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Epoxy crack injection for concrete (the basics)

Epoxy injection offers a permanent repair for cracks (and delaminations) in concrete. The repair is structural, permanent and water-tight with the same lifespan as the surrounding concrete. It can be performed at temperatures as low 35°F, on cracks as narrow as 5 mils (5/1000”) and even underwater.

The cured epoxy restores the monolithic integrity of the concrete, protects the internal reinforcing steel from corrosion and is unaffected by water, chemicals and sunlight. University studies confirm that the repaired concrete matches the original strength of the uncracked concrete. A useful performance specification for the epoxy adhesive is ASTM C881, Type IV for load bearing (structural) applications. The cured high modulus epoxy generally exhibits more than 3 times the compressive strength and over 10 times the tensile strength of the surrounding concrete.

Typical structures repaired using epoxy injection include: parking decks, stadiums, concrete framed buildings, residential foundations, swimming pools, airport runways and taxiways, concrete bridge decks, floor cracking and delaminations in warehouses and manufacturing facilities, concrete pipe and tanks, concrete beams and piers and port facilities including docks, piers and pilings. Facilities where crack injection is often employed include water/sewage treatment plants, industrial sites, machinery foundations, and refrigerated and frozen food storage warehouses.

Specially trained contractors should be considered to properly perform crack repair using proper surface preparation procedures and positive displacement metering pumps to properly proportion and deliver the two component epoxy.

Benefits of Epoxy Injection

• Fast cure strength — up to 5,000 psi compressive yield in less than 5 hours,
• Vibration tolerant during cure — repairs can be made while structure is open,
• Unique concrete crack injection solutions for underwater, corrosive, large void (low exotherm) and other extreme exposures,
• O VOC concrete crack repair adhesives and seals,
• Can be used in temperatures as low as 35°F,
• Restores cracked concrete and structural members including beams and columns to original monolithic strength,
• Stops water leakage through foundations,
• Prevents corrosion of embedded reinforcing steel,
• Useful in secondary containment areas to prevent leaks and
• Unlike urethane chemical grouts, the epoxy crack repair is structural and permanent.

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Epoxy crack injection for concrete (the basics)

  1. 1. Epoxy Crack Injection (the basics) John Bors ChemCo Systems
  2. 2. J Bors ChemCo Systems Introduction  Overview of pressure crack injection  Practical and technical issues – Choose a primary repair technique  Epoxy properties  ChemCo Systems – epoxies and structural concrete repair – metering pumps and equipment – 50 years of experience – Kemko® applicator program
  3. 3. J Bors ChemCo Systems Crack evaluation  What is a crack? – width and depth limitations – pocket microscope, crack cards – Structural vs. non structural – Identify cause and need for repair 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: Wetting and drying 0.006 0.15 Water retaining structures (excluding pressure pipes) 0.004 0.10
  4. 4. J Bors ChemCo Systems Know when to inject  OK – Shrinkage cracks – One time or temporary overload – Leaks – Cold joints after concrete has aged (and shrunk) – Settlement – Delamination  Not OK – Service load has increased beyond design limits – Inadequate design – Moving joints
  5. 5. J Bors ChemCo Systems Why inject?  Restore structural and/or design strength to the cracked concrete structure  Eliminate serious spalling of concrete initiated by cracking and aggravated by freeze thaw cycling  Prevent corrosion of reinforcing steel and pre- stress tendons by encapsulating them against moisture  Stop water leakage through concrete structures  Repair concrete architecturally without the unsightly surface marks caused by standard surface crack repairs
  6. 6. J Bors ChemCo Systems Injection Process, part 1 1. Identify cracks for repair 2. Optimum port spacing and location 3. Surface preparation 4. Seal crack at surfaces 5. Inject 6. Remove seal 7. Restore surface
  7. 7. J Bors ChemCo Systems Injection Process, part 2  Seal crack at surfaces  Inject  Remove seal  Restore surface  QC
  8. 8. J Bors ChemCo Systems Crack Preparation  Wire brushing or grinding – remove laitance  Seal selection – conditions dependent  Ports or portless (taped)?  Crack chasing or routing?  Useful tools – scalpel, razor, tape, wax, wire brush  Cleaning up – solvent, stripper, propane torch, hot air gun Taped (open) ports are considered to be more time efficient. When full, sealed by wax or soap.
  9. 9. J Bors ChemCo Systems Special surface seals  Epoxy pastes – high mod. vs. flexible – short vs. long potlife (useable mix life)  Wax, hot melt seals  Cementitious (hydraulic cement)  StripSEALTM (peelable)  Considerations – wet conditions – post-repair surface appearance – ease of removal – seal cracking (thermal cycling)StripSEAL—a unique removal surface seal
  10. 10. J Bors ChemCo Systems Epoxy Injection  Port locations – access to both sides?  Sequence  Is water present?  Pressure and duration  Finished appearance Pacoima Dam in Southern CA
  11. 11. J Bors ChemCo Systems Equipment  Positive displacement mix pumps – gear vs. piston – portability – reliability  Static mixers  Ports  Pressure test kit  Functional gauges  Flush kit ChemCo Systems Model B Epoxy Injection Pump
  12. 12. J Bors ChemCo Systems Injection QC  Daily pump ratio check – volumetric samples at pressure  Static mixer condition  Temperature vs. crack width  Cure time and temp relationship  Core examinationsChemCo’s Ratio and Pressure Check Device
  13. 13. J Bors ChemCo Systems Strength of Injected Repair  Standardized reinforced concrete beams were tested to failure  Cracked beams were injected then retested  Repaired beams had same failure strengths as original beams Study by Dr. H.W. Chung, University of Hong Kong
  14. 14. J Bors ChemCo Systems Epoxy Bond stronger than concrete Slant shear test bond line
  15. 15. J Bors ChemCo Systems Epoxy behavior  Temperature behavior – viscosity change – reaction/cure rate change  Crack size and viscosity  Exothermal in bulk (large quantities and voids)  Excellent shelf life (3 years typical)
  16. 16. J Bors ChemCo Systems Epoxy cure time C U R E R A T E O F E P O X Y IN J E C T IO N A D H E S IV E S 0 20 40 60 80 100 120 140 160 40 50 60 73 80 90 C ure T e m p e ra ture D e g . F T yp ica l inje ctio n re sin Slo we r Fa ste r When can you move a panel or vibrate the concrete?
  17. 17. J Bors ChemCo Systems Injection resin typical properties (ASTM tests) Tensile Strength 6-9,000 psi Elongation 2% Compressive 14-16,000 psi Flexural 10-12,000 psi Viscosity 200-500 cps HDT 120-165°F Gel time 14-210 min. For structural repairs: Select adhesive that meets ASTM C881, Type IV
  18. 18. J Bors ChemCo Systems Special applications  Large voids, honeycombs  old-to-new concrete  Leaks or underwater  No backside seal – slump pumping – paste injection  Internal splices  External plates  Cold joints  Water tanks
  19. 19. J Bors ChemCo Systems Safety  Eye protection – glasses or shield – eyewash (flush for 5 minutes)  Solvents & strippers – in confined spaces – grounded containers  Skin protection – use gloves – long sleeves and pants – dermatitis  SDS on site access  Cleanliness – wash-up every time  Disposal
  20. 20. J Bors ChemCo Systems Where to find more information  Company training sessions – ChemCo Systems Kemko® applicator training (free)  ICRI booklet and specification  Epoxy Injection in Construction, Trout Aberdeen Grp.  ACI repair committees