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Historic Preservation - Technical Procedures

Spectitle:

Reattaching Loose Or Spalled Limestone

Procedure code:

0446007R

Source:

Departmental Auditorium Bldg (Hsr) - Grier, Brown, Renfrow..

Division:

Masonry

Section:

Limestone

Last Modified:

07/30/2013

Details:

Reattaching Loose Or Spalled Limestone



REATTACHING LOOSE OR SPALLED LIMESTONE


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on reattaching loose or
         spalled limestone that is reusable and has not been
         extensively damaged.

    B.   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).

1.02 REFERENCES

    A.   American Society for Testing and Materials (ASTM), www.astm.org
         


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Axson Technologies (formerly Akemi Plastics, Inc.)
         www.axsontech.us

    B.   Sika Corporation
         http://usa.sika.com
         
         

2.02 MATERIALS

    A.   Replacement limestone - reuse any loose or fallen stone
         fragments that are still sound; re-use such stone in its
         original position and location; replacement stone should
         match existing limestone in color, texture and type.

    B.   Epoxy Adhesive such as "Sikadur 32 Hi Mod" epoxy adhesive, or
         approved equal (Sika Corporation).

         1.   High modulus, high strength, moisture insensitive
              epoxy adhesive with a pot life of 30 minutes at 70
              degrees F.

         2.   Can be applied at temperatures as low as 40 degrees
              F.

         3.   Colored to match existing limestone.

    C.  A color-matched polyester-based adhesive such as "Limestone Super",(Wood & Stone Company, a Axson Technologies US, Inc. company),           or approved equal.

         1.   10-12 minute cure depending on ambient temperature; temperatures below 32 degrees F (O degrees C) require heated mixture.

         2.   Can be applied at temperatures as low as 20 degrees
              F

         3.   Colored to match existing limestone.

    D.   Permanent coloring agent as required, compatible with
         adhesive, and as recommended by adhesive manufacturer.

    E.   Stainless steel rods for reinforcement:  1/4 inch
         diameter threaded rods, length as required.

2.03 EQUIPMENT

    A.   Stiff bristle brushes (natural fiber or nylon)

    B.   Polyethylene plastic mixing vessel for mixing adhesives
         and patching mortar


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   Carefully remove all loose fragments of stone.  Set aside
         all pieces in good condition for reuse.

    B.   Clean exposed metal anchors.  Remove corrosion by
         scraping with a stiff wire bristle brush.

    C.   Remove unsound metal anchors and replace with new
         stainless steel anchors of similar size and shape.  Bed
         anchors in epoxy grout.

    D.   Remove dust and debris from building stone and fragments
         using a stiff bristle brush.

    E.   For small fragments (.5 cubic feet or less):

         1.   Coat building stone surface with adhesive such as
              noted above, or approved equal.  Be sure to cover the
              entire surface, filling all voids.

         2.   While adhesive is still tacky, set stone fragment
              in place.  Prevent fragment from moving until
              adhesive is fully cured.

         3.   Clean any residual adhesive from the stone surface
              using water and stiff bristle brush.  Wet stone and
              fill any chips with lime-based patching mortar of
              appropriate color, texture and composition.  Tool
              surface level with surrounding stone.

    F.   For large fragments (more than 4 inches by 4 inches by 4
         inches):

         1.   Follow procedures in E.1. above.

         2.   After adhesive has cured, anchor fragments with 1/4
              inch smooth stainless steel rods.

              a.   Drill 1/4 inch holes at a 45 degree downward
                   angle through the face of the newly set stone
                   fragment.  Drill holes should extend at least
                   2 inches into the backing stone, 2 inches into
                   the fragment and should allow for the rod to
                   be countersunk at least 3/4 inches from the
                   face of the stone.

              b.   Space the anchor rods between 3 and 5 inches
                   apart and no less than 2 inches from any edge.

         3.   Clean any residual adhesive from the stone surface
              using water and a stiff bristle brush.  Wet stone
              and fill holes from countersunk rods with patching
              mortar.  Tool surface level with surrounding stone.

                         END OF SECTION
 


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