SPECIAL SPECIFICATION 4897 Repair Structural Concrete

Transcription

1 1993 Specifications CSJ SPECIAL SPECIFICATION 4897 Repair Structural Concrete 1. Description. This Item shall govern for the repair of delaminated, spalled and chipped areas of concrete foundations, portions of concrete bent columns and concrete tie beams at locations indicated on the plans or as directed by the Engineer. This item shall also govern repairing, sealing and bonding of cracks in concrete structures by pressure injection of epoxy adhesive into such cracks in accordance with the details shown on the plans and this specification. 2. Materials. All materials shall conform to the pertinent requirements of the following items: Item 440, Reinforcing Steel Item 575, Epoxy Item 421, Portland Cement Concrete Epoxy mortar or epoxy based bonding agents shall not be used when performing patch type repairs. The materials used for sealing the surface of cracks to be injected shall be an epoxy adhesive capable of bonding to wet or dry surfaces. The epoxy adhesive shall be gray in color. It shall have adequate strength and adhesion to confine the injection material in the cracks being injected until the injection material has cured. Where exceptionally wide cracks are encountered, the epoxy should be extended with an approved filler. All materials used shall be free of soluble chlorides or other ingredients capable of causing corrosion to steel reinforcement. The epoxy used for injection shall be a two component epoxy conforming to all requirements shown herein and in departmental material specification DMS6100. The viscosity of the epoxy shall be adjusted as necessary to obtain penetration and retention in the cracks. Where there is considerable variation in crack widths, it may be necessary to use more than one epoxy formulation. The epoxy shall contain no solvents and no solvents shall be added at any time. The mixing ratio of the components in terms of volume and weight shall be clearly stated. Specific requirements for the injection epoxy are shown in the departmental material specification DMS6100. Unless otherwise indicated, the test procedure used shall be as set forth in Epoxy Adhesive of the department DMS6100specifications. The pot life at 77 F, shall be a maximum of 30 minutes. Mortar specimens for wet strength test shall be soaked in tap water at 70 F to 80 F for 24 hours, then removed and free water wiped from the surface prior to bonding

2 A polymer-latex modified, mortar/concrete patching material containing microsilica shall be used for repairs. The selected material shall achieve a minimum compressive strength of 4,500 psi in seven days and 5,500 in 28 days. Proposed material and method of application including manufacturer s technical specifications and formulation of applicable, shall be submitted for approval by the Engineer prior to commencing work. Aggregates shall meet all requirements of Item Construction Methods. Epoxy crack injection (Ty IX) shall be used for sealing and bonding cracks. Cracks 1/16 inch wide or less shall be repaired by epoxy injection as directed by the Engineer. For cracks wider than 1/16 inch or for interconnected cracks networks, the full depth patch repair method should be used. Cracks narrower than 1/32 inch will not require repair work unless directed by the Engineer The Contractor shall provide a detailed work plan to the Engineer for the proposed repair work subject to the Engineer s approval, prior to beginning of any repair work. The Contractor shall work with the Engineer to identify and locate repair structural concrete (Item ) and repair structural concrete-seal cracks (Item ) locations that are to be designated and approved for repair. The Contractor shall provide the Engineer safe work access to the repair sites. All equipment, materials and labor required to provide inspection access to the Engineer will not be paid for directly, but will be considered incidental to the various bid items. The concrete repair areas shall be sounded using a hammer to locate repair area limits, with the exact limits of the repair being approved by the Engineer. (1) Repair Conrete Areas Existing concrete areas designated to be repaired shall be prepared by chipping or other methods to remove all loose or defective concrete. Feather edges shall be eliminated by saw cutting and/or chipping a perpendicular or back-tapered face, approved by the Engineer, along the periphery of the area to be repaired so that the minimum depth of repair is approximately one-half inch. The area being prepared shall be cleaned by sandblasting, or other means approved by the Engineer to remove all loose particles, dirt deteriorated concrete or other substance that would impair the bond between the old concrete and the repair material. Materials removed from the bridge shall become property of the Contractor and shall be removed to disposal sites out of the right of way arranged by the Contractor and approved by the Engineer or otherwise disposed of in a manner satisfactory to the Engineer. Surface preparation shall include the removal of all loose or delaminated concrete and an additional 1 behind the reinforcing within the spalled area. All reinforcing shall be maintained at original position and all exposed steel shall be sandblasted to a near white condition to meet SSPC-SP10 requirements prior to placement of patching material. Severely damaged reinforcing steel as established by the engineer shall be repaired by lap splicing as approved by the Engineer. Bonding agent shall be the term used to designate the bonding bridge material between the new polymer-latex modified Portland cement mortar/concrete with microsilica and the existing hardened Portland cement concrete

3 Apply a bonding compound to entire spall area to be repaired prior to new concrete placement. Bonding compound shall also be applied to all exposed reinforcing steel within the repair area (including back of rebars). Bonding compound shall be a threecomponent epoxy resin/portland cement adhesive. Mixing, application and curing shall be performed as per manufacturer s specifications. Mixed material shall be uniform in appearance. No lumps or irregularities shall be allowed. Application time shall not exceed manufacturer s specified pot life. Removal of forms will be as approved by the Engineer. Care shall be taken to prevent freezing of the mortar or concrete during the curing period. Upon completion of curing, repairs shall be sounded by hammer to locate any defective areas. Any repaired areas found defective shall be removed and repaired at the complete expense of the Contractor. (2) Crack Injection The cracks to be injected shall be designated by the Engineer. Unless otherwise approved by the Engineer, injection will not be permitted unless the concrete temperature is above 50 F and the air temperature is above 50 F and rising. Equipment used in drilling injection port holes shall be equipped with a vacuum attached swivel drill chuck and hollow drill bits capable of removing the dust and debris when drilling. The equipment used will be tested and approved by the Engineer prior to drilling to insure satisfactory operation. There shall be no evidence of any dust or debris remaining in the drilled holes, which will be detrimental to the injection process. Injection ports may be placed in the epoxy or epoxy mortar, used to seal cracks to be epoxy injected. Care shall be used to prevent blockage of the ports when placed. Any injection ports that are blocked will be replaced with another port. The epoxy shall be injected with automatic two component proportioning and mixing equipment. The machine shall be equipped with positive displacement type pumps for each component provided with interlock to insure proper proportioning. The two components shall be mixed by the machine just prior to injection. The machine must be capable of proportioning the materials within ± 5% of the ratio stated by the epoxy supplier. The mixing head must be designed so that an intimate mix of the two components will be obtained. Dwell time in the mixing head shall not exceed ten seconds. The injection pressure shall not exceed the maximum psi as recommended by the epoxy manufacturer. The top surface of cracks designated for injection shall be cleaned free of dust, silt, laitance, oil and grease or any other material that would interfere with the bond of the surface sealer. Entry ports for epoxy shall be provided, spaced far enough apart to assure that when the adhesive material shows at the adjacent port, it has completely filled the crack to its full depth. Entry ports shall be spaced along cracks a maximum of 12 inches on centers and usually determined by the tightness of the crack and the depth of the concrete substrate. Spacing is generally between 4 and 10 inches with the port to be recessed a minimum of 1/2 inch. A small reservoir shall be provided below the bottom of the port to aid in resin flow. Care shall be exercised not to drill beyond a crack which may be running at an angle to the surface. A surface seal or epoxy patch meeting the requirements of these specifications shall first be applied to the exterior

4 crack to prevent the escape of the epoxy. The cracks shall be covered with a bead of patch and smoothed with a putty knife to insure sealing. Injection ports shall be inserted into the drilled holes to a depth of approximately 1/2 inch allowing for the small reservoir below the port. The ports are then bonded into position with the epoxy patch being careful not to seal the ports from resin flow. After allowing adequate curing time for the patch, generally overnight, it is recommended that water be injected through the entire crack area. Injection of the epoxy into a given crack unless otherwise permitted by the Engineer, shall begin first at the entry port of lowest elevation and continue until the epoxy begins to flow out of the adjacent port. Injection pressure shall be kept as low as practical and shall not exceed 30 psi. The connection between entry port and head of the injection gun must be sufficiently tight to prevent epoxy from running out onto the concrete surface. After injection at a given port is complete, this port shall be sealed and injection started at the next adjacent port. This procedure shall be repeated until the crack is completely filled. Where exceptionally wide cracks are encountered, the adhesive shall be modified by addition of an approved filler, provided it can be demonstrated that the modified adhesive will readily penetrate the full depth of the crack without void inclusions and will flow from the entry port adjacent to that in which the modified adhesive is injected. Before beginning injection at hourly intervals during injection work, a small sample of the mixed epoxy shall be taken from the injection gun. Should these samples show any evidence of improper proportioning or mixing, injection work shall be suspended until the equipment or procedures are corrected. The surface of the crack herein treated shall be finished flush with the adjacent concrete surfaces and show no indentations or evidence of port fittings. Sampling and Testing. Samples of the injection epoxy shall be taken by the Engineer and tested by the Department for compliance with specification requirements prior to use. Quality of Work. The overall quality of work will be judged by the Contractor s ability to achieve full penetration of the cracks. Experience of Workmen. This work shall only be performed by contractors who are authorized applicators of the process. The injection application shall be supervised by factory trained technicians who are certified by the epoxy injection resin manufacturer to be proficient in the art of injection repairs. The epoxy injection technicians shall have completed a minimum of two similar jobs. The contractor shall provide evidence of the experience and certifications of the technicians for approval by the Engineer. 4. Measurement. The Repair Structural Concrete item will be measured by the square foot, in place, as measured on the surface of the repair. When a repair involves multiple surfaces, such as a corner, measurement will be made of all surfaces repaired. The Repair Structural Concrete (Seal Cracks) item will be measured by the linear foot of epoxy injection complete in place

5 5. Payment. The work performed and the materials furnished in accordance with this Item and measured as provided under Measurement, will be paid for at the unit price bid for the pertinent concrete repair item. This shall include all transportation, labor, equipment, tools and incidentals necessary to complete the planned work as well as repair any damage to the structure and surroundings caused by this work. (1) Repair Structural Concrete This price shall be full compensation for furnishing and placing all materials, removing and disposal of all loose or defective concrete, sawcutting as required, surface preparation, cleaning reinforcing steel. (2) Repair Structural Concrete (Seal Cracks) This price shall be full compensation for furnishing and placing all materials, cleaning cracks, drilling, our surface preparation epoxy crack injection and finishing of surface