Specification:Concrete cleaning: removal of atmospheric soiling, staining, graffiti, and biogrowth

__NUMBEREDHEADINGS__ =GENERAL=

DESCRIPTION
 This specification provides guidance for cleaning historic concrete, including the removal of soiling, staining, graffiti, and biogrowth. This specification has been developed for use on historic properties (defined as any district, site, building, structure, or object that is listed in or eligible for listing in the National Register of Historic Places) and provides an overview of accepted practices. All work described herein and related work must conform to the Secretary of Interior’s Standards for the Treatment of Historic Properties. The Contractor shall provide all labor, materials, equipment, and operations required to complete the rehabilitation work indicated herein. All work described herein and related work must have the approval of a Cultural Resources Manager, Conservator, Historic Architect, or other professional who meets the standards outlined in the Secretary of the Interior’s Standards – Professional Qualifications Standards pursuant to 36 CFR 61. Such person is referred to in this document as the Architect. The Architect will provide site-specific specifications, when appropriate. 

SECTION INCLUDES
 Concrete Cleaning of Atmospheric Soiling</li> Concrete Cleaning of Staining </li> Concrete Cleaning of Graffiti</li> Concrete Cleaning of Biogrowth and Bird Droppings</li> </ol>

RELATED SECTIONS
<ol type="A"> Specification:Masonry poulticing and salt removal </li> </ol>

DEFINITIONS
<ol type="A"> Atmospheric Soiling: The dust, aerosols, and particulate matter deposited from the air directly on the material surface. Particulates can result from vehicle exhaust, sea salts and other contaminants.</li> Biological soiling: Discolorations that include biological growth (biogrowth) and biological deposits. Biogrowth includes microorganisms, including lichens, bacteria, algae, fungi, and molds that discolor the material surface. Factors influencing biogrowth include exposure, orientation, position, and surface texture of the material. Deposited material, such as bird droppings, aphid “honey dew,” and others, are considered biological soiling.</li> Chemical Cleaning: Cleaning methods that involve applying a substance to the material that interacts with the material and any discoloration on the surface. Chemical cleaning methods may include water, organic solvents, and alkaline or acidic chemicals.</li> Cleaning Test Patch: A small unobtrusive area, usually less than six inches by six inches, in which the Contractor tests a particular cleaning method. Several cleaning test patches are usually performed side by side to directly compare methods.</li> Complexing and Sequestering agent: an organic chemical that acts to grab and bind metals to itself.</li> Concrete: Concrete encompasses any of number of material compositions consisting of sand, gravel, crushed stone, or other coarse material, bound together with various kinds of cementitious materials, such as Portland cement, lime, or natural hydraulic cements. When mixed with water, the composition hardens due to the chemical interaction of the constituent parts. </li> Cutback asphalt: a combination of asphalt cement and petroleum solvent used in the paving industry.</li> Detergent: any chemical substance, other than soap, that is an effective cleanser and functions equally well as a surface-active agent in hard or soft water.</li> Graffiti: Usually an unwanted painting or marking in any manner on property.</li> Physical Cleaning: Physical cleaning methods generally involve the removal of material from the surface using abrasive methods. Physical methods include pressure washing at low and medium pressures, and mechanical or manual brushing.</li> Poultice: The term poultice is extended to a wide range of cleaning materials and techniques. In general, it is a cleaning method that involves application of a mixture consisting of a cleaner and an absorbant substance to a surface to draw out contaminants and stains from the surface of a material. </li> Staining: a penetrating discoloration or soiled spot found on the material. </li> </ol>

SUBMITTALS
<ol type="A"> <li>Treatment Schedule: Submit a detailed schedule to the Architect for approval of the areas to be cleaned, 	including an assessment of the problem surfaces, detailed procedure of concrete cleaning methods to be used and approved methods for handling of hazardous materials, such as guano.</li> <li>Product Literature: Submit manufacturer’s product literature to the Architect for all proprietary products specified for concrete cleaning, removal of graffiti, stain and/or biogrowth removal, guano removal and surface testing. Product literature shall include specification data, Material Safety Data Sheets and instructions for storage, handling and use.</li> <li>Submit to the Architect test samples or examples of similarly executed concrete cleaning, as required. </li> <li>D. Submit photographs of the repaired areas taken before, during and after the work upon conclusion of the cleaning. </li> </ol>

QUALITY ASSURANCE
<ol type="A"> <li>Work Experience: The Contractor shall have a minimum of seven years experience in historic concrete and masonry cleaning. He/she shall have successfully completed at least three concrete restoration projects of similar scope within the previous five years. Said work shall be conducted in accordance with the Secretary of Interior’s Standards for the Treatment of Historic Properties. </li> <li>The Contractor shall provide the following warranties for cleaning: The Contractor is responsible for and assures this agency that hazardous materials and/or products are handled and discarded in accordance with accepted environmentally safety practices. He/She will use perform work in compliance with Occupational Safety and Health Administration (OSHA) regulations and standards.</li> </ol>

MOCK-UPS
<ol type="A"> <li>The Contractor, at location(s) determined by the Architect, shall carry out cleaning samples, not to exceed 100 square feet per sample, of the product on inconspicuous areas, preferably conducted by the operator undertaking the final work. Allow for proper drying time prior to examination of mock-up.</li> <li>More than one test site and/or sample of product testing may be required to be acceptable for approval. The Contractor shall conduct five such product/surface test samples without further compensation. Approved test area(s) shall become part of the work and shall serve as the quality standard for all similar work.</li> </ol>

DELIVERY, STORAGE AND HANDLING
<ol type="A"> <li>Deliver restoration cleaning and testing materials and proprietary products to the project site in manufacturer’s or distributor’s packaging, undamaged, complete with application instructions and Material Safety Data Sheets.</li> <li>Store and transport cleaning agents, chemicals, and solvents within the temperature range recommended by the manufacturer and away from direct sunlight. Handle all materials following manufacturer’s instructions.</li> </ol>

PROJECT / SITE
<ol type="A"> <li>The work of this Section shall be executed only when the air and surface temperatures are 40 degrees F and rising or less than 90 degrees F and falling. Minimum temperature for masonry cleaning shall be 50 degrees F and above for at least two hours after completion and above freezing for at least 24 hours after completion. Work shall not commence when rain, snow or below-freezing temperatures are expected within the next 24 hours. All surfaces shall be free of standing water, frost and ice.</li> <li>The Contractor is responsible for protecting existing adjacent materials during the execution of the work. Provide all necessary protection and work procedures to avoid damage to existing material assemblies not a part of the work of this Section. </li> <li>Provide visible barriers and/or warning tape around the perimeter of the work area for visitor protection. Protect nearby vehicles and adjacent structures from damage during the course of the work.</li> <li>The Contractor shall coordinate concrete cleaning operations with the other trades involved in exterior and interior restoration work including, but not limited to, masonry restoration, sealants, painting.</li> </ol> =PRODUCTS=

CONCRETE CLEANING OF ATMOSPHERIC SOILING
<ol type="A"> <li>Investigations and Method Selection: <ol> <li>Identification of types of materials, surface and substrate conditions, previous treatments, and the nature, cause and pattern of the soiling type for each area shall be determined. Testing may require additional technical expertise from a materials scientist, architectural conservator, microbiologist, and/or other technical expert. The Contractor shall choose the gentlest method possible to remove the soiling without damaging the substrate material. </li> <li>The Contractor shall conduct cleaning test patches, usually less than six inches by six inches, in unobtrusive locations on the concrete to be cleaned. The purpose of the test patch is to determine the most effective, gentlest method to remove soiling from the concrete. Several cleaning methods are generally tested side by side.</li> <li>Flame cleaning, sandblasting, and shot blasting are not recommended for cleaning historic concrete surfaces.</li> <li>The method of cleaning and the level of clean shall be approved by the Architect. The contractor shall protect adjacent materials, installed non concrete materials, and openings. </li> </ol> </li> <li>Cleaning Methods: <ol> <li>Cleaning shall be undertaken through the mildest, least abrasive method. </li> <li>Consider gentlest methods first. Consider the following treatments: <li>Water with soft brushes</li> <li> Water with mild soap</li> <li> Water with stronger soap</li> <li> Water with stronger soap plus ammonia.</li> <li> Water with stronger soap plus vinegar</li> </ol> </li> <li>Water Washing: Washing the surface with low to medium jet pressure (500 psi or less at four to six gpm using a 45-degree fan-type nozzle) for water soluble dirt and chemical compounds. Optimal water pressure and wand distance are to be determined during preparation of cleaning test patches. Note that most commercial pressure washing systems operate at significantly higher pressures than those recommended. Use of a pressure regulator to reduce pressures may be needed.</li> <li>Nebulous Sprays: Application of intermittent mist spray under low pressure to dampen surface. Dirt is removed through differences in drying rates of the soiling and substrate. Swelling of the soiling generally loosens its attachment to the substrate. Optimal water pressure, timed cycles, and duration of the cleaning technique are to be determined during preparation of cleaning test patches.</li> <li>Detergents: Formulations made with dilutions of detergents, surfactants, and chelating agents in water. Neutral or non-ionic detergents or surfactants are added to water for use on hydrophobic stains. </li> </ol> </li> <li>Equipment for Concrete Cleaning: <ol> <li>Pipes and hoses used for water cleaning shall be plastic or other similar material that is not subject to corrosion, which can cause discoloration and staining of surfaces being cleaned.</li> <li>Natural bristle brushes shall be used for scrubbing.</li> <li>Hoses, fittings and equipment to be used for application of proprietary cleaning compounds shall be solvent, acid or alkali-resistant as recommended by the manufacturer of the cleaning products.</li> <li>Buckets, trowels, and other tools to be used for mixing and application of poultices shall be solvent-resistant plastic. Wood scrapers and trowels are also permitted. No metal tools are to be used.</li> </ol> </li> <li>Water/rinsing Method: <ol> <li>Surfaces shall be rinsed with water after cleaning. Rinse water will be collected and disposed of in accordance with federal, state, and local environmental standards. Rates of water pressure shall be no greater than 500 psi at three to six gpm.</li> </ol> </li> </ol>

CONCRETE CLEANING OF STAINING
<ol type="A"> <li>Investigations and method selection: <ol> <li>   Identification of types of materials, surface and substrate conditions, previous treatments, and the nature, cause and pattern of the stain, corrosion, or deposits for each area shall be determined. Testing may require additional technical expertise from a materials scientist, architectural conservator, microbiologist, and/or other technical expert. The contractor shall choose the gentlest method possible to remove the stain without damaging the substrate material. </li> <li>The most common stains found on concrete tend to be metallic stains, oil, and cutback asphalt. Metallic stains and their removal represent a chemically different problem than the removal of soiling and encrustations mentioned in Sec. 2.01. The Contractor may use chemical complexing or sequestering agents to remove metal stains. Cutback asphalt is one of the most difficult stains to remove.</li> <li>The Contractor shall conduct cleaning test patches, usually less than six inches by six inches, in unobtrusive locations on the concrete to be cleaned. The purpose of the test patch is to determine the most effective, gentlest method to remove stains from the concrete. Several cleaning methods are generally tested side by side.</li> <li>The Architect shall approve the method of cleaning and the level of clean. </li> </ol> </li> <li> Cleaning Methods: <ol> <li>Poultices: A paste or slurry made with an inert material and solvent or liquid. The two are blended together into a smooth paste which is applied by a trowel or spatula over the stain. The solvent or liquid is absorbed by the concrete and dissolves the stain. It then is pulled back into the absorbent material of the poultice. Absorbent materials or powder-inert clay used for poultices include kaolin or sepiolite, diatomaceous earth (fuller’s earth); or Cellulose products such as pulp cellulose or shredded paper that is mixed with a cleaning solution. Seek professional assistance in identifying the appropriate poultice for the particular stain to be removed. Cleaning solutions to be used in a poultice mixture may include chelating agents such as EDTA (ethylenediaminetetraacetic acid), ammonium citrate, sodium citrate, citric acid, and oxalic acid. Seek additional professional advice if chelating agents are to be used in a poultice. </li> <li>Organic solvents or inorganic chemicals in water, either ready-made or site mixed, can be used to remove some stains. Care must be exercised so that the stain isn’t pushed further into the concrete. Also, many cleaners can be toxic to workers as well as damaging to adjoining building materials. Always follow the manufacturer’s recommendations and safety standards.</li> </ol> </li> <li>Equipment for Application: See sec 2.01 C above.</li> <li>Water/rinsing method: See sec 2.01 D above.</li> </ol>

CONCRETE CLEANING OF GRAFFITI
<ol type="A"> <li>Investigations and Method Selection: <ol> <li>Identification of types of materials, surface and substrate conditions, previous treatments, and the materials used to create the graffiti for each area shall be determined. Testing may require additional technical expertise from a materials scientist, architectural conservator, microbiologist, and/or other technical expert. The Contractor shall choose the gentlest method possible to remove the graffiti without damaging the substrate material. </li> <li>The contractor shall conduct cleaning test patches in unobtrusive locations on the concrete to be cleaned. The purpose of the test patch is to determine the most effective, gentlest method to remove stains from the concrete. Several cleaning methods are generally tested side by side.</li> <li>The method of cleaning and the level of clean shall be approved by the Architect. Incised graffiti cannot be addressed by cleaning, and therefore is not covered under this section. </li> <li>Graffiti is most easily removed when it has been freshly applied, therefore, timely removal of graffiti is important.</li> </ol> </li> <li>Cleaning Methods: <ol> <li>Water and Detergent: Washing the surface with water at low to medium jet pressure, 200-500 psi or less at four to six gpm. Neutral or non-ionic detergents may be introduced. Note that most commercial pressure washing systems operate a significantly higher pressures than those recommended. Use of a pressure regulator to reduce pressures may be needed.</li> <li>Poultices: A paste or slurry made with absorbent material or powder-inert clay such as kaolin or sepiolite, diatomaceous earth (fuller’s earth); or Cellulose products such as fluff pulp cellulose or shredded paper that is mixed with a cleaning solution (a liquid reagent such as water, organic solvent, or paint stripper, among others).</li> <li>Organic Solvents and Paint Removers: Use of proprietary graffiti-removal products and commercial paint strippers containing organic solvents, sol gels, gel or paste removers, or paper or cloth-backed removers. Do not use “off-the-shelf” aerosol graffiti removers as these can cause additional staining and redistribution of pigments to clean areas.</li> </ol> </li> <li>Equipment for Application: See sec 2.01 C above.</li> <li>Water/rinsing method: See sec 2.01 D above.</li> </ol>

CONCRETE CLEANING BIOGROWTH AND BIRD DROPPINGS
<ol type="A"> <li>Investigations and Method Selection: </li> <ol> <li>Identification of types of materials, surface and substrate conditions and the nature, cause and pattern of biomaterials for each area. The method of cleaning shall be approved by the Architect. </li> </ol> <li>Cleaning Methods: <ol> <li>Water Washing: Cold water is applied at 500 psi or less pressure. A commercially available biocide, generally containing a quaternary ammonium treatment, may be introduced for treatment of algae, fungi, molds, and mildew.</li> <li>Acidic Cleaners: Formulations of acids, surfactants, and chelating agents.</li> <li>Poultices: See sec 2.02 B above.</li> </ol> </li> <li>Equipment for Application: See sec 2.01 C above.</li> <li>Water/rinsing method: See sec 2.01 D above. </li> </ol> =EXECUTION=

GENERAL
<ol type="A"> <li>The initial cleaning test patches shall be reviewed by the Architect to determine the mildest cleaning method to be used. </li> <li>The extent of the cleaning (clean level) and areas to be cleaned shall be reviewed by the Architect at the site prior to beginning operations. The Contractor shall submit testing schedule and a cleaning schedule, including the methods and materials to be used. </li> <li>The Contractor shall protect adjacent materials, installed non-concrete materials, and openings. </li> <li>Hazardous bio-materials such as bird droppings are to be handled in accordance with accepted environmental safety procedures.</li> <li>The cleaning runoff will be collected in plywood troughs lined with polyethylene sheeting. Polluted liquid gathered shall be pumped into tanker trucks or drums for properly controlled disposal. Acidic runoff shall be neutralized with lime or soda ash prior to release.</li> </ol>

PREPARATION FOR CLEANING
<ol type="A"> <li>Locate and seal (with a temporary barrier) all wall penetrations that might permit water passage to the interior. Window openings shall be protected with waterproof covering during pressure washing operations. No pressure washing shall be performed within six inches of a window opening. These areas, including the window head, jambs and sills shall be scrubbed by hand with plain water and a soft bristle brush.</li> <li>Plastic sheeting shall be placed on grade from the building line to a point five feet from the building line to direct run-off away from the base of the building.</li> </ol>

SYSTEM FOR CLEANING ATMOSPHERIC SOILING ON CONCRETE
<ol type="A"> <li>Cleaning of masonry walls shall proceed from the bottom of the wall upward to minimize streaking.</li> <li>Apply masonry cleaning product in accordance with manufacturer’s instructions and approved cleaning procedure submittal. Use tampico fiber brushes, rollers or low-pressure spray (less than 50 psi) for application. Do not use high-pressure spray equipment to apply cleaning product.</li> <li>After completion of the appropriate dwell time, remove loosened soiling using a moderate-pressure water rinse. DO NOT allow the cleaning products to dry on masonry surfaces. Rinse surfaces from top to bottom using a 45 degree fan-tip nozzle with a nozzle pressure not to exceed 500 psi and a flow of approximately four gallons per minute. Maintain a minimum distance of 18 inches between the nozzle tip and the masonry surface.</li> <li>After cleaning is completed, remove protective coverings from adjacent surfaces and repair any damage or staining caused by the cleaning operation to adjacent surfaces.</li> </ol>

SYSTEM FOR CLEANING STAINING ON CONCRETE
<ol type="A"> <li>In a plastic bucket or container, combine poultice ingredients in accordance with manufacturer’s printed instructions. Stir continuously until a smooth, wet paste forms.</li> <li>Apply a layer of poultice paste 1/8 inch to 1/4 inch in thickness immediately to the stained surface. Surfaces to be cleaned should be dry and free of surface dirt and dust. In hot weather, cover poultice paste with a layer of cloth, paper or plastic sheeting to inhibit evaporation.</li> <li>Leave poultice paste on the masonry surface until completely dry or for a maximum of 24 hours. </li> <li>Once the poultice is completely dried, scrape mixture from the surface using wood, plastic or rubber spatulas. Rinse the treated area thoroughly with water and a soft brush to remove remaining residue.</li> </ol>

SYSTEM FOR CLEANING GRAFFITI ON CONCRETE
<ol type="A"> <li>Apply the specified paint stripper using a low-pressure spray apparatus equipped with a nozzle .019 inch or larger. Spray equipment must be equipped with chemical resistant packing and hoses. Apply to a minimum thickness of 10-mils.</li> <li>Allow stripper to remain on the surface in accordance with the dwell time determined during preparation of the approved test panel. Dwell time will increase as temperatures decrease.</li> <li>After dwell time is completed, remove lifted layers using a squeegee, plastic scraper or wet vacuum device as required. Collect paint and stripper residue and dispose of in accordance with local, state and federal regulations. </li> <li>Thoroughly rinse surface with clean water. Reapply stripper as required to remove all existing paint layers.</li> </ol>

SYSTEM FOR CLEANING BIOGROWTH AND BIRD DROPPINGS ON CONCRETE
<ol type="A"> <li>General Cleaning: <ol> <li>Remove colonies of moss and loose growth from masonry surfaces to be cleaned using wooden scrapers.</li> <li>Apply selected cleaning agent in accordance with manufacturer’s instructions and approved test panel. Allow product to dwell on soiled surfaces to achieve optimal cleaning. </li> <li>After completion of required dwell time, agitate with a bristle brush to lift and remove embedded growth. Flush surfaces with low to moderate pressure (up to 500 psi) water rinse as required to remove staining. </li> </ol> </li> <li>Spot Cleaning for Heavily Soiled Areas <ol> <li>Spot cleaning to be performed only after general cleaning is completed for approximately two weeks.</li> <li>Thoroughly wet surfaces to be treated with spot cleaner. Apply product using a synthetic brush, roller or low-pressure spray and allow it to dwell on the surface. Dwell time to be in accordance with the approved test panel.</li> <li>After dwell time has elapsed, thoroughly rinse the surface with clean water at moderate pressure (up to 500 psi), working from the bottom up.</li> <li>Apply neutralizing rinse (if required) and allow to dwell on the cleaned surface three to five minutes. After completion of the required dwell time, rinse the surface again with clean water at moderate pressure (up to 500 psi) working from the bottom up.</li> </ol> </li> </ol>

FINAL REPORT
<ol type="A"> <li>Provide a final report of complete work including all approved submittals and photographs of the repaired areas taken before, during and after the work. </li> </ol>