SECTION CONCRETE REPAIR AND PATCHING

Transcription

1 SECTION CONCRETE REPAIR AND PATCHING PART 1 - GENERAL 1.1 RELATED DOCUMENTS A. Drawings and general provisions of the Contract, including General Conditions, General Specifications, and Division 1 Specification Sections, apply to this Section. 1.2 SUMMARY A. This Section specifies cement-based, pre-packaged structural repair mortars for repairing horizontal surfaces of concrete floor slabs. B. Patching material shall be applied by forming and pouring, or hand troweling, as specified and as recommended by the manufacturer for the specific application. C. Provide the necessary labor, materials, equipment and supervision for the removal of unsound and sound concrete, the sand/water blast-cleaning of newly exposed underlying sound concrete and steel, and coating of concrete and exposed steel. D. Concrete removal, sand blast-cleaning and air blast-cleaning shall achieve a sound, clean, porous surface similar to that of freshly-fractured, high-quality portland cement concrete, free of unsound concrete, asphalt concrete, existing membrane and contaminants. 1.3 REFERENCES A. International Concrete Repair Institute (ICRI): 1. ICRI No R 2008 Guide for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing Steel Corrosion. 2. ICRI No R 1996 Guide for Selecting Application Methods for the Repair of Concrete Surfaces. B. American Society of Testing Materials (ASTM): 1. ASTM C109 / C109M - 08 Standard Test Method for Compressive Strength of Hydraulic Cement Mortars. 2. ASTM A185 / A185M - 07 Standard Specification for Steel Welded Wire Reinforcement, Plain, for Concrete. 3. ASTM C Standard Test Method for Flexural Strength of Hydraulic-Cement Mortars. Contract V CONCRETE REPAIR AND PATCHING

2 4. ASTM C469-02e1 Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression. 5. ASTM C Standard Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement. 6. ASTM A615 / A615M - 09b Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement. 7. ASTM C666 / C666M - 03(2008) Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing. 8. ASTM C Standard Test Method for Restrained Expansion of Expansive Cement Mortar. 9. ASTM C882 / C882M - 05e1 Standard Test Method for Bond Strength of Epoxy- Resin Systems Used With Concrete By Slant Shear. 10. ASTM C Standard Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate Solution. 1.4 MEASUREMENT A. Where necessary, concrete repair quantities will be measured as follows: For area-based repairs actual area of work done at any location shall be measured in place in square feet. Where required to be measured, repair depth shall be the average depth of four readings in each area taken at a distance equal to 1/5 of the patch from the edge at approximately four corners of the patch, or along the major and minor axis of the patch, or the quantity shall be determined by other means as approved by the District. 1.5 SUBMITTALS A. Submit for approval complete manufacturer s literature for the patching material, anti-corrosion coating and bonding agent including product description, composition, material and performance properties, installation and application procedures, use limitations and recommendations. B. Submit for approval plan for confining, collecting and disposing of broken concrete and other waste materials as a result of removal operations. PART 2 - PRODUCTS 2.1 MATERIALS A. Use concrete products from a single manufacturer for concrete repair system including repair mortar, anti-corrosion coating and bonding agent, curing compound, etc. CONCRETE REPAIR AND PATCHING Contract V

3 Contractor shall be responsible for ascertaining compatibility of products with the manufacturer and following manufacturer s instructions. B. Repair Mortar A (For hand-troweling): Provide a repair mortar blend of Portland cement, silica fume, specially graded aggregates, and set-control admixtures including shrinkage compensating additives. Repair mortar for horizontal repair shall be SikaTop 122 Plus by Sika Corporation, or an approved equal that when cured produces the following properties: 1. Compressive Strength: Minimum, 1-day 3,000 psi, 28-day 7,000 psi. 2. Flexural Strength: Minimum, 1-day 650 psi; 28-day 1,300 psi. 3. Shear Bond Strength: Minimum, 1-day 400 psi; 28-day 2,200 psi. 4. Permeability: 500 Coulombs Maximum. 5. Drying Shrinkage: Maximum 0.09% shrinkage at 28 days. 6. Freeze-Thaw Resistance (300 cycles): Minimum RDF 85%. 7. Sulfate Resistance (15 weeks): 0.09% expansion (maximum difference between control bars in water and test bars). 8. Modulus of Elasticity: 4,000 ksi minimum C. Repair Mortar B (For forming and pouring): Provide a repair mortar that is a two-component, polymer-modified, cementitious, fast-setting, screed mortar. Repair mortar shall be SikaTop 111 Plus by Sika Corporation, or an approved equal. For patch thickness over 1 inch, repair mortar shall be extended using 3/8 non-reactive coarse aggregate other than limestone. The aggregate type and quantity per unit volume of repair mortar shall be as recommended by the repair mortar manufacturer. When cured the mortar produces the properties as for Repair Mortar A, except as noted below: 1. Compressive Strength: Minimum, 1-day 2,500 psi, 28-day 7,000 psi. 2. Slant Shear Bond Strength: Minimum, 1-day 700 psi; 28-day 2,500 psi. D. Repair Mortar C (For hand-troweling and/or form and pour): Epoxy based structural repair grout/mortar is pre-packed in a multi-wall bags. The grout consist of epoxy (components A and B) and specially graded aggregate (component C) including shrinkage compensating additives. Repair grout for window curb repair shall be Sikadur 42, Grout-Pak by Sika Corporation, or an approved equal that when cured produces the following properties: 1. Compressive Strength: Minimum, 1-day 12,000 psi, 28-day 15,000 psi. 2. Flexural Strength: Minimum, 7-day 4,000 psi. Contract V CONCRETE REPAIR AND PATCHING

4 3. Shear Bond Strength (to concrete): Minimum, 7-day 4,200 psi. 4. Tensile Strength: Minimum 7-day 2,300 psi. 5. Modulus of Elasticity: 1.3x10 6 psi. 6. Effective Bearing Area: >95%. E. Welded Wire Mesh: ASTM A 185, 4x4-W1.4xW1.4, where required unless noted otherwise. F. Reinforcing steel: conform to ASTM A615, Grade 60 G. Anti-corrosion coating for exposed and new reinforcing bars: Zincrich (MasterProtect P 8100AP) manufactured by BASF Corporation, or an approved equal. Product utilized shall be compatible with the repair mortar that will be used. H. Bonding agent for concrete: Do not use bonding agent. I. Water: Potable. J. Curing Compounds: See provisions of Article 19 of General Specifications Concrete. 2.2 EQUIPMENT A. Hand-held pneumatic chipping hammers of nominal 25-pound class or less, unless noted otherwise, for removal of concrete beneath reinforcing bars. B. Sandblasting equipment capable of removing rust from the exposed reinforcement and contaminants and laitance from newly exposed concrete surface. C. Compressed air equipment capable of removal of dust and dirt from exposed concrete and steel surfaces. D. Water blasting equipment capable of cleaning the reinforcement and roughened concrete, without exceeding specified water pressure. E. All equipment and cleaning material used shall be such that neither the reinforcing steel nor the concrete substrate will become contaminated with oil. PART 3 EXECUTION 3.1 PROJECT CONDITIONS A. Weather Conditions: Apply repair mortar only when ambient and surface temperatures are 50 F (10 C) and rising. Do not make the repair if the ambient temperature is CONCRETE REPAIR AND PATCHING Contract V

5 expected to fall below 40 F (5 C) within 24 hours after placement. Do not apply repair mortar when surface temperatures are 100 F (38 C) and above. B. Follow manufacturer s recommendations regarding additional installation information. 3.2 CONCRETE REMOVAL A. Prior to any concrete removal work, the Contractor shall perform the following operations: 1. Scan the area at concrete removal and around to identify existing metallic embedments including concrete reinforcement. 2. Remove or temporarily support all utilities as necessary and after obtaining approval of the Engineer. All utilities shall be reattached at the completion of the work. 3. Protect all utilities and equipment from damage and overspray or runoff of repair materials, removed debris and construction debris. 4. Install temporary lighting as necessary. 5. Install shoring where shown on the Drawings, where required to support the structure, or where designated by the District s representative. B. Identify and mark areas of concrete requiring repair, including spalled, delaminated and unsound concrete areas identified by visual inspection, sounding and other suitable means. The geometry of the marked repair areas shall be of simple rectangular pattern. The areas marked for repair are subject to approval of the engineer before any concrete removal work begins. C. Where possible, areas of concrete removal shall be rectangular in shape. Saw-cut perimeter of the area to be repaired to a depth of 1 without nicking or cutting existing steel reinforcement. Feather edging shall not be permitted. Do not saw through reinforcement or embedments. D. Remove a minimum of 1 1/2 of existing concrete facing and continue removal of additional unsound and delaminated concrete as required to expose sound concrete. Substrate should have a minimum amplitude of 1/4. E. When directed by the District s Resident Engineer, Contractor shall remove additional depth of sound concrete at the repair areas to provide a patch depth up to that indicated in the work item or up to a 3 patch depth at no additional cost to the District. F. During the chipping process, care shall be exercised to avoid cracking the underlying sound concrete. Do not damage deck embedments, such as floor drains. G. Where part of reinforcing bars are exposed, the District s representative will determine if the embedded portion of the bar is soundly bonded to the remaining concrete. If, in the judgment of the District s representative, the bar is not soundly bonded, or if half or Contract V CONCRETE REPAIR AND PATCHING

6 more of the diameter of the reinforcing steel is exposed, the Contractor shall remove concrete around and behind the bar for a length as determined by the District s representative. H. All fully exposed reinforcing bars shall be no closer than 1, measured radially, from existing concrete before the placement of fresh concrete. I. The newly exposed sound concrete shall be roughened by sandblasting and cleaned by vacuuming, or blowing away loose material with a compressed air jet, or water blasting with or without abrasives may be permitted as an alternative to sandblasting, at no additional expense to the District, subject to the procedure being approved by the District. Contractor shall be responsible for determining suitable water-blasting pressures and any damage resulting to the structure. J. The Contractor shall determine that all unsound concrete has been removed by sounding the final prepared surfaces prior to the inspection by the District s representative. K. The District s representative shall be allowed a minimum of 24 hours for the inspection of properly prepared concrete surfaces and reinforcement before the scheduled concrete placement. The Contractor shall inspect all prepared concrete surfaces and reinforcement, and complete surface preparation work prior to the inspection by the District s representative. L. The Contractor shall not exceed the rated capacity of any structure when storing debris from concrete removal, equipment or other materials. M. The concrete and rebar surfaces for repair shall be prepared in accordance with the International Concrete Repair Institute Guideline Number whenever the procedures of the guidelines are more stringent than the specifications herein. 3.3 REINFORCEMENT CLEANING AND/OR REPLACEMENT A. Exposed steel bars, embedments, etc. shall be thoroughly cleaned by sandblasting to remove all rust, contaminants and attached concrete pieces. Water blasting with or without abrasives may be permitted as an alternative to sandblasting, at no additional expense to the District, subject to the procedure being approved by the District. Contractor shall be responsible for determining suitable water-blasting pressures and any damage resulting to the structure. B. Bars that are damaged, dislocated, fractured or that have lost more than 15 percent of their original area at any point along the length shall be brought to the attention of the District s representative. Remedial action will be at the direction of the District s representative. C. If during the removal of unsound concrete, the Contractor encounters existing reinforcing with less than 1/2 of cover from the member surface, he shall notify the District s representative. CONCRETE REPAIR AND PATCHING Contract V

7 D. Splice existing reinforcement bars where corrosion has depleted the cross-section area by more than 15 percent, unless otherwise directed by the engineer. The lap length shall conform to the typical details for repair of spalled concrete on the contract plans, and/or as directed by the Engineer. E. If additional concrete removal is required for providing proper lap length, additional concrete removal shall extend for a length as required, and a width of 3 on each side (total 6 width) of the reinforcement bar to be spliced. Newly exposed concrete and reinforcement surfaces from additional removal, shall also be thoroughly cleaned by sand/water blasting, as approved. F. Reinforcement shall be secured in position so as to be unaffected by concreting operations. 3.4 ANTI-CORROSION COATING AND BONDING AGENT A. Thoroughly clean the roughened surface and exposed reinforcement of rust, dirt, loose chips, and dust using high-pressure water jet at a pressure not exceeding 3,000 psi. Contractor shall test for a suitable water pressure to use, on a small test area. If pressure utilized erodes and damages concrete surface to be patched, contractor shall further reduce water pressure, as approved by the resident engineer. B. Maintain substrate in a saturated, surface dry condition. Concrete shall not be placed on any surface with standing water. Prior to patching, coat exposed reinforcing steel with anti-corrosion coating and surrounding exposed concrete with bonding agent, with the following exception. For formed repairs, if the open time, between coating the steel/concrete and placing the patching material, is expected to exceed the time recommended by the manufacturer, or if the patching material cannot be placed on the same day the steel/concrete coating is applied, the concrete and reinforcing steel shall not be coated unless otherwise directed by the Engineer. Follow manufacturer s recommendations for use as stated in the manufacturer s current printed literature. 3.5 SURFACE PREPARATION A. Build forms for vertical repair surfaces, where required. B. In the tunnels and at high temperature areas prepare the area per these steps: 1. Remove existing spalled concrete as per the details of the contract documents. 2. Repair/Replace reinforcements as per the contract documents. 3. Install and remove concrete formwork for area to be repaired. (test fit) 4. Sandblast all exposed rebar the day before pouring the mortar. Contract V CONCRETE REPAIR AND PATCHING

8 5. Provide potable water spray system the day before pouring the mortar to continuously spray repair area overnight, to cool the substrate as much as possible. 6. Remove water spray from patch area and begin spraying formwork pieces that may not have been precooled on the day of the mortar pour. 7. Apply bonding agent to existing concrete and rebar as per manufacturers recommendations on the day of the mortar pour. 8. Apply release agent to the formwork and then reinstall formwork. 9. Pour mortar into patch area formwork. 10. Provide potable water spray system to continuously spray repair area formwork for at least seven days. All unformed surfaces will be covered with burlap prior to spray being applied. C. Four days after the spray system is removed, the formwork may be removed. 3.6 USE OF WELDED-WIRE REINFORCEMENT / MESH A. When applying product in repairs greater than 3 lineal feet in the longest direction at depths of 1.5 or greater - and for overhead applications of the same size - a 4 x 4 low gauge mesh (10-12 gauge) or engineer approved equal must be firmly tied to the properly prepared substrate. B. Locate the mesh no closer than 1/2 and no more than 1 from the finished surface, using spacers and concrete anchors. A minimum cover of mortar over the mesh should be 1/2. C. Mesh is not necessary in applications where side restraint exists, or where existing reinforcement will provide adequate restraint. 3.7 MIXING A. Comply with mortar manufacturer s recommendations for water quantity and mixing procedures. 3.8 APPLICATION A. Maintain substrate in a saturated, surface-dry condition. B. For hand applications, a bond scrub coat may be required, if recommended by the mortar manufacturer. C. For hand troweling apply repair mortar as follows: 1. Vertical Applications: Repair mortar may be applied on vertical applications up to a 2 depth in one lift. CONCRETE REPAIR AND PATCHING Contract V

9 2. Overhead Applications: Do not exceed 1 thickness per pass. 3. Multiple Passes: Place succeeding lifts after repair mortar has developed initial set. Scarify the surface of the first lift to ensure integral bond between successive layers. 4. Follow manufacturer s recommendations for application of the repair mortar. D. Follow repair mortar manufacturer s recommendations on repair thickness limits. Obtain specific recommendations for actual thickness of intended repair. 3.9 FINISHING (for unformed surfaces) A. Finished concrete surface shall be even and flush with adjacent concrete surfaces. All corners and edges shall match the existing concrete in the area. B. Level surface of repair mortar using a float or screed. C. Apply final finish when mortar has begun to stiffen using a wooden, plastic, or synthetic sponge float or trowel. D. Spray-apply evaporation reducer, Sikafilm by Sika Corporation or approved equal, lightly to reduce surface moisture evaporation, especially in windy, hot conditions. Follow manufacturer s printed instructions CURING A. Protect fresh mortar from premature evaporation. Cure finished repair mortar by one of the following methods: 1. Preferred Method: Keep area continuously moist with water as soon as mortar surface has hardened (thumb print hard), for a minimum of seven days. 2. Acceptable Method: Apply two coats of curing compound. Apply the first coat immediately after completing finishing operations. Apply the second coat about 24 hours later. 3. Curing compound shall not be used where additional layers of patching material are to be placed, or where protective coatings are to be installed QUALITY CONTROL TESTING A. Testing agency: the District may engage a qualified, independent, testing and inspection agency to sample materials, perform laboratory and field testing, and submit test reports. B. The Contractor shall assist the District or its testing lab in taking concrete test samples for slump, air entrainment, and 1, 7 and 28-day compressive strength tests. C. Contractor shall patch all test areas suitably with repair mortar. Contract V CONCRETE REPAIR AND PATCHING

10 D. All unsatisfactory repair work not conforming to specified requirements shall be replaced as directed by the Engineer at Contractor s expense, and at no additional cost to the District. Contractor shall also pay for any related re-testing costs associated with the replacement CLEAN-UP A. The Contractor shall remove all debris from the site as soon as possible and leave the area broom clean. B. Debris shall not be flushed down the existing drains. END OF SECTION CONCRETE REPAIR AND PATCHING Contract V