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Historic Preservation - Technical Procedures

Spectitle:

Removing Fire, Smoke, Soot, Pitch And Wood Tar Stains From Concrete

Procedure code:

0371019R

Source:

Hstrc Concrete: Investigation & Rpr/Pre-Conf Training - 1989

Division:

Concrete

Section:

Concrete Cleaning

Last Modified:

02/24/2012

Details:

Removing Fire, Smoke, Soot, Pitch And Wood Tar Stains From Concrete



REMOVING FIRE, SMOKE, SOOT, PITCH AND WOOD TAR STAINS FROM CONCRETE


THE CLEANING OR REMOVAL OF STAINS FROM CONCRETE MAY INVOLVE THE
USE OF LIQUIDS, DETERGENTS OR SOLVENTS WHICH MAY RUN OFF ON
ADJACENT MATERIAL, DISCOLOR THE CONCRETE OR DRIVE THE STAINS DEEPER
INTO THE POROUS CONCRETE.  USE THE PRODUCTS AND TECHNIQUES
DESCRIBED HERE ONLY FOR THE COMBINATIONS OF DIRT/STAIN AND
CONCRETE SPECIFIED.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on removing fire, smoke,
         soot, pitch and wood tar stains from concrete by
         scrubbing with scouring powder or by using chemical
         solvents in a bandage or poultice.

    B.   Safety Precautions:

         1.   DO NOT save unused portions of stain-removal
              materials.

         2.   DO NOT store any chemicals in unmarked containers.

         3.   EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY
              SOLVENT IS USED.  USE RESPIRATORS WITH SOLVENT
              FILTERS.

              NOTE:  SOME OF THE SOLVENTS LISTED ARE KNOWN
              CARCINOGENS AND MAY BE BANNED IN SOME STATES.

         4.   No use of organic solvents indoors should be
              allowed without substantial air movement.  Use only
              spark-proof fans near operations involving
              flammable liquids.

         5.   Provide adequate clothing and protective gear where
              the chemicals are indicated to be dangerous.

         6.   Have available antidote and accident treatment
              chemicals where noted.

    C.   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).

    D.   For additional information on poulticing, see 04455-02-R.


PART 2---PRODUCTS

2.01 MATERIALS

    NOTE:  Chemical products are sometimes sold under a common
    name.  This usually means that the substance is not as pure as
    the same chemical sold under its chemical name.  The grade of
    purity of common name substances, however, is usually adequate
    for stain removal work, and these products should be purchased
    when available, as they tend to be less expensive.  Common
    names are indicated below by an asterisk (*).

    A.   Scouring Powder

    B.   For Bandage Treatment:

         1.   Trichloroethylene (highly refined solvent):

              CAUTION:  TRICHLOROETHYLENE IS HIGHLY TOXIC AND MAY
              REACT WITH STRONG ALKALIS SUCH AS FRESH CONCRETE TO
              FORM DANGEROUS GASES.

              a.   Other chemical or common names include Ethinyl
                   trichloride.

              b.   Potential Hazards:  TOXIC.

              c.   Available from automotive supply distributor,
                   chemical supply house (both commercial and
                   scientific), dry cleaning supply distributor,
                   paint store, photographic supply distributor
                   (not camera shop), or printer's supply
                   distributor.

         2.   Undyed flannel, cotton or cotton batting

    C.   For Poulticing:

         1.   Sodium Hypochlorite (NaOCl):

              a.   An unstable salt produced usually in aqueous
                   solution and used as a bleaching and
                   disinfecting agent.

              b.   Other chemical or common names include
                   Bleaching solution*; Household bleach*;
                   Laundry bleach*; Solution of chlorinated
                   soda*.

              c.   Potential Hazards:  CORROSIVE TO FLESH.

              d.   Available from chemical supply house, grocery
                   store or supermarket, hardware store or
                   janitorial supply distributor.

         -OR-

              Javelle Water:  Made by user, see 03710-02-S for
              guidance on preparation.

              a.   Calcium Hypochlorite (CaCl2O2):

                   1)   A white powder used especially as a
                        bleaching agent and disinfectant.

                   2)   Other chemical or common names include
                        Chlorinated calcium oxide; Bleaching
                        powder*; Calcium oxymuriate*; Chloride of
                        lime*; Chlorinated lime*; Hypochlorite of
                        lime*; Oxymuriate of lime*.

                   3)   Potential Hazards:  CORROSIVE TO FLESH;
                        FLAMMABLE (WHEN IN CONTACT WITH ORGANIC
                        SOLVENTS).

                   4)   Available from chemical supply house, dry
                        cleaning supply distributor, drugstore or
                        pharmaceutical supply distributor,
                        janitorial supply distributor, swimming
                        pool supply distributor, or water and
                        sanitation supply distributor.

              b.   Sodium Carbonate (Na2CO3):

                   1)   A sodium salt of carbonic acid used
                        especially in making soaps and chemicals,
                        in water softening, in cleaning and
                        bleaching and in photography; A
                        hygroscopic crystalline anhydrous
                        strongly alkaline salt.

                   2)   Other chemical or common names include
                        Carbonate of soda*; Sal soda*; Soda*;
                        Soda ash*; Washing soda*.

                   3)   Available from chemical supply house,
                        grocery store or supermarket, hardware
                        store, paint store, or water and
                        sanitation supply distributor.

         2.   Filler material such as powdered talc or
              diatomaceous earth

         3.   Mineral water

    D.   Clean dry towels for blotting the area after treatment

    E.   Clean, potable water

    F.   Accessible source of water, soap and towels for washing
         and rinsing in case of emergencies associated with the
         use of chemicals

2.02 EQUIPMENT

    A.   Poulticing Equipment:

         1.   Glass or ceramic container for mixing the solution

         2.   Wooden utensil for stirring the ingredients

    B.   Wood or plastic spatula

    C.   Stiff bristle brush (non-metallic)


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         1.   Provide adequate wash solutions (i.e. water, soap
              and towels) before starting the job.

         2.   Whenever acid is used, the surface should be
              thoroughly rinsed with water as soon as its action
              has been adequate.  Otherwise it will continue
              etching the concrete even though the stain is gone.

3.02 ERECTION, INSTALLATION, APPLICATION

    NOTE:  DO NOT TRY MORE THAN ONE TREATMENT ON A GIVEN AREA
    UNLESS THE CHEMICALS USED FROM PRIOR TREATMENT HAVE BEEN
    WASHED AWAY.

    A.   Remove as much surface staining as possible by scrubbing
         with water and scouring powder, powdered pumice or grit.

    B.   Apply a Bandage Treated with a Chemical Solvent:

         1.   Swab the stained concrete with trichloroethylene.

         2.   Soak 3- or 4-layers of undyed flannel, cotton or
              cotton batting in trichloroethylene.

         3.   Apply the treated bandage to the stained area.  Be
              sure to spread the bandage well beyond the stained
              area.

         4.   Remove the bandage periodically, wring out,
              resaturate and reapply.  On horizontal surfaces,
              use concrete slabs or flat stones to hold the
              bandage in place.  On vertical surfaces some kind
              of prop should be devised to hold the bandage
              against the concrete.  

         5.   Repeat the process as necessary to achieve the
              desired level of cleanliness.

         6.   Thoroughly rinse the area with clean, clear water
              and allow to dry.

    -OR-

    C.   Apply a Poultice:

         1.   Mix 1 part sodium hypochlorite (commercial
              household bleach, which is about 5% hypochlorite)
              or Javelle water (diluted with 4 to 6 parts of
              water) with a talc or other suitable fine material
              to make a smooth paste.  For guidance on making
              Javelle water, see 03710-02-S for guidance.

         2.   Thoroughly wet the concrete surface to be treated
              with clean, clear water.

         3.   Apply the poultice mixture to the stained area
              using a wood or plastic spatula and allow to dry.
              Be sure to spread the poultice well beyond the
              stained area.  The liquid portion of the paste will
              migrates into the concrete where it will dissolve
              some of the staining material.  Then the liquid
              will gradually move back beyond the concrete
              surface and into the poultice, where it will
              evaporate, leaving the dissolved staining material
              in the poultice.

         4.   When the poultice has dried, brush or scrape it off
              with a wooden scraper.  

         5.   Using a stiff bristle brush, scrub the surface with
              scouring powder and clean water to remove any
              residual staining.

         6.   Thoroughly rinse the area with clean, clear water
              and allow to dry.

         7.   Repeat the process as necessary to sufficiently
              remove the stain.

         NOTE:  BOTH SODIUM HYPOCHLORITE AND JAVELLE WATER WILL
         BLEACH COLORED CLOTHING AND ARE SOMEWHAT CORROSIVE TO
         METALS.

                         END OF SECTION