Specification:Removing coal tar stains from concrete

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=GENERAL=

SUMMARY
 This procedure includes guidance on removing coal tar such as roofing tar from concrete using freezing agents and poulticing. The types of tar staining addressed here include the following:  Hot-Applied Coal Tar: Like molten asphalt, this type of tar usually does not penetrate concrete deeply. Cutback Coal Tar: This is likely to penetrate deeply.   Safety Precautions:  DO NOT save unused portions of stain-removal materials. DO NOT store any chemicals in unmarked containers. THE ORGANIC SOLVENTS LISTED FOR REMOVING COAL TAR ARE POISONOUS, CARCINOGENIC OR FLAMMABLE. EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY SOLVENT IS USED. USE RESPIRATORS WITH SOLVENT FILTERS.</li>

No use of organic solvents indoors should be allowed without substantial air movement. Use only spark-proof fans near operations involving flammable liquids.</li> Provide adequate clothing and protective gear where the chemicals are indicated to be dangerous.</li> Have available antidote and accident treatment chemicals where noted.</li> </ol> </li> See Specification:General project guidelines for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:  Safety Precautions</li> Historic Structures Precautions</li> Submittals</li> Quality Assurance</li> Delivery, Storage and Handling</li> Project/Site Conditions</li> Sequencing and Scheduling</li> General Protection (Surface and Surrounding)</li> </ol> </li> These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the State Historic Preservation Officer (SHPO). For additional information related to this procedure, see also 03710-05-R "Removing Asphalt Stains From Concrete".</li> For additional information on poulticing, see 04455-02-R.</li> </ol> =PRODUCTS=

MATERIALS
<ol type="A">

Aerosol Freezing Agent or Ice</li> <li>For Hot-Applied Coal Tar: <ol> <li>Scouring powder</li> </ol> </li> <li>For Cut-Back Coal Tar: <ol> <li>Benzene (C6H6): <li>A colorless, volatile, flammable, toxic, liquid, aromatic hydrocarbon used in organic synthesis, as a solvent and as a motor fuel.</li> <li>Other chemical or common names include Benzol; Benzole; Phene; Phenyl hydride; Coal naphtha*; Motor benzol*.</li> <li>Potential Hazards: FLAMMABLE.</li> <li>Available from automotive supply distributor, chemical supply house, dry cleaning supply distributor, hardware store or paint store.</li> <li>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.</li> </ol> </li> <li>Filler material such as talc</li> <li>Mineral water</li> </ol> </li> <li>Clean dry towels for blotting the area after treatment</li> <li>Clean, potable water</li> <li>Accessible source of water, soap and towels for washing and rinsing in case of emergencies associated with the use of chemicals</li> </ol>

EQUIPMENT
<ol type="A"> <li>For Poulticing: <ol> <li>Glass or ceramic container for mixing the solution</li> <li>Wooden utensil for stirring the ingredients</li> </ol> </li> <li>Wood or plastic spatula</li> <li>Stiff bristle brushes (non-metallic)</li> </ol> =EXECUTION=

PREPARATION
<ol type="A"> <li>Protection: <ol> <li>Provide adequate wash solutions (i.e. water, soap and towels) before starting the job.</li> <li>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.</li> </ol> </li> </ol>

ERECTION, INSTALLATION, APPLICATION
<ol type="A">

<li>Removing Hot-Applied Coal Tar: <ol> <li>Chill the coated area with an aerosol freezing agent or ice and scrape or chip while the material is brittle.</li> <li>Using a stiff bristle brush, scrub the surface with scouring powder and water.</li> <li>Thoroughly rinse the surface with clean, clear water and allow to dry.</li> <li>Repeat the process as necessary to achieve the desired level of cleanliness.</li> </ol> </li> <li>Removing Cutback Coal Tar: <ol>

<li>Remove as much as possible by chilling with an aerosol freezing agent or ice and chipping (See 3.02 A. above).</li> <li>Mix a poultice of benzene and talc. A quantity of talc should be used which is adequate to cover the affected area. Benzene should be added to achieve the consistency of a thick paste.</li> <li>Thoroughly wet the concrete surface to be treated with clean, clear water.</li> <li>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 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.</li> <li>When the poultice has dried, brush or scrape it off with a wooden scraper.</li> <li>Using a stiff bristle brush, scrub the surface with scouring powder and clean water to remove any residual staining.</li> <li>Thoroughly rinse the area with clean, clear water and allow to dry.</li> <li>Repeat the process as necessary to sufficiently remove the stain.</li> <li>If a brown color remains on the surface, treat the area using the procedure for removing light stains of iron rust from concrete (see 03710-26-R).</li> </ol> </li> </ol>