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.

1. Epoxy Crack Injection (the basics)
John Bors
ChemCo Systems

2. J Bors ChemCo Systems www.chemcosystems.com
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

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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. J Bors ChemCo Systems www.chemcosystems.com
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. J Bors ChemCo Systems www.chemcosystems.com
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

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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

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Injection Process, part 2
 Seal crack at surfaces
 Inject
 Remove seal
 Restore surface
 QC

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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. J Bors ChemCo Systems www.chemcosystems.com
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

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Epoxy Injection
 Port locations
– access to both sides?
 Sequence
 Is water present?
 Pressure and duration
 Finished appearance
Pacoima Dam in Southern CA

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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

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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

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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

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Epoxy Bond stronger than concrete
Slant shear test bond line

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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)

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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?

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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

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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

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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

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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