Recommended Construction Specifications and Process Control Manual for Repair and Retrofit of Concrete Structures Using Bonded FRP Composites (2008)

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A-1 A T T A C H M E N T A Recommended Construction Specifications The proposed Construction Specifications are the recommendations of NCHRP Project 10- 59B staff at Florida International University. These specifications have not been approved by NCHRP or any AASHTO committee or formally accepted for the AASHTO specifications. Contents 1 General, A-2 2 Submittals, A-8 3 Storage, Handling and Disposal, A-10 4 Substrate Repair and Surface Preparation, A-11 5 Installation of FRP System, A-15 6 Inspection and Quality Assurance, A-21 7 Repair of Defective Work, A-24 8 Measurement and Payment, A-25 9 Cited References, A-26

1 General This Specifications is intended for use in the construction of repair and retrofit of concrete structures using bonded fiber- reinforced polymer (FRP) composites. This Specifications does not include design aspects of FRP system, and the extent and limitations of the repair and retrofit of an existing concrete structure. 1.1 Scope This Specifications covers construction of FRP systems used as externally bonded or near-surface mounted (NSM) rein- forcement to enhance axial, shear, or flexural strength or duc- tility of a concrete member, such as column, beam, slab or wall. 1.2 Definitions The following terms used in this Specifications are primarily taken from ACI 440.2R-02 with some changes: Batch—A quantity of material formed during the same field installation in one continuous process, and having identical characteristics throughout. Bi-Directional Laminate—Reinforced polymer laminate with fibers oriented in two different directions in its plane. Binder—Resin constituent that holds together the other constituents of an FRP composite. Bond-Critical Applications—Applications of FRP systems for strengthening structures that rely on bond to the concrete substrate. Examples are flexural and shear strengthening of beams and slabs. Catalyst—A substance that initiates a chemical reaction and enables it to proceed under milder conditions than otherwise required and which does not, itself, alter or enter into the re- action. See hardener. Composite—A combination of two or more materials dif- fering in form or composition on a macro-scale. The con- stituents retain their identities; they do not dissolve or merge completely into one another, although they act in concert. Nor- mally, the components can be physically identified and exhibit an interface between one another. (See Composite FRP.) Composite FRP—A polymer matrix, either thermosetting or thermoplastic, reinforced with a fiber or other material with a sufficient aspect ratio (length to thickness) to provide a dis- cernible reinforcing function in one or more directions. (See Composite.) Contact-Critical Applications—Applications of FRP sys- tems that rely on intimate contact between concrete substrate C1 General FRP systems may be used to increase live load capacity of a structure, repair members that are damaged by impact or cor- rosion, reduce stresses in the internal steel reinforcement, or increase ductility in seismic retrofit. For design issues, consult with relevant guidelines such as ACI 440.2R-02. C1.1 Scope FRP system may include externally bonded sheets, strips, plates, and shells; and near-surface mounted FRP bars and strips that are bonded inside a groove cut into the surface of concrete. C1.2 Definitions The definitions of the terms given herein are for consistent application of this Specifications, and may not always corre- spond to the ordinary usage of the term. For a glossary of the most commonly used terms related to concrete construction and FRP systems, consult with ACI 116R-00, ACI 440R-96, and ACI 440.2R-02. A-2 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary

and FRP system to function as intended. An example is con- finement of columns for seismic retrofit. In this Specifica- tions, contact-critical applications are treated the same as bond-critical applications. (See Bond-critical applications.) Creep Rupture—Failure of FRP system resulting from its gradual, time dependent reduction of capacity due to sustained loading. Cure—The process of causing irreversible changes in the properties of a thermosetting resin by chemical reaction. Cure is typically accomplished by addition of curing agents or initia- tors, with or without heat and pressure. Full cure is the point at which a resin reaches its specified properties. Resin is under- cured if its specified properties have not been reached. Cure Time—The time necessary to cure a thermosetting resin system, thermoset based composite or prepreg at a given temperature. Curing Agent—A catalytic or reactive agent that, when added to resin, causes polymerization. Also called hardener. Debonding—A separation at the interface between substrate and the reinforcing layer. Delamination—Separation of the layers of the FRP laminate from each other. Development Length—The bonded distance required for transfer of stresses from concrete to the FRP to develop tensile capacity of FRP. Durability—The ability of a material to resist cracking, oxi- dation, chemical degradation, delamination, wear, or the effects of foreign object damage for a specified period of time, under the appropriate load conditions and specified environmental conditions. Epoxy—A polymerizable thermosetting polymer containing one or more epoxide groups, cured by reaction with phenols, anhydrides, polyfunctional amines, carboxylic acids, or mer- captans. An important matrix resin in FRP; also used as struc- tural adhesive. Fabric—Arrangement of fibers held together in two or three dimensions. It may be woven, nonwoven, knitted or stitched. Fabric architecture is the specific description of the fibers, their directions and construction. Fiber—A general term used to refer to filamentary materi- als. The smallest unit of a fibrous material. Often, fiber is used synonymously with filament. Fiber Content—The amount of fiber present in a compos- ite, usually expressed as volume fraction or mass fraction of the composite. Recommended Construction Specifications A-3 Specifications Commentary

Fiber Fly—Short filaments that break off dry fiber tows or yarns during handling and become air borne, classified as nui- sance dust. Fiber Reinforced Polymer (FRP) System—Composite material consisting of a polymer matrix reinforced with cloth, mat, strands, or any other fiber form. (See Composite.) Filament—(See Fiber.) Filler—A relatively inert substance added to a resin to alter its properties or to lower cost or density. Also used to term particulate additives. Also called extenders. Fire Retardant—Chemicals used to reduce the tendency of resin to burn. They can be added to the resin or coated on the surface of the FRP. Flow—The movement of uncured resin under pressure or gravity loads. Glass Transition Temperature (Tg)—The approximate midpoint of the temperature range over which a transition in material response from elastic to viscoelastic takes place [ASM 2001]. Hardener—Substance added to thermosetting resin to cause polymerization. Usually applies to epoxy resins. Impregnation—The process of saturating the interstices of a reinforcement or substrate with a resin. Inhibitor—A substance that retards a chemical reaction, such as ultraviolet degradation. Also used to prolong shelf life of certain resins. Initiator—Chemicals, most commonly peroxides, used to initiate the curing process for unsaturated polyester and vinyl ester resins. See Catalyst. Laminate—One or more layers or plies of fiber, boded together in a cured resin matrix. Lay-Up—The process of placing the FRP reinforcing ma- terial in position for installation. Lot—A quantity of material manufactured during the same plant production in one continuous process, and having iden- tical characteristics throughout. In this Specifications, Batch is used interchangeably. See Batch. Mat—A fibrous material for reinforced polymer consisting of randomly oriented chopped filaments, short fibers (with or without a carrier fabric), or long random filaments loosely held together with a binder. Matrix—The essentially homogeneous resin or polymer material in which the fiber system of a composite is embedded. A-4 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary

Micro-cracking—Cracks formed in composites when stresses locally exceed the strength of the matrix. MSDS—Material Safety Data Sheet. Near-Surface Mounted (NSM)—Alternative repair system, where an FRP bar or strip is inserted and anchored into a pre- cut groove. Pin Holes—A small cavity, typically less than 0.06 in. (1.5 mm) diameter that penetrates the surface of a cured com- posite part. Pitch—Petroleum or coal tar precursor base used to make carbon fiber. Ply—A single layer of fabric or mat. Polyester—A thermosetting polymer synthesized by the condensation reaction of certain acids with alcohols, and sub- sequently cured by additional polymerization initiated by free radical generation. Polyesters are used as binders for resin mor- tars and concretes, fiber laminates, and adhesives. Commonly referred to as “unsaturated polyester.” Polymer—A compound formed by the reaction of simple molecules, which permit their combination to proceed to high molecular weights under suitable conditions. Polyurethane—A thermosetting resin prepared by the reac- tion of disocyanates with polyols, polyamides, alkyd polymers, and polyether polymers. Postcure—Additional elevated-temperature cure to increase the level of polymer cross linking; final properties of the lami- nate or polymer are enhanced. Pot Life—Time that a catalyzed resin retains a viscosity low enough to be used in processing. Also called working life. Prepreg—A fiber or fiber sheet material containing resin whose reaction has progressed to the stage where consistency is tacky. Multiple plies of prepreg are typically cured with applied heat and pressure. Also preimpregnated fiber or sheet. Pultrusion—A continuous process that combines pulling and extrusion for manufacturing composites that typically have a constant cross-sectional shape. The process consists of pulling a fiber material through a resin bath and then through a heated shaping die, where the resin is cured. Resin—A component of a polymeric system that requires a catalyst or hardener to polymerize or cure for use in compos- ites. Resin often refers to the mixed polymer component or matrix of the FRP. Resin Content—The amount of resin in a laminate expressed as either a percentage of total mass or total volume. Recommended Construction Specifications A-5 Specifications Commentary

Roving—A number of yarns, strands, tows, or ends of fibers collected into a parallel bundle with little or no twist. Shelf Life—The length of time a material, substance, product, or reagent can be stored under specified environmental con- ditions and continue to meet all applicable specifications or remain suitable for its intended function. Also called storage life. Structural Adhesive—A resinous bonding agent used for transferring required loads between adherents. Substrate—The original concrete and any cementitious repair materials used to repair or replace the original concrete. It can consist entirely of original concrete, entirely of repair materials or of a combination of the two. The FRP is installed on the surface of the substrate. Thermoplastic—A non-cross-linked polymer capable of being repeatedly softened by an increase of temperature and hardened by a decrease in temperature. Examples are nylon, polypropylene, and polystyrene. Thermoset—A cross-linked polymer which cannot be soft- ened and reformed by an increase in temperature. Cross-linking is an irreversible process; thermosets cannot be returned to a molten state. Examples are epoxy, phenolic, and vinyl ester. Tow—An untwisted bundle of continuous filaments. Unidirectional Laminate—A reinforced polymer laminate in which substantially all of the fibers are oriented in the same direction. Vinyl Ester—A polymerizable thermosetting resin contain- ing vinyl and ester components, cured by additional polymer- ization initiated by free-radical generation. Vinyl esters are used as binders for fiber laminates and adhesives. Viscosity—The property of resistance to flow exhibited within the body of a material, expressed in centipoises. A higher viscosity has higher resistance to flow. Volatiles—Materials such as water and solvents in a resin formulation that are capable of being driven off as vapor. Wet Lay-Up—A method of making a laminate system by applying the resin system as a liquid, when the fabric or mat is put in place. Wet-Out—The process of coating or impregnating roving, yarn, or fabric in which all voids between the strands and fila- ments are filled with resin. It is also the condition at which this state is achieved. Wetting Agent—A substance capable of lowering surface tension of liquids, facilitating the wetting of solids surfaces and permitting the penetration of liquids into the capillaries. A-6 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary

Witness Panel—A small FRP panel, manufactured on site under conditions similar to the actual construction. The panel may be later tested to determine mechanical and physical properties to confirm the expected properties for the full FRP structure. 1.3 References The following standards or documents are referred to in this Specifications: ACI—American Concrete Institute 116R-00: Cement and Concrete Terminology. 117-90: Specifications for Tolerances for Concrete Con- struction and Materials, and Commentary. 224.1R-93: Causes, Evaluation, and Repair of Cracks in Concrete Structures. 224R-01: Control of Cracking in Concrete Structures. 440R-96: State-of-the-Art Report on Fiber Reinforced Plastic Reinforcement for Concrete Structures. 440.2R-02: Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening of Concrete Structures. 503R-93: Use of Epoxy Compounds with Concrete. 503.4-92: Standard Specification for Repairing Concrete with Epoxy Mortars. 503.5R-92: Guide for the Use of Polymer Adhesives in Concrete. 503.6R-97: Guide for the Application of Epoxy and Latex Adhesives for Bonding Freshly Mixed and Hardened Concrete. 546R-96: Concrete Repair Guide. ASTM—American Society for Testing and Materials D3039: Test Method for Tensile Properties of Polymer Matrix Composite Materials. D3418: Test Method for Transition Temperatures of Polymers by Differential Scanning Calorimetry. D4541: Test Method for Pull-off Strength of Coatings Using Portable Adhesion Tester. D5687: Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Preparation. ICBO—International Conference of Building Officials AC125: Acceptance Criteria for Concrete and Reinforced and Unreinforced Masonry Strengthening Using Fiber- Reinforced Polymer (FRP) Composite Systems. AC178: Acceptance Criteria for Inspection and Verifica- tion of Concrete and Reinforced and Unreinforced Masonry Strengthening Using Fiber-Reinforced Polymer (FRP) Composite Systems. Recommended Construction Specifications A-7 Specifications Commentary C1.3 References

ICRI—International Concrete Repair Institute No. 03730: Guide for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing Steel Corrosion. No. 03732: Selecting and Specifying Concrete Surface Preparation for Sealers, Coatings, and Polymer Overlays. No. 03733: Guide for Selecting and Specifying Materials for Repairs of Concrete Surfaces. 1.4 Tolerances Tolerances recommended by the manufacturer shall be fol- lowed, unless more stringent requirements are specified in this Specifications or in the Contract Documents. In case of any conflict or appearance of any conflict, the Engineer shall pro- vide clarification before proceeding. 1.5 Site Considerations The Contractor shall provide necessary pathways, scaffold- ings and other means of access to the general project site and to the specific repair area for the personnel, equipment and mate- rials. All obstructions such as pipes, conduits and wiring shall be removed at the expense of the Contractor, upon approval of the Engineer and after making records for subsequent re- installation by the Contractor at the completion of the project. Plants, fences and other obstructions that prevent access for repair shall be removed, and upon approval of the Engineer, re-installed or disposed of according to Section 3.4, at the expense of the Contractor. 1.6 Fire Considerations Fire is a life safety issue with the design of FRP systems. Most FRP systems are assumed to be lost completely in a fire due to their low temperature resistance. 2 Submittals The Contractor shall submit the following documents for Engineer’s approval before starting the work. 2.1 Working Drawings Working (shop) drawings shall include the type of FRP sys- tem, repair locations, relevant dimensions of the system and the work plan including the necessary preparations of the existing structure. The drawings must be accompanied by the design cal- culations, the MSDS and the manufacturer’s system data sheet A-8 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary C1.4 Tolerances Adherence to proper tolerances is necessary to produce acceptable work. It is important to avoid accumulating toler- ances. The Owner may accept the manufacturer tolerances, if appropriate test data is shown that warrants the change based on the unique characteristics of a particular system. C1.5 Site Considerations FRP systems can generally be installed in most locations with very limited access and minimal equipment. In most applications, the impact of FRP system on the existing utilities is minimal. C1.6 Fire Considerations Fire resistance of FRP system may be improved by adding fire retardants to the resin or by coating on the surface of the FRP. Other methods of fire protection may also be used. C2 Submittals C2.1 Working Drawings The necessary information for each FRP system may be dif- ferent. Shop drawings for wet lay-ups may include, for exam- ple, fiber orientation, nominal thickness, aerial weight of dry fabric, number of layers, fiber volume or weight fraction, loca- tions and lengths of lap splices, end details, and anchoring.

identifying mechanical, physical and chemical properties of all components of the FRP system; application guide, including the installation and maintenance procedures; and time schedule for various steps in the repair process. The installation procedure must clearly identify the environmental and substrate conditions that may affect the application and curing of the FRP system. 2.2 Quality Control/Quality Assurance Plan The Contractor shall be responsible for the quality control of all materials and processes in the project. The quality control and quality assurance (QC/QA) plan must be approved by the Owner or its representative. It shall include specific procedures for personnel safety, tracking and inspection of all FRP compo- nents prior to installation, inspection of all prepared surfaces prior to FRP application, inspection of the work in progress to assure conformity with specifications, quality assurance sam- ples, inspection of all completed work including necessary tests for approval, repair of any defective work, and clean-up. Any part of the work that fails to comply with the requirements of the Contract Documents shall be rejected by the Engineer, and shall be remedied, or removed and replaced by the Contractor at its own expense to be in full compliance with the Contract Documents. 2.3 Qualifications Manufacturer/Supplier must be pre-qualified by the Owner or its representative for each of its FRP systems after providing the following necessary information: 1) System data sheets and MSDS for all components of the FRP system; 2) Minimum of 5 years of documented experience or 25 doc- umented similar field applications with acceptable refer- ence letters from respective owners; 3) Minimum of 50 test data sets (total) from an independent agency approved by the Owner on mechanical properties, aging and environmental durability of the system; and 4) Comprehensive hands on training program for each FRP system to qualify Contractors/Applicators. Contractor/Applicator must be pre-qualified by the Owner or its representative for each FRP system after providing the following necessary information: 1) Minimum of 3 years of documented experience or 15 docu- mented similar field applications with acceptable reference letters from respective Owners; and Recommended Construction Specifications A-9 Specifications Commentary Shop drawings for near-surface mounted FRP may include, for example, locations and sizes of grooves and bars or strips. Shop drawings may also include necessary corner radii and sur- face conditions of the existing structure. The system data sheets may also include, for example, mix ratio, pot life, temperature- cure time data, and gel time at proposed cure temperature, and acceptable humidity and temperature range for mixing and applying the resin. C2.2 Quality Control/Quality Assurance Plan The quality control/quality assurance program should be comprehensive and cover all aspects of the FRP system. Qual- ity assurance is achieved through a set of inspections and applicable tests to document the acceptability of the installa- tion. Details of the plan in terms of inspection, testing, and record keeping may be developed to match the size and com- plexity of the project. Additional information regarding the necessary elements of the quality control/quality assurance plan is included in the Process Control Manual that accom- panies this document. The manual ensures that the specifica- tions are followed, and provides guidance and specific check- lists for quality assurance by the Owner or its representative. C2.3 Qualifications Qualification of Manufacturer/Supplier for each of its FRP systems assures acceptability of the system, as well as compe- tence of the Manufacturer/Supplier to provide it. The Owner or its representative may also require the Manufacturer/ Supplier to provide a specified number of samples of the com- ponents and the complete FRP system for in-house or inde- pendent testing prior to qualification. The Owner may accept the total experience of the key personnel on similar field appli- cations. For specific items on system data sheets, refer to Sec- tion C2.1. Test data sets may follow appropriate protocols such as those developed by HITEC [Reynaud et al. 1999, CERF 2001]. The training program by the Manufacturer/Supplier should provide hands on experience with surface preparation and installation of the same FRP system for which the certifi- cate is issued. Qualification of Contractor/Applicator for each FRP sys- tem assures competence of the Contractor/Applicator for sur- face preparation and application of a particular FRP system through evidence of appropriate training and related past experience. The Owner may accept the total experience of the

2) Certificate of completed training from Manufacturer/ Supplier for at least one field representative who will be present on site throughout the project. 3 Storage, Handling and Disposal 3.1 Storage 3.1.1 Storage Requirements All components of FRP system must be delivered and stored in the original factory-sealed unopened packaging or contain- ers with proper labels identifying the manufacturer, brand name, system identification number and date. Store catalysts and initiators separately. All components must be protected from dust, moisture, chemicals, direct sunlight, physical dam- age, fire, and temperatures outside the range specified in the sys- tem data sheets. Any component that has been stored in a con- dition different from that stated above must be disposed of, as specified in Section 3.4. 3.1.2 Shelf Life All components of the FRP system, especially resins and adhesives, that have been stored longer than the shelf life spec- ified on the system data sheet, shall not be used, and must be disposed of, as specified in Section 3.4. 3.2 Handling All components of the FRP system, especially fiber sheets, must be handled with care according to the manufacturer rec- ommendations to protect them from damage and to avoid mis- alignment or breakage of the fibers by pulling, separating or wrinkling them or by folding the sheets. After cutting, sheets shall be either stacked dry with separators, or rolled gently at a radius no tighter than 12 in. (305 mm) or as recommended by the manufacturer. 3.2.1 Safety Hazards All components of the FRP system, especially resins and adhesives, must be handled with care to avoid safety hazards, including but not limited to skin irritation and sensitization, and breathing vapors and dusts. Mixing resins shall be moni- tored to avoid fuming and inflammable vapors, fire hazards, or violent boiling. The Contractor is responsible to ensure that all components of the FRP system at all stages of work conform to the local, state, and federal environmental and worker’s safety laws and regulations. A-10 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary key personnel on similar field applications. The field repre- sentative may be employed by either the Contractor/Applica- tor or the Manufacturer/Supplier. C3 Storage, Handling and Disposal C3.1 Storage C3.1.1 Storage Requirements These requirements are intended to help preserve proper- ties of FRP system and maintain safety of the work place. The components may include sheets, plates, bars, strips, resins, solvents, adhesives, saturants, putty, and protective coatings. System identification number may be the batch number from the factory. Typically, temperature in the storage area should be within 50°–75°F (10°–24°C), unless otherwise noted on the system data sheet. Typically, components should be stored in a dry environment, unless an acceptable moisture level is spec- ified on the system data sheet. C3.1.2 Shelf Life Properties and reactivity of resins and adhesives may degrade with time, temperature or humidity. C3.2 Handling Fiber sheets with higher modulus fibers are more suscepti- ble to misalignment damages, and therefore must be handled with greater care. Dusts or residue can enter fiber sheets, if not protected. Rolling pre-cut short lengths of fiber sheets may cause damage through fiber movement and fabric shearing. Contamination of any component of FRP system with an organic solvent may reduce tensile strength and other proper- ties of the cured laminates. C3.2.1 Safety Hazards Consult Chapter 9 of the ACI 503R-93 for additional infor- mation on safety hazards of epoxy. Ignition or fire in the proximity of epoxy resins could be hazardous. Appropriate references may be used for other types of resin such as vinyl esters. Placing carbon FRP sheets, bars or strips near electri- cal equipment may cause short-circuit or electrical shock, because carbon is a conductive material. Glass fibers are known to cause severe itching and skin irritation.

3.2.2 Material Safety Data Sheets The MSDS for all components of the FRP system shall be accessible to all at project site. Specific handling hazards and disposal instructions shall be specified in the MSDS. 3.2.3 Personnel and Work-place Protection The Contractor is responsible for providing proper means of protection for safety of the personnel and the work place. The Contractor shall inform the personnel of the dangers of inhal- ing fumes of primer, putty or resin, and shall take all necessary precautions against injury to personnel. The resin mixing area shall be well vented to the outside. 3.3 Clean-up The Contractor is responsible for the clean-up of the equip- ment and the project site from hazardous and aesthetically undesirable FRP components using appropriate solvents, as recommended in the system data sheet. 3.4 Disposal Any component of the FRP system that has exceeded its shelf life or pot life, or has not been properly stored, as specified in Section 3.1, and any unused or excess material that is deemed waste, shall be disposed of in a manner amiable to the protec- tion of the environment and consistent with the MSDS. 4 Substrate Repair and Surface Preparation The concrete substrate shall be repaired, if necessary, and all concrete surfaces shall be cleaned and prepared prior to installing the FRP system. 4.1 Removal of Defective Concrete All defective areas of concrete substrate shall be removed according to ACI 546R-96 and ICRI No. 03730, using appro- priate equipment such as air or electric powered jack hammer or saw, at a sufficient depth of at least 1⁄2 in. (12.7 mm) beyond the repair area to expose sound aggregates. If any reinforcing or prestressing steel is exposed in the process, and it is either dete- riorated or its bond with concrete is broken in the process, an additional nominal depth of 3⁄4 in. (19 mm) or at least 1⁄4 in. (6.4 mm) larger than the largest aggregate in repair material shall be cut from its underneath. If any deterioration is noticed Recommended Construction Specifications A-11 Specifications Commentary C3.2.2 Material Safety Data Sheets Code of Federal Regulations (CFR 16) regulates the label- ing of hazardous substances and includes thermosetting-resin materials. C3.2.3 Personnel and Work-Place Protection Safety measures may include protective clothing and devices, such as disposable plastic or rubber gloves, safety glasses or goggles, dust masks, safety gear respirators, fire extinguishers, and ventilators, depending on the FRP system, working conditions, and the job site. Disposable gloves may degrade in presence of vinyl esters and solvents, if not specif- ically designed for use with FRP system. C3.3 Clean-up The Contractor may additionally consult with the prevail- ing environmental protection and health agencies for proper clean-up of the project site. Some clean-up solvents may be flammable. C3.4 Disposal Pot life depends on the system, mixed quantity, and ambient temperature. The Contractor may also consult the prevailing environmental protection and health agencies for proper dis- posal of FRP components. Allow un-used mixed primer, putty or resin to harden in their containers before disposal. C4 Substrate Repair and Surface Preparation A clean and sound concrete substrate is essential to the effectiveness of the FRP system in achieving the design strength and the intended design objectives. C4.1 Removal of Defective Concrete Defects may include loose and broken debris or delami- nated and spalled sections of concrete, voids and honeycombs, and deteriorated concrete. Defects in concrete substrate can compromise the integrity of the FRP system. Any attempt at covering the deteriorated (carbonated or chloride contami- nated) concrete with FRP system without correcting the source of deterioration may be detrimental to the effectiveness of the repair. Investigations to date [Harichandran and Baiyasi 2000] have shown that placement of externally bonded FRP, espe- cially when used for full confinement, may arrest cracking of

in the repair area, its source shall be located and treated to the satisfaction of the Engineer prior to restoring the section. Upon removing defective concrete, and before restoring the section, the substrate shall be cleaned from any dust, laitance, grease, oil, curing compounds, impregnations, foreign particles, wax and other bond inhibiting materials, as per Section 4.4.6. 4.2 Repair of Defective Reinforcement All defective reinforcement shall be repaired according to ICRI No. 03730, and to the satisfaction of the Engineer. FRP systems shall not be applied to concrete suspected of contain- ing corroded reinforcement. Corroded or otherwise defective reinforcement that is to be supplemented shall be cleaned and prepared thoroughly by abrasive cleaning to near white appear- ance. Damaged reinforcement that needs to be replaced shall be cut at sufficient length, according to the Contract Documents and the approval of the Engineer, to ensure full section and sound material in the remaining portion. Splice for the rup- tured or cut reinforcing or prestressing steel shall be provided at sufficient length, according to the Contract Documents and approval of the Engineer. 4.2.1 Mechanical Anchorage Mechanical anchorage of the repair material with the sub- strate shall be placed, if specified in the Contract Documents. Anchors shall be secured in place by tying to other secured bars, and shall not protrude outside concrete surface. If that is not possible, the concrete surface shall be built up to cover the protrusions. 4.3 Restoration of Concrete Cross Section The area of removed concrete substrate, and any void larger than 1⁄2 in. (12.7 mm) diameter and depth, shall be filled with repair material that conforms to ICRI No. 03733. The repair material shall have a compressive strength equal to or greater than that of the original concrete, but no less than 4,500 and 5,500 psi (31 and 38 MPa) at 7 and 28 days, respectively. The design mix for all repair materials shall be approved by the Engineer. The bond strength of the repair material to the exist- ing concrete shall be a minimum of 200 psi (1.4 MPa) in the pull-off test according to ASTM D4541. The concrete sub- strate and the exposed reinforcing or prestressing steel shall be clean, sound and free of surface moisture and frost before restoring the section. Before placement of patching materials, a water-based epoxy cementitious bonding agent shall be applied to concrete and exposed reinforcement. Also, cracks A-12 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary concrete and slow down the rate of corrosion of steel rein- forcement, but does not stop or reverse the corrosion process [Sohanghpurwala and Scannell 1994]. Precautions may be nec- essary in cases of carbonation, alkali-silica reactivity (ASR) or reactive aggregate. C4.2 Repair of Defective Reinforcement Defects in the reinforcement may include section loss or rup- ture due to impact or corrosion. Any attempt at covering the deteriorated section with FRP without arresting the corrosion process may be detrimental to the entire repair, because of the expansive forces associated with corrosion. If not treated prop- erly, repair in one section may lead to an accelerated corrosion in an adjacent section. The exposed steel may be treated by applying corrosion inhibitors prior to restoring the section. The Owner may require other treatment forms for corroded steel, or placement of sensors to monitor the corrosion process. The splice detail is intended to provide strength and ductility in both longitudinal and transverse directions in case the FRP system is lost due to fire, vandalism, or any other cause. C4.2.1 Mechanical Anchorage Mechanical steel or plastic anchorage is to ensure adequate bond with the existing cross section, where new concrete patch material is placed. A grid of 4 in. × 4 in. (102 mm × 102 mm) with a minimum embedment depth of 11⁄2 in. (38 mm) is usu- ally adequate. If the anchors protrude outside the concrete sur- face, they may damage fibers used in the FRP system. C4.3 Restoration of Concrete Cross Section The repair material may be an approved polymer/latex mod- ified mortar/concrete or an approved factory bagged mortar/ concrete patching material of equal characteristics. It is recom- mended that the manufacturer be consulted on the compatibil- ity of the repair material with the FRP system. At locations where due to the size of the voids or other constraints, pre- bagged mortar/concrete can not be used, a Class III latex mod- ified concrete may be used, as approved by the Engineer. No formwork is necessary for small voids, where repair materials may be placed by hand and troweled to match the original sec- tion. Formwork for larger areas may be built around the dam- aged area to ensure that the restored section is smooth and uni- form, and that it conforms to the original shape of the section. The instruction for most patching materials specifies a bond- ing agent, often a diluted mixture of the patching mix rubbed

within solid concrete in the substrate shall be stabilized using epoxy injection methods, as specified in Section 4.4.3. If water leak through cracks or concrete joints is significant, water pro- tection and a water conveyance and weep holes shall be pro- vided before restoring the section. The repair material shall be cured a minimum of 7 days before installing the FRP system, unless its curing and strength are verified by tests. 4.4 Surface Preparation All necessary repair and restoration of concrete section shall be approved by the Engineer, prior to surface preparation. In this Specifications, contact-critical applications are treated the same as bond-critical applications. An adhesive bond with adequate strength shall always be provided between FRP and concrete. Surface preparation shall also promote continuous intimate contact between FRP and concrete by providing a clean, smooth, and flat or convex surface. Surface preparation for near-surface mounted FRP bars or strips is specified in Section 4.4.4. Surface preparation for FRP shell systems where grout is pumped into the gap between the shell and the existing column surface is specified in Section 4.4.5. All surface prepa- rations shall be approved by the Engineer, before installing the FRP system. 4.4.1 Surface Grinding All irregularities, unevenness, and sharp protrusions in the surface profile shall be grinded away to a smooth surface with less than 1⁄32 in. (0.8 mm) deviation. Disk grinder or other sim- ilar devices shall be used to remove stain, paint, or any other surface substance that may affect the bond. Concrete surface shall be grinded to the concrete surface profile range of CSP 2–3 defined by ICRI as minimum surface roughness level. Voids with diameters larger than 1⁄2 in. (12.7 mm) and depres- sions on the concrete surface deeper than 1⁄16 in. (1.6 mm) measured from a 12 in. (305 mm) straight edge placed on the surface, shall be filled according to Section 4.4.5. 4.4.2 Chamfering Corners All inside and outside corners and sharp edges shall be rounded or chamfered to a minimum radius of 1⁄2 in. (12.7 mm) as per ACI 440.2R-02. Ridges, form lines, and sharp or rough- ened edges greater than 1⁄4 in. (6.4 mm) shall need to be ground down or filled with putty, as specified in Section 4.4.5. Obstruc- tions and embedded objects shall be removed before installing the FRP system, if required by the Engineer. Recommended Construction Specifications A-13 Specifications Commentary into the concrete. Curing time depends on the type of patch- ing materials. C4.4 Surface Preparation Surface roughness has a significant effect on the bond between FRP system and concrete [Shen et al. 2002]. Surface preparation depends on the type of application and the type of FRP system. Even though bond may not be structurally nec- essary for contact-critical applications such as confinement of columns, it would help improve durability of the structure. Many applications of column wrapping occur in aggressive environments. Any debonding between FRP and concrete that may result due to less stringent criteria could lead to signifi- cant damage during freeze-thaw cycles. C4.4.1 Surface Grinding Consult with the ACI 546R-96 and ICRI No. 03730 for grinding of concrete surfaces and for assuring proper surface preparation. Vacuum cleaning could help reduce the dusts in environmentally sensitive areas. Test results of NCHRP 10-59 Phase II suggest that surface roughness higher than CSP 2–3 does not necessarily improve bond performance. The same study also shows that void depth does not have an influence on the repair system. On the other hand, valleys deeper than 1⁄16 in. (1.6 mm) over 12 in. (305 mm) length could lower flex- ural strength of FRP systems. C4.4.2 Chamfering Corners Chamfering of corners improves bond between FRP and concrete, reduces stress concentrations in FRP, and helps pre- vent voids between FRP and concrete [Yang et al. 2001a&b] (Figure C4.4.2). This is especially critical for carbon FRP sys- tems, because their transverse strength and modulus are sub- stantially lower than their longitudinal values, and therefore, could easily fracture when bent over a sharp edge. Obstruc- tions, reentrant corners, concave surfaces, and embedded objects can affect the performance of the FRP system.

4.4.3 Crack Injection All cracks in the surface of concrete or the substrate wider than 0.01 in. (0.25 mm) and with spacing less than 1.5 in. (38 mm) or cracks wider than 1⁄32 in. (0.8 mm) shall be filled using pressure injection of epoxy according to ACI 224.1R. Smaller cracks may also require resin injection in aggressive environments. Follow ACI 224R-01 crack width criteria for various exposure conditions. FRP system shall be installed no earlier than 24 hours after crack injection. Any surface rough- ness caused by injection shall be removed as per Section 4.4.1. 4.4.4 Grooves for Near-Surface Mounted FRP A groove with dimensions specified in the Contract Docu- ments shall be made in concrete, where the FRP bar or strip is to be placed. Care shall be taken to avoid local fracture of the concrete surrounding the groove. The groove in which FRP is to be placed shall be free of loose, unsound or bond inhibiting materials such as oil, efflorescence or moisture. All obstruc- tions and embedded objects shall be removed from the groove area, upon approval of the Engineer. 4.4.5 Surface Profiling After surface grinding, any remaining unevenness in the sur- face greater than that specified in Section 4.4.3, including out- of-plane variations, fins, protrusions, bug holes, depressions voids, and roughened corners shall be filled and smoothed over using putty made of epoxy resin mortar or polymer cement mortar with strength equal to or greater than the strength of the original concrete. The patching material shall be cured a minimum of 7 days before installing the FRP system, unless its curing and strength are verified by tests. A-14 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary C4.4.3 Crack Injection Movement of cracks wider than that specified may cause delamination or fiber crushing in externally bonded FRP sys- tems. Crack injection helps restore concrete strength and pre- vent water leakage behind the FRP system. The procedure usually includes cleaning of the cracks, sealing of the surfaces, installing the entry and venting ports, mixing the epoxy, pres- sure injecting the epoxy, and removing the surface seal. Test results of NCHRP 10-59 Phase II show crack width tolerance of 1⁄100 in. (0.25 mm) to be too conservative, especially if spaced wider than 1.5 in. (38 mm). However, the tolerance is main- tained for the purpose of durability of FRP system and inter- nal steel reinforcement. C4.4.4 Grooves for Near-surface Mounted FRP It is recommended to first examine the existing conditions to assess the quality of the concrete substrate, identify poten- tial obstructions, and verify the dimensions and geometries shown in the Contract Documents. The groove is often made using a grinder or concrete saw with a suitable blade. Embed- ded obstructions and objects can affect the performance of the FRP system. Test results of NCHRP 10-59 Phase II suggests that groove size tolerance of ± 1⁄8 in. (3.2 mm) may be accept- able for near-surface mounted FRP systems for groove size of 9⁄16 in. (14 mm). C4.4.5 Surface Profiling Consult the ACI546R and ICRI Guideline No. 03730 for surface profiling. Surface profile of the concrete substrate may provide an open roughened texture for pre-cured FRP shell systems, where grout is pumped into the space between the shell and the existing column surface. Curing time depends on the type of patching materials. Existing Edges Sharp Edges Rounded Smooth Figure C4.4.2. Chamfering Corners.

4.4.6 Surface Cleaning Substrate concrete and finished surface of concrete shall be cleaned to the approval of the Engineer. Cleaning shall remove any dust, laitance, grease, oil, curing compounds, wax, impreg- nations, stains, paint coatings, surface lubricants, foreign parti- cles, weathered layers or any other bond-inhibiting material. If power wash is used, the surface shall be allowed to dry thor- oughly before installing the FRP system. The cleaned surface shall be protected against re-deposit of any bond-inhibiting materials. Newly repaired or patched surfaces that have not cured a minimum of 7 days shall be coated with a water-based epoxy paint or other approved sealers. 5 Installation of FRP System This section specifies general installation procedures for three types of FRP systems: wet lay-up, pre-cured, and near- surface mounted. Specific procedures for installing FRP systems may vary slightly for each system and manufacturer. 5.1 Environmental Conditions for Installation Environmental conditions shall be examined before and dur- ing installation of the FRP system to ensure conformity to the Contract Documents and manufacturer’s recommendations. Do not apply primers, putty, saturating resins, or adhesives on cold, frozen, damp, or wet surfaces. Ambient and concrete sur- face temperatures shall be within 50°–90°F (10°–32°C), unless specified by the manufacturer. Moisture level on all contact sur- faces shall be less than 4.3% at the time of installation of FRP system, as evaluated according to ACI 503R-93. Moisture restrictions may be waived for resins that have been formulated for wet applications. Relative humidity at the time of FRP appli- cation should be in the range of 65%–82%. 5.1.1 Moisture Vapor Transmission Application of bonded FRP systems shall not proceed, if any moisture vapor transmission is present. Concrete dryness is necessary, when using elevated temperature cure. Any bubble that develops from moisture vapor transmission can effectively be injected with the same adhesive material used for the FRP system, following the procedure specified in Section 7.2. 5.1.2 Applications in Inclement Weather When inclement weather does not allow installation of FRP system, as specified in Section 5.1, auxiliary measures may be Recommended Construction Specifications A-15 Specifications Commentary C4.4.6 Surface Cleaning This section relates to surface cleaning for the substrate after removal of defective concrete and prior to restoring the concrete section, as specified in Section 4.1. It also relates to surface cleaning of the finished surface of concrete before installing the FRP system. Cleaning may be performed with blast cleaning, air blower, pressure washing, or other equiva- lent means. Clean wiping rags may also be used for removing any dust that may have been generated on the concrete surface during the grinding operation. Vacuum cleaning could help reduce the dusts in environmentally sensitive areas. C5 Installation of FRP System Contract Documents provide specific procedures for the specific type of FRP system. Other less common FRP systems, such as dry lay-up and machine-applied or automated, are not included in this Specifications. C5.1 Environmental Conditions for Installation Moisture may hinder adhesion of the primer and resin. Work may be postponed, if adverse weather, rain or dew con- densation is anticipated. Although moisture primarily affects the polymers and concrete surface, it may also collect on the surface of the fiber sheets, if not stored properly, as specified in Section 3.1.1. Moisture on fiber sheets can cause problems with wet-out and cure of the system. Surface moisture may be measured using a mortar moisture meter, or alternatively an absorbent paper. Cold weather may cause improper curing of the resin and saturation of fibers, compromising the integrity of the FRP system. C5.1.1 Moisture Vapor Transmission This section only applies to the conditions at the time of construction, and not those that should be addressed in the design process. Moisture vapor transmission from concrete surface through uncured resin may cause air pockets and sur- face bubbles, compromising bond between FRP system and concrete. These effects have primarily been observed in wet lay-ups, but are not excluded from other FRP systems. C5.1.2 Applications in Inclement Weather Different heating systems, such as spotlights, electrical heaters, infrared heating, and heating blankets may be used.

employed to correct the conditions. Auxiliary heat source may be used in cold weather to raise the ambient and concrete sur- face temperatures to acceptable levels, as recommended by the manufacturer, but no more than the glass transition temper- ature (Tg). Pressurized air may be used to dry the surface dampness. 5.2 Shoring Repaired members shall be shored temporarily with conven- tional methods, if specified in Contract Documents, or required by the Engineer for safety. Shoring shall not be removed until the FRP system has fully cured and gained its design strength, as rec- ommended by the manufacturer and approved by the Engineer. 5.3 Equipment The Contractor shall provide all necessary equipment, in sufficient quantities and in clean and operating conditions, for continuous uninterrupted FRP installation. 5.4 Application of Wet Lay-Up FRP Systems This section specifies the necessary measures for install- ing wet lay-up systems using dry or prepreg fiber sheets and saturants. 5.4.1 Mixing of Resin Components All resin components, including main agent and hardener shall be mixed at proper temperature using appropriate weight ratio and for a duration specified by the manufacturer, until thorough mixing with uniform color and consistency is achieved. Resins shall not be diluted with any organic solvents such as thinner. Manual stirring and small electrically powered mixing blades are allowed. Resin shall be mixed in quantities sufficiently small to ensure that it can be used within its pot life. Any mixed resin that exceeds its pot life, or begins to generate heat or show signs of increased viscosity, shall not be used, and shall be disposed of according to Section 3.4. Mixing of some resins may be accompanied by noxious fumes. Precautions must be taken, as specified in Section 3.2.1, regarding their impact on the environment, including emission of volatile organic compounds and toxicology. 5.4.2 Primer and Putty A primer coat is generally required in all available FRP sys- tems. Apply one or two coats of primer on the concrete surface to penetrate its open pores. Ambient and concrete surface tem- peratures must be within the range specified in Section 5.1. The A-16 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary Electrical conductivity of carbon fibers may be used to apply a current, thereby providing fast in-situ curing in about 3 hours [CEB-FIP 2001]. The maximum elevated temperature depends on the system used. This procedure, however, is not yet widely accepted as providing a uniform and consistent cure profile. C5.2 Shoring In most applications, the FRP system may be applied, while the structure is in service. Shoring may be provided to either support the existing structure prior to repair, or to reduce its initial deflections prior to strengthening. Shoring may also be used to induce an initial camber in the system, thereby stress- ing the FRP system. C5.3 Equipment The equipment may vary for different FRP systems. They may include resin impregnators, rollers, sprayers, and lifting and positioning devices. C5.4 Application of Wet Lay-Up FRP Systems Wet lay-up systems may alternatively be applied using spe- cial equipment (saturator) to automate and speed up the process. C5.4.1 Mixing of Resin Components The term resin is a generic denomination used to identify all polymers employed in wet lay-up systems. Depending on its function, resin is more specifically identified as primer, putty, and saturant. Not all FRP systems use putty. Excessive agita- tion, when using electrically powered mixers, may cause froth and bubbles that can be entrapped as voids in the resin. Resin components are often contrasting colors, hence full mixing is achieved when color streaks are eliminated. The stoichiome- try of the resin will not be met, unless resin solids at the bot- tom of the container are completely mixed. Pot life of resin depends on its type and the ambient temperature. Viscosity of a mixed resin that has exceeded its pot life will continue to increase, adversely affecting its ability to penetrate the con- crete surface or saturate the fiber sheet. C5.4.2 Primer and Putty Primer may be applied using a clean roller or brush. The primer, when applied uniformly, helps hatch and strengthen the most external layer of concrete, and improves the bond between the concrete substrate and the FRP system. The rate

putty, if used in the FRP system, shall be applied as soon as the primer becomes tack-free or until not-sticky to the fingers. The putty shall be applied within 7 days after primer applica- tion; otherwise, the primer coated surface shall be roughened with sandpaper or similar tool. The resulting surface shall be cleaned according to Section 4.4.6, before applying the putty. Apply a thin coat of putty in one or two layers, and smoothen over the surface to fill in any small voids, cracks or uneven areas. Any swelling on the surface after applying the putty shall be cor- rected to meet surface profile as specified in Section 4.4.5. The surfaces of primer and putty shall be protected from dust, mois- ture and any other contaminants before applying the FRP. 5.4.3 Saturant The first coat of saturating resin, saturant, shall be uniformly applied as an undercoat to all locations on the concrete surface where the FRP system is to be installed. The saturant shall have sufficiently low viscosity to ensure full impregnation of the fiber sheets prior to curing. To maintain proper viscosity of the sat- urant, the ambient and concrete surface temperatures must be within the range specified in Section 5.1. Any mixed saturant that exceeds its pot life shall be disposed of, according to Sec- tion 3.4. 5.4.4 Applying Fiber Sheet and Saturant Upon uniformly applying the first layer of saturant as under- coat, the fiber sheet previously cut to the length specified in the Contract Documents, shall be installed in place and gently pressed onto the wet saturant. Any entrapped air between fiber sheet and concrete surface shall be released or rolled across the sheet in the direction parallel to the fibers, while allowing the resin to impregnate the fibers and achieve intimate contact with the substrate. Rolling perpendicular to the fiber direction is not allowed. In bi-directional fabrics, rolling shall be initially in the fill direction end to end, and then in the warp direction. Suffi- cient saturant shall be applied on top of the fiber sheet, as over- coat, to ensure full saturation of the fibers. Undercoat, fiber sheets and overcoat shall be applied with no interruption. 5.4.5 Multiple Fiber Plies In multi-ply installations, the sequence specified in Sec- tion 5.4.4 shall be repeated for each additional fiber sheet. The amount of resin overcoat for intermediate plies is approxi- mately 15%–20% greater than a single-ply installation, because the saturant serves as overcoat for the applied ply and under- coat for the next ply. Follow the Contract Documents for the fiber orientation and ply stacking sequence. Each ply shall be applied before the onset of complete gelation of the previous layer. The number of plies that can be applied in a single day Recommended Construction Specifications A-17 Specifications Commentary of surface coverage of primer is typically listed in the system data sheet. Not all FRP systems use putty. The primary func- tion of the putty, if used, is to smoothen the concrete surface. The putty may be applied using a clean towel or spatula or any other suitable method. Adding silicate sand to the putty may improve its stability and prevent its swelling. C5.4.3 Saturant The resin which impregnates the fibers is the key compo- nent to form the FRP laminate that repairs or retrofits the con- crete member. Rate of coverage of the resin is listed on the sys- tem data sheet, but it generally depends on the type of resin, the ambient temperature, and the porosity of concrete surface. Typical rate of application is about 0.1 lb/ft2 (4.9 kg/m2). C5.4.4 Applying Fiber Sheet and Saturant This installation procedure is for a single fiber sheet or the first fiber sheet or ply in a multi-ply application. Alternatively, the fiber sheet may be separately impregnated using a resin- impregnating machine before placement on the concrete sur- face. For ease of handling and to avoid wrinkling, fiber sheets are typically cut in segments shorter than 15 to 20 ft (4.6 to 6.1 m) lengths. Metal serrated rollers are often used to force resin between fibers and to remove entrapped air. However, when used with excessive force, these rollers may cause frac- ture of the fibers. Rolling perpendicular to the fiber direction may misalign or damage the fibers. C5.4.5 Multiple Fiber Plies Some repair and retrofit applications may require more than a single fiber ply to be installed by wet lay-up. The wait- ing time between plies depends on the type of resin, type of fiber sheet, and ambient temperature. It is good practice to wait for the resin to fully impregnate the fibers to avoid form- ing air pockets. Rate of coverage of the resin overcoat is listed on the system data sheet, but it generally depends on the type of resin and fibers and the ambient temperature. Typical rate of application is about 0.05 lb/ft2 (2.4 kg/m2). Application of

shall be determined based on the manufacturer’s recommen- dation and the approval of the Engineer. Multiple plies can also be applied in several days. When previous layers are cured, interlayer surface preparation, such as light sanding and filling with putty may be required, as specified in Section 5.4.2. 5.4.6 Overlapping A lap joint shall be constructed when an interruption occurs in the direction of the fibers. The length of lap splice shall be as specified by the Contract Documents, but at least 6 in. (152 mm). Staggering of lap splices on multiple plies and adjacent strips shall be required, unless permitted by Contract Documents. No lap joint is necessary in the transverse direc- tion, unless specified in the Contract Documents. 5.4.7 Alignment of FRP Materials The fiber plies shall be aligned on the structural member according to the Contract Documents. Any deviation in the alignment more than 5° (approximately 1 in./ft or 87 mm/m) is not acceptable, as specified in Section 6.3. Once installed, the fibers shall be free of kink, folds and waviness. 5.4.8 Anchoring of FRP Sheets Anchoring of FRP sheets to the concrete substrate shall follow the method specified in the Contract Documents, or approved by the Engineer. When using mechanical clamps and fasteners, care shall be taken to avoid damage to the FRP system or to the concrete substrate. Precautions shall be taken when steel fasteners are used for carbon FRP to avoid galvanic corro- sion. FRP anchors shall be sufficiently embedded into concrete. 5.4.9 Stressing Applications Stressing of FRP systems shall follow the method specified in Contract Documents. Active end anchorages shall be used for linear prestressing. For circular prestressing of wet lay-up sys- tems, the gap left between the FRP system and the concrete col- umn shall be filled using expansive mortar or pressure injection of epoxy grout, as specified in Section 5.5.4. 5.5 Application of Pre-Cured FRP Systems Installation of pre-cured FRP systems is generally similar to single ply wet lay-up. Surface preparation of the concrete sub- strate shall provide an open roughened texture. 5.5.1 Application of Adhesive Apply the adhesive uniformly onto all surface areas of concrete substrate where the pre-cured FRP system is to be A-18 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary too many plies in a single day may result in slippage or sepa- ration due to self-weight of fiber sheets. The number of plies that can be applied in a single day depends on the ambient temperature, weight of fiber sheet, and whether the repair is overhead or on a vertical surface. C5.4.6 Overlapping When the length of the sheet to be installed exceeds the length suggested by the manufacturer for proper installation, lap jointing becomes necessary. Lap splice length depends on the type of resin and fibers [Yang and Nanni 2002, Belarbi et al. 2002]. For large coverage areas, it is recommended that all lap joints in the longitudinal direction of fibers be made in a single day. Transverse lap joints, if necessary, may be made in several days. C5.4.7 Alignment of FRP Materials Performance of unidirectional FRP system depends heavily on fiber orientation and straightness. Misalignment may occur due to improper rolling or wrong placement of fiber sheets. Fiber misalignment is known to affect the strength more signif- icantly than the elastic modulus [Yang et al. 2002]. C5.4.8 Anchoring of FRP Sheets Anchoring of fiber sheets helps prevent delamination fail- ure of the FRP system. Different methods can be employed to anchor the fiber sheets. When possible, U-wraps may provide additional anchorage against premature delamination of the FRP system. C5.4.9 Stressing Applications Stressing and active confinement with glass FRP system is NOT recommended due to concerns related to its creep rup- ture. The prestrain in carbon should be limited to 50% of the ultimate strain due to damage tolerance concerns with uni- directional carbon FRP. C5.5 Application of Pre-Cured FRP Systems Pre-cured FRP systems consist of laminates in the form of plates, strips, open grid forms, or shells. These systems are typ- ically installed with an adhesive resin. C5.5.1 Application of Adhesive Adhesives may be applied with a spatula or any other suit- able method. Rate of coverage of the adhesive is listed on the

installed. Thickness and viscosity of the adhesive layer shall be according to the manufacturer’s recommendations. Ambi- ent and concrete surface temperatures must be within the range specified in Section 5.1, prior to applying the adhesive. Any mixed adhesive that exceeds its pot-life shall be disposed of, as specified in Section 3.4. 5.5.2 Placement of Pre-Cured System Pre-cured FRP system shall be cleaned, cut to the length spec- ified in the Contract Documents, and placed into the wet adhe- sive within the pot life of the adhesive. Entrapped air between laminate and concrete shall be released, and excess adhesive shall be removed. Do not disturb the applied FRP system before the adhesive fully cures. 5.5.3 Anchoring of Pre-Cured System Anchoring of pre-cured systems is typically the same as the FRP sheets, as specified in Section 5.4.8. 5.5.4 Grouting of Pre-Cured Shells Pre-cured shells around concrete columns shall be grouted no less than 24 hours after installation. Pressure grouting shall follow the Contract Documents and the manufacturer rec- ommendations. The grout shall have a shrinkage strain of less than 0.0005 and a compressive strength greater than 4,000 psi (27.6 MPa). 5.5.5 Stressing Applications Installation of prestressed FRP systems begins requires a moveable anchorage, which usually consists of gluing the FRP laminate termination between two steel plates, held in place by means of screws. After curing of the moveable anchorage, the fixed anchorage at the other end of the member shall be installed, and the FRP laminate shall be glued between a steel plate and the concrete surface. Fasten the steel plate to the con- crete surface using inserts. The fixed anchorage must be cured, before the FRP laminate can be stressed. Install another fixed anchorage on the concrete surface at the other end of the mem- ber using insert. Once the two fixed anchors have been installed, the system is ready for stressing with hydraulic jacks. During the prestressing process, an epoxy gel is spread uniformly on the entire concrete surface where the laminate has contact. The thickness of the epoxy gel shall follow the manufacturer’s rec- ommendation. Any entrapped air shall be released by pressing on the FRP. After the epoxy gel has cured, the moveable anchor is removed and the laminate is cut. Both fixed anchors remain in place. Recommended Construction Specifications A-19 Specifications Commentary system data sheet, but it generally depends on the type of resin, the ambient temperature, and the porosity of concrete surface. Typical rate of application is about 0.1 lb/ft2 (4.9 kg/m2). The adhesive is not necessary, when an intentional gap is left between concrete surface and the FRP shell, to be later filled with grout, as specified in Section 5.5.4. C5.5.2 Placement of Pre-Cured System Since there are a number of different pre-cured systems, it is important to follow the manufacturer’s recommendations on the timing and sequence of stacking, overlap and banding, horizontal and vertical joints, staggering of splices and over- lap and butt joints. The use of a dust mask is recommended when cutting pre-cured FRP systems. C5.5.3 Anchoring of Pre-Cured System Temporary clamping and shoring may be necessary in over- head applications of the pre-cured systems until the adhesive cures. C5.5.4 Grouting of Pre-Cured Shells Pressure grouting creates an active confinement in the col- umn. Active confinement with glass fiber systems is NOT rec- ommended due to concerns related to creep rupture. The pre- strain in carbon should be limited to 50% of its ultimate strain, as described in Section C5.4.9. C5.5.5 Stressing Applications Prestressed FRP systems often require proprietary materi- als, procedures, and anchoring system. The stressing hardware may be found on the shop drawings, as specified in Section C2.1. The movable anchorage generally cures in 24 hours, while the fixed anchorage takes about 48 hours to cure. Prestressing of glass FRP system is NOT recommended due to concerns related to creep rupture. Prestressing of carbon FRP system above 50% of the ultimate strain may affect its damage toler- ance, hence requiring additional protection against accidental impact

5.6 Application of Near-Surface Mounted FRP Systems Near-surface mounted (NSM) FRP system is an alternative to externally bonded FRP systems. In this system, a bar or strip is inserted and anchored into a pre-cut groove, as specified in Section 4.4.4. The NSM FRP system shall not be installed when surface moisture is present on the substrate or when rainfall or condensation is anticipated. 5.6.1 Application of Embedding Paste Components of the embedding paste shall be mixed by the ratio specified by the manufacturer, until thorough mixing with uniform color and consistency is achieved. All grooves, where the NSM FRP system is to be placed, shall be half-filled with the paste. Ambient and concrete surface temperatures must be within the range specified in Section 5.1, prior to applying the paste. Mixed paste that exceeds its pot-life shall be disposed of, as specified in Section 3.4. 5.6.2 Placing FRP Reinforcement The round FRP bar or rectangular FRP strip, shall be cleaned, cut to the length specified in the Contract Documents, placed at mid-depth of the groove, and lightly pressed so as to force the paste to flow around it and completely fill the space between FRP and the sides of the groove. The groove shall then be fully filled with additional paste and the surface be leveled. 5.7 Curing The FRP system shall be allowed to cure, as recommended by the manufacturer. Field modification of resin chemistry for rapid curing is not allowed. Elevated cure temperature may be used, as specified in Section 5.1.2, if rapid curing is necessary. Cure of installed plies shall be monitored before placing sub- sequent plies. In case of any curing irregularity, installation of subsequent piles shall be halted. Unless otherwise noted in the Contract Documents and approved by the Engineer, full load shall not be applied until curing is complete. Protect the FRP system while curing, as specified in Section 5.9. 5.8 Protective Coating and Finishing Protective coating shall be applied on the surface of the FRP system. The coating shall be non-vapor-barrier, flexible, water- proofing, and compatible with the FRP system. The coating may be a polymer-modified Portland cement coating or a poly- mer-based latex coating. The mortar finish shall be made with silicate sand between sieves No. 40 (1⁄64 in. or 0.42 mm) and A-20 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary C5.6 Application of Near-Surface Mounted FRP Systems The NSM FRP system allows anchoring the reinforcement into adjacent members, and upgrading members in their neg- ative moment region without exposure to any potential mechanical or abrasion damage. C5.6.1 Application of Embedding Paste Any void that develops between concrete substrate and the embedding paste can be detrimental to the performance of the NSM FRP system. C5.6.2 Placing FRP Reinforcement FRP bars and strips may be cut with a high-speed grinding cutter or a fine blade saw. FRP bars or strips should not be sheared. The use of a dust mask is recommended when cutting FRP bars or strips. There is not yet sufficient data to support prestressing of NSM FRP systems. C5.7 Curing Curing is a time and temperature-dependent process, and may take several days in ambient temperature. In some FRP sys- tems, pressure must be continuously applied through external means to prevent sag and pull-off during cure. C5.8 Protective Coating and Finishing Protective coating is applied for aesthetics appeal or protec- tion against impact, fire, ultra violet and chemical exposure, moisture, or vandalism. FRP systems are usually durable to weather conditions, sea water, and many acids and chemicals. Mortar finish can provide protection against impact or fire. Weather-resistant paint of the family of urethane or fluorine or

No. 6 (1⁄8 in. or 3.36 mm), spread over the FRP system before the resin hardens. Appropriate methods shall be used for vertical or overhead work. The thickness of the coating shall be specified in Contract Documents. Final appearance is to match, within reason, the color and texture of the adjacent concrete. Surface preparation shall be as recommended by the manufacturer. Solvent-wipes shall not be used to clean the FRP surface, unless approved by the FRP manufacturer. If abrasive cleaning is nec- essary, air pressure shall be limited to avoid any damage to fibers. Ambient and surface temperatures shall be within the range specified in Section 5.1, prior to applying the protective coating. Do not apply the coating when surface moisture is present or when rainfall or condensation is anticipated. 5.9 Temporary Protection Temporary protection shall be installed, as specified in Con- tract Documents, until the resin has fully cured, as approved by the Engineer. 6 Inspection and Quality Assurance All inspections and tests in this section will be performed by a trained inspector, acting on behalf of the Owner for quality assurance of the project, in the presence of the Contractor and the Engineer. The Contractor may have its own inspector for quality control. 6.1 Inspection of Materials Manufacturer’s certifications for all delivered and stored FRP components will be inspected for conformity to the Contract Documents before starting the project. Materials testing will be conducted on samples of pre-cured or NSM FRP or witness panels of wet lay-ups, if specified in the Contract Documents. Any material that does not meet the requirements of the Con- tract Documents will be rejected. Additional witness panels may be taken during the installation process, if specified in the Con- tract Documents. 6.2 Daily Inspection Daily inspection will include date and time of repair; ambi- ent and concrete surface temperatures; relative humidity; general weather conditions; surface dryness per ACI 503.4; surface preparation and surface profile using ICRI surface- Recommended Construction Specifications A-21 Specifications Commentary epoxide can provide protection against direct sunlight. The amount of paint finish coat is usually indicated in the shop drawings, as specified in Section C2.1. Use of solvent-wipes may cause deleterious effects on polymer resins. Abrasive cleaning is generally not required, when the first coat of paint is applied within 2–3 days after mixing of the components for the final 15 mil resin coating. It is a good practice to allow a minimum of 1–2 hours before applying the second coat. The Engineer may request the Contractor to provide a sample mock-up of the coating system for about 1 ft2 (0.1 m2) area. C5.9 Temporary Protection Temporary tents or plastic screen may help protect the installed FRP system against rain, dust, dirt, excessive sunlight, extreme temperatures, and high humidity. They may also serve as deterrence for vandalism. C6 Inspection and Quality Assurance The specific quality assurance plan for each project may be developed from the tests identified in this section, based on the size and complexity of the project. Checklists for quality assurance are provided in the accompanying Process Control Manual. C6.1 Inspection of Materials Testing in this section is for acceptance and not for qualifi- cation. For qualification testing, consult with the AASHTO Materials Specifications for FRP Systems, when it becomes available. The extent of materials testing depends on the size and complexity of the project. Testing may include tensile strength and modulus, glass transition temperature (Tg), pot life, adhesive shear strength, lap splice strength, and hardness, according to ASTM standards, such as ASTM D3039. C6.2 Daily Inspection Consult ACI 440.2R-02 and the checklists in the accompa- nying Process Control Manual for daily inspection and record keeping. The Owner is recommended to retain the inspection records and witness panels for at least 10 years.

C6.3 Inspection for Fiber Orientation See Section C5.4.7 for an explanation of the importance of fiber alignment and straightness. C6.4 Inspection for Debonding The inspector may look for changes in color, debonding, peeling, blistering, cracking, crazing, deflections, indications of reinforcing-bar corrosion, and other anomalies. Signifi- cance of debonding defects depends on their size, location, and quantity relative to the overall application area. Addi- tional tests such as ultrasonic scanning [Littles et al. 1996], microwave detection [Hughes et al. 2001] or infrared ther- mography [Mandic et al. 1998] may be performed, if specified in the Contract Documents or approved by the Engineer, when an area is deemed to be suspect. C6.5 Inspection for Cure of Resin Data on resin cure time and temperature is specified on sys- tem data sheets. The sampling frequency depends on the size and complexity of the project. For visual inspection of the cure of resin, the inspector may use physical observation of resin tackiness and hardness of work surfaces or hardness of resin- cup samples. profile-chips; qualitative description of surface cleanliness; type of auxiliary heat source, if any; widths of cracks not injected with epoxy; fiber or precured laminate batch numbers and their locations in structure; batch numbers, mixture ratios, mixing times, and qualitative descriptions of the appearance of all mixed resins, primers, putties, saturants, adhesives, and coatings; observations of progress of cure of resins; conformance with installation procedures; adhesion test results: bond strength, failure mode, and location; FRP properties from tests of field sample panels or witness panels, if required; location and size of any delaminations or air voids; and general progress of work. 6.3 Inspection for Fiber Orientation Fiber or ply orientation, fiber kinks and waviness will be examined by visual inspection for conformity to the Con- tract Documents. Tolerances will follow Section 5.4.7. Non- conforming FRP area will be removed, and repaired as per Section 7.4. 6.4 Inspection for Debonding After at least 24 hours for the initial cure of the resin, a visual inspection of the surface will be performed for any swelling, bubbles, voids or delaminations. If an air pocket is suspected, an acoustic tap test will be carried out with a hard object to identify delaminated areas by sound, with at least one strike per 1 ft2 (0.1 m2). Defects smaller than 1⁄4 in. (6.4 mm) diameter will require no corrective action, unless as speci- fied in Section 7.2. Defects larger than 1⁄4 in. (6.4 mm) but smaller than 11⁄4 in. (32 mm) diameter will be repaired as per Section 7.2. Defects larger than 11⁄4 in. (32 mm) but smaller than 6 in. (152 mm) diameter, and frequency of less than 5 per any unit surface area of 10 ft (3 m) length or width will be repaired as per Section 7.3. Larger defects will be repaired as per Section 7.4. 6.5 Inspection for Cure of Resin If specified in the Contract Documents, relative cure of resin in FRP systems will be examined by visual inspection, or labo- ratory testing of witness panels or resin-cup samples using ASTM D3418. Follow recommendations of the resin manu- facturer for acceptance criteria. If cure of resin is found un- acceptable, the entire area will be marked and repaired as per Section 7.4. A-22 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary

C6.6 Inspection for Adhesion The sampling frequency depends on the size and complex- ity of the project. It is recommended that test locations be on flat surfaces and representative of the variations in the FRP system and the concrete substrate. If possible, test areas need to be selected, where lower stresses are expected during service conditions. Other adhesion tests such as surface adherence shear test or torque test may be used, if specified in the Con- tract Documents or approved by the Engineer. It is recom- mended that an initial pull-off test be conducted on 1 ft2 (0.1 m2) sample coverage of FRP system on the concrete sub- strate before the installation proceeds. This will ensure that the FRP system will work effectively. C6.7 Inspection for Cured Thickness The sampling frequency depends on the size and complex- ity of the project. Instead of taking additional cores, the same samples from the adhesion tests may be used for measurement of the cured thickness. If possible, core samples should not be taken from high-stress or lap splice areas. C6.8 Load Tests The Owner may anticipate in the Contract Documents a load rating of the structure upon completion of the project. C6.9 Auxiliary Tests The Owner may anticipate in the Contract Documents addi- tional tests for durability and accelerated aging of the FRP sys- tem with its protective coating against moisture, chemicals and UV radiation. Other auxiliary tests may include inter-laminar shear strength of FRP systems following ASTM D3165 or D3528. 6.6 Inspection for Adhesion After at least 24 hours for the initial cure of the resin and before applying the protective coating, direct pull-off test will be performed following ASTM D4541 to verify tensile bond between FRP system and concrete. Test locations and sampling frequency are as specified on the Contract Docu- ments, or recommended by the Contractor and approved by the Engineer. At a minimum, three pull-off tests with at least one test per span or one test per 1000 ft2 (93 m2) of the FRP sys- tem, and one test per substrate concrete type will be performed. Inspect failure surface of the core specimen to ensure that it is by cohesive failure within concrete. Failure at the bond line at tensile stresses below 200 psi (1.4 MPa) is unacceptable. If one or more of the pull-off tests is found unacceptable the work will be rejected, and repair will follow Section 7.4. Repair cored areas as per Section 7.3. 6.7 Inspection for Cured Thickness If specified in the Contract Documents, or required by the Engineer, 1⁄2 in. (12.7 mm) diameter core samples will be taken to inspect the cured laminate thickness and number of plies. Sampling frequency will be the same as that specified in Sec- tion 6.6, unless otherwise specified in the Contract Documents. Repair cored areas as per Section 7.3. The FRP system will be not acceptable, if the number of plies is less than that specified in the Contract Documents, or if the cured thickness of the FRP system is less than that specified in the Contract Documents by more than 1⁄32 in. (0.8 mm). The entire area of FRP system marked unacceptable will be repaired as per Section 7.4. 6.8 Load Tests If specified in the Contract Documents, an in-situ conven- tional load testing will be conducted on the retrofitted structure. 6.9 Auxiliary Tests If specified in the Contract Documents, auxiliary tests on witness panels will be carried out. The most common is the tensile test following ASTM D3039 on at least 5 witness pan- els for each type of FRP system to measure strength, elastic modulus, and ultimate strain. The measured thickness of the FRP laminate will also be recorded. The FRP system will be not acceptable, if the average tensile strength or the lowest ten- sile strength are more than 5% and 10% below that specified in the Contract Documents, respectively. Recommended Construction Specifications A-23 Specifications Commentary

C7 Repair of Defective Work Defects in FRP systems [Kaiser and Karbhari 2001a&b] may include (1) voids and air encapsulation between concrete and layers of primer, resin or adhesive, and within the FRP system itself; (2) delaminations between layers of FRP system; (3) bro- ken or damaged edges of the FRP system; (4) wrinkling and buckling of fiber and fiber tows; (5) discontinuities due to frac- ture of fibers, breakage in the fabric, or cracks in pre-cured shells; (6) cracks, blisters and peeling of the protective coating; (7) resin-starved areas or areas with non-uniform impregnation or wet-out; (8) under-cured or incompletely cured resin; and (9) incorrect fiber orientation. C7.1 Repair of Protective Coating Although primarily aesthetic in nature over the short-term, defects in protective coating may cause long-term degradation of the FRP system due to concentrated moisture ingress. Local defects in coatings are analogous to cracks or blistering in epoxy coating of steel bars. Surface cracks may develop due to a variety of reasons. They are often non-structural, and may be due to excessive coating thickness, excessive shrinkage during cure, or external abrasion. Sandblasting and rotary water pres- sure should not be used to remove the coating as they leave small pits and craters that cause damage to the FRP system. Blisters are caused when moisture passes through the outer- most layer and then causes the development of osmotic pres- sure from within. Blister is often a sign of moisture entrap- ment, and hence all moisture needs to be removed prior to applying another coat to ensure that further damage is not caused after re-coating. Large localized blisters are often a result of solvent softening of the coating. Spot repairs should be conducted with a two-part epoxy only. Signs of excessive peeling indicate that the original coating was applied incor- rectly most often due to inappropriate surface preparation of the FRP system. Applying a new coating directly on top of the old peeling or any defective coating encapsulates the defects and accelerates internal degradation, which in turn cause rapid deterioration of the new coating itself. C7.2 Epoxy Injection of Small Defects Defects at edges or regions of discontinuity, no matter how small, can serve as stress risers that lead to rapid delaminations and growth of other types of defects. Care should be taken to ensure that the internal pressure caused between FRP layers due to injection does not cause further delaminations. Large disbonds close to the edge should not be injected but should be cut open and patched. 7 Repair of Defective Work This section specifies the conditions and types of defects that require repair, and the acceptable methods of repair. Defects are of different types, and may be generally classified as aesthetic, short-term critical, or long-term critical. Repair procedure depends on the type, size and extent of defects. Repair proce- dures for any condition not addressed in this Specifications or in the Contract Documents shall be submitted by the Contrac- tor and approved by the Engineer prior to proceeding with the work. 7.1 Repair of Protective Coating Defects in protective coating can be of three types: small hair- line cracks, blistering, and peeling. In all cases, moisture content of the substrate should be below 0.05% before applying a new coating. Prior to any repair of protective coating, the FRP sys- tem shall be examined visually or otherwise to ensure that no defect exists within or on the surface of the FRP. Defects in FRP, if found, shall be repaired as per Sections 7.2–7.5. If protective coating appears to show small areas with cracks, the local sur- face shall be lightly sanded. Then, a new coating with appropri- ate primer shall be applied based on the manufacturer’s recom- mendations. At the minimum, the coating shall be applied over an area extending 1 in. (25 mm) on either side of the defect. If the protective coating shows signs of blistering, the entire area of blisters as well as the surrounding area to a distance of at least 12 in. (305 mm) shall be carefully scraped clean. In no case, should a blistered surface be re-coated without complete removal of the existing coating. The area shall be wiped clean and then dried thoroughly. Once dry, the area can be re-coated after application of the primer coat, if required by the manu- facturer. If the surface shows signs of excessive peeling, the entire coating shall be scraped off, and the surface lightly sanded, wiped cleaned and thoroughly dried, before applying a new coat according to the manufacturer’s recommendations. 7.2 Epoxy Injection of Small Defects Small entrapped voids or surface discontinuities no larger than 1⁄4 in. (6.4 mm) diameter shall not be considered defects, and require no corrective action, unless occurred next to edges or when there are more than 5 such defects in an area of 10ft2 (0.9 m2). Small defects of size between 1⁄4 and 11⁄4 in. (6.4 and 32 mm) diameter shall be repaired using low pressure epoxy injection, as long as the defect is local and does not extend A-24 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary

C7.3 Patching of Minor Defects Minor defects to the FRP system may include cracking, abra- sion, blemishes, chips, and cuts. The FRP patches should have the same characteristics (e.g., thickness, fiber orientation, ply stacking, resin type, etc.) as the original laminate over damaged area of which it will be bonded. Extending the FRP patch on all sides of the removed area helps with the load transfer. Recent study by Delaney and Karbhari (2006) recommends epoxy injection of minor disbonds for durability purposes. C7.4 Replacement of Large Defects Large defects are generally indications of significant debond- ing between layers, lack of adhesion to the concrete substrate, or extended moisture entrapment causing resin degradation. They may include peeling and debonding of large areas, and non-local defects that may require full replacement. Large defects should be carefully examined, since they may be symp- tomatic of either significant short-term degradation or poor quality of materials or installation. If the extent of the defect is large and in areas of critical to the structural integrity, it may be advisable to completely remove and re-apply the entire FRP system. C8 Measurement and Payment C8.1 Method of Measurement For small projects, the substrate repair may be considered incidental to the FRP system. Often, upon removal of concrete, additional deteriorated areas may be delineated that warrants further undercutting and treating of the substrate or the rein- forcement. The Owner may require the Contractor to obtain approval from the Engineer before extending the limits of con- crete removal from those clearly identified in the Contract Doc- uments. Crack injections may also be measured as number of locations, crew days, or lump sum. through the complete thickness of the laminate in case of multi- ply FRP systems. If any delamination growth is suspected between the FRP plies due to injection, the procedure shall be halted, and repair shall follow Section 7.3. 7.3 Patching of Minor Defects Minor defects are those with diameter between 11⁄4 and 6 in. (32 and 152 mm), and frequency of less than 5 per any unit sur- face area of 10 ft (3 m) length or width. The area surrounding the defects to an extent of at least 1 in. (25 mm) on all sides shall be carefully removed. The area shall be wiped cleaned and thoroughly dried. The area shall then be patched by adding an FRP patch of the same type of the original laminate and extending at least 1 in. (25 mm) on all sides of the removed area. Repair can also be conducted using the procedure in Sec- tion 7.4. 7.4 Replacement of Large Defects Defects large than 6 in. (152 mm) diameter shall be care- fully marked and scarfed out extending to a minimum of 1 in. (25 mm) on all sides. Scarfing shall be progressive through the layers, in the case of multi-ply FRP systems until past the defec- tive area. In case the defect extends to the first FRP ply adjacent to the concrete, the entire thickness of FRP and primer shall be removed. The substrate shall be appropriately prepared and primer re-applied after ensuring that the surface and FRP are clean and dry. Application of a new FRP system within the scarfed area shall follow procedures for the original FRP system, except that an additional layer extending a minimum of 6 in. (152 mm) on all sides of the scarfed area shall be added as a patch. Once cured, the protective coating shall be applied over the entire area. 8 Measurement and Payment 8.1 Method of Measurement Measurement shall be taken as follows: • Substrate repair, including removal of unsound concrete, sandblasting, cleaning of reinforcement and concrete, fur- nishing and placing new concrete, surface preparations, and all other incidentals by lump sum; • Crack repair by epoxy injection by the linear meter (linear foot) of the injected cracks; • Furnishing and placing corrosion inhibitors by the square meter (square foot) of concrete surface; Recommended Construction Specifications A-25 Specifications Commentary

• Furnishing and placing wet lay-up FRP system by the square meter (square foot) of each layer applied; • Furnishing and placing pre-cured FRP system by the square meter (square foot) of each layer applied, accounting for different layer thicknesses; • Furnishing and placing near-surface mounted FRP system by the linear meter (linear foot) of each bar or strip; and • Furnishing and placing protective coating for the FRP system by the square meter (square foot) of each layer of coating applied. 8.2 Basis of Payment Payments shall be made as follows: • “Substrate Repair” as lump sum; • “Crack Injection” per linear meter (linear foot); • “Furnishing and Placing Corrosion Inhibitors” per square meter (square foot); • “Furnishing and Placing Wet Lay-up FRP System” per square meter (square foot); • “Furnishing and Placing Pre-Cured FRP System” per square meter (square foot); • “Furnishing and Placing Near-Surface Mounted FRP System” per linear meter (linear foot); and • “Furnishing and Placing Protective Coating” per square meter (square foot). 9 Cited References ASM (2001). ASM Handbook Volume 21: Composites. ASM Inter- national, Materials Park, OH. Belarbi, A., Myers, J. J., and Puliyadi, S. (2002). “Evaluation of Lap Splice Length Requirement of CFRP Sheets in RC Beams under Fatigue Loads.” Proceedings of the 2nd International Conference on Durability of FRP Composites for Construction, B. Benmokrane and E. El-Salakawy (Eds.), Montreal, Canada, pp. 701–711. CEB-FIP. (2001). Externally Bonded FRP Reinforcement for RC Struc- tures. Technical Report Bulletin 14, Geneva, Switzerland. CERF. (2001). HITEC Evaluation Plan for FRP Composite Systems for Concrete Structure Repair and Strengthening. Civil Engineering Research Foundation, ASCE, Washington, D.C. Delaney, J. C., and Karbhari V. M. (2006). “The Assessment of Aspects Related to Defect Criticality in CFRP Strengthened Concrete Flexural Members.” Report No. SSRP 06/11, Department of Structural Engi- neering, University of California—San Diego, La Jolla, CA. Harichandran, R. S., and Baiyasi, M. I. (2000). “Repair of Corrosion- Damaged Columns Using FRP Wraps.” Final Report, Michigan Department of Transportation, Lansing, MI. Hughes, D., Kazemi, M., Marler, K., Zoughi, R., Myers, J. J., and Nanni, A. (2001). “Microwave Detection of Delaminations Between Fiber Reinforced Polymer (FRP) Composite and Hardened Cement Paste.” A-26 Recommended Specifications and Manual for Concrete Repair Using FRP Composites Specifications Commentary C8.2 Basis of Payment For small projects, the substrate repair may be considered incidental to the pay item of the FRP system. The Owner may also place limits on the Substrate Repair pay item by requiring the Contractor to receive approval from the Engineer on the limits of the removal area. Proceedings of the 28th Annual Review of Progress in Quantitative Non- destructive Evaluation, D. O. Thomson and D. E. Chimenti (Eds.), Brunswick, ME, Vol. 21, pp. 512–519. Kaiser, H., and Karbhari, V. M. (2001a). “Quality and Monitoring of Structural Rehabilitation Measures. Part 1: Description of Potential Defects.” Final Report, Contract 18347, Oregon Department of Transportation. Kaiser, H., and Karbhari, V. M. (2001b). “Quality and Monitoring of Structural Rehabilitation Measures. Part 2: Assessment of Potential Non-Destructive Evaluation (NDE) Methods.” Final Report, Con- tract 18347, Oregon Department of Transportation. Littles, J. W., Jacobs, L. and Zureick, A. (1996). “Ultrasonic Characteriza- tion of FRP Composites for Bridge Applications.” Proceedings of the 11th Engineering Mechanics Conference, ASCE, Fort Lauderdale, FL, Vol. 2, pp. 959–962. Mandic, D. G., Martin, R. E., and Hermann, J. H. (1998). “Thermal Imag- ing Technique to Detect Delaminations in CFRP Plated Concrete.” Proceedings of the Nondestructive Evaluation of Materials and Com- posites, International Society for Optical Engineering, San Antonio, TX. Vol. 3396, pp. 22–27. Mirmiran, A., Shahawy, M., Nanni, A., Karbhari, V., Yalim, B., Kalayci, A. S. (2007). “Construction Specifications for Bonded Repair and Retrofit of Concrete Structures Using FRP Composites.” NCHRP

Yang, X., and Nanni, A. (2002). “Lap Splice Length and Fatigue Perfor- mance of FRP Laminates.” Materials Journal, ACI, Vol. 99, No. 4, pp. 386–392. Yang, X., Nanni, A., and Chen, G. (2001a). “Effect of Corner Radius on Per- formance of Externally bonded FRP Reinforcement.” Proceedings of the 5th Conference on Non-Metallic Reinforcement for Concrete Struc- tures, Cambridge, pp. 197–204. Yang, X., Nanni, A., Haug, S., and Sun, C. L. (2002). “Strength and Mod- ulus Degradation of CFRP Laminates from Fiber Misalignment.” Jour- nal of Materials in Civil Engineering, ASCE, Vol. 14, No. 4, pp. 320–326. Yang, X., Wei, J., Nanni, A., and Dharani, L. R. (2001b). “Stresses in FRP Laminates Wrapped around Corners.” Proceedings of the 16th Annual Conference, ASC, M. W. Hyer and A. C. Loos (Eds.), Blacksburg, VA, Paper 088, CD-ROM. Recommended Construction Specifications A-27 Project 10-59 Phase II Draft Final Report, Transportation Research Board, Washington, DC. Reynaud, D., Karbhari, V. M., and Seible, F. (1999). “The HITEC Eval- uation Program for Composite Column Wrap Systems for Seismic Retrofit.” Proceedings of the International Composites Exposition, Nashville, TN, pp. 4A/1–6. Shen, X., Myers, J. J., Maerz, N., and Galecki, G. (2002). “Effect of Surface Roughness on the Bond Performance Between FRP Laminates and Concrete.” Proceedings of the 2nd International Conference on Durability of FRP Composites for Construction, B. Benmokrane and E. El-Salakawy (Eds.), Montreal, Canada, pp. 607–616. Sohanghpurwala, A., and Scannell, W. T. (1994). “Repair and Protection of Concrete exposed to Sea Water.” Concrete Repair Bulletin, Vol. 7, No. 4, pp. 8–13.