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Historic Preservation - Technical Procedures

Spectitle:

Cementitious Patch Repair Of Granite Spalls Or Failed Patches

Procedure code:

0446528R

Source:

National Capitol Region Specifications

Division:

Masonry

Section:

Granite

Last Modified:

06/19/2012

Details:

Cementitious Patch Repair Of Granite Spalls Or Failed Patches



CEMENTITIOUS PATCH REPAIR OF GRANITE SPALLS OR FAILED PATCHES


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on the removal and
         replacement of existing loose or deteriorated
         cementitious patches.  For guidance on attaching small
         granite fragments using epoxy adhesive, see 04465-21-R.
             
    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 SUBMITTALS

    A.   Product Data:  Submit manufacturer's product literature
         for epoxy adhesives or resins.

    B.   Samples: Submit samples of dowels for patch anchorage.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:  No work in this section
         shall be performed when the ambient temperature is less
         than 40 degrees F and falling, or higher than 90 degrees F.

    B.   Existing Conditions:

         1.   The Contractor shall be responsible for the
              protection of all adjacent materials during the
              execution of the work.

         2.   The Contractor shall repair all damage to adjacent
              materials caused by the execution of the work of
              this section at no expense to the Owner.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.  Jahn Restoration Mortars
         www.cathedralstone.com

    B.  Sika Corporation
         www.usa.sika.com

2.02 MATERIALS

    A.   Patch dowels:  Threaded rods of A.I.S.I. Type 302/304
         stainless steel, sizes as required.

    B.   Cementitious patching material such as "M160 Granite
         and Bluestone Repair Mortar" (Jahn Restoration Mortar), or approved
         equal, through various vendors.

    C.   Clean, soft cloths

    D.   Clean, potable water

    E.   Epoxy grout: High-modulus, low viscosity, high strength
         epoxy grouting/sealing/binder adhesive such as "Sikadur
         35, Hi-Mod LV" (Sika Corporation), or approved equal.

2.03 EQUIPMENT

    A.   Stiff natural bristle brushes

    B.   Stiff wire bristle brushes

    C.   Trowel

    D.   Chisel

    E.   Hammer


PART 3---EXECUTION

3.01 PREPARATION

    A.   Temporarily remove and store light fixtures, mounting
         brackets, conduit, signs and other building accessories
         to facilitate the restoration work.  Reinstall all
         removed items.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Cut back to sound stone with chisel and hammer.  Score
         surface to receive patch with chisel to provide a
         mechanical key with patching material.

    B.   Thoroughly clean all stone dust and debris from areas
         that are to be repaired by air and then with a soft brush
         and water.

    C.   Clean any exposed metal anchors of all corrosion by
         scraping and brushing with stiff wire brushes.  Replace
         any unsound anchors as necessary with new stainless steel
         anchors of same approximate size and shape.  Bed new
         anchors in epoxy grout.

    D.   Pre-moisten stone with clean water and a stiff natural
         bristle brush to prevent patching mortar from drying out
         prematurely.  Avoid over wetting stone, which inhibits
         adhesion.  Prepare test patches as required for approval
         by the Contracting Officer's Representative to determine
         the correct degree of moistening.

    E.   First mix the cementitious patching material well in a
         dry state, then add water as per manufacturer's
         instructions. Patching mortar should be shapable without
         using molds and as it is being applied should hold its
         shape right away.  Do not mix more material than can be
         used within 30 minutes.

    F.   Apply with trowel so that patch is slightly higher than
         adjacent surfaces.  Jahn repair mortar can be put on
         from 3 mm to any required thickness at once.  Allow to
         harden for 7 days, then carefully cut back and tool to
         match adjacent surfaces.  Maintain mortar joints; do not
         install patch across joints.

    G.   Keep patches damp for 72 hours after installations.

                         END OF SECTION
 


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