Specification:Composite and mechanical concrete repair

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=GENERAL=

DESCRIPTION
 This specification provides guidance for concrete patching and epoxy grouting repair methods. 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 repair through patching.</li> Mechanical concrete repair.</li> </ol>

RELATED SECTIONS
<ol type="A"> 03700.01 – Concrete Properties and In Kind Replacement.</li> 03710.01 – Cleaning and Testing of Atmospheric Soiling, Graffiti, Staining, and Biogrowth</li> 04100 – Historic Mortar</li> 04500 – Masonry Restoration</li> 04720 – Historic Cast Stone</li> 07100.01 – Water Repellents</li> 07900.01 – Joint Sealer Properties and Application</li> </ol>

SUBMITTALS
<ol type="A"> Submit a detailed schedule to architect for approval of the survey and evaluation of materials, construction methods, deterioration, and causes.</li> Historic concrete analysis: Submit laboratory report from completed mortar analysis. Concrete analysis shall be completed prior to beginning test panel preparation. Analysis shall be limited to wet chemical and microscopic analyses to characterize the insoluble aggregate, determine binder-aggregate ratio, prepare a mix design for replacement concrete, and identify appropriate sources for sand aggregate.</li> The Contractor shall submit manufacturer’s product literature for all concrete repair materials including, but not limited to, cement, grout, form release agents, reinforcing, and aggregate. Product literature shall demonstrate material compliance with these specifications and the standards referenced herein.</li> Samples: Where color and texture matching is a requirement, submit three cured samples of the proposed concrete patching material for evaluation by the Architect. Samples shall be a minimum of six inches by six inches with a minimum thickness of two inches. Samples shall be finished / tooled in the same manner as the final installation to match the original concrete. The samples will be inspected for color, texture, composition, and other visual characteristics. Multiple batches of patching material samples may be necessary to meet requirements. The Contractor shall prepare up to five such sample batches without further compensation. Approved samples shall become part of the work and shall serve as the quality standard for all similar work.</li> </ol>

QUALITY ASSURANCE
<ol type="A"> The Contractor shall have a minimum of seven years experience in repair and restoration of historic concrete and masonry, and employ personnel skilled in the restoration process and operations indicated. He/she shall have successfully completed at least three concrete restoration projects of similar scope within the previous five years. He/she shall demonstrate a working knowledge of the Secretary of the Interior’s Standards for the Treatment of Historic Properties.  Only skilled journeyman masons and/or cement finishers who have experience using the materials and methods specified, and also are familiar with the design requirements, shall be used for concrete repairs and/or restoration.</li> Where proprietary concrete repair materials are used, provide one skilled journeyman mason or cement finisher, trained and certified by the concrete repair system manufacturer who shall be present at all times during concrete repair/restoration and shall personally direct the work.</li> </ol> </li> <li>The Contractor shall provide a ten (10) year warranty on material and workmanship for concrete replacement and repairs.</li> </ol>

MOCK-UPS
<ol type="A"> <li>All personnel proposed for concrete patching work shall prepare mock-ups of each type of concrete repair required for the project. Where multiple colors and/or textures of historic concrete are to be patched, a separate mock-up will be required for each. Each test panel shall be executed in the same manner as the final installation. Personnel whose mock-ups are not approved will not be permitted to work on the concrete patching portion of the project. <ol> <li>The test panels will be inspected for color, texture, composition, and other visual characteristics, as well as for installation technique.</li> <li>Test panels will be evaluated close up and at a distance under both wet and dry conditions.</li> </ol> </li> <li>Allow for a minimum of one week curing prior to examination of the mock-ups. Keep mock-up areas dry prior to scheduled inspection. If cleaning tests are also to take place, test panels should be in the same area. Test panels should not be undertaken in areas that are highly visible.</li> <li>Multiple sets of mock-up panels may be required to be acceptable for approval. The Contractor shall prepare up to three sets of product mock-ups without further compensation. Approved samples 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>Concrete restoration materials shall be delivered to the site in original packaging, unopened, with manufacturer’s name and product identification thereon. Cementitious materials shall be protected from contamination by foreign matter and deterioration by moisture or temperature. Contaminated or deteriorated material shall not be used. Products stored longer than six months shall not be used.</li> <li>Concrete materials shall be stored in such a manner as not to interfere with the work of other trades involved in the project or with the Owner’s site operations. The Owner shall review proposed storage locations prior to the delivery of materials.</li> <li>Waste material and packaging debris shall be disposed of offsite in accordance with local, state, and federal environmental regulations.</li> <li>Concrete for formed repairs to existing surfaces shall be factory-mixed and delivered to the site for immediate placement. Concrete that has achieved initial set by the time of delivery will be rejected.</li> </ol>

PROJECT/SITE CONDITIONS
<ol type="A"> <li>Normal temperature range for the work of this Section shall be air and surface temperatures of 40 degrees F and rising or less than 90 degrees F and falling. Outside this temperature range, hot or cold weather procedures as defined by the American Concrete Institute shall be followed.</li> <li>Do not perform patching work if precipitation is expected. In case of unexpected precipitation, work shall cease and all uncured material shall be adequately protected with an impermeable polyethylene sheet.</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 prevent damage to existing material assemblies not a part of the work of this Section. At a minimum, the Contractor shall: <ol> <li>Minimize levels of dust during surface preparation operations including drilling, chipping, and grinding.</li> <li>Protect existing masonry surfaces, windows and exterior doors and frames from mechanical damage and staining during concrete restoration operations.</li> </ol> </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>Concrete scrap, excess mortar, waste material, packaging, and other debris associated with the repair work shall be disposed of in accordance with local, state, and federal environmental regulations. Remove debris from concrete restoration work from the site on a timely basis and at the completion of the work.</li> <li>The Contractor shall coordinate concrete restoration operations with the other trades involved in exterior restoration work including, but not limited to, masonry restoration, waterproofing, painting, caulking, etc.</li> </ol> =PRODUCTS=

EQUIPMENT
<ol type="A"> <li>All equipment for excavation and preparation shall be subject to Architect approval. Standard equipment is as follows: <ol> <li>Handheld manual or power type low-impact energy output chisel, using gad points. The use of chisel points is prohibited.</li> <li>Surface grinders shall be small, handheld equipment with low to moderate RPM, using stone grinding wheels.</li> <li>Saw cutting equipment shall use circular diamond blades, with blade diameter appropriate for the application.</li> <li>Lightweight demolition hammers not to exceed 18 pounds in weight.</li> <li>Stiff bristle brushes (non-metallic).</li> <li>Compressed air shall be clean, oil and moisture free and have at least two in-line air filters to remove oil and moisture from the air supply.</li> <li>Excavation equipment shall be subject to approval by the Architect.</li> </ol> </li> <li>Equipment for concrete patching: <ol> <li>Equipment for mixing, transporting, placing and confining concrete shall be clean and free of old materials and contaminants.</li> <li>Equipment shall conform to the material manufacturer’s standards.</li> <li>Paddle or drum type mixers.</li> <li>Molds and Forms: Shall be free from dirt and contaminants.</li> <li>Drilling: Standard handheld masonry power drills, using rotary drilling mode, for drilling small holes in concrete for patch anchors or other applications. Impact and rotary impact type drills are prohibited.</li> <li>Trowels.</li> <li>Brushes.</li> <li>Impermeable polyethylene sheeting and clean, unprinted burlap.</li> </ol> </li> <li>Equipment for epoxy injection repairs: <ol> <li>Type: Equipment to meter and mix injection adhesive components and inject the mixture into the crack shall be portable, positive displacement type pumps with interlock to provide positive control of exact proportions of the components at the nozzle. The pumps shall be electric or air powered and shall provide in-line metering and mixing.</li> <li>Discharge Pressure: The injection equipment shall have automatic pressure control capable of discharging the grout or adhesive at any pre-set pressure up to 200 psi and shall be equipped with a manual pressure control override. For injection of gel epoxy, the equipment shall be as specified above and be able to pump up to 5,000 psi.</li> <li>Ratio Tolerance: The equipment shall have the capability of maintaining the volume ratio prescribed by the manufacturer of the adhesive within a tolerance of 5 percent by volume at any discharge pressure up to 200 psi. For gel epoxies, the ratio will be checked by weight at up to 5,000 psi.</li> <li>Automatic Shut-Off Control: The injection equipment shall have sensors on both the Component A and B reservoirs that will automatically stop the machine when only one component is being pumped to the mixing head.</li> <li>The manufacturer of the injection equipment and the epoxy resin adhesive for injection shall be the same manufacturer.</li> </ol> </li> <li>Equipment for Cementitious Injection Grouting: <ol> <li>Drill with paddle attachment for grout mixing.</li> <li>Removable, non-staining putty or sealant.</li> <li>Assorted sizes of stainless steel or plastic cannulae or syringes.</li> </ol> </li> </ol>

PATCHING MATERIALS
<ol type="A"> <li>General: Materials shall match the physical and chemical properties, composition, color, and texture of the existing concrete to be repaired, unless samples and testing determine that the existing mixtures and materials are faulty or non-performing. Existing historic concrete may not meet ASTM standards. As these standards are not written for historic materials and a large difference in properties can cause further damage, careful judgment must be used when determining a balance between existing properties and current standards. <ol> <li>Patching compound shall be prepackaged, customized by manufacturer so that compressive strength does not exceed 4000 psi, or 500 psi above the existing concrete’s compressive strength, whichever is lower, as measured by ASTM C 109.</li> <li>Patching compound shall develop a minimum 200 psi direct tensile adhesion with host substrate, when applied in accordance with specification. Material shall be vapor permeable.</li> <li>Cementitious Materials shall each be of one type and from one source when used in concrete which will be exposed in the finished structure.</li> <li>Cement composition shall match that of cement used in the existing concrete as determined by samples and testing.</li> </ol> </li> <li>If Portland cement is required, it shall be Type I, ASTM C-150. Gray and white cement may be combined as required to match existing concrete.</li> <li>Sand aggregate shall be clean, well-graded sand free from silt, clay, soluble salts, and organic matter in accordance with ASTM C-144. A combination of white, yellow, and brown sands may be required to match the material to be patched.</li> <li>Concrete aggregate shall match the sample provided by the Architect. Maximum aggregate size shall be ½ inch.</li> <li>Mortar colorant, if required to match the existing concrete, shall be a non-fading, alkali resistant natural earth pigment and shall approved by the Architect. Pigments will only be permitted if an acceptable color match cannot be achieved by varying the cement and sand components.</li> <li>Water shall be clean, potable, and free from contaminants or substances that may be deleterious to concrete/mortar or any embedded metal.</li> <li>Natural cements or Pozzolan additives shall conform to ASTM C 618, Class F, including limit on available alkalis.</li> <li>Lime additions shall conform to ASTM C 207.</li> <li>Admixtures. <ol> <li>No air-entraining admixtures or material containing air-entraining admixtures shall be added to concrete</li> <li>No antifreeze compounds shall be added to concrete.</li> <li>No admixtures containing chlorides shall be added to concrete.</li> </ol> </li> <li>Proprietary Patching Materials: Substitution of proprietary repair mortars for job-mixed mortars may be permitted based on submittal of historic concrete analysis and complete product analysis and approval by the Architect.</li> </ol>

EPOXY GROUT
<ol type="A"> <li>Epoxy-Resin Grout shall be a two-component material, 100 percent solids by weight, formulated to meet the requirements of ASTM C 881C/ 881M, Type I or II. Type I shall be used when materials or atmospheric temperatures are 70 degrees F (20 degrees C) or above. Type II material shall be used when materials or atmospheric temperatures are below 70 degrees F (20 degrees C). Epoxy-resin grout shall have the ability to structurally rebond cracks, delaminations, and hollow plane conditions in concrete; shall be insensitive to the presence of water; and shall have the capability to penetrate cracks down to 0.12 mm 5 mils in width.</li> <li>Acceptable Patching Materials: Materials shall have been used in similar conditions for a period of at least five years. Products must be from an Architect-approved manufacturer.</li> </ol>

ACCESSORIES
<ol type="A"> <li>Epoxy adhesive for embedding anchors and pins shall be a high modulus epoxy resin conforming to ASTM C-881, Type I, II, IV, and V, Grade 3 epoxy resin adhesives.</li> <li>Coating for exposed embedded reinforcing bars shall be an approved single-component, water-based barrier coat.</li> <li>Bonding agent for non-reinforced patches shall be an approved single-component, water-based barrier coat.</li> <li>Reinforcement for formed repairs shall be one or both of the following as indicated on the Drawings: <ol> <li>Deformed Reinforcing Bars: ASTM A 615, Grade 60, epoxy coated.</li> <li>Welded Steel Wire Fabric: Plain type, galvanized ASTM A 185. Spacing and gauge of mesh shall be as noted in the drawings.</li> <li>Reinforcing steel shall be non-corroding stainless steel and shall conform with ASTM A 36/A 36M, sizes as indicated.</li> <li>Tie wire shall be 18-8 stainless steel.</li> <li>Plates, angles, and anchors shall conform to ASTM A 36/A 36M, and shall be prime painted with inorganic zinc primer.</li> <li>Stainless steel pins for anchoring patches shall be Type 304 stainless steel all-thread rods, 1/4-inch diameter. Length shall be as required by the depth of the patch. All other embedments such as wire and eye bolts to be used for anchoring reinforcing pins shall be stainless steel.</li> </ol> </li> <li>Forms for exposed finish concrete shall be plywood, metal, metal-framed plywood faced or other acceptable panel-type materials, to provide straight, smooth exposed surfaces when removed. <ol> <li>Formwork shall be as indicated on the drawings and shall be subject to approval by the Architect.</li> <li>Form-release agents shall be the manufacturer’s standard, non-staining, nonpetroleum-based, compatible with surface finish and subsequent surface treatments.</li> </ol> </li> </ol> =EXECUTION=

GENERAL
<ol type="A"> <li>Concrete repairs shall be undertaken only after a complete evaluation and analysis of the areas to be repaired is completed and shall include sampling and testing of the existing concrete, a condition survey of the area to be repaired, and strength evaluation. Examination and sampling procedures shall conform to ASTM C 823.</li> <li>Cleaning. Following inspection and evaluation, concrete surfaces shall be cleaned prior to the start of excavation, sampling and testing, and concrete repairs; see Section 03710.01 Cleaning of exterior concrete surfaces shall remove all traces of moss, dirt, and other contaminants and provide a clean surface to allow determination of the color, finish, texture, and other properties.</li> <li>Surfaces of the structure and adjacent surfaces and materials shall be protected from damage from excavation, cleaning, and concrete repair operations.</li> <li>Repairs shall be in accordance with ACI C-10, ACI C-20, ACI 301, ACI 304R, ACI 224.1R. Detailing shall conform with ACI SP-66. Repaired surfaces shall match adjacent existing surfaces in all respects.</li> <li>Products will be used in accordance with manufacturer’s instructions.</li> <li>If work is found to be unacceptable to the Architect, all work shall cease without additional cost to the owner until deficiencies in tools, workmanship, or methodology have been corrected to the Architect’s satisfaction.</li> </ol>

CONCRETE REPAIR PREPARATION
<ol type="A"> <li>Concrete Removal to be performed in accordance with ICRI Guidelines: <ol> <li>The extent of concrete removal and repair shall be reviewed and approved by the Architect prior to construction. Historic concrete will only be removed where it poses structural problems or if further deterioration is expected.</li> <li>Surface of area to be patched shall be rough with undercut edges, dovetailed 15 degrees. The bottom or back shall be parallel with the exposed surface. The area shall be shaped to remove excess variations and form uniform dimensions. Feathering at the edges shall not be permitted.</li> <li>Caulking or grout shall be removed from previously repaired cracks where failure is exhibited.</li> <li>The area shall be cleaned of all dust, dirt, debris, paint chips, and concrete dust/chips.</li> </ol> </li> <li>Treatment of exposed reinforcement: <ol> <li>Concrete shall be removed from exposed or deteriorated reinforcing steel. All removal to be performed in accordance with ICRI Guideline No. 03730.</li> <li>All reinforcing bars in the patch area shall be cleaned of rust and free from any visible rust or scale. <li>When reinforcing bars cannot be cleaned adequately, replace reinforcing bars or remove (when not structurally necessary) them as needed. Removal of reinforcement shall be reviewed by the Architect.</li> <li>Place reinforcement at proper position in accordance with the drawings. Provide a minimum surface coverage of three inches for concrete placed in direct contact with soil. Coverage may be reduced to 1-1/2 inches for #5 bars or smaller in surfaces exposed to soil.</li> <li>Lap reinforcing bar splices in accordance with ACI 318. Support and secure against displacement. Welding of reinforcement is not permitted. Number, type and spacing of supports shall be as indicated in ACI 315. Clean reinforcement of rust, scale, dirt and foreign coatings prior to placing concrete.</li> </ol> </li> <li>Immediately following cleaning and prior to patching, apply a high-quality, cementitious corrosion/rust-inhibiting primer and bonding agent to all steel surfaces in accordance with manufacturer’s instructions. Create a continuous coating on the entire surface, including the underside of the undercut reinforcement. Follow manufacturer’s guidelines for minimum and maximum timing “windows” for patching after application of primer.</li> <li>Cut back reinforcing bars as needed to accept the new material. Reinforcement shall extend from existing concrete into patch at least 25 mm (one inch) minimum to provide mechanical bond with the patch material.</li> </ol> </li> <li>Cleaning Excavations <ol> <li>Patches and cracks shall be cleaned by scrubbing and rinsing with clean water. Pressure washing should use less than 1000 psi pressure and a fan tip of at least 45 degrees. See Treatment Report 03710.01 for details. Sandblasting shall not be used. Cracks and voids shall be flushed with water and allowed to dry.</li> <li>Blow out cracks and areas for repair with filtered, dry, compressed air.</li> <li>Concrete in contact with freshly placed concrete shall be continuously damp for 24 hours prior to concrete placement.</li> </ol> </li> </ol>

CONCRETE PATCH REPAIR
<ol type="A"> <li>Spalls less than 25 mm (one inch) deep, where indicated to be repaired, shall be packed with an approved patching mortar. Spalls greater than 25 mm (one inch) deep shall be excavated and patched with formed concrete.</li> <li>Install anchors/reinforcement as specified on the drawings and as approved by the Architect. Areas that do not have reinforcement or other metal embedments shall be provided with patch anchors. <ol> <li>Drill holes in location of anchors/reinforcement with a masonry drill.</li> <li>The reinforcement anchors (stainless steel hooked pins) shall be cleaned to remove all contaminants which may hinder epoxy bond.</li> <li>Epoxy adhesive shall fill the holes so that when the anchors or reinforcing steel are inserted, the epoxy fills the holes and excess epoxy is not exuded from the holes. Embed noncorrosive anchors securely. The metal shall be set back from the face 25 mm or one inch from the surface.</li> <li>Excess epoxy and spills shall be removed from the surface of the excavation and from adjacent surfaces immediately.</li> </ol> </li> <li>Immediately prior to placement, areas to be patched shall be cleaned, rinsed with water, and followed by blowing dry with filtered, dry, compressed air to remove excess or standing water and to provide a saturated, surface-dry, damp condition at the surface to be repaired.</li> <li>Smooth surfaces that will be in contact with new concrete should be scraped with a hammer and chisel.</li> <li>Apply a slurry coat of cement paste to the dampened patch area.</li> <li>Immediately after slurry has been brushed on and while still wet, mix concrete patch material according to the approved sample, following manufacturer’s instructions.</li> <li>Place patching material so that all corners and gaps under reinforcing steel and entire cavity profile are completely filled and properly compacted to prevent formation of voids or unbonded areas. Work the material into corners and gaps and onto cavity sidewall, applying pressure on the trowel to assure good contact between patch and substrates. Depending on the size of the area to be patched, layers or lifts can be applied, not more than 12 inches deep, to ensure adequate compaction of larger patches. Large patches can be consolidated immediately by rodding or vibration. <ol> <li>Patches deeper than 1-1/2 inches (38 mm) may be extended by coarse aggregate addition. Not more than 20 pounds of 3/8 inch pea stone, suitable in composition and surface profile for use as a concrete aggregate, may be added to each 50 pound bag of patching compound.</li> <li>Construct forms to proper size, alignment and elevation in accordance with ACI 318. Formwork shall conform to the drawings in shape, form, line, and grade and shall be sufficiently rigid to prevent deformation. Clean interior surfaces and coat with appropriate form release agent prior to pour.</li> </ol> </li> <li>Finish according to texture and finish of the existing concrete. Do not retemper material which has begun to set. Discard any unused material 30 minutes after initial preparation. Do not wet patch surface excessively after placement or as an aid to troweling. Limit surface water addition to light misting and do not wet or rework repeatedly.</li> <li>To limit shrinkage and cracks, the patch can be misted or kept wet with damp burlap bags for several days.</li> </ol>

CONCRETE CRACK REPAIR
<ol type="A"> <li>Cementitious grouts and compounds are not to be used to fill dynamic cracks or joints caused by structural failures such as ongoing settling, structural instability, thermal expansion or corrosion due to embedded metals.</li> <li>Small Cracks: Crack repair for small dynamic cracks less than 1/16 inch (62 mills, 1.5 mm) shall be performed following pressure washing and drying by gravity filling with elastomeric crack sealant. Dormant cracks less than 1/16 inch do not require repair.</li> <li>Large Cracks: Dynamic cracks wider than 1/16 inch shall be grooved out to a nominal 1/2x 1/2 inch (3mm x 3mm) and filled with an approved crack sealant. Dormant cracks wider than 1/16 inch can be filled with a mixture of cement, water, and sand.</li> </ol>

ADJUSTING/FINAL CLEANING
<ol type="A"> <li>After mortar has fully hardened, no sooner than 72 hours after the curing period and after joints are sealed, wash faces and other exposed surfaces of concrete with clean water. Thoroughly clean exposed masonry surfaces and remove excess mortar and foreign matter using stiff nylon or non-metal bristle brushes, wooden scrapers, and clean water that is spray applied at low pressure. Discolorations will be considered defective work.</li> <li>Do not use metal scrapers or brushes.</li> <li>Do not use acid or alkali cleaning agents.</li> <li>Final cleaning work shall be done when temperature and humidity conditions are such that surfaces dry rapidly. Protect adjacent surfaces from damage during cleaning operations.</li> <li>Finish, color, shade and surface tolerances of the patches shall be inspected to verify that all requirements have been met. All surfaces exhibiting defects shall be repaired as directed.</li> </ol>

FINAL REPORT
<ol type="A"> <li>After the new concrete has cured at least one week, revisit the site to compare the finish and color of the repair to see if the desired effect has been achieved.</li> <li>Document the work and finished product with before and after photographs. Pay special attention to “before” documentation.</li> <li>Provide a written summary of the project and results upon final inspection and approval. Outline steps taken or new findings not specified in the initial documentation.</li> </ol>