Concrete Repair: Bridges and Tunnels--Epoxies

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Examples of maintenance, rehabilitation and repair of transportation structures including bridges and tunnels using epoxy products for structural repair and protection. ASTM C881 catagories are explained. ChemCo Systems, Redwood City, CA manufactures epoxies for these applications (www.chemcosystems.com).

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Concrete Repair: Bridges and Tunnels--Epoxies

  1. 1. Epoxy ApplicationsTransportation Concrete Repair: Bridges and Tunnels ChemCo Systems
  2. 2. Epoxy ApplicationsTransportation Civil uses  Major roles: • Repair and Protection • Infrastructure Renovation – Bridges & Tunnels – Airports – Rail • Structural Rehabilitation – Commercial, Industrial & Residential – Public & Private Sectors ChemCo Systems
  3. 3. Epoxy ApplicationsTransportation 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. 4. Epoxy ApplicationsTransportation Salt: tough on steel and concrete ChemCo Systems
  5. 5. Epoxy ApplicationsTransportation Monitor crack movement (strain gauge) ChemCo Systems
  6. 6. Epoxy ApplicationsTransportation 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. 7. Epoxy ApplicationsTransportation 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. 8. Epoxy ApplicationsTransportation 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. 9. Epoxy ApplicationsTransportation 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. 10. Epoxy ApplicationsTransportation 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. 11. Epoxy ApplicationsTransportation 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. 12. Epoxy ApplicationsTransportation 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. 13. Epoxy ApplicationsTransportation 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. 14. Epoxy ApplicationsTransportation 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. 15. Epoxy ApplicationsTransportation 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. 16. Epoxy ApplicationsTransportation 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. 17. Epoxy ApplicationsTransportation 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. 18. Epoxy ApplicationsTransportation Surface prep Shotblasting Hydroblasting ChemCo Systems
  19. 19. Epoxy ApplicationsTransportation 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. 20. Epoxy ApplicationsTransportation 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. 21. Epoxy ApplicationsTransportation 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. 22. Epoxy ApplicationsTransportation 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. 23. Epoxy ApplicationsTransportation 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. 24. Epoxy ApplicationsTransportation 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. 25. Epoxy ApplicationsTransportation Restore monolithic strength ChemCo Systems
  26. 26. Epoxy ApplicationsTransportation Structural Crack Repairs ChemCo Systems
  27. 27. Epoxy ApplicationsTransportation Injection: beams and columns ChemCo Systems
  28. 28. Epoxy ApplicationsTransportation Injection--tunnels ChemCo Systems
  29. 29. Epoxy ApplicationsTransportation Injection--Rail ChemCo Systems
  30. 30. Epoxy ApplicationsTransportation Injection--airports ChemCo Systems
  31. 31. Epoxy ApplicationsTransportation Injection--bridges ChemCo Systems
  32. 32. Epoxy ApplicationsTransportation Injection: pile caps Mass pours (large volume single pours) can develop severe cracks associated with high heat buildup during cure ChemCo Systems
  33. 33. Epoxy ApplicationsTransportation 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. 34. Epoxy ApplicationsTransportation Spray Applied – Gravity feed ChemCo Systems
  35. 35. Epoxy ApplicationsTransportation QC Check: Taking Cores ChemCo Systems
  36. 36. Epoxy ApplicationsTransportation Visual Inspection Can penetrate cracks as small as 0.002” (0.05 mm) ChemCo Systems
  37. 37. Epoxy ApplicationsTransportation 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. 38. Epoxy ApplicationsTransportation 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. 39. Epoxy ApplicationsTransportation Bonding: Hardened to Hardened ChemCo Systems
  40. 40. Epoxy ApplicationsTransportation Trowel Applied ChemCo Systems
  41. 41. Epoxy ApplicationsTransportation Set Precast Panel ChemCo Systems
  42. 42. Epoxy ApplicationsTransportation Spray Applied Concrete Bonder ChemCo Systems
  43. 43. Epoxy ApplicationsTransportation Fresh Concrete Pour (over epoxy) ChemCo Systems
  44. 44. Epoxy ApplicationsTransportation 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. 45. Epoxy ApplicationsTransportation 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. 46. Epoxy ApplicationsTransportation 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. 47. Epoxy ApplicationsTransportation Broadcast overlay ChemCo Systems
  48. 48. Epoxy ApplicationsTransportation Seed with aggregate to excess ChemCo Systems
  49. 49. Epoxy ApplicationsTransportation Completed thin overlay ChemCo Systems
  50. 50. Epoxy ApplicationsTransportation 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. 51. Epoxy ApplicationsTransportation 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. 52. Epoxy ApplicationsTransportation 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. 53. Epoxy ApplicationsTransportation Apply by Hand ChemCo Systems
  54. 54. Epoxy ApplicationsTransportation Place Segments ChemCo Systems
  55. 55. Epoxy ApplicationsTransportation Epoxy Squeeze-Out ChemCo Systems
  56. 56. Epoxy ApplicationsTransportation 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. 57. Epoxy ApplicationsTransportation Why add Strengthening?  Insufficient reinforcement  Corrosion of reinforcement  Change in use  Excessive deflections  Structural/Fire damage  Seismic upgrade ChemCo Systems
  58. 58. Epoxy ApplicationsTransportation Failed columns ChemCo Systems
  59. 59. Epoxy ApplicationsTransportation Beam damage ChemCo Systems
  60. 60. Epoxy ApplicationsTransportation External fixes: Stitching Mid 1960s drawing from US Army Corp of Engineers ChemCo Systems
  61. 61. Epoxy ApplicationsTransportation Plate strengthening used with epoxy injection ChemCo Systems
  62. 62. Epoxy ApplicationsTransportation Steel saddle (3-sides) over concrete beam used with epoxy injection ChemCo Systems
  63. 63. Epoxy ApplicationsTransportation Column grouting Steel (or rigid fiberglass) jackets ChemCo Systems
  64. 64. Epoxy ApplicationsTransportation Composite Systems ChemCo Systems
  65. 65. Epoxy ApplicationsTransportation Bridge Column Upgrade Applying fairing epoxy to corner ChemCo Systems
  66. 66. Epoxy ApplicationsTransportation Test substrate adhesion (after surface prep) ASTM D4541 (Elcometer) ChemCo Systems
  67. 67. Epoxy ApplicationsTransportation Prime Substrate ChemCo Systems
  68. 68. Epoxy ApplicationsTransportation Saturate Fabric – Wet Lay-Up ChemCo Systems
  69. 69. Epoxy ApplicationsTransportation Apply Saturated Fabric ChemCo Systems
  70. 70. Epoxy ApplicationsTransportation Dry Lay-Up ChemCo Systems
  71. 71. Epoxy ApplicationsTransportation 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

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