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Historic Preservation - Technical Procedures

Spectitle:

Removing Asphalt Stains From Concrete

Procedure code:

0371005R

Source:

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

Division:

Concrete

Section:

Concrete Cleaning

Last Modified:

02/24/2012

Details:

Removing Asphalt Stains From Concrete




REMOVING ASPHALT 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 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 asphalt
         stains from concrete using chemical or freezing agents.
         The types of asphalt staining addressed here include the
         following:

         1.   Molten asphalt - usually does not penetrate the
              surface.

         2.   Emulsified asphalt - minute droplets of asphalt in
              water.

         3.   Cutback asphalt - an organic, bituminous roof
              coating or flashing cement in a volatile solvent,
              applied without heat; also used for dampproofing
              and for priming concrete and masonry surfaces;
              these stains are almost impossible to remove
              completely but may be attempted using a poultice.

    B.   Safety Precautions:

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

         2.   DO NOT store any chemicals in unmarked containers.

         3.   THE ORGANIC SOLVENTS LISTED FOR REMOVING ASPHALT
              ARE POISONOUS, CARCINOGENIC OR FLAMMABLE.
              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).


PART 2---PRODUCTS

2.01 MATERIALS

    A.   For Molten Asphalt and Emulsified Asphalt Stains:

         1.   Ice

         2.   Scouring Powder

    B.   For Cut-back Asphalt Stains:  (see Safety Precautions in
         Section 1.01 above)

         1.   Use one of the following solvents in a poultice
              (see Section 3.02 below for related procedures):

              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 (*).

              Benzene (C6H6):

              a.   A colorless, volatile, flammable, toxic,
                   liquid, aromatic hydrocarbon used in organic
                   synthesis, as a solvent and as a motor fuel.

              b.   Other chemical or common names include Benzol;
                   Benzole; Phene; Phenyl hydride; Coal naphtha*;
                   Motor benzol*.

              c.   Potential Hazards:  FLAMMABLE.

              d.   Available from automotive supply distributor,
                   chemical supply house, dry cleaning supply
                   distributor, hardware store or paint store.

              e.   Benzene and benzine should not be confused.
                   Benzene is a distinct chemical compound
                   obtained from coal tar.  Benzine is a mixture
                   of aromatic hydrocarbons of similar boiling
                   points derived from petroleum.

              -OR-

              Carbon Tetrachloride (CCl4):

              a.   A colorless, nonflammable, toxic liquid that
                   has an odor resembling chloroform and is used
                   as a solvent (as in dry cleaning) and a fire
                   extinguisher.

              b.   Other chemical or common names include
                   Perchloromethane; Tetrachloromethane.

              c.   Potential Hazards:  TOXIC.

              d.   Available from chemical supply house, dry
                   cleaning distributor, hardware store, paint
                   store or photographic supply distributor (not
                   camera shop).

              -OR-

              Dimethyl Sulfoxide (CH3)2SO:

              a.   A compound obtained as a biproduct in wood-pulp
                    manufacture and used as a solvent and in
                   experimental medicine.

              b.   Other chemical or common names include Methyl
                   sulfoxide; Methylsulfinylmethane.

              c.   Potential Hazards:  TOXIC AND FLAMMABLE.

              d.   Available from chemical supply house.

              -OR-

              Kerosene:

              a.   A flammable hydrocarbon oil usually obtained
                   by distillation of petroleum and used for a
                   fuel and as a solvent and thinner.

              b.   Other chemical or common names include Astral
                   oil*; Coal oil*.

              c.   Potential Hazards:  FLAMMABLE.

              d.   Available from automotive supply distributor,
                   gasoline service station or hardware store.

              -OR-

              Toluene (C7H8):  A liquid, aromatic hydrocarbon
              that resembles benzene but is less volatile,
              flammable and toxic; Is produced commercially from
              light oils from coke-oven gas and coal tar and from
              petroleum, and is used as a solvent, in organic
              synthesis and an antiknock agent for gasoline.

              -OR-

              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.   Filler material such as diatomaceous earth, talc,
              undyed cloth or cotton batting

         3.   Mineral water

         4.   Plastic sheeting

         5.   Clean dry towels for blotting the area after
              treatment

         6.   Masking tape

    C.   Clean, potable water

    D.   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.   For Poulticing Cut-back Asphalt Stains:

         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.   For Molten Asphalt Stains:

         1.   Chill the asphalt with regular ice (not dry ice)
              and then scrape or chip using a wood or plastic
              spatula while it is cold and brittle.

         2.   Using a stiff, non-metallic bristle brush, scrub
              the surface with scouring or abrasive powder and
              clean water to remove any remaining discoloration.

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

    B.   For Emulsified Asphalt Stains:

         NOTE:  DO NOT APPLY SOLVENTS TO EMULSIFIED ASPHALT
         STAINS.  Emulsified asphalt does not penetrate deeply
         into concrete.  Solvents will carry the emulsions deeper
         into the concrete, making stain removal virtually
         impossible.

         1.   Remove any asphalt blobs from the surface of the
              concrete, remove these first by chilling the
              surface with ice and scraping as described in
              Section 3.02 A. above for molten asphalt stains.

         2.   Using a stiff, non-metallic bristle brush, scrub
              any residual staining with scouring powder and
              clean water.

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

    C.   For Cutback Asphalt Stains:

         1.   Mix one of the solvents listed under Section 2.01
              B. above with diatomaceous earth or talc to form a
              paste having the consistency of oatmeal.

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

         3.   Apply the 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 migrate 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.

         -OR-

         1.   Soak a bandage of undyed cloth or cotton batting in
              dimethyl sulfoxide.

         2.   Apply the treated bandage to the stained surface
              and allow to sit for one hour.

         3.   Remove the bandage and scrub the surface with a
              stiff bristle brush, scouring powder and clean
              water.

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

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

                         END OF SECTION