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Item No. 21082 Joint Surface Preparation Standard NACE No. 6/SSPC-SP 13 Surface Preparation of Concrete This NACE International (NACE)/SSPC: The Society for Protective Coatings standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. It is intended to aid the manufacturer, the consumer, and the general public. Its acceptance does not in any respect preclude anyone, whether he has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not addressed in this standard. Nothing contained in this NACE/SSPC standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents current technology and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE and SSPC assume no responsibility for the interpretation or use of this standard by other parties and accept responsibility for only those official interpretations issued by NACE or SSPC in accordance with their governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE/SSPC standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE/SSPC standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE/SSPC standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE/SSPC standards are subject to periodic review, and may be revised or withdrawn at any time without prior notice. The user is cautioned to obtain the latest edition. NACE and SSPC require that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. Reaffirmed 2003-03-17 Approved 1997 ISBN 1-57590-045-9 ©2003, NACE International and SSPC: The Society for Protective Coatings NACE International 1440 South Creek Drive Houston, TX 77084-4906 (telephone +1 281/228-6200) SSPC: The Society for Protective Coatings 40 24th Street, Sixth Floor Pittsburgh, PA 15222 (telephone +1 412/281-2331) Printed by NACE International

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NACE No. 6/SSPC-SP 13 NACE International i ________________________________________________________________________ Foreword This standard covers the preparation of concrete surfaces prior to the application of protective coating or lining systems. This standard should be used by specifiers, applicators, inspectors, and others who are responsible for defining a standard degree of cleanliness, strength, profile, and dryness of prepared concrete surfaces. This standard was originally prepared in 1997 by NACE/SSPC Joint Task Group F on Surface Preparation of Concrete. It was reaffirmed in 2003 by NACE Specific Technology Group 04 on Protective Coatings and Linings—Surface Preparation and SSPC Group Committee C.2 on Surface Preparation. This standard is issued by NACE International under the auspices of STG 04, and by SSPC Group Committee C.2. ________________________________________________________________________

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NACE No. 6/SSPC-SP 13 ii NACE International ________________________________________________________________________ Joint Surface Preparation Standard NACE No. 6/SSPC-SP 13 Surface Preparation of Concrete Contents 1. General ......................................................................................................................... 1 2. Definitions ..................................................................................................................... 1 3. Inspection Procedures Prior to Surface Preparation .................................................... 2 4. Surface Preparation ...................................................................................................... 3 5. Inspection and Classification of Prepared Concrete Surfaces ..................................... 5 6. Acceptance Criteria....................................................................................................... 6 7. Safety and Environmental Requirements ..................................................................... 6 References.......................................................................................................................... 6 Appendix A: Comments...................................................................................................... 8 Table 1: Suggested Acceptance Criteria for Concrete Surfaces After Surface Preparation ............................................................................................. 6 Table A1: Typical Surface Properties of Finished Concrete............................................... 9 Table A2: Surface Preparation Methods .......................................................................... 14 ________________________________________________________________________

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NACE No. 6/SSPC-SP 13 NACE International 1 ________________________________________________________________________ Section 1: General 1.1 This standard gives requirements for surface prepara-tion of concrete by mechanical, chemical, or thermal meth-ods prior to the application of bonded protective coating or lining systems. 1.2 The requirements of this standard are applicable to all types of cementitious surfaces including cast-in-place con-crete floors and walls, precast slabs, masonry walls, and shotcrete surfaces. 1.3 An acceptable prepared concrete surface should be free of contaminants, laitance, loosely adhering concrete, and dust, and should provide a sound, uniform substrate suitable for the application of protective coating or lining systems. 1.4 When required, a minimum concrete surface strength, maximum surface moisture content, and surface profile range should be specified in the procurement documents (project specifications). 1.5 The mandatory requirements of this standard are given in Sections 1 to 7 as follows: Section 1: General Section 2: Definitions Section 3: Inspection Procedures Prior to Surface Preparation Section 4: Surface Preparation Section 5: Inspection and Classification of Prepared Concrete Surfaces Section 6: Acceptance Criteria Section 7: Safety and Environmental Requirements 1.6 Appendix A does not contain mandatory requirements. ________________________________________________________________________ Section 2: Definitions Coating: See Protective Coating or Lining System. Concrete: A material made from hydraulic cement and inert aggregates, such as sand and gravel, which is mixed with water to a workable consistency and placed by various methods to harden and gain strength. Curing (Concrete): Action taken to maintain moisture and temperature conditions in a freshly placed cementitious mix-ture to allow hydraulic cement hydration so that potential properties of the mixture may develop. Curing Compound (Membrane Curing Compound): A liquid that can be applied as a coating to the surface of newly placed concrete to retard the loss of water.1 Efflorescence: A white crystalline or powdery deposit on the surface of concrete. Efflorescence results from leaching of lime or calcium hydroxide out of a permeable concrete mass over time by water, followed by reaction with carbon dioxide and acidic pollutants.2 Fin: A narrow linear projection on a formed concrete sur-face, resulting from mortar flowing into spaces in the form work.1 Finish: The texture of a surface after consolidating and fin-ishing operations have been performed.1 Finishing: Leveling, smoothing, consolidating, and other-wise treating surfaces of fresh or recently placed concrete or mortar to produce desired appearance and service.1 Hardener (Concrete): A chemical (including certain fluoro-silicates or sodium silicate) applied to concrete floors to reduce wear and dusting.1 High-Pressure Water Cleaning (HP WC): Water cleaning performed at pressures from 34 to 70 MPa (5,000 to 10,000 psig).3 High-Pressure Waterjetting (HP WJ): Waterjetting per-formed at pressures from 70 to 210 MPa (10,000 to 30,000 psig).3 Honeycomb: Voids left in concrete due to failure of the mortar to effectively fill the spaces among coarse aggregate particles.1 Laitance: A thin, weak, brittle layer of cement and aggre-gate fines on a concrete surface. The amount of laitance is influenced by the type and amount of admixtures, the de-gree of working, and the amount of water in the concrete.2 Lining: See Protective Coating or Lining System. Placing: The deposition, distribution, and consolidation of freshly mixed concrete in the place where it is to harden.1 Porosity: Small voids that allow fluids to penetrate an otherwise impervious material. Protective Coating or Lining System (Coating): For the purposes of this standard, protective coating or lining sys-tems (also called protective barrier systems) are bonded thermoset, thermoplastic, inorganic, organic/inorganic hy-

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NACE No. 6/SSPC-SP 13 2 NACE International brids, or metallic materials applied in one or more layers by various methods such as brush, roller, trowel, spray, and thermal spray. They are used to protect concrete from degradation by chemicals, abrasion, physical damage, and the subsequent loss of structural integrity. Other potential functions include containing chemicals, preventing staining of concrete, and preventing liquids from being contaminated by concrete. Release Agents (Form-Release Agents): Materials used to prevent bonding of concrete to a surface.1 Sealer (Sealing Compound): A liquid that is applied as a coating to a concrete surface to prevent or decrease the penetration of liquid or gaseous media during exposure. Some curing compounds also function as sealers. Soundness: A qualitative measure of the suitability of the concrete to perform as a solid substrate or base for a coat-ing or patching material. Sound concrete substrates usually exhibit strength and cohesiveness without excessive voids or cracks. Spalling (Concrete): The development of spalls which are fragments, usually in the shape of a flake, detached from a larger mass by a blow, by the action of weather, by pres-sure, or by expansion within the larger mass.1 Surface Porosity: Porosity or permeability at the concrete surface that may absorb vapors, moisture, chemicals, and coating liquids. Surface Preparation: The method or combination of meth-ods used to clean a concrete surface, remove loose and weak materials and contaminants from the surface, repair the surface, and roughen the surface to promote adhesion of a protective coating or lining system. Surface Profile (Texture): Surface contour as viewed from edge. Surface Air Voids: Cavities visible on the surface of a solid. ________________________________________________________________________ Section 3: Inspection Procedures Prior to Surface Preparation 3.1 Concrete shall be inspected prior to surface prepara-tion to determine the condition of the concrete and to deter-mine the appropriate method or combination of methods to be used for surface preparation to meet the requirements of the coating system to be applied. Inherent variations in sur-face conditions seen in walls and ceilings versus those in floors should be considered when choosing surface prepar-ation methods and techniques. For example, walls and ceil-ings are much more likely than floors to contain surface air voids, fins, form-release agents, and honeycombs. 3.2 Visual Inspection All concrete surfaces to be prepared and coated shall be visually inspected for signs of concrete defects, physical damage, chemical damage, contamination, and excess moisture. 3.3 Concrete Cure All concrete should be cured using the procedures de-scribed in ACI(1) 308.4 Curing requirements include main-taining sufficient moisture and temperatures for a minimum time period. Surface preparation performed on insufficiently cured or low-strength concrete may create an excessively coarse surface profile or remove an excessive amount of concrete. 3.4 Concrete Defects Concrete defects such as honeycombs and spalling shall be repaired. The procedures described in NACE Standard RP0390,5 ICRI(2) 03730,6 or ACI 3017 may be used to en-sure that the concrete surface is sound prior to surface preparation. 3.5 Physical Damage 3.5.1 Concrete should be tested for soundness by the qualitative methods described in NACE Publication 6G1918 or Paragraph A1.4.3. 3.5.2 When qualitative results are indeterminate, or when a quantitative result is specified, concrete shall be tested for surface tensile strength using the meth-ods described in Paragraph A1.6. 3.5.3 Concrete that has been damaged because of physical forces such as impact, abrasion, or corrosion of reinforcement shall be repaired prior to surface prep-aration if the damage would affect coating perform-ance. Repairs should be made in accordance with ACI 301,7 NACE Standard RP0390,5 or Paragraph A1.4. 3.6 Chemical Damage 3.6.1 Concrete is attacked by a variety of chemicals, as detailed in ACI 515.1R9and PCA(3) IS001.10 ___________________________ (1) American Concrete Institute International (ACI), 38800 International Way, Country Club Drive, Farmington Hills, MI 48331. (2) International Concrete Repair Institute (ICRI), 3166 S. River Road, Suite 132, Des Plaines, IL 60018. (3) Portland Cement Association (PCA), 5420 Old Orchard Rd., Skokie, IL 60077.

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NACE No. 6/SSPC-SP 13 NACE International 3 3.6.2 All concrete surfaces that have been exposed to chemicals shall be tested and treated for contamination as described in Paragraph 3.7. 3.6.3 Concrete that has been exposed to chemicals shall be tested for soundness by the qualitative meth-ods described in NACE Publication 6G1918 or Para-graph A1.4.3. 3.7 Contamination 3.7.1 Contamination on concrete surfaces includes all materials that may affect the adhesion and perform-ance of the coating to be applied. Examples include, but are not limited to, dirt, oil, grease, chemicals, and existing incompatible coatings. 3.7.2 Contamination may be detected by methods de-scribed in NACE Publication 6G1918 and Paragraph A1.5. These methods include, but are not limited to, visual examination, water drop (contact angle) meas-urement, pH testing, petrographic examination, and various instrumental analytical methods. Core samp-ling may be required to determine the depth to which the contaminant has penetrated the concrete. 3.7.3 Concrete surfaces that are contaminated or that have existing coatings shall be tested by the method described in Paragraph A1.6.3 to determine whether the contamination or existing coating affects the ad-hesion and performance of the coating to be applied. Concrete surfaces that have existing coatings shall also be tested by the method described in Paragraph A1.6.3 to determine whether the existing coating is sufficiently bonded to the concrete. 3.7.4 In extreme cases of concrete damage or degra-dation, or thorough penetration by contaminants, com-plete removal and replacement of the concrete may be required. 3.8 Moisture Moisture levels in the concrete may be determined by the methods described in Paragraph 5.6. ________________________________________________________________________ Section 4: Surface Preparation 4.1 Objectives 4.1.1 The objective of surface preparation is to pro-duce a concrete surface that is suitable for application and adhesion of the specified protective coating sys-tem. 4.1.2 Protrusions such as from burrs, sharp edges, fins, and concrete spatter shall be removed during sur-face preparation. 4.1.3 Voids and other defects that are at or near the surface shall be exposed during surface preparation. 4.1.4 All concrete that is not sound shall be removed so that only sound concrete remains. 4.1.5 Concrete damaged by exposure to chemicals shall be removed so that only sound concrete remains. 4.1.6 All contamination, form-release agents, efflor-escence, curing compounds, and existing coatings determined to be incompatible with the coating to be applied shall be removed. 4.1.7 The surface preparation method, or combination of methods, should be chosen based on the condition of the concrete and the requirements of the coating system to be applied. 4.1.8 All prepared concrete surfaces shall be repaired to the level required by the coating system in the in-tended service condition. 4.2 Surface Cleaning Methods 4.2.1 The surface cleaning methods described in Par-agraphs 4.2.2 and 4.2.3 shall not be used as the sole surface preparation method of concrete to be coated as they do not remove laitance or contaminants or alter the surface profile of concrete. These methods shall be used as required, before and/or after the mechan-ical and chemical methods described in Paragraphs 4.3 and 4.4. 4.2.2 Vacuum cleaning, air blast cleaning, and water cleaning as described in ASTM(4) D 425811 may be used to remove dirt, loose material, and/or dust from concrete. 4.2.3 Detergent water cleaning and steam cleaning as described in ASTM D 425811 may be used to remove oils and grease from concrete. 4.3 Mechanical Surface Preparation Methods 4.3.1 Dry abrasive blasting, wet abrasive blasting, vac-uum-assisted abrasive blasting, and centrifugal shot blasting, as described in ASTM D 4259,12 may be used to remove contaminants, laitance, and weak concrete, ___________________________ (4) ASTM International, 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959.

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NACE No. 6/SSPC-SP 13 4 NACE International to expose subsurface voids, and to produce a sound concrete surface with adequate profile and surface porosity. 4.3.2 High-pressure water cleaning or waterjetting methods as described in NACE No. 5/SSPC-SP 12,2 ASTM D 4259,12 or “Recommended Practices for the Use of Manually Operated High Pressure Water Jetting Equipment,”(5)13 may be used to remove contaminants, laitance, and weak concrete, to expose subsurface voids, and to produce a sound concrete surface with adequate profile and surface porosity. 4.3.3 Impact-tool methods may be used to remove existing coatings, laitance, and weak concrete. These methods include scarifying, planing, scabbling, and rot-ary peening, as described in ASTM D 4259.12 Impact-tool methods may fracture concrete surfaces or cause microcracking and may need to be followed by one of the procedures in Paragraphs 4.3.1 or 4.3.2 to produce a sound concrete surface with adequate profile and surface porosity. The soundness of a concrete surface prepared using an impact method may be verified by one of the surface tensile strength tests described in Paragraph A1.6. 4.3.4 Power-tool methods, including circular grinding, sanding, and wire brushing as described in ASTM D 4259,12 may be used to remove existing coatings, lait-ance, weak concrete, and protrusions in concrete. These methods may not produce the required surface profile and may require one of the procedures de-scribed in Paragraphs 4.3.1 or 4.3.2 to produce a con-crete surface with adequate profile and surface poro-sity. 4.3.5 Surface preparation using the methods de-scribed in Paragraphs 4.3.1 through 4.3.4 shall be per-formed in a manner that provides a uniform, sound sur-face that is suitable for the specified protective coating system. 4.4 Chemical Surface Preparation Acid etching, as described in ASTM D 426014 and NACE Standard RP0892,15 may be used to remove laitance and weak concrete and to provide a surface profile on horizontal concrete surfaces. This method requires complete removal of all reaction products and pH testing to ensure neutrali-zation of the acid. Acid etching is not recommended for ver-tical surfaces and areas where curing compounds or seal-ers have been used. Acid etching shall only be used where procedures for handling, containment, and disposal of the hazardous materials are in place. Acid etching with hydro-chloric acid shall not be used where corrosion of metal in the concrete (rebar or metal fibers) is likely to occur. 4.5 Flame (Thermal) Cleaning and Blasting 4.5.1 Flame cleaning using a propane torch or other heat source may be used to extract organic contamin-ants from a concrete surface. To remove the extracted contaminants this type of cleaning may need to be fol-lowed by the cleaning methods described in ASTM D 4258.11 4.5.2 Flame cleaning and blasting using oxygen-acet-ylene flame blasting methods and proprietary delivery equipment may be used to remove existing coatings, contaminants, and laitance and/or create a surface pro-file on sound concrete. 4.5.3 The extent of removal when employing flame methods is affected by the rate of equipment advance-ment, the flame adjustment, and the distance between the flame and the concrete surface. Surface prepara-tion using flame methods shall be performed in a man-ner that provides a uniform, sound surface that is suit-able for the specified protective coating system. 4.5.4 High temperatures reduce the strength of or damage concrete; therefore, surfaces prepared using flame methods shall be tested for soundness and sur-face tensile strength. Concrete surfaces found to be unsound or low in tensile strength shall be repaired or prepared by other mechanical methods described in Paragraph 4.3. 4.6 Surface Cleanliness After the concrete surface has been prepared to the required soundness and surface profile, surfaces may still need to be cleaned by one of the methods described in Paragraph 4.2 to remove the residue created by the surface preparation method or to remove spent media. 4.7 Moisture Content If the moisture level in the concrete is higher than the spec-ified limit tolerable by the coating, the concrete shall be dried or allowed to dry to the level specified in the procure-ment documents before inspection and application of the coating (see Paragraph 5.6). 4.8 Patching and Repairs 4.8.1 Prior to proceeding with patching and repairs, the prepared concrete surface shall be inspected according to Section 5. After the patching and repairs of the concrete surface are completed, the repaired areas shall be reinspected according to Section 5. 4.8.2 All gouges, surface air voids, and other surface anomalies shall be repaired to a level required by the coating system as specified in the procurement docu-ments. ___________________________ (5) WaterJet Technology Association, 917 Locust, Suite 1100, St. Louis, MO 63101-1419.

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NACE No. 6/SSPC-SP 13 NACE International 5 4.8.3 All repair materials, both cementitious and poly-meric, should be approved or recommended by the coating manufacturer as being compatible with the coating to be applied. Repair materials not recom-mended or approved by the coating manufacturer shall be tested for compatibility prior to their application. 4.8.4 The repair material shall be cured according to the manufacturer’s published instructions. 4.8.5 The repaired section may require additional sur-face preparation prior to coating application. ________________________________________________________________________ Section 5: Inspection and Classification of Prepared Concrete Surfaces 5.1 Surface Tensile Strength 5.1.1 All prepared concrete surfaces should be tested for surface tensile strength after cleaning and drying but prior to making repairs or applying the coating. 5.1.2 Surface tensile strength should be tested using a method agreed upon by all parties. (See Paragraph A1.6 for commentary on these methods.) 5.2 Coating Adhesion 5.2.1 If specified in the procurement documents and accepted by all parties, a test patch shall be applied to determine the compatibility of and adhesion between the prepared surface and the coating system. (See Paragraph A1.6.3 for commentary on this method.) 5.2.2 Coating adhesion should be tested using one of the methods agreed upon by all parties. (See Para-graph A1.6 for commentary on these methods.) 5.3 Surface Profile 5.3.1 If a specific surface profile is required for the per-formance of the coating system to be applied, the pro-file shall be specified in the procurement documents. 5.3.2 The surface profile of prepared concrete sur-faces should be evaluated after cleaning and drying but prior to repairs or application of the coating. 5.3.3 The surface profile may be evaluated by com-paring the profile of the prepared concrete surface with the profile of graded abrasive paper, as described in ANSI(6) B 74.18,16 by comparing the profile with the ICRI Guideline No. 0373217 (surface profile chips), or by another agreed-upon visual comparison. 5.4 Surface Cleanliness 5.4.1 All prepared concrete surfaces shall be inspect-ed for surface cleanliness after cleaning and drying but prior to making repairs or applying the coating. If the concrete surfaces are repaired, they shall be reinspect-ed for surface cleanliness prior to applying the coating. 5.4.2 Prepared concrete surfaces may be inspected for surface cleanliness by lightly rubbing the surface with a dark cloth or pressing a translucent adhesive tape on the surface. The test method and acceptable level of residual dust shall be agreed on by all parties. 5.4.3 The method used to verify compatibility of the coating to be applied over a contaminated surface or over contaminated surfaces that have been cleaned and prepared should be approved by the coating man-ufacturer and specified in the procurement documents. 5.5 pH 5.5.1 If a specific pH range is required for proper per-formance of the coating system to be applied, the pH of the concrete shall be specified in the procurement doc-uments. 5.5.2 The pH of concrete surfaces prepared by acid etching should be tested after etching and rinsing but before the prepared surface has dried. 5.5.3 ASTM D 426218 should be used to determine pH. 5.6 Moisture Content 5.6.1 If a specific moisture content is required for pro-per performance of the coating system to be applied, the moisture content of the concrete shall be specified in the procurement documents. 5.6.2 Prepared concrete surfaces should be tested for residual moisture after cleaning and drying but prior to the application of the coating. 5.6.3 ASTM D 4263,19 ASTM F 1869,20 or ASTM F 217021 should be used to determine the residual moist-ure content in concrete. 5.6.4 If required or accepted by all parties, any of the methods described in Paragraph A1.8.4 may be used to determine the moisture content of the concrete sur-face. ___________________________ (6) American National Standards Institute (ANSI), 1819 L Street NW, Washington, DC 20036.

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NACE No. 6/SSPC-SP 13 6 NACE International ________________________________________________________________________ Section 6: Acceptance Criteria 6.1 The acceptance criteria for prepared concrete surfaces shall be specified in the procurement documents. 6.2 The procurement documents may refer to the specifi-cations in Table 1. Table 1: Suggested Acceptance Criteria for Concrete Surfaces After Surface Preparation Property Test Method Light Service(A) Severe Service(B) Surface tensile strength See Paragraph A1.6 1.4 MPa (200 psi) min. 2.1 MPa (300 psi) min. Surface profile Visual comparison16 Fine (150) abrasive paper min. Coarse (60) abrasive paper min. Surface cleanliness Visible dust11 No significant dust No significant dust Residual contaminants Water drop15,22 0° contact angle 0° contact angle pH ASTM D 426218 (pH of rinse water) -1, +2(C) (pH of rinse water) -1, +2(C) Moisture content(D) ASTM D 426319 No visible moisture No visible moisture Moisture content(D) ASTM F 186920 15 g/24 hr/m2 (3 lb/24 hr/1,000 ft2) max. 15 g/24 hr/m2 (3 lb/24 hr/1,000 ft2) max. Moisture content(D) ASTM F 217021 80% max. 80% max. __________________________________________ (A) Light service refers to surfaces and coatings that have minimal exposure to traffic, chemicals, and changes in temperature. (B) Severe service refers to surfaces and coatings that have significant exposure to traffic, chemicals, and/or changes in temperature. (C) The acceptance criterion for ASTM D 4262 is as follows: The pH readings following the final rinse shall not be more than 1.0 lower or 2.0 higher than the pH of the rinse water (tested at the beginning and end of the final rinse cycle) unless otherwise specified. (D) Any one of these three moisture content test methods is acceptable. ________________________________________________________________________ Section 7: Safety and Environmental Requirements 7.1 Disposal of contaminants, old coatings, acid from etch-ing, and contaminated water and blasting media shall com-ply with all applicable facility, local, state, and federal regula-tions. 7.2 Handling of hazardous materials, machinery opera-tions, worker protection, and control of airborne dust and fumes shall comply with all applicable facility, local, state, and federal health and safety regulations. ________________________________________________________________________ References 1. ACI 116R (latest revision), “Cement and Concrete Terminology” (Farmington Hills, MI: ACI). 2. SSPC-Guide 11 (latest revision), “Guide for Coating Concrete” (Pittsburgh, PA: SSPC). 3. NACE No. 5/SSPC-SP 12, “Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating” (Houston, TX: NACE, and Pittsburgh, PA: SSPC). 4. ACI 308 (latest revision), “Standard Practice for Curing Concrete” (Farmington Hills, MI: ACI). 5. NACE Standard RP0390 (latest revision), “Mainten-ance and Rehabilitation Considerations for Corrosion Con-trol of Existing Steel-Reinforced Concrete Structures” (Houston, TX: NACE). 6. ICRI Guideline No. 03730 (latest revision), “Guide for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing Steel Corrosion” (Des Plaines, IL: ICRI). 7. ACI 301 (latest revision), “Specifications for Structural Concrete” (Farmington Hills, MI: ACI). 8. NACE Publication 6G191 (withdrawn), “Surface Prep-aration of Contaminated Concrete for Corrosion Control” (Houston, TX: NACE ). (Available from NACE as an historical document only). 9. ACI 515.1R (latest revision), “Guide to the Use of Waterproofing, Dampproofing, Protective, and Decorative Barrier Systems for Concrete” (Farmington Hills, MI: ACI).

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NACE No. 6/SSPC-SP 13 NACE International 7 10. IS001 (latest revision), “Effects of Substances on Con-crete and Guide to Protective Treatments” (Skokie, IL: PCA). 11. ASTM D 4258 (latest revision), “Standard Practice for Surface Cleaning Concrete for Coating” (West Consho-hocken, PA: ASTM). 12. ASTM D 4259 (latest revision), “Standard Practice for Abrading Concrete” (West Conshohocken, PA: ASTM). 13. “Recommended Practices for the Use of Manually Operated High-Pressure Water Jetting Equipment” (latest revision) (St. Louis, MO: WaterJet Technology Assoc-iation). 14. ASTM D 4260 (latest revision), “Standard Practice for Acid Etching Concrete” (West Conshohocken, PA: ASTM). 15. NACE Standard RP0892 (latest revision), “Coatings and Linings Over Concrete for Chemical Immersion and Containment Service” (Houston, TX: NACE). 16. ANSI B74.18 (latest revision), “Specifications for Grad-ing of Certain Abrasive Grain on Coated Abrasive Products” (Washington, DC: ANSI). 17. ICRI Guideline No. 03732 (latest revision), “Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays” (Des Plaines, IL: ICRI). 18. ASTM D 4262 (latest revision), “Standard Test Method for pH of Chemically Cleaned or Etched Concrete Surfaces” (West Conshohocken, PA: ASTM). 19. ASTM D 4263 (latest revision), “Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method” (West Conshohocken, PA: ASTM). 20. ASTM F 1869 (latest revision), “Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride” (West Con-shohocken, PA: ASTM). 21. ASTM F 2170 (latest revision), “Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ Probes” (West Conshohocken, PA: ASTM). 22. F.S. Gelfant, “Contaminated Concrete—Effect of Sur-face Preparation Methods on Coating Performance,” Jour-nal of Protective Coatings and Linings (JPCL) 12, 12 (1995): pp. 60-72. 23. T.I. Aldinger, B.S. Fultz, “Keys to Successfully Prep-aring Concrete for Coating,” JPCL 6, 5 (1989): pp. 34-40. 24. T. Dudick, “Concrete Standards for Resinous Top-pings,” SSPC 93-06: Innovations for Preserving and Pro-tecting Industrial Structures, November 13-18, 1993 (Pitts-burgh, PA: SSPC, 1993). 25. R. Boyd, “Quality Control in Cleaning and Coating Con-crete,” SSPC 91-19: Protective Coatings for Flooring and Other Concrete Surfaces, November 10-15, 1991 (Pitts-burgh, PA: SSPC, 1991), pp. 5-7. 26. L.D. Vincent, Corrosion Prevention by Protective Coat-ings, 2nd ed. (Houston, TX: NACE, 1999). 27. NACE 6G197/SSPC-TU 2 (latest revision), “Design, Installation, and Maintenance of Coating Systems for Con-crete Used in Secondary Containment,” (Houston, TX: NACE, and Pittsburgh, PA: SSPC). 28. ASTM PCN: 03-401079-14, “Manual of Coating Work for Light-Water Nuclear Power Plant Primary Containment and Other Safety-Related Facilities” (West Conshohocken, PA: ASTM, 1979), pp. 114-119. 29. H.H. Baker, R.G. Posgay, “The Relationship Between Concrete Cure and Surface Preparation,” JPCL 8, 8 (1991): pp. 50-56. 30. F. Hazen, “Repairing Concrete Prior to Lining Second-ary Containment Structures,” JPCL 8, 1 (1991): pp. 73-79. 31. ASTM PCN: 03-401079-14, “Manual of Coating Work for Light-Water Nuclear Power Plant Primary Containment and Other Safety-Related Facilities” (West Conshohocken, PA: ASTM, 1979), pp. 120-123. 32. C.T. Grimm, “Cleaning Masonry: A Review of the Liter-ature,” Publication #TR 2-88, Construction Research Cen-ter, (Arlington, TX: University of Texas at Arlington, Novem-ber 1988). 33. S. Lefkowitz, “Controlled Decontamination of Con-crete,” Concrete: Surface Preparation, Coating and Lining, and Inspection (Houston, TX: NACE, 1991). 34. R.A. Nixon, “Assessing the Deterioration of Concrete in Pulp and Paper Mills,” Concrete: Surface Preparation, Coating and Lining, and Inspection, January 28-30, 1991 (Houston, TX: NACE, 1991). 35. IS214 (latest revision), “Removing Stains and Cleaning Concrete Surfaces,” (Skokie, IL: PCA). 36. J. Steele, “Testing Adhesion of Coatings Applied to Concrete,” Materials Performance (MP) 33, 11 (1994): pp. 33-36. 37. ASTM D 4541 (latest revision), “Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers” (West Conshohocken, PA: ASTM). 38. ACI 503R (latest revision), “Use of Epoxy Compounds with Concrete” (Farmington Hills, MI: ACI). 39. T.K. Greenfield, “Dehumidification Equipment Reduces Moisture in Concrete During Coating Application,” MP 33, 3 (1994): pp. 39-40.

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NACE No. 6/SSPC-SP 13 8 NACE International 40. L. Harriman, “Drying and Measuring Moisture in Con-crete—Part I,” MP 34, 1 (1995): pp. 34-36. 41. L. Harriman, “Drying and Measuring Moisture in Con-crete—Part II,” MP 34, 2 (1995): pp. 34-36. 42. W.H. Riesterer, “Hydrostatic, Capillary, Osmotic and Other Pressures,” Innovations for Preserving and Protecting Industrial Structures,” November 13-18, 1993 (Pittsburgh, PA: SSPC, 1993). 43. ASTM E 1907 (latest revision), “Standard Practices for Determining Moisture-Related Acceptability of Concrete Floors to Receive Moisture-Sensitive Finishes” (West Con-shohocken, PA: ASTM). 44. N.C. Duvic, “Surface Preparation of Concrete for Appli-cation of Protective Surfacing or Coating,” Concrete: Sur-face Preparation, Coating and Lining, and Inspection (Hous-ton, TX: NACE, 1991). 45. P.J. Fritz, “The Use of Captive Shot (Roto-Peening) for Preparing the Surface of Concrete,” SSPC 93-06: Innova-tions for Preserving and Protecting Industrial Structures, November 13-18, 1993 (Pittsburgh, PA: SSPC, 1993), pp. 144-147. 46. K. Pashina, “Planning, Proper Surface Preparation Essential for Successful Coatings,” Concrete Repair Bulletin 7, 1 (1994): pp. 4-8. 47. ASTM PCN: 03-401079-14, “Manual of Coating Work for Light-Water Nuclear Power Plant Primary Containment and Other Safety-Related Facilities” (West Conshohocken, PA: ASTM, 1979), pp. 124-127. 48. T.I. Aldinger, “Coating New Concrete: Why Wait 28 Days?” SSPC 91-19: Protective Coatings for Flooring and Other Concrete Surfaces, November 10-15, 1991 (Pitts-burgh, PA: SSPC, 1991), pp. 1-4. 49. J. Steele, “Effective Sealing, Priming and Coating of New and Uncured Concrete,” Concrete: Surface Prepara-tion, Coating and Lining, and Inspection, January 28-30, 1991 (Houston, TX: NACE, 1991). ________________________________________________________________________ Appendix A: Comments (This section does not contain any mandatory requirements.) A1.1 General23,24,25,26 A1.1.1 This standard does not recommend surface preparation methods or differentiate levels of surface preparation that are specifically required for various protective system designs, types, thicknesses, and end-use requirements. These specifications should be decided and agreed upon by all parties (the specifier, facility owner, coating manufacturer, and contractor). A1.1.2 Concrete and its surfaces are not homogen-eous or consistent and, unlike steel, cannot be dis-cretely defined. Therefore, visual examination of a con-crete surface is somewhat subjective. The acceptance or rejection of a prepared concrete surface should be based on the results of specific tests, including, but not limited to, tests for surface tensile strength, contam-ination, and moisture. A1.1.3 Joints, cracks, and curing shrinkage of con-crete should be considered in the design of the protect-ive coating system; however, these topics are beyond the scope of this standard. See NACE Standard RP0892,15 ACI 515.1R,9 and NACE 6G197/SSPC-TU 227 for more information. A1.1.4 When a significant amount of weak, deterior-ated, or contaminated concrete is removed during the course of surface preparation to achieve a sound sur-face, the profile of the remaining concrete is often too rough for the intended coating system. In these cases, and where form voids and surface air voids must be filled, patching or grouting materials are specified to repair or level the concrete surface. See NACE Stand-ard RP0892,15 ACI 515.1R,9 NACE Standard RP0390,5 NACE 6G197/SSPC-TU 2,27 and Paragraph A1.4.4 for more information about patching materials. A1.2 Concrete Finishing and Surface Characteristics23 A1.2.1 The method used to finish concrete surfaces affects the concrete’s surface profile, composition, por-osity, and density. These surface properties affect the adhesion and performance of concrete coatings. Typi-cal surface properties obtained using the most common finishing methods are given in Table A1. These prop-erties are evaluated prior to surface preparation. A1.2.2 No preferred method of finishing concrete to accept coatings has been established by the concrete coating industry. The surface cure, surface preparation method, and type of coating system to be applied are all factors in determining the suitability of any specific concrete finishing method. For example, broom finish-ing is sometimes used because it gives a profile for the coating; however, most of the profile may be removed during surface preparation if the surface is not properly cured, negating this inherent advantage of the broom finish. When sacking is used to fill voids in formed con-crete surfaces, subsurface voids are created, and the added cement is usually removed during surface prep-aration due to improper cure of the added cement paste.

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NACE No. 6/SSPC-SP 13 NACE International 9 Table A1: Typical Surface Properties of Finished Concrete Method Profile(A) Porosity(A) Strength(A) Problems Formed concrete Smooth to medium Low to medium Medium Voids, protrusions, release agents Wood float Medium Medium Medium Metal trowel Smooth Low High Power trowel Smooth Very low High Very dense Broom finish Coarse to very coarse Medium Medium Sacking Smooth Low to medium Low to high(B) Weak layer if not properly cured Stoning Smooth to medium Low to medium Low to high(B) Weak layer if not properly cured Concrete block Coarse to very coarse Very high Medium Pinholes Shotcrete(C) Very coarse Medium Medium Too rough for thin coatings _______________________________ (A) These surface properties are based on similar concrete mix, placement, and vibration and prior to surface preparation. (B) Strength depends on application and cure. (C) Shotcrete may be refinished after placement, which would change the surface properties given in this table. A1.2.3 Use of a metal trowel is gaining acceptance as the preferred finishing method for horizontal sur-faces to be coated, provided the surface is not exces-sively trowelled, the concrete is cured properly, and the laitance is removed prior to coating. A1.2.4 Photographic examples of concrete finishes are shown in ASTM PCN:03-401079-14.28 A1.3 Concrete Cure29 A1.3.1 Maintaining sufficient moisture and proper temperature in concrete in the early stages of cure is important to ensure development of the designed strength. Keeping the surface moist until sufficient strength has developed at the surface is important to ensure formation of sufficient surface strength, to reduce curling, and to reduce surface cracking. A1.3.2 ACI 3084 recommends seven days of moist curing for Type I portland cement concrete and three days for Type III portland cement concrete, if the temp-erature is above 10°C (50°F). ACI 308 also recom-mends numerous methods to properly cure concrete, including the use of sealing materials and other meth-ods to keep concrete moist. A1.3.3 ACI 3084 also gives recommendations on the use of curing compounds, which are commonly used immediately after placement and finishing of concrete surfaces to reduce moisture loss and improve surface cure. The curing compound should either be compat-ible with the coating or be removed during surface preparation. A1.4 Identification and Repair of Surface Defects and Damage30 A1.4.1 Physical and Chemical Damage A1.4.1.1 Existing concrete structures that have been subjected to mechanical damage (caused by impact or abrasion), chemical attack, or rebar cor-rosion are restored to provide a uniform, sound substrate prior to coating application. A1.4.1.2 In order to best receive and hold the patching material all deteriorated concrete should be removed and the surrounding sound concrete cut using the procedures described in ICRI 03730.6 Some contaminants have a detrimental effect on the rebar or the applied coating if they are not completely removed. A1.4.1.3 A number of polymeric grouts and patch-ing materials can be used, especially when the coating is to be applied immediately. These mat-erials should be compatible with the coating to be applied. A1.4.2 Other Defects and Imperfections A1.4.2.1 Defects such as honeycombs, scaling, and spalling do not provide a sound, uniform sub-strate for the coating. These defects are repaired by removing all unsound concrete and then patch-ing the concrete prior to surface preparation. NACE Standard RP03905 and ICRI 037306 de-scribe removal and repair procedures for concrete

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NACE No. 6/SSPC-SP 13 10 NACE International that is spalled because of rebar corrosion. A1.4.2.2 Surface air voids, pinholes, or excessive porosity may affect the application or performance of the coating. The maximum substrate void size or surface porosity that can be tolerated depends on the coating system under consideration. If voids are not filled before the coating is applied, the trapped air vapor expands and contracts and may affect the performance of the coating. For liquid-rich coatings, excess porosity at the surface may result in pinholes in the coating. Voids are usually filled after surface preparation and prior to coating application. A1.4.2.3 Protrusions such as form lines, fins, sharp edges, and spatter may cause holidays or thin sections in the coating if they are not removed. Protrusions and rough edges are usually removed during surface preparation. A1.4.3 Testing for Surface Soundness A1.4.3.1 NACE Publication 6G1918 describes the following commonly used methods for determining surface soundness: A screwdriver, file, or pocket knife is lightly scratched across the concrete surface. If the metal object rides over the surface without loosen-ing any particles and leaves no more than a shiny mark, the surface is sound. If this process gouges the surface, the surface is not sound. The concrete surface is lightly struck with the edge of a hammer head. If the hammer rebounds sharply with no more than a small fracture at the impact area, the surface is sound. If it lands with a dull thud and leaves powdered dusts in the indent-ation, the surface is not sound. A chain is dragged across horizontal concrete sur-faces. Differences in sound indicate unsound con-crete and holes or pockets within the concrete. A1.4.4 Patching of Concrete Surface Imperfections A1.4.4.1 Materials such as grouts, putties, and sealers are used to repair, patch, smooth, or seal the concrete surface to provide a substrate that is suitable for the coating system to be applied. These materials are applied after surface prepar-ation and require the following characteristics: (1) good adhesion; (2) adequate strength; (3) low volumetric and linear shrinkage; (4) compatibility with the coating to be applied; and (5) proper consistency for the application. In addition, the patching material is often required to cure sufficiently, be traffic bearing, and be ready to recoat in a short time frame (usually within 24 hours). A1.4.4.2 Shrinkage of the patching material may reduce the adhesion of that material to the con-crete substrate. Differences in thermal expansion between the concrete, patching material, and coat-ing system cause stresses during thermally in-duced movement that may reduce adhesion be-tween these layers. A1.4.4.3 The most common types of patching mat-erials are cementitious, polymer-modified cementi-tious (usually acrylic), and polymeric (usually epoxy). Cementitious materials are lower in cost than polymeric materials, but polymeric materials generally cure faster and have higher strengths, better adhesion, and increased chemical resist-ance. A1.4.4.4 Patching materials are available in a range of consistencies for application to vertical or horizontal surfaces by a variety of methods. The amount of filler also varies. For example, grouts for deep patching are typically highly filled, while porosity sealers may be minimally filled or unfilled. Numerous proprietary materials are low-shrinking, nonshrinking, or expanding. A1.4.4.5 Additional surface preparation may need to be performed on cured patching materials to ensure that the laitance is removed and/or that the patched surface meets the profile requirements of the coating system. A1.4.4.6 Photographic examples of patched con-crete surfaces are shown in ASTM PCN:03-401079-14.31 A1.5 Identification and Removal of Contaminants22,32,33,34 A1.5.1 Hydrophobic Materials A1.5.1.1 Hydrophobic materials such as form-release agents, curing compounds, sealers, exist-ing coatings, oil, wax, grease, resins, and silicone may be detected by a simple water drop test. Analytical techniques such as infrared analysis or gas chromatography may also be used to detect and identify these contaminants. A1.5.1.2 Oils and greases can be removed by steam cleaning, flame blasting, baking soda blast-ing, or using degreasers and absorbents.

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NACE No. 6/SSPC-SP 13 NACE International 11 A1.5.1.3 If they are incompatible with the coating to be applied, existing curing compounds, sealers, form-release agents, and coatings should be re-moved by the least destructive, most practical, economical, and safe method that is successful. Methods such as grinding, abrasive blasting, wet abrasive blasting, waterjetting, scarifying, flame blasting, or paint stripping may be used. A1.5.2 Salts and Reactive Materials A1.5.2.1 Salts and reactive materials such as lait-ance, efflorescence, acids, alkalis, and by-prod-ucts of chemical attack of concrete can sometimes be detected by pH testing, soundness testing us-ing the screwdriver test, or visual examination (see PCA IS214).35 When these methods are not suc-cessful, chemical analysis techniques are required. A1.5.2.2 Residual acids and alkalis are first neu-tralized and then removed by high-pressure water cleaning. Salts and efflorescence can be removed by abrasive blasting, high-pressure water cleaning, or applying a weak acid or alkali solution and then high-pressure water cleaning. A1.5.3 Microorganisms A1.5.3.1 Microorganisms such as fungus, moss, mildew, algae, decomposing foods, and other or-ganic growths can sometimes be detected by vis-ual examination (see PCA IS214).35 A1.5.3.2 Microorganisms are removed by washing with sodium hypochlorite (household bleach) and rinsing with water. High-pressure water cleaning or abrasive blasting may also be used. A1.6 Adhesion Testing36 The two commonly used methods for testing adhesion of coatings to concrete substrates are ASTM D 454137 (modi-fied for concrete substrates as discussed in Paragraph A1.6.1) and ACI 503R.38 Testing for surface tensile strength consists of scoring (core drilling) the concrete sur-face, bonding a test fixture with an adhesive, pulling the fix-ture with an adhesion tester, and noting the pull-off strength or adhesion value. Testing for coating adhesion is per-formed using the same procedure, noting the adhesion val-ue, and noting the adhesion failure mode (see Paragraph A1.6.4). A1.6.1 The procedure described in ASTM D 454137 may be used to determine pull-off strength or coating adhesion strength using a portable adhesion tester, typically either a manual tester with a 20-mm (0.78-in.)-diameter loading fixture (test dolly) or a pneumatic ad-hesion tester with a 13-mm (0.5-in.) loading fixture. ASTM D 4541 states that “Scoring around the fixture violates the fundamental in situ criterion that an unalt-ered coating be tested,” but it also states that scoring should be noted in the results when employed.37 The procedure in ASTM D 4541 should be modified for use on concrete substrates by scoring or core drilling prior to attaching the loading fixture. Scoring around the test fixture ensures that the pulling force is applied only to the area directly beneath the fixture. Without scoring, stress is transferred through the coating film beyond the area of the test fixture. This could result in signif-icant error when testing thick or reinforced coatings. A water-lubricated diamond-tipped core bit should be used for scoring to reduce the possibility of microcracks in either the coating or the concrete substrate. The procedure may also be modified by using a larger (5-cm [2-in.] or more) loading fixture. A larger test fixture typically yields more accurate results than a smaller fix-ture because the greater surface area reduces the effect of inconsistencies, such as a piece of aggregate or a void, in the substrate. A1.6.2 ACI 503R38 discusses the process of applying a coating or adhesive coring to the substrate, bonding a 5-cm (2-in.) pipe cap to the coating, and applying ten-sion with a mechanical testing device attached to a dynamometer. As with ASTM D 4541,37 the tensile load and mode of failure are noted. A1.6.3 A test patch involves applying the coating sys-tem to a small section (with the minimum size to be specified) of prepared concrete and testing for tensile strength and adhesion by either of the methods de-scribed in Paragraphs A1.6.1 and A1.6.2. The pre-pared concrete substrate—at least the portion to be patched—should meet the acceptance criteria as de-tailed in Section 6. The coating system should be ap-plied in accordance with the coating manufacturer’s published instructions. The last coat of the coating sys-tem serves as the adhesive for the loading fixture, or, when this is not recommended (e.g., for solvent-based topcoats), the loading fixture is attached to the coating system by an adhesive. If agreed by all parties, the pri-mer alone may suffice as the test patch and the ad-hesive for the loading fixture. A1.6.4 The acceptable adhesion strength and mode of failure may vary depending on the type of coating tested. The coating manufacturer should be consulted to determine the preferred test method, the suitability of that method, and acceptance criteria for the specified coating. When adhesion testing is performed, the mode of failure should be noted. The failure can be described using one or more of the following terms. (1) Concrete (substrate) cohesive failure: This failure mode is defined as failure within the concrete, below the concrete/coating interface. This result, if the adhe-sion value is sufficient, is considered to be the most desirable for coatings applied to concrete. If concrete cohesive failure occurs but the adhesion value is low, the failure may be because of low concrete strength or microcracking from scoring. If only a thin layer of con-crete is pulled with the fixture and the adhesion value is

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NACE No. 6/SSPC-SP 13 12 NACE International low, it may be because of a weak concrete surface layer or laitance. (2) Coating adhesive failure: This failure mode is de-fined as failure directly at the concrete/coating inter-face. For most coating systems, failure in this mode indicates a problem with surface preparation, residual contamination, or the coating. (3) Coating cohesive failure or coating intercoat adhe-sion failure: This failure mode is defined as failure with-in the coating system, above the concrete/coating inter-face. This mode of failure indicates a problem with the coating material or with the coating application. (4) Fixture adhesive failure: This failure mode is de-fined as failure within the fixture adhesive or at the fix-ture adhesive/coating interface. When this failure mode is encountered, the test should be repeated. A1.7 Surface Profile A1.7.1 In addition to removing laitance, weak con-crete, and contamination at the concrete surface, sur-face preparation usually opens the pores and/or cre-ates a profile on the concrete surface. Profile increas-es the surface area available for bonding between the concrete and the coating, enhances adhesion at the concrete/coating interface, and helps the coating resist peeling and shear forces. A1.7.2 The depth of surface profile required depends on: (1) tensile and shear strength of the concrete and the coating system; (2) adhesion of the coating system to the concrete; (3) internal stresses in the coating system created during application (e.g., from shrinkage); (4) difference in the coefficient of thermal expansion between the coating and the concrete; (5) modulus or stress-relaxation properties of the coat-ing system; (6) thermal and chemical exposure environment; and (7) coating thickness. A1.7.3 At this time, no recognized testing equipment or method is used to quantify the surface profile of con-crete that is analogous to the replica tape method used on steel. The profile can be subjectively compared to the standard classification for coated abrasive paper as described in ANSI B74.18,16 or by comparing the profile with the ICRI Guideline No. 0373217 (surface profile chips). For extremely coarse prepared concrete sur-faces (assuming that the coating system can cover and perform over such a substrate), the profile may be esti-mated as an average distance between peaks and val-leys on the concrete surface and quantified in mm (mils). A1.8 Moisture in Concrete39,40,41,42 A1.8.1 The movement of moisture in concrete during the curing process and after application of the coating is important to consider in the design of the concrete structure. Concrete is normally placed with water lev-els in excess of that required to completely hydrate the cement. Excess free water in the concrete can ad-versely affect the application and cure of many coat-ings. Pressure caused by excess moisture in the con-crete or from ground water may be substantial and, in some instances, may be sufficient to disbond barrier coating systems that appear to be well bonded. These pressures are commonly referred to as hydrostatic, capillary, and osmotic pressures. A1.8.2 Concrete has traditionally been coated no sooner than 28 days after concrete placement (see Paragraph A1.10). In addition to allowing the concrete to sufficiently cure (see Paragraph A1.3), this waiting period allows excess moisture to evaporate prior to ap-plying a barrier coating system. The waiting period is especially important if a vapor barrier (or positive-side waterproofing) is installed, which prevents moisture from exiting into the ground. A1.8.3 The drying rate of concrete is a function of the concrete temperature, thickness, porosity, and initial free-water content. The drying rate is also a function of the velocity and dew point of the drying air. Excess free water can be removed by dehumidifiers, surface air movers, or surface heaters provided that (1) the forced drying does not begin until sufficient concrete strength is developed and (2) it does not adversely af-fect the concrete properties. Dehumidifiers lower the air dew point, can increase the air temperature, and perform best when the area is enclosed. Surface air movers direct low-dew point air across the concrete surface at high velocities, but they should be periodic-ally repositioned to ensure uniform drying over the entire surface. Surface heaters increase the mobility of free water; they work best if the heat penetrates the concrete and if they do not raise the dew point of the drying air. A1.8.4 Moisture Test Methods40,41 The following are some of the common methods used to identify or quantify the free moisture in concrete prior to the application of coatings. ASTM D 4263, Plastic sheet method19 ASTM F 1869, Calcium chloride test20 ASTM F 2170, Relative humidity test21

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NACE No. 6/SSPC-SP 13 NACE International 13 ASTM E 1907, Conductivity test43 ASTM E 1907, Calcium carbide method43 ASTM E 1907, Capacitance-impedance method43 A1.8.5 Use and Interpretation of Moisture Test Methods A1.8.5.1 The plastic sheet method19 and the cal-cium chloride test are commonly used and accept-ed in the United States. The hygrometer and con-ductivity tests are cited in numerous British stand-ards and are accepted in the United Kingdom, while the carbide method is accepted in other parts of Europe. A1.8.5.2 All of these methods are quantitative ex-cept the plastic sheet method.19 The plastic sheet, calcium chloride, and capacitance-impedance methods are nondestructive, while the hygrometer, conductivity, and calcium carbide methods involve drilling into the concrete. A1.8.5.3 Testing duration is 16+ hours for the plastic sheet method19 and 72 hours for the cal-cium chloride and relative humidity tests. The other methods give results immediately if the test-ing equipment has been calibrated. A1.8.5.4 The plastic sheet method may indicate whether excess moisture is present at the time of the test. However, because the method depends on a moisture differential—a higher relative humid-ity in the concrete than in the air above the con-crete surface—during the test span, potential prob-lems are not always evident at the time the test is performed. A1.8.5.5 Information on the tolerance of a specific coating system for free water or moisture migration should be provided by the coating manufacturer. A free water content of less than 5% by weight is acceptable for most coatings. Alternatively, con-crete with a relative humidity of less than 80% or a moisture transmission rate of less than 15 g/24 hr/m2 (3 lb/24 hr/1,000 ft2) has proved acceptable for most coatings. A1.8.5.6. Occasionally, despite moisture testing, a problem is not identified until after a low-perme-ability coating is applied. A1.9 Surface Preparation Methods17,32,44,45,46 The surface preparation methods described in this standard are listed in Table A2 with their intended use, profile cre-ated, typical problems encountered when using each meth-od, and solutions to those problems. A1.9.1 Photographic examples of prepared concrete surfaces are shown in ASTM PCN:03-401079-14.47 A1.10 The 28-Day Waiting Period48,49 A1.10.1 The traditional 28-day waiting period after concrete placement and prior to coating installation is a controversial topic that involves all parties. Although the waiting period is not usually required for surface preparation, it affects the timing of surface preparation because many coatings are applied within 24 hours after surface preparation. A1.10.2 The 28-day waiting period originated from the structural benchmark to test concrete strength at 28 days after placement to verify that the tested strength met the design strength. The 28-day benchmark be-came the industry standard to identify the point in time when the concrete was considered fully cured. The 28-day waiting period was adopted by the coating industry because it usually allows sufficient time for concrete surface strength to develop and for excess moisture to evaporate. A1.10.3 Many factors can reduce or increase the time required for strength and moisture levels to be accept-able. In addition, many construction schedules do not allow for a 28-day waiting period. For these reasons, quantifying surface requirements as in Paragraph A1.12 are preferred over the traditional 28-day waiting period. A1.10.4 NACE Standard RP089215 and ACI 515.1R9 do not recommend a specific cure period but do ad-dress surface dryness, surface strength requirements, and other surface quality issues. A1.11 Temperature Considerations The temperature of the surface at the time of the coating application and the temperature progression during the ap-plication are both important. Rising concrete temperatures during the application of the coating systems may cause blistering and pinhole problems in the coating caused by out-gassing from the concrete. Coating application during periods of falling temperatures may be required to prevent this problem. Although controlling the ambient temperature in outdoor installations is difficult, concrete is often shaded from direct sunlight during coating application. In addition to potential problems from moisture in the concrete as de-scribed in Paragraphs A1.8.1 and A1.8.2, monitoring the dew point during periods of changing weather is often recommended to ensure that coatings are not applied over moisture that has condensed on the concrete surface.

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NACE No. 6/SSPC-SP 13 14 NACE International Table A2: Surface Preparation Methods Preparation Method When Used Profile Created(A) Problems Solutions Dry abrasive blasting Removal, profile, cleaning Fine (150) to extra coarse (40) -Dust on surface -Airborne dust -Noise -Vacuum cleaning -Vacuum attachments -None Wet abrasive blasting Removal, profile, cleaning Fine (150) to extra coarse (40) -Wets concrete -Creates sludge -Let concrete dry -Cleaning High-pressure water cleaning Removal, cleaning Fine (150) to extra coarse (40) -Wets concrete -Creates sludge -Let concrete dry -Cleaning Waterjetting (with or without abrasive) Removal Rougher than extra coarse -Creates sludge -Wets concrete -Coarse profile -Cleaning -Let concrete dry -None(B) Impact tools Removal, profile, cleaning Rougher than extra coarse -Airborne dust -Fracturing -Coarse profile -Vacuum attachments -Other methods -None(B) Power tools Removal Smooth (no grit equivalent) -Airborne dust -Fine profile -Vacuum attachments -Other methods Flame blasting Removal, profile, cleaning Rougher than extra coarse -Excess removal -Damages concrete -Experience(B) -Remove damaged concrete Acid etching Profile, cleaning Fine (150) to coarse (60) -Hazardous -Not for vertical or overhead surfaces -Neutralization -Wets concrete -Curing membrane -Other acids -Other methods -pH testing -Let concrete dry -Other methods ___________________________ (A) Profile is described using graded abrasive paper sizes. These are typical surface profile values only. Results may vary significantly because of concrete properties and surface preparation practices. (B) For coating systems that do not perform over a coarse profile, refinishing the concrete or an underlayment may be required. A1.12 Recommendations for Procurement Documents (Project Specifications) for Concrete Surface Preparation Because of the wide range of concrete types, existing con-crete conditions, ambient conditions, types of protective coatings to be applied, and project scheduling, producing a comprehensive standard that can be used as a project specification is not possible. Therefore, the following is a checklist of items that should be included in a compre-hensive procurement document. A1.12.1 NACE No. 6/SSPC-SP 13 A1.12.2 Contaminants A1.12.2.1 Types anticipated A1.12.2.2 Detection methods A1.12.2.3 Preferred removal method A1.12.2.4 Other acceptable removal methods A1.12.3 Surface Preparation A1.12.3.1 Preferred method A1.12.3.2 Other acceptable methods A1.12.4 Surface Tensile Strength A1.12.4.1 Minimum allowable A1.12.4.2 Test method and mode of failure A1.12.5 Surface Profile A1.12.5.1 Minimum and maximum allowable A1.12.5.2 Test method or visual comparison

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NACE No. 6/SSPC-SP 13 NACE International 15 A1.12.6 Surface Uniformity A1.12.6.1 Maximum allowable void size A1.12.7 Repairs and Patching A1.12.7.1 Preferred materials A1.12.7.2 Other acceptable materials A1.12.8 Cleanliness A1.12.8.1 Maximum allowable residual dust level A1.12.8.2 Test method or visual comparison A1.12.9 Moisture Content A1.12.9.1 Maximum allowable A1.12.9.2 Test method and when to test (e.g., before or after surface preparation, or immediately before coating) A1.12.10 Surface Flatness and Levelness A1.12.10.1 Minimum and maximum slope allowed A1.12.10.2 Minimum flatness allowed A1.12.10.3 Test method or visual comparison