Coatings • Control joints and wire loops – Airport runway lighting (see right) – Traffic control • High strength grouts • Polymer concrete • Handicapped access warning strip adhesives Adhesive Anchoring (ICC-ES/AC308) External Structural Strengthening ChemCo Systems
- 21. Epoxy Applications Transportation ASTM C-881 used in crack repair Type I – Non-load bearing, bond hardened concrete to hardened concrete Type IV – Load bearing, bond hardened concrete to hardened concrete ChemCo Systems
- 22. Epoxy Applications Transportation Why Repair Cracks? Extend structural lifespan Fix spalls due to freeze/thaw cycles, unrepaired cracks, Repair settling from poor steel corrosion soils Stop leakage in fluid Earthquake damage repair containing structures (see Cracked member unable to above) transfer design load Cracks are unsightly in architectural concrete ChemCo Systems
- 23. Epoxy Applications Transportation Crack Treatment Considerations Some moving cracks may re- appear after injection Cracks with hydrostatic pressure (i.e., running water) are frequently epoxy treated, but may also be candidates for urethane grouting if non-structural Vertical / Overhead applications – Injection technique Horizontal applications – Gravity- feed or injection Voids and honeycombed concrete may require special low exotherm epoxy ChemCo Systems
- 24. Epoxy Applications Transportation Crack Treatment Considerations (for reinforced concrete used in structural applications) ACI 224 guidelines for crack width Exposure condition Tolerable crack width (in.) Tolerable crack width (mm) Dry air or protective membrane 0.016 0.41 Humidity, moist air, soil 0.012 0.30 De-icing chemicals 0.007 0.18 Seawater and seawater spray: 0.006 0.15 Wetting and drying Water retaining structures (excluding 0.004 0.10 pressure pipes) ChemCo Systems
- 25. Epoxy Applications Transportation Restore monolithic strength ChemCo Systems
- 26. Epoxy Applications Transportation Structural Crack Repairs ChemCo Systems
- 27. Epoxy Applications Transportation Injection: beams and columns ChemCo Systems
- 28. Epoxy Applications Transportation Injection--tunnels ChemCo Systems
- 29. Epoxy Applications Transportation Injection--Rail ChemCo Systems
- 30. Epoxy Applications Transportation Injection--airports ChemCo Systems
- 31. Epoxy Applications Transportation Injection--bridges ChemCo Systems
- 32. Epoxy Applications Transportation Injection: pile caps Mass pours (large volume single pours) can develop severe cracks associated with high heat buildup during cure ChemCo Systems
- 33. Epoxy Applications Transportation Bridge--Gravity Feed Crack Repair For concrete decks with high amounts of small crack networks Gravity feed Very low viscosity systems use epoxies and HMWM (methacrylates) Open to traffic in 5 hrs Restore monolithic integrity to deck Protect reinforcing steel from corrosion Also available in special long potlife version ChemCo Systems
- 34. Epoxy Applications Transportation Spray Applied – Gravity feed ChemCo Systems
- 35. Epoxy Applications Transportation QC Check: Taking Cores ChemCo Systems
- 36. Epoxy Applications Transportation Visual Inspection Can penetrate cracks as small as 0.002” (0.05 mm) ChemCo Systems
- 37. Epoxy Applications Transportation ASTM Standard C-881 (continued) Type II – Non-load bearing, bond freshly mixed concrete to hardened concrete Type V – Load bearing, bonding freshly mixed concrete to hardened concrete Typical Applications: • Introduction of newly poured concrete for large area repairs. • Primers for overlays (Type III) & patch repairs with epoxy and cementitious mortars. ChemCo Systems
- 38. Epoxy Applications Transportation Concrete Bonding Requirements for “fresh to hardened” • Achieve monolithic structural bond of new material to old concrete • Epoxy must have proper viscosity to maintain uniform film thickness of 20 mils • Epoxy must be tacky when new concrete or new material is placed ChemCo Systems
- 39. Epoxy Applications Transportation Bonding: Hardened to Hardened ChemCo Systems
- 40. Epoxy Applications Transportation Trowel Applied ChemCo Systems
- 41. Epoxy Applications Transportation Set Precast Panel ChemCo Systems
- 42. Epoxy Applications Transportation Spray Applied Concrete Bonder ChemCo Systems
- 43. Epoxy Applications Transportation Fresh Concrete Pour (over epoxy) ChemCo Systems
- 44. Epoxy Applications Transportation Bridge deck overlay delamination repair Modification of structural crack injection practices Observed more frequently in climates with high cold-to-hot temp ranges (Canada and parts of China) Fill voids between overlay and structural slab Considerable savings compared to replacement of deck overlay ChemCo Systems
- 45. Epoxy Applications Transportation ASTM Standard C881 (cont.) Type III – Bond skid resistant materials to hardened concrete (low modulus) • Binders in epoxy mortars used on traffic bearing surfaces (overlays) • Impact resistant joint nosing repair on bridge decks • Handicapped access warning strips ChemCo Systems
- 46. Epoxy Applications Transportation Polymer Overlays What is an Overlay? • A resurfacing of an existing horizontal surface (bridge deck or parking structure) Function of overlay • Protects structure • Provides non-skid surface • Extends life of the structure Properties • Low modulus. • Medium viscosity. • Excellent adhesive properties. • Long term abrasion resistance. ChemCo Systems
- 47. Epoxy Applications Transportation Broadcast overlay ChemCo Systems
- 48. Epoxy Applications Transportation Seed with aggregate to excess ChemCo Systems
- 49. Epoxy Applications Transportation Completed thin overlay ChemCo Systems
- 50. Epoxy Applications Transportation ASTM Standard C-881 (continued) Segmental bridges Type VI – Bonding / sealing segmental precast elements with internal tendons (temporary post tensioning applied) • Normal Set Type VII – For use as a nonstress carrying sealer for segmental precast elements (temporary post tensioning not applied) • Slow Set ChemCo Systems
- 51. Epoxy Applications Transportation Segmental Bridges Technology first developed in France and Switzerland in the 1940’s Early projects left segment joints dry Epoxies used since early 1970’s for sealing segments ASBI (American Segmental Bridge Institute) • Developed a standard epoxy specification ChemCo Systems
- 52. Epoxy Applications Transportation Functions of Epoxy Resin (Segmental use) Lubricant - allows segments to slide easily into place during construction Distributes compressive/shear stresses across each joint Provides water-tight seal between segments Prevents loss of cementitious grout at joints when pumped through cable ducts Specific temperature ranges often used ChemCo Systems
- 53. Epoxy Applications Transportation Apply by Hand ChemCo Systems
- 54. Epoxy Applications Transportation Place Segments ChemCo Systems
- 55. Epoxy Applications Transportation Epoxy Squeeze-Out ChemCo Systems
- 56. Epoxy Applications Transportation External strengthening Early applications used steel plate Change in use Used in seismic upgrades Steel and fiberglass forms used on columns Steel saddles on beams Epoxy resin and hand-applied composite fiber wrapping technologies are popular today Fabrics are glass or carbon fiber ChemCo Systems
- 57. Epoxy Applications Transportation Why add Strengthening? Insufficient reinforcement Corrosion of reinforcement Change in use Excessive deflections Structural/Fire damage Seismic upgrade ChemCo Systems
- 58. Epoxy Applications Transportation Failed columns ChemCo Systems
- 59. Epoxy Applications Transportation Beam damage ChemCo Systems
- 60. Epoxy Applications Transportation External fixes: Stitching Mid 1960s drawing from US Army Corp of Engineers ChemCo Systems
- 61. Epoxy Applications Transportation Plate strengthening used with epoxy injection ChemCo Systems
- 62. Epoxy Applications Transportation Steel saddle (3-sides) over concrete beam used with epoxy injection ChemCo Systems
- 63. Epoxy Applications Transportation Column grouting Steel (or rigid fiberglass) jackets ChemCo Systems
- 64. Epoxy Applications Transportation Composite Systems ChemCo Systems
- 65. Epoxy Applications Transportation Bridge Column Upgrade Applying fairing epoxy to corner ChemCo Systems
- 66. Epoxy Applications Transportation Test substrate adhesion (after surface prep) ASTM D4541 (Elcometer) ChemCo Systems
- 67. Epoxy Applications Transportation Prime Substrate ChemCo Systems
- 68. Epoxy Applications Transportation Saturate Fabric – Wet Lay-Up ChemCo Systems
- 69. Epoxy Applications Transportation Apply Saturated Fabric ChemCo Systems
- 70. Epoxy Applications Transportation Dry Lay-Up ChemCo Systems
- 71. Epoxy Applications Transportation Reinforce Tension Zone with CF strips Fiberglass bars inset in pre-cut channels used in a “stitching” technique are an alternative to strips ChemCo Systems