DIVISION 2400 CONCRETE

Transcription

1 DIVISION 2400 CONCRETE SECTION 2405 CAST-IN-PLACE CONCRETE PART 1 - GENERAL 1.01 SCOPE This section covers cast-in-place concrete, including, joints, reinforcing steel, forms, finishing, curing, weather limitations, ready mix plant requirements and other appurtenant work. Additional sections shall be referenced that contain pertinent information relating to different concrete applications, including but not limited to curbs, concrete pavement, storm drainage structures REFERENCES A. KDOT Standard Specification: 1. Section 1501 Hot Joint Sealing Compound 2. Section 1602 Epoxy Coated Steel for Concrete Reinforcement B. Kansas City Metro Materials Board: ( C. ACI: Specifications for Structural Concrete for Buildings Guide for Measuring, Mixing, Transporting, and Placing Concrete Standard Specification for Hot Weather Concreting Standard Specification for Cold Weather Concreting D. ASTM: 1. A185 Standard Specification for Steel Welded Wire Reinforcement, Plain, for Concrete 2. A615 Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement 3. A934 Standard Specification for Epoxy-Coated Prefabricated Steel Reinforcing Bars 4. A996 Standard specifications for Rail-Steel and Axle-Steel Deformed Bars for concrete Reinforcement 5. C94 Standard Specification for Ready-Mixed Concrete 6. C309 Standard Specification for Liquid Membrane Forming Compounds for Curing Concrete 7. D1751 Standard Specification for Preformed Expansion Joint Filler for Concrete Paving and Structural Construction (Nonextruding and Resilient Bituminous Types) 8. D1752 Standard Specification for Preformed Sponge Rubber Cork and Recycled PVC Expansion Joint Fillers for Concrete Paving and Structural Construction Division 2400 Concrete

2 E. Concrete Reinforcing Steel Institute, Manual of Standard Practice: 1. Chapter 3 Bar Supports 1.03 SUBMITTALS All items listed in Part 2 of this section shall be submitted to the Engineer for approval, including cut sheets and certifications prior to use on the project. A. Mix Designs: Concrete mix designs shall be submitted to the Engineer prior to placing any concrete. The mix design shall provide the name of the supplier and the unique number designated by the supplier indicating the mix design is an approved KCMMB mix. The unique name/number on the batch ticket delivered to the jobsite must match the unique name/number assigned or the concrete will be rejected. B. Reinforcement Steel: The Contractor shall submit shop drawings, bar lists, and bending diagrams to the Engineer for approval prior to confirming any order for reinforcement. C. Reinforcement Supports: Representative samples of supporting elements shall be submitted and approved by the Engineer prior to their use in the project. D. Large Placements: For concrete placements in excess of two hundred (200) cubic yards per project, the following is required: 1. A concrete delivery plan shall be prepared and submitted to the City Engineer detailing the location of the concrete plant, required truck routes and distance from the plant to the project site, and the anticipated rate of placement. 2. A representative from the concrete supplier shall be on-site at all times DEFINITIONS A. Expansion Joint: Expansion joints permit volume change movement of the concrete and utilize a pre-formed, or pre-molded elastic/resilient material to allow this movement. The material used shall be the same dimension as the concrete is thick. Refer to the Standard Details for concrete applications that requires the use of expansion joints. B. Contraction Joint: The contraction joint, also often referred to as a control joint or saw-cut joint, is a joint that is formed by the Contractor with the use of a saw, hand tools, or other methods. The joints are placed at increments determined by the Standard Details or Construction Documents to control shrinkage cracking. C. Construction Joint: The construction joint, also often referred to as a cold joint or longitudinal joint, is a joint located between two sections of concrete. The second section of concrete is placed against a section of concrete already in place which has hardened to the extent that consolidation cannot be effected by vibration or re-vibration. PART 2 - PRODUCTS 2.01 MATERIALS A. Concrete: Concrete shall conform to the specifications of the Kansas City Metro Materials Board (KCMMB), including all materials and admixtures used in the production of the concrete. Concrete mixes used for bridge construction shall be as designated by the Engineer. 1. A KCMMB 4k mix shall be used for the construction of concrete pavement, curbs, sidewalks, driveways, recreational trails, storm drainage structures (excluding the cast- Division 2400 Concrete

3 in-place tops), concrete inverts, storm structure aprons, pipe collars, concrete ditch liner, and median noses and as otherwise designated within the Construction Documents. 2. A KCMMB 5k mix shall be used for the construction of all cast-in-place reinforced box culverts, retaining walls and headwalls, integral sidewalk retaining walls, cast-in-place storm drainage structure tops, and as otherwise designated within the Construction Documents. B. Reinforcement: Reinforcement shall conform to the following: 1. Steel Bars: ASTM A615, A996/A996M-09b, Grade 60 unless otherwise noted on the drawings or Standard Details. 2. Epoxy Bars: KDOT Section Dowels: ASTM A Welded Wire Fabric: ASTM A185, Grade 60. Wire fabric shall be supplied in sheets, not rolls. 5. Reinforcing Steel Accessories: (a) Plastic Protected Wire Bar Supports shall conform with Concrete Reinforcing Steel Institute, Class 1 for epoxy coated, and Class 1, 2 or 3 for all other materials. (b) Stainless Steel Protected Wire Bar Supports shall conform with Concrete Reinforcing Steel Institute, Class 2 with legs made wholly from stainless steel wire. (c) Precast Concrete Bar Supports shall have equal or greater strength than the surrounding concrete. C. Expansion Joint Fillers: Expansion joint fillers shall conform to ASTM D1752 for concrete pavement and ASTM D1751 for sidewalk, recreation trail, curb, and drive approach applications. D. Joint Sealing Compounds: Hot-poured joint sealing compounds shall conform to KDOT Section E. Curing Membrane: The curing membrane shall be of the liquid membrane type and shall conform to ASTM C309. All curing membranes shall contain a white pigment except curing membranes used for recreational trails. Curing membranes applied to recreational trails shall be clear drying. F. Admixtures: KCMMB Concrete shall not be supplied with any admixtures designated as optional in the Mix Design Testing Data without prior approval of the City Engineer. Additionally, admixtures shall not be added to the concrete at the job-site to increase workability unless approved by the City Engineer EQUIPMENT A. Forms: All forms shall be in good condition, clean, and free from imperfections. 1. Forms shall be made of steel, unless the City Engineer allows the use of wood forms due to an unusual shaped section or small quantity of concrete being placed. 2. Forms shall be cleaned and oiled before each use. Division 2400 Concrete

4 3. Forms shall be in good condition with not more than 1/4-inch variation in horizontal and vertical alignment for each ten (10) feet in length. 4. Forms shall have a height equal to or greater than the thickness of the concrete to be placed. 5. Forms shall be of such cross-section and strength, and secured to resist the pressure of the concrete when struck off, vibrated, and finished, and the impact and vibration of all equipment. B. Ready Mix Batch Plants: Ready mix batch plants shall conform to the requirements of ASTM C94. PART 3 - EXECUTION 3.01 PREPARATION A. Notification: Contractor shall notify the City at least twenty-four (24) hours in advance of the times and locations that concrete will be placed. B. Limits: The limits of each concrete pour shall be predetermined by the Contractor and shall be agreed upon by the Engineer. All concrete within such limits shall be placed in one continuous operation INSTALLATION A. Concrete: The consistency of the concrete shall be suitable for the type placement being performed. Aggregates shall float uniformly throughout the mass and the concrete shall flow sluggishly when vibrated or spaded. Concrete which does not meet the slump requirements identified in the approved mix design shall be rejected. B. Forms: Prior to placement of the concrete pavement, all debris and foreign material shall be removed from the inner surfaces of the forms and all forms and subgrade properly moistened. 1. Forms shall be set true to line and grade, supported through their length and joined neatly in such a manner that the joints are free from movement in any direction. Each form shall not vary more than one quarter (1/4) inch in horizontal and vertical alignment for each ten (10) feet in length. 2. Forms shall be cleaned and lubricated prior to each use and shall be so designed to permit their removal without damage to the new concrete. C. Reinforcement: Reinforcing steel of the size and type specified shall be placed in accordance with the Standard Details. All reinforcing steel shall be tied and supported on chairs. All required reinforcement and accessories shall be properly and firmly set into position to prevent movement during placement of the concrete. D. Subgrade Conditions: Concrete shall not be placed on frozen subgrade or in excavations which have not been dewatered. E. Mixing and Transport: Mixing and transport of the concrete to the job site shall conform to requirements of ACI 304R-00. F. Time Constraints: Concrete shall be placed within ninety (90) minutes of mixing operations, with the exception that the City Engineer may extend the period dependent upon weather conditions. Division 2400 Concrete

5 G. Sampling and Control Testing: A recognized testing laboratory, or other agency satisfactory to the Engineer, shall test all concrete and concrete mixtures delivered to the job site on a continuing basis with three copies of the certified test results provided to the Engineer. 1. Slump (ASTM C143) once per day, or as directed during placement to control changes made to mix proportions. 2. Air Entrainment (ASTM C231) once per day, or as directed to control changes made to mix proportions. 3. Yield Test (ASTM C138) once per day, or as directed during placement to control changes made to mix proportions. 4. Compressive Strength (ASTM C39) three (3) test specimens for each 50 cubic yards or less placed per day for each class of structural concrete placed during one day, with one cylinder to be tested at 7 days and the other two at 28days. Test specimens to be prepared to ASTM C Flexural Strength (ASTM C231) three (3) test specimens for each 100 cubic yards or less placed per day for each class of concrete pavement placed during one day. With one beam to be tested at 7 days and the other two at 28days. Test specimens to be prepared according to ASTM C31. H. Placement: Concrete shall be deposited over the entire width of the prepared subgrade between the forms in such a manner to prevent segregation and to require as little handling as possible. Concrete shall be placed to the required depth and width in successive batches and in a continuous operation without the use of intermediate forms or bulkheads. While being placed, the concrete shall be vibrated and compacted with suitable tools so that the formation of voids or honeycomb pockets is prevented. When it is necessary to drop concrete a distance of more than three (3) feet, troughs, pipes, or chutes shall be used as aides in placing concrete and shall be arranged and used in such a manner that the material components of the concrete do not become separated. Where steep slopes are required, the chutes shall be equipped with baffle boards or short lengths that reverse the direction of movement. All chutes, troughs, and pipes and reinforcing steel shall be kept clean and free from coatings of hardened concrete. At no time shall concrete drop freely for a distance of more than three (3) feet. The concrete shall be well vibrated and tamped against the forms and along all joints. For concrete pavement, care shall be taken in the distribution of the concrete to deposit a sufficient volume along the outside form lines so that the curb section can be consolidated and finished simultaneously with the slab. Vibratory tools shall not be used to move concrete horizontally. No concrete shall be placed around manholes or other structures until they have been brought to the required grade, alignment, and cross slope. Concrete shall not be allowed to extrude below the forms. I. Finishing: For finishing techniques, refer to the individual sections as they apply. J. Curing: As soon as practical after the concrete is finished, it shall be cured with a liquid curing membrane, applied in accordance with the manufacturer's recommendations. 1. The curing compound shall be applied after final finishing operations have been completed, and immediately after the free water has left the surface of the concrete. Division 2400 Concrete

6 2. A nozzle producing a uniform fan pattern shall be used on all spray equipment when applying the liquid curing membrane. 3. Two (2) smooth coats shall be applied to ensure complete coverage and effective protection, with each coat applied at an application rate not less than three hundred (300) square feet per gallon. 4. If the forms are removed from finished concrete pavement within a period of seventytwo (72) hours or if a slip form paving machine has been used, all exposed surfaces shall also be cured. 5. Contractor shall reapply curing membrane damaged during joint sawing operations. K. Protection: Contractor shall protect the concrete work against damage or defacement of any kind until it has been accepted by the City. All vehicular traffic shall be prohibited from using the new concrete pavement until it has attained seventy percent (70%) of the 28-day compressive design strength. Concrete strength will be determined by cylinders cast and tested in accordance with this Section. Concrete pavement which is not acceptable to the City Engineer because of damage or defacement, shall be removed and replaced, or repaired to the satisfaction of the City Engineer, at the expense of the Contractor JOINTS Joints shall be formed at right angles to the true alignment of the pavement and to the depths and configuration specified by the Standard Details or as defined within the Construction Documents. A. Expansion Joints: Expansion joints shall be placed at all locations where shown within the Construction Documents or as directed by the Engineer. 1. General: Expansion joint filler shall extend the entire width of the pavement and from the sub-grade to one (1) inch below the surface of the pavement or the material will have a suitable tear strip provided to allow for the application of the joint sealer. Expansion joint filler shall remain free from excess concrete. 2. Material: Expansion joints shall be formed by continuous 1/2-inch thick preformed joint filler cut to the configuration of the pavement section. 3. Stability: Expansion joints shall be secured in such a manner that they will not be disturbed during the placement, consolidation, and finishing of the concrete. 4. Dowels: If expansion joints are to be equipped with dowels they shall be of the size and type specified, and shall be firmly supported in place, by means of a dowel basket which shall remain in place. One half of each dowel shall be painted or lubricated with a product approved by the Engineer. B. Contraction Joints: Contraction joints shall be of the type and dimensions and at the spacing shown within the Construction Documents. 1. Hand Tooled: Contraction joints for sidewalk and curb shall be hand tooled if the concrete is not placed with a slip form machine. Contraction joints for recreational trails shall be saw-cut. 2. Sawing: The saw cut shall be approximately 1/4-inch wide, and the depth shall be one fourth (1/4) the thickness of the slab, or as shown within the Construction Documents. Division 2400 Concrete

7 (a) Sawed contraction joints shall be cut by means of wet sawing with an approved concrete saw. The joints shall not be sawed until the concrete has hardened to the extent that tearing and raveling is precluded. (b) Joints shall be sawed during the initial curing period and the sawing shall begin before the pavement starts shrinking and before uncontrolled cracking begins to occur. (c) In no case shall the pavement be left over night without having the joints sawed (d) Material created by sawing shall be flushed from the pavement before it has had time to dry or set. 3. Dowels: If contraction joints are to be equipped with dowels they shall be of the size and type specified within the Construction Documents, and shall be firmly supported in place and accurately aligned parallel to the pavement line and grade with allowable tolerance of 1/8-inch. C. Construction Joints: Construction Joints shall be placed as shown on the plans or where the Contractor s construction procedure may require them to be placed. Construction joints shall be placed wherever concrete placement is suspended for more than thirty (30) minutes. The joint shall be placed in a location consistent with a planned contraction or expansion joint. All construction joint tie bars shall be drilled and epoxy coated, unless keyways are permitted by the City Engineer. D. Tiebars: Tiebars shall be of deformed steel of the dimensions specified within the Construction Documents. Tiebars shall be installed at the specified spacing and firmly secured so as not to be disturbed by the construction procedure. Tiebars shall be drilled to a minimum depth of 6 inches unless specified otherwise by the City Engineer. Tiebars shall be evenly spaced along the length of the slab and no tiebar shall be within two (2) feet of a contraction joint. Tiebars shall be supported in the proper position by chairs driven into the subgrade or may be placed by approved mechanical methods into the plastic concrete within the limits of the finishing screed. Tie bars shall not be inserted by driving or stabbing them into the finished consolidated concrete. E. Backfill: A minimum of twenty-four (24) hours shall lapse before forms are removed and five (5) days shall lapse or the concrete must have attained seventy percent (70%) of its 28- day compressive strength before pavement shall be backfilled, unless otherwise approved by the Engineer. Backfill shall be placed in accordance with Section Earthwork and Section 2120 Stabilized Subgrade. The Contractor shall be responsible for the repair and/or replacement of any existing street pavement disturbed by the backfilling operations to the satisfaction of the City Engineer. F. Joint Sealing and Cleanup: All joint material shall be installed in accordance with the manufacturer's directions. Joints shall be sealed with within seven (7) days of the placement of the concrete. The Contractor shall be responsible for the removal of excess dirt, rock, broken concrete, concrete splatters and overspray from the area of the construction. G. Repairing Defects: Any concrete found not to be formed as indicated on the plans, or out of alignment or level, or having a defective surface, or damaged prior to acceptance of the project by the City shall be considered as not conforming to the intent of these Division 2400 Concrete

8 specifications and may be ordered removed and replaced at the Contractor s expense unless the City Engineer authorizes patching of the defective or damaged area. Surface defects such as ridges and bulges shall be removed by grinding. Honeycombed and other defective concrete that does not affect the structural integrity of the structure shall be chipped out and the vacated area shall be filled. The methods used in this type of repair shall be approved by the City Engineer. Materials used for patching shall be a non-shrink, non-metallic grout with a minimum 28-day compressive strength of five thousand (5,000) psi or a similar material approved by the City Engineer. Prior to placement of the repair filling, the contact surface of the affected area shall be thoroughly cleaned of all loose and foreign material and shall be coated with an epoxy bonding agent. Concrete repair work shall conform to Chapter 9 of ACI 301 and shall be performed in a manner that will not interfere with thorough curing of surrounding concrete. Repair work shall be adequately cured and protected from further damage WEATHER LIMITATIONS A. Cold Weather Concrete: The Contractor shall comply fully with the provisions of ACI 306. The following additional conditions apply: 1. Unless authorized by the City Engineer, mixing and concreting operations shall be discontinued when the descending ambient air temperature reaches 40 F or when forecast to drop below 40 F within 24 hours of placement, and shall not be resumed until an ascending ambient air temperature reaches 35 F. 2. Concrete shall be protected from freezing by covering and insulating the concrete or by heating an enclosed area surrounding the concrete whenever the temperature is expected to drop below 40 F. The concrete shall be protected immediately after placement, and for three (3) days after placing the concrete. 3. When concrete work is authorized during cold weather, the aggregates may be heated by methods approved by the City Engineer prior to being placed in the mixer. No ingredient that is frozen or contains ice shall be placed in the mixer. 4. The temperature of the concrete shall be not less than 60 F and not more than 100 F at the time of placement in the forms. 5. Under no circumstances shall concreting operations continue when the air temperature is less than 20 F. No concrete shall be placed on frozen subgrade. 6. Sudden cooling of concrete shall not be permitted. 7. Concrete damaged by frost action or freezing weather shall be removed and replaced at the Contractor's expense. B. Hot Weather Concrete: The Contractor shall comply fully with the provisions of ACI 305. The following additional conditions apply: 1. Any time the ambient air temperature exceeds 80 F at the time of placement, the provisions of ACI 305 shall be implemented. 2. In no case shall the temperature of the concrete, when placed, exceed 100 F. Forms, reinforcing and subgrade surfaces against which the concrete is to be placed shall be wetted down immediately before placement. 3. When the ambient air temperature exceeds 90 F and as soon as practicable without causing damage to the surface finish, all exposed concrete shall be kept continuously moist by means of fog sprays, wet burlap, cotton mats, or other means acceptable to Division 2400 Concrete

9 the City Engineer. This cooling with water shall be in addition to the initial sealing by membrane curing compound. The curing compound shall be applied within five (5) minutes of completing the finishing operation on the portion of the concrete being installed. Cooling water shall be continued for twenty-four (24) hours. PART 4 - MEASUREMENT AND PAYMENT Refer to the individual sections for measurement and payment requirements. END OF SECTION Division 2400 Concrete