Specification:Removing gypsum plaster stains from concrete

__NUMBEREDHEADINGS__

=GENERAL=

SUMMARY
 This procedure includes guidance on removing gypsum plaster stains from concrete using hydrochloric acid and detergent. Safety Precautions:  DO NOT save unused portions of stain-removal materials. DO NOT store any chemicals in unmarked containers. EXCELLENT VENTILATION MUST BE PROVIDED WHEREVER ANY SOLVENT IS USED. USE RESPIRATORS WITH SOLVENT FILTERS. No use of organic solvents indoors should be allowed without substantial air movement. Use only spark-proof fans near operations involving flammable liquids. Provide adequate clothing and protective gear where the chemicals are indicated to be dangerous. 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: <ol> 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> </ol> 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). =PRODUCTS=

MATERIALS
<ol type="A">

Hydrochloric Acid (30-35%): <ol> A strong corrosive irritating acid.</li> Other chemical or common names include Chlorhydric acid; Hydrogen chloride; Muriatic acid* (generally available in 18 degree and 20 degree Baume solutions); Marine acid*; Spirit of salt*; Spirit of sea salt*.</li> Potential Hazards: TOXIC, CORROSIVE TO FLESH; CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS, FLAMMABLE.</li> Available from chemical supply house, drugstore or pharmaceutical supply distributor, or hardware store.</li> </ol> </li> Detergent</li> </ol>

EQUIPMENT
<ol type="A"> Wood or plastic scraper</li> <li>Stiff bristle brush (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>Scrape off all blobs and masses; then scrub with cold or luke-warm (not hot) water and detergent.</li> <li>If this is not effective, apply a solution of 1 part hydrochloric acid in 19 parts water and scrub with a stiff (non-metallic) bristle brush.</li> <li>Thoroughly rinse the area with clean, clear water and allow to dry.</li> <li>Repeat the process as necessary to achieve the desired level of cleanliness.</li> </ol>