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Historic Preservation - Technical Procedures

Spectitle:
Removing Bitumen From Limestone

Procedure code:
0446008R

Source:
National Capitol Region Specifications

Division:
Masonry

Section:
Limestone

Last Modified:
02/24/2012

Details:
Removing Bitumen From Limestone



REMOVING BITUMEN FROM LIMESTONE


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on cleaning and removing
         localized bitumen residue from limestone surfaces.  For
         guidance on the general cleaning of surface dirt on
         limestone, see 04460-03-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 QUALITY ASSURANCE

    A.   Qualifications:  

         1.   Contractor performing the work shall have a minimum
              of 5 years experience in masonry restoration work
              of the type described for this project.

         2.   If requested by the Owner, furnish a statement of
              the experience and qualifications of the firm and
              of the key personnel who will work on this project.
              Include the names and addresses of successful
              projects completed, and for each, the name and
              address of the owner and the architect.

    B.   Reference Standards:

         1.   Secretary of the Interior's "Standards for
              Rehabilitation".

         2.   Preservation Brief No. 1, "The Cleaning and
              Waterproofing of Historic Masonry Buildings".

    C.   Test Panels:  Each alternative method for each type of
         cleaning.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Hydrochemical Techniques, Inc.
         P.O. Box 2078
         Hartford, CT 06145
         203/527-6350

    B.   ProSoCo, Inc.
         755 Minnesota Avenue
         P.O. Box 1578
         Kansas City,  KS  66117
         800/255-4255 or 913/281-2700

    C.   KRC Research Corp.

2.02 MATERIALS

    A.   Alkaline cleaners and water rinse, such as "HT907"
         (Hydrochemical Techniques, Inc.), "Sure-Klean Limestone
         Pre-Wash/After-wash" (ProSoCo, Inc.), "Ion 417 fluoro-
         surfactant" (KRC Research Corp.), or approved equal.

    B.   Bitumen removal:  Following scraping to remove bulk,
         apply solvent containing petroleum distillate (in
         poultice, if required) equal to Sure-Klean Asphalt and
         Tar Remover.

    C.   White absorbent material (molding plaster, untreated
         white flour, white tissue, paper towels, powdered chalk,
         talc, fullers earth or laundry whiting).

    D.   Mineral water

    E.   Plastic sheeting

    F.   Clean dry towels for blotting the area after treatment

    G.   Masking tape

    H.   Clean, potable water

2.03 EQUIPMENT

    A.   Pressure water rinsing equipment (measuring between 100
         and 400 psi for low-pressure; between 400 and 800 psi for
         medium pressure).

    B.   Fan-type spray tips (15 degree fan spray)

    C.   Soft fiber-bristle brushes

    D.   Stiff natural fiber-bristle brush (Tampico)

    E.   Glass or ceramic container for mixing the solution

    F.   Wooden utensil for stirring the ingredients

    G.   Wooden spatula


PART 3---EXECUTION

3.01 ERECTION, INSTALLATION, APPLICATION

    A.   General rinsing of unsoiled stone:  

         1.   All limestone surfaces shall be water rinsed in
              order to blend in areas that are chemically cleaned
              to remove stains with unsoiled areas of stone.

         2.   Water rinse:  Maximum 600 PSI, 5-10 GPM, 15  fan
              angle, not less than 6" from stone surface, at an
              angle of 45  to 90  from wall surface, hot water
              (180 F).

    B.   Cleaning of soiled limestone with alkaline cleaner:

         1.   Pre-wet area to be cleaned.

         2.   Apply alkaline cleaner with soft fiber brush or
              spray.  Allow to stand on surface approximately one
              hour.  Agitate with a stiff natural fiber bristle
              brush.

         3.   Pressure rinse surfaces.  Repeat rinsing until all
              traces of chemical have been removed.

         4.   Apply acid neutralizer.  Repeat pressure rinse.

         5.   Repeat the process as required.

    C.   Bitumen Removal:  

         1.   Protect adjacent stone with polyethylene sheeting.

         2.   Scrape off bulk of bitumen using a wooden spatula,
              taking care not to damage the stone surface.

         3    Dissolve remainder with specified solvent.  Swab
              run-off immediately.  

         4.   If required to dissolve deep stains, apply solvent
              in poultice and keep wet for 4-8 hours by sealing
              in plastic sheeting.  For guidance on preparing and
              applying poultices, see 04455-02-R.

                         END OF SECTION