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Historic Preservation - Technical Procedures

Spectitle:
Repairing Cracks In Concrete By Injecting Epoxy Resin

Procedure code:
0373201R

Source:
Hspg Prepared For Nps - Sero

Division:
Concrete

Section:
Concrete Repair

Last Modified:
02/24/2012

Details:
Repairing Cracks In Concrete By Injecting Epoxy Resin



REPAIRING CRACKS IN CONCRETE BY INJECTING EPOXY RESIN


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on patching cracks in
         concrete by injecting an epoxy adhesive.

    B.   Epoxy Injection should be used for DORMANT CRACKS -
         cracks that remain unchanged.  Dormant cracks generally
         pose little danger.  However, if left unrepaired, they
         will provide channels for moisture penetration.

    C.   The calculated maximum crack width for concrete should
         not exceed 0.3 mm.  Consult a professional to determine
         the cause for cracking and its source, as superficial
         repairs can aggravate the problem.

    D.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   General Protection (Surface and Surrounding)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).

    E.   For guidance in monitoring cracks, see 04200-02-S.

1.02 REFERENCES

    A.   American Society for Testing and Materials (ASTM), 100
         Barr Drive, West Conshohocken, PA 19428, (610) 832-9585
         or FAX (610) 832-9555.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Abatron, Inc.
         5501 95th Ave.
         Kenosha, WI  53144
         800/445-1754 or 414/653-2000

    B.   Sika Corporation
         201 Polito Ave.
         Lyndhurst, NJ  07071
         201/933-8800

2.02 MATERIALS

    A.   Epoxy Resin (Abatron, Inc., Sika Corp.), or approved
         equal.

         1.   For Fine Cracks:  

              a.   Epoxy shall be a two-part type, low viscosity
                   epoxy adhesive material containing 100% solids
                   and shall meet or exceed the following
                   characteristics when tested in accordance with
                   the standards specified.

              b.   Characteristics of Components:

                   1)   Component A - shall be a blend of
                        modified epoxy resins.

                   2)   Component B - shall be a blend of
                        modified amine curing agents.

              c.   Test Method Requirements:

                   1)   Component A - Brookfield RVT, 700
                        maximum; Viscosity @ 77 +/- 3 degrees F.,
                        cps; Spindle No. 2 @ 20 rpm.

                   2)   Component B - Brookfield RVT, 240
                        maximum; Viscosity @ 77 +/- 3 degrees F,
                        cps; Spindle No. 2.

              d.   Properties of Combined Components:  When mixed
                   in the ratio of two parts Component A to one
                   part Component B by volume; or 100 parts
                   Component A to 44 parts Component B by weight,
                   shall be:

                   1)   Potlife, 60g @ 77 +/- 3 degrees F.,
                        minutes; 25 minutes maximum.

              e.   Properties of the Cured Adhesive:  When cured
                   for seven days @ 77 +/- 3 degrees F., unless
                   otherwise specified, shall be:

                   1)   Ultimate Tensile Strength:  ASTM D638;
                        8000 minimum.

                   2)   Compressive Yield Strength, psi:  ASTM
                        D695*; 15,000 minimum.

                   3)   Heat Deflection Temperature:  ASTM D648*;
                        130 F. minimum.

                   NOTE:  Test specimens must be cured in a
                   manner such that the peak exothermic
                   temperature of the adhesive does not exceed 77
                   degrees F.

         2.   For Wide Cracks:  

              a.   Epoxy shall be a two-part gel epoxy adhesive
                   material containing 100% solids and shall meet
                   or exceed the following characteristics when
                   tested in accordance with the standards
                   specified.

              b.   Properties of Combined Components:  When mixed
                   in the ratio of two parts Component A to one
                   part Component B by volume; or 100 parts
                   Component A to 34 parts Component B by weight
                   shall be:

                   1)   Potlife, 200g @ 77 degrees F. +/- 3
                        degrees F., minutes.

              c.   Properties of the Cured Adhesive:  When cured
                   for seven days @ 77 degrees F. +/- 3 degrees
                   F., unless otherwise specified, shall be:

                   1)   Ultimate Tensile Strength:  ASTM D638;
                        1,500 psi minimum.
                   2)   Compressive Yield Strength:  ASTM D695;
                        6,000 psi minimum.

                   3)   Heat Deflection Temperature:  ASTM D648;
                        105 F. minimum.

    B.   Surface Seal:  (Epoxy Mortar or Oil-free Clay)

         1.   Description:  The surface seal material is that
              material used to confine the injection adhesive in
              the joints or cracks during injection and cure.

         2.   Properties:  The surface seal material shall have
              adequate strength to hold injection fittings firmly
              in place and to resist injection pressures
              adequately to prevent leakage during injection.
              The material shall not leave a residue upon
              removal.

         NOTE:  Provide adhesive crack fillers and other related
         materials that are compatible with one another and with
         substrates under conditions of severe weather,
         demonstrated by sealant manufacturer based on testing and
         field experience.

2.03 EQUIPMENT

    A.   Equipment for Injection:

         1.   Type:  The equipment used to meter and mix the two
              injection adhesive components and inject the mixed
              adhesive into the crack shall be portable, positive
              displacement type pumps with interlock to provide
              positive ratio control of exact proportions of the
              two components at the nozzle.  The pumps shall be
              electric or air powered and shall provide in-line
              metering and mixing.

         2.   Discharge Pressure:  The injection equipment shall
              have automatic pressure control capable of
              discharging the mixed adhesive at any pre-set
              pressure up to 200 psi + 5 psi and shall be
              equipped with a manual pressure control override.
              For injection of the gel epoxy, the equipment shall
              be equipped with the above features and be able to
              pump at up to 5,000 psi.

         3.   Ratio Tolerance:  The equipment shall have the
              capability of maintaining the volume ratio for the
              injection adhesive prescribed by the manufacturer
              of the adhesive within a tolerance of + 5% by
              volume at any discharge pressure up to 200 psi.
              For gel epoxies, the ratio will be checked by
              weight at up to 5,000 psi.

         4.   Automatic Shut-Off Control:  The injection
              equipment shall be equipped with sensors on both
              the Component A and B reservoirs that will
              automatically stop the machine when only one
              component is being pumped to the mixing head.

         5.   The manufacturer of the injection equipment and the
              manufacturer of the epoxy resin adhesive for
              injection shall be one and the same.


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Examine the nature and severity of the crack:  

         1.   What direction are the cracks going and where are
              they the widest?

         2.   Note sloped floors, bulging walls and doors that do
              not fit.

    B.   Determine the probable cause:

         1.   Foundation erosion

         2.   Decay of materials

         3.   Structural failure

         4.   Change in materials or geometry

         5.   Thermal and moisture changes

    C.   Determine possible consequences if left unrepaired.

    D.   Evaluate alternative methods of repair.

    E.   For cracks associated with thermal movement look for:

         1.   Horizontal or diagonal cracks near the ground at
              piers in long walls:  due to horizontal shearing
              stresses between the upper wall and the wall where
              it enters the ground.

         2.   Vertical cracks near the ends of walls

         3.   Vertical cracks near the top and ends of the facade

         4.   Cracks around stone sills or lintels:  due to
              expansion of the masonry against both ends of the
              tight fitting stone piece that cannot be
              compressed.

3.02 PREPARATION

    A.   Surface Preparation:

         1.   Substrate Conditions:  Do not proceed with
              installation of joint sealers until contaminants
              capable of interfering with their adhesion are
              removed from joint substrates.

         2.   Surfaces adjacent to joints or other areas of
              application shall be cleaned of dirt, dust, grease,
              oil or other foreign matter detrimental to bond of
              epoxy injection surface seal system.

         3.   Entry ports shall be provided along the crack at
              intervals of not less than the thickness of the
              concrete member at that location.

         4.   Surface seal material shall be applied to the face
              of the crack or end.  For through cracks, surface
              seal shall be applied to both faces.

         5.   Enough time for the surface seal material to gain
              adequate strength shall pass before proceeding with
              the injection.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   If, before repairs are made, the crack is still damp, be
         sure to use an epoxy appropriate for damp conditions.

    B.   Seal both sides of cracks with an epoxy mortar or oil-free
          clay, leaving small holes through which epoxy resin
         will be injected.  1/8" to 1/4" diameter tubing can be
         used to form holes.  Holes should be 2"-4" long, roughly
         8" apart.

    C.   Inject 2-component epoxy using device as provided by
         manufacturer.

    D.   Injection of epoxy adhesive shall begin at lower entry
         port and continue until there is an appearance of epoxy
         adhesive at the next entry port adjacent to the entry
         port being pumped.

    E.   When epoxy adhesive travel is indicated by appearance at
         the next adjacent port, injection shall be discontinued
         on the entry port being pumped, and epoxy injection shall
         be transferred to next adjacent port where epoxy adhesive
         has appeared.

    F.   Perform epoxy adhesive injection continuously until
         cracks are completely filled.

    G.   If port to port travel of epoxy adhesive is not
         indicated, the work shall immediately be stopped and the
         engineer notified.

    H.   When cracks or joints are completely filled, epoxy
         adhesive shall be cured for sufficient time to allow
         removal of injection or port sealing devices.

    I.   The outermost quarter inch of the crack shall be filled
         with a colored epoxy material of the installers choice
         subject to prior approval of the RHPO.  The colored epoxy
         filler shall match the existing material which it is
         filling and shall not be discernible from a distance of
         15 feet.

3.04 ADJUSTING/CLEANING

    A.   Upon completion of work, remove all seal material and
         other residue from site.  Remove and clean exposed
         surfaces of residue or staining resulting from this
         work.

                         END OF SECTION