616.01 634 SECTION 616 – POST-TENSIONED PRESTRESSED CONCRETE
616.01 Description ................................ ................................ ................... 634
616.02 Prestressing Methods ................................ ................................ ... 634
616.03 Materials ................................ ................................ ...................... 635
616.04 Reserved ................................ ................................ ....................... 635
616.05 Protection and Installation of Prestressing Steel .......................... 635
616.06 Anchorages and Distribution ................................ ........................ 637
616.07 Ducts ................................ ................................ ............................ 638
616.08 Prestressing ................................ ................................ .................. 639
616.09 Bonding and Grouting ................................ ................................ .. 641
616.10 Form Work ................................ ................................ ................... 644
616.11 Sampling and Testing ................................ ................................ ... 644
616.12 Method of Measurement ................................ .............................. 644
616.13 Basis of Payment ................................ ................................ .......... 644
DESCRIPTION
616.01 Description
This work consists of prestressing cast -in-place concrete by furnishing, placing, and tensioning prestressing steel in accordance with the Plans and these Specifications, and furnishing and installing all appurtenant items necessary for the particular prestressing system to be used, including ducts, anchorage assemb lies, prestressing steel, and grout.
616.02 Prestressing Methods
Perform prestressing using post -tensioning methods. Submit to the Engineer for review and approval complete details of the proposed method, materials, and equipment to use in the prestressin g operations, including any additions or rearrangement of reinforcing steel from that shown on the Plans. Such details shall outline the method and sequence of stressing and shall include complete specifications and details of the prestressing steel and a nchoring devices, working stresses, bursting stresses, anchoring stresses, type of ducts, and all other data pertaining to the 616.03 635 prestressing operation, including the proposed arrangement of the prestressing steel in the members, pressure grouting materials, and equipment. Do not cast any member to be prestressed until the Engineer approves the shop detail drawings. MATERIALS
616.03 Materials
Provide materials as specified in: Portland Cement (Type I or III) ................................ ............. 901.01 Prestressing Reinforcement Steel and Anchorages ................ 907.04 Water ................................ ................................ ..................... 921.01 All components of the post -tensioning system shall be certified to meet the Post-Tensioning Institute (PTI) Acceptance Standards for P ost-Tensioning Systems.
616.04 Reserved
CONSTRUCTION REQUIREMENTS
616.05 Protection and Installation of Prestressing Steel
Locate the pre stressing steel in the girder stems with an equal force in each stem. At the Co ntractor’s option, the prestressing force may vary 5% from the theoretical equal force per girder provided the required total force is obtained and the force is distributed symmetrically about the centerline of the typical section. Tension stressing units a few at a time in each girder to minimize stress differentials. Obtain the Engineer’s approval of the stressing sequence. Protect prestressing steel against physical damage and rust or other results of corrosion at all times. Do not use prestressing st eel that is physically damaged. Light surface rust is not a cause for rejection. Package prestressing steel in containers or other shipping forms to protect the steel against physical damage and corrosion during shipping and storage. Place an approved co rrosion inhibitor in the package or form. Alternatively, the Contractor may use a corrosion inhibitor carrier type packaging material 616.05 636 or, when allowed by the Engineer, may apply corrosion inhibitor directly to the steel. Ensure that the corrosion inhibitor will have no deleterious effect on the steel or concrete or bond strength of steel to concrete. Immediately replace or restore to original condition all damaged packaging or forms. If choosing to use a corrosion inhibitor carrier type packaging material, ensure that the material conforms to Federal Specification MIL -P-3420. Mark the shipping package or form with a statement that the package contains high-strength prestressing steel that should be handled with car e. Also identify the type, kind, and amount of corrosion inhibitor used, including the date when placed, safety regulations, and instructions for use. Submit the following for the corrosion inhibitor:
1.A sample, a list of chemicals and their proportions , and instructions for use.
2.Evidence that the prestressing steel will be protected from rust and other results of corrosion.
3.A certificate of compliance. When acceptable prestressing steel for post -tensioning is installed in ducts after completion of concrete curing, complete the stressing and grouting within 10 calendar days after installing the prestressing steel. Rust that may form during these 10 days will not be cause for rejection of the steel. If prestressing steel is installed, tensioned, an d grouted within 10 calendar days after concrete curing, it is not necessary to use a corrosion inhibitor in the duct following installation of the prestressing steel. If prestressing steel is installed as specified above but is not grouted within 10 cale ndar days, use an approved corrosion inhibitor in the duct. Ensure that the corrosion inhibitor is maintained at an effective level until grouting is complete. Do not make any welds or grounds for welding equipment on the forms or on the steel in the member after the prestressing steel has been installed. Place tendons in rigid ducts after completing concrete placement. Provide ducts as shown on the Plans and as specified in 616.07. 616.06 637 616.06 Anchorages and Distribution Anchor post -tensioned prestressing steel at the ends using approved permanent type anchoring devices capable of producing a stress of not less than 95% of the guaranteed minimum tensile strength of the prestressing steel. Distribute the load from the anchoring device to the concrete using approved devices. Place bearing plates normal to the tendon path and tight against forms. Brace and anchor forms to support the weight of the bearing plates. Use appro ved plates and assemblies that conform to the following requirements:
1.The final unit compressive stress on the concrete directly underneath the plate or assembly shall not exceed 3,000 pounds per square inch.
2.Bending stresses in the plates or assembl ies induced by the pull of the prestressing shall not exceed the yield point of the material or cause visible distortion in the anchorage plate when 100% of the ultimate tensile strength is applied as determined by the Engineer. If the anchoring device is sufficiently large and is used in conjunction with a steel grillage embedded in the concrete that effectively distributes the compressive stresses to the concrete, the Contractor may omit steel distribution plates or assemblies. Where the end of a post -tensioned assembly will not be covered by concrete, recess the anchoring devices so that the ends of the prestressing steel and all parts of the anchoring devices will be at least 2 inches inside of the end surface of the members, unless a greater embedment i s shown on the Plans. Following post -tensioning, fill the recesses with grout, and finish flush. Use a suitable corrosion inhibitor to protect exposed anchorage hardware before final embedment in concrete. Include complete details of jacking chairs in fa brication drawings to allow verification of proper reinforcement clearances. 616.07 638 616.07 Ducts Use mortar -tight ducts that are sufficiently rigid to maintain their shape and alignment during concrete placement and grout installation. Ducts shall remain water tight. Use ducts having the following minimum wall thicknesses:
1.High Density Polyethylene (HPDE): 2.0 millimeter
2.High Density Polypropylene (HDPP): 2.0 millimeter For tendons composed of single prestressing bars, provide ducts with a minimum internal duct diameter of at least ¼ inch larger than the outside diameter of the prestressing bar. For multiple wire, bar, or strand tendons, provide a duct nominal internal cross -sectional area of at least 2.25 times the net area of the prestressi ng steel. Make positive joints between duct sections. Do not make angles at the joints. Use waterproof tape at the joints. Bend ducts without crimping or flattening. Use ferrous metal or polyethylene couplings to connect ducts to anchoring devices. Protect ducts against crushing, excessive bending, dirt contamination, and corrosive elements, during transport, storage, and handling of ducts. In case of damage to a duct, seal it with tape, or splice a duct coupler over the damaged section to form a seal t hat prevents cement paste from entering the duct during the placement of concrete and that prevents leakage during grouting operations. Provide all ducts and anchorage assemblies with inlets for the injection of grout into the duct after prestressing accor ding to the PTI Guide Specification for Grouting of Post -Tensioned Structures . Provide all ducts with outlets to allow the escape of air, water, grout, and bleed water according to the PTI Guide Specification for Grouting of Post - Tensioned Structures . Provide inlets and outlets with an inner diameter of at least ¾ -inch for strand tendons and of at least 3/8 inch for single bar tendons. Extend the length of outlets a sufficient distance out of the concrete member to allow for the proper closing of the outle ts. 616.08 639 Place inlets and outlets, at a minimum, in the following locations:
1.The anchorage area of the tendon;
2.All high points of the duct, when the vertical distance between the highest and lowest point is more than 2 feet; and
3.At major changes in the cross-section of the duct, such as couplers and anchorages. In addition, place:
1.An inlet at or near the lowest point of the tendon ;
2.A free draining outlet at all low points of the duct; and
3.An outlet at a distance less than 3 feet downstream from high point outlets. Show all inlet and outlet locations on drawings. Provide positive mechanical shut -off valves for all inlets and outlets. Provide inlets and outlets with valves, caps, or other devices capable of withstanding the groutin g pressure. Securely fasten ducts in place to prevent movement. Maintain distances from the forms by stays, blocks, ties, hangers, or other approved supports. Use precast blocks. Space all duct supports in accordance with the PTI Guide Specification for Grouting of Post -Tensioned Structures . Cover the ends of ducts to prevent the entry of water or debris. Connect inlets and outlets to the duct with metallic or plastic structural fasteners. Do not use components that react with the concrete, cause corrosion of the prestressing steel, or contain water -soluble chlorides.
616.08 Prestressing
Tension prestressing steel using hydraulic jacks so that the force in the prestressing steel is not less than the value shown on the Plans. Do not perform stressing on a single strand pull. Use a jack that is capable of making a multiple pull on all strands in a tendon. 616.08 640 Unless otherwise specified or shown on the Plans, the stress in the prestressing steel after all losses shall not exceed 80% of the yield point stress of the prestressing steel. The maximum temporary tensile stress (jacking stress) in the prestressing steel shall not exceed 90% of the yield point stress of the prestressing steel. Anchor the prestressing steel at stresses (initial stress) that will result in the ultimate retention of working forces of not less than those shown on the Plans, but in no case shall the initial stress at the anchor exceed 70% of the specified minimum u ltimate tensile strength of the prestressing steel. Working force and working stress will be considered as the force and stress remaining in the prestressing steel after all losses, including creep and shrinkage of concrete, elastic compression of concrete, relaxation of steel, losses in post -tensioned prestressing steel due to sequence of stressing, friction and take up of anchorages, and all other losses peculiar to the method or system of prestres sing have taken place or have been provided for. The loss in stress due to all causes in post -tensioned prestressing steel shall be in accordance with the AASHTO LRFD Bridge Design Specifications designated on the Plans. Equip each jack used to stress tend ons with either a pressure gauge or a load cell for determining the jacking stress. Use a pressure gauge that has an accurately reading dial at least 8 -inches in diameter. Calibrate each jack and its gauge as a unit with the cylinder extension in the app roximate position that it will be at final jacking force. Keep a certified calibration chart with each gauge. Ensure that each gauge is capable of reading loads directly in pounds or is accompanied by a chart from which the dial reading can be converted to pounds. If a load cell is used, calibrate it and provide it with an indicator that will allow determination of the prestressing force in the tendon. Do not use the lower 10% of the manufacturer’s rated capacity of the load cell to determine the jacking stress. Provide means for measuring the elongation of reinforcement to at least the nearest 1/16 -inch. The Engineer may check the certified calibration charts for the hydraulic jacks, pressure gauges, or load cells used for tensioning prestressing steel before and during tensioning operations. 616.09 641 Prior to placing forms for closing slabs of box girder cells, demonstrate to the satisfaction of the Engineer that all ducts are unobstructed. Except as herein provided, do not prestress cast -in-place concrete unti l at least 10 days after the last concrete has been placed in the member to be prestressed and until the compressive strength of the last placed concrete has reached the strength specified for the concrete at the time of stressing. Conduct the tensioning p rocess so that the tension being applied, and the elongation of the prestressing steel may be measured at all times. Keep a record of gauge pressures or load cell readings and elongations for each tendon stressed. Use elongation measurements as the primar y control of the stressing operation; however, ensure that the hydraulic pressure gauge readings or the load cell readings at the time of the measured net elongation are within 5% of the calculated gauge or load cell reading for that particular elongation. If the gauge or load cell pressure readings vary by more than 5% from their calculated reading, stop all work and correct the defect before proceeding. A variance of more than 5% may be cause for jacking at both ends. Tension prestressing tendons in con tinuous post -tensioned members by jacking at each end of the tendon unless otherwise shown on the Plans. Such jacking of both ends need not be done simultaneously. When approved by the Engineer, the Contractor may tension bent cap tendons by jacking from one end only. The Contractor may tension prestressing tendons in single span post - tensioned members by jacking from one end only. When tensioning is done from one end only, tension half of the prestressing steel in each member from one end of the span an d the other half from the opposite end, unless otherwise allowed by the Engineer.
616.09 Bonding and Grouting
Provide Class A, B, C, or D grout as specified in the PTI Guide Specifications for Grouting of Post -Tensioned Structures . Bond all post -tensioned prestressing steel to the concrete by filling the void space between the duct and tendon with grout according to the PTI Guide. Provide prestressing steel that is free of dirt, loose rust, grease, or other deleterious substances. 616.09 642 Perform all grouting operations using staff with grouting experience on projects of a similar type and magnitude . Perform grouting operations under the immediate supervision of an individual skilled in various aspects of grouting and who is certified by the American Segmental Bridge Institute (ASBI) Grouting Certification or equivalent certification program, approved by the Engineer. Furnish the name of the grouting operations supervisor and proof of their ASBI certification and grouting experience to the Engineer before beginning grouting operations. Make available on -site, before beginning grouting operations, all the required testing equipment for checking grout workability (flow -cone), temperatures, and other specified tests. Provide written certification that all ingredients used in the grout meet the ASTM requirements contained in the PTI Guide S pecification for Grouting of Post -Tensioned Structures . This includes, but is not limited to, the following: • Cement mill test reports; • Mineral additives test reports; • Chemical admixtures reports; and • Test reports for any other ingredients used in the grou t. For prepackaged grouts, provide the manufacturer’s current certified mill test reports for the product. Use grouting equipment capable of continuous operation with little variation of pressure, which includes a system for recirculating the grout while a ctual grouting is not in progress. Use grouting equipment capable of maintaining a pressure on completely grouted ducts and fitted with a valve that can be locked off without loss of pressure in the duct. Do not use compressed air to aid in the pumping of grout. Provide grout pumps of a positive displacement type, capable of providing a continuous flow of grout, and capable of maintaining an outlet pressure of at least 150 pounds per square inch and with a pressure gauge having a full - scale reading of not more than 300 pounds per square inch. Determine the flowability of the grout according to ASTM C939. The efflux time of a grout sample immediately after mixing shall be between 11 and 30 seconds. Do not begin grouting until this test is passed. When hot weather 616.09 643 conditions may cause quick setting of the grout, cool the grout by approved methods, as necessary, to prevent blockages during pumping operations. When freezing weather conditions are possible during and following placement of grout, protect the grout from damage by freezing according to the PTI Guide Specification for Grouting of Post -Tensioned Structures . Provide a supply of potable water and standby flushing equipment capable of developing a pumping pressure of 250 pounds per square inch and of sufficient capacity to flush out any partially grouted ducts. Clean ducts of all material that would impair bonding of the grout or interfere with grouting procedures. Blow out each duct with compressed, oil -free air. Check all inlets and outlets for th eir capacity to accept injection of grout by blowing compressed, oil -free air through the system, and proving each inlet and outlet in turn. Pass all grout through a screen with 1/8 -inch maximum clear openings before entering the grout pump. Open all grou t vents before the start of grouting. Completely fill the duct by injecting grout from the lowest end of the tendon in an uphill direction. Pump grout continuously through the duct and waste at the outlet until no visible slugs of water or air are ejecte d, and the efflux time of the ejected grout is between 11 and 30 seconds. Maintain a continuous, one -way flow of grout within a grouting stage. Close all outlets in a similar manner one after the other in the direction of the flow. For outlets placed a s hort distance downstream from a high point, close that outlet before its associated high point outlet. Increase the grouting pressure at the injection end to at least 100 pounds per square inch and hold for at least 10 seconds. Do not remove or open valv es and caps until the grout has set. Abrasive blast -clean the concrete surface of recessed anchorage assemblies. Fill anchor recesses with concrete conforming to the requirements for the structure, and finish flush. Remove ends of vents 1 inch below the r oadway surface after grouting has been completed. Permanently seal all recess areas. Do not release the falsework under the bottom slab supporting the superstructure until at least 48 hours after grouting of the post -tension prestressing steel or until th e grout strength is obtained. 616.10 644 616.10 Form Work Do not remove falsework until all prestressing is complete and the structure has been post -tensioned to the Engineer’s satisfaction.
616.11 Sampling and Testing
Provide the following to the Engineer well i n advance of anticipated use:
1.Furnish one sample of each size strand for each reel in accordance with Departmental procedures.
2.Test one completely fabricated tendon at a laboratory approved by the Department and furnish a notarized letter to the Divi sion of Materials and Tests from the laboratory stating that no deformation has occurred in the anchor head and no slippage of strand has occurred at the wedges. When prestressing systems have been previously tested and approved for similar projects by an agency acceptable to the Department, testing will not be required, provided the Contractor furnishes the Engineer with a notarized letter stating that the system is the same as a previously tested system. COMPENSATION
616.12 Method of Measurement
The Department will measure prestressing of cast -in-place concrete by the lump sum as shown on the Plans. The Department will not measure, and will consider incidental to the work, the furnishing and placing of additional deformed b ar reinforcing steel required by the particular system used; ducts, anchoring devices, distribution plates or assemblies, and incidental parts; and the grouting of recesses and pressure grouting of ducts.
616.13 Basis of Payment
The Department will pay f or prestressing cast -in-place concrete by the lump sum. 616.13 645 Such payment is full compensation for furnishing all labor, materials, tools, equipment, and incidentals, and for doing all work involved in furnishing, placing, and tensioning the prestressing stee l in cast -in-place concrete structures, complete in place, as shown on the Plans, as specified in these Specifications, and as directed by the Engineer. If the Engineer allows the concrete that does not meet the specified strength to remain in the permanen t construction, the Department will adjust the bid price in accordance with 604.31. 617.01 646 SECTION 617 – BRIDGE DECK SEALANT
617.01 Description ................................ ................................ ................... 646
617.02 Materials ................................ ................................ ...................... 646
617.03 Reserved ................................ ................................ ....................... 646
617.04 General ................................ ................................ ......................... 646
617.05 Weather Limitations ................................ ................................ ..... 647
617.06 Membrane Application ................................ ................................ . 647
617.07 Method of Measurement ................................ .............................. 649
617.08 Basis of Payment ................................ ................................ .......... 649
DESCRIPTION
617.01 Description
This work consists of furnishing and placing a waterproofing system over a properly prepared concrete bridge deck for the purpose of protecting structural concrete from the deterioration caused by absorption of deicing salts and water. MATERIAL
617.02 Materials
Provide materials as specified in: Bridge Deck Sealant, System A or B ................................ ..... 906.04
617.03 Reserved
CONSTRUCTION REQUIREMENTS
617.04 General
To minimize the amount of construction traffic on the bridge deck seal after placement, do not install the seal until all major phases of roadway construction have been completed. Complete the roadway base and pavement up to the surface course before begi nning installation of the bridge
Source: Tennessee Standard Specifications for Road and Bridge Construction, 2021 Edition. Pages 643–654 of 1,072.