Post-Tensioning Concrete POST-TENSIONING CONCRETE
Part 1 — General
1.1 Section Includes
A.Post-tensioning (PT) system and grouting of prestressing steel for concrete elements .
B.Items necessary for the particular prestressing PT system used, including but not limited to ducts, anchorage assemblies, supplementary reinforcing bars, and grout used for pressure grouting ducts.
1.2 Related Sections
A.Section 03211: Reinforcing Steel and Welded Wire
1.3 References
A.AASHTO M 203: Steel Strand, Uncoated Seven- Wire for Concrete Reinforcement
B.AASHTO M 204: Uncoated, Stress -Relieved Steel Wire for Prestressed Concrete
C.AASHTO M 275: Uncoated High- Strength Steel Bar s for Prestressed Concrete
D.AASHTO LRFD Bridge Construction Specifications, current edition
E.AASHTO LRFD Bridge Design Specifications, current edition
F.ASTM A 53 : Pipe, Steel, Black and Hot -Dipped, Zinc -Coated, Welded and Seamless
G.ASTM A 240: Chromium and Chromium -Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and General Applications
H.ASTM A 653 : Steel Sheet, Zinc -Coated (Galvanized) or Zinc -Iron Alloy - Coated (Galvannealed) by the Hot -Dip Process Post-Tensioning Concrete
I.ASTM C 307: Tensile Strength of Chemical -Resistant Mortar, Grouts, and Monolithic Surfacings
J.ASTM C 531: Linear Shrinkage and Coefficient of Thermal Expansion of Chemical -Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes
K.ASTM C 579: Compressive Strength of Chemical -Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes
L.ASTM C 881: Epoxy -Resin -Base Bonding Systems for Concrete
M.ASTM C 882 : Bond Strength of Epoxy -Resin Systems Used With Concrete by Slant Shear
N.ASTM C 1583 : Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull -Off Method)
O.ASTM D 3035 : Polyethylene (PE) Plastic Pipe (DR- PR) Based on Controlled Outside Diameter
P.ASTM D 3350 : Polyethylene Plastics Pipe and Fittings Materials
Q.ASTM D 3895 : Oxidative -Induction Time of Polyolefins by Differential Scanning Calorimetry
R.ASTM D 4285: Indicating Oil or Water in Compressed Air
S.ASTM D 5989: Extruded and Monomer Cast Shapes Made From Nylon (PA)
T.ASTM F 593: Stainless Steel Bolts, Hex Cap Screws, and Studs
U.ASTM F 714 : Polyethylene (PE) Plastic Pipe (DR- PR) Based on Outside Diameter
V.ASTM F 2136: Notched, Constant Ligament -Stress (NCLS) Test to Determine Slow -Crack -Growth Resistance of HDPE Resins or HDPE Corrugated Pipe
W.MIL-PRF-3420: Wrapping Materials, Volatile Corrosion Inhibitor Treated, Opaque
X.PTI M5 0.3: Post-Tensioning Institute (PTI) Guide Specification for Grouted Post-Tensioning Post-Tensioning Concrete
Y.PTI M55.1: Post-Tensioning Institute (PTI) Specification for Grouting of Post-Tensioned Structures
1.4 Definitions
A.Inlet and outlet pipes – The terms inlet pipes and outlet pipes are synonymous with vents, drains, injection, ejection, or inlet/outlet ports. Inlet and outlet pipes are devices connected to the PT system used for the injection of materials into or the ej ection of materials from inside the ducts.
B.Jacking force – The force applied to the tendon before anchorage and the occurrence of losses, including the anchor set loss.
C.Permanent force – The force remaining in the prestressing steel after all losses, including long term creep and shrinkage of concrete, elastic shortening of concrete, relaxation of steel, losses in prestressing steel due to sequence of stressing, fricti on, unintended wobble of ducts, anchor set, friction in anchorages, and all other losses particular to the method or system of prestressing have taken place or have been provided for.
D.Torpedo – A rigid object sized to fit through undamaged post -tensioning ducts. Used to prove that installed ducts have not been blocked or damaged during the concrete pour.
1.5 Submittals
A.Working Drawings
1.Detailed drawings of the PT system for review. Include at least the following:
a.Anchorage and bearing details including local zone and grillage reinforcement
b.Duct placement including individual tendon center of gravity (CG) locations and combined tendon CG location at anchorages, low points, and high points 1) Not required for segmental bridges or precast deck panels 2) Distribute the prestressing force in cast -in-place post - tensioned bridge girders with approximately equal quantity in each girder and place the force symmetrically about the centerline of the structure
c.Meth od and spacing of duct supports
d.Duct ties and stirrup ties
e.Inlet and outlet pipe locations
f.Expected friction coefficient, wobble coefficient, and anchor set Post-Tensioning Concrete
g.Jacking forces, jacking ends, initial stresses, and sequence
h.Permanent grout cap detail
i.Material data sheets for tendons, ducts, and permanent grout cap
j.Calculated elongations and tolerances
k.Bar couplers when shown
l.High point outlet inspection details
m.Anchorage inspection details
2.Include supporting engineering calculations.
a.Design the post -tensioning system according to AASHTO LRFD Bridge Design Specifications
b.Include computations and a typical tendon force diagram after friction and anchor set losses based upon expected actual coefficients and values for the PT system to be used.
3.Provide detailed congestion drawings integrating PT system and concrete reinforcing at locations where duct or anchorage passes through grids of reinforcing steel, such as at anchorage zones, diaphragms, bents, and other highly conges ted areas .
a.Indicate additions or rearrangement of reinforcing steel and revision s to concrete dimensions from that shown.
B.Personnel Qualifications
1.Provide names and current certifications of qualified supervisors for approval .
a.Refer to this Section, article 1.6
C.Grouting Procedures and Safety Procedures
1.Submit grouting procedures at least 45 calendar days in advance of scheduled grouting operations for review.
a.Include the following: 1) Names, proof of training and experience records for the grouting crew and the crew supervisor in conformance with this Specification 2) Type, quantity, brand, and certifications for materials used in grouti ng, include product data sheets 3) Equipment data, including capacity in relation to demand, as well as provisions for back -up equipment 4) General grouting procedure 5) Duct cleaning procedure 6) Duct pres sure test and repair procedure. 7) Mixing and pumping procedure 8) Method to be used to control the rate of flow within ducts 9) Theoretical grout volume calculations 10) Direction of grouting and sequence of inlet and outlet pipe usage Post-Tensioning Concrete 11) Procedures for handling blockages and potential regrouting and post grouting repair.
2.Submit safety procedures for information.
D.Prestressing Steel
1.Accompany each lot of prestressing steel with a mill certificate and a test report including the following:
a.Chemical compos ition (not required for strand)
b.Cross -sectional area
c.Yield and ultimate strengths
d.Elongation at rupture
e.Modulus of elasticity
f.Stress strain cur ve for the actual pres tressing steel intended for use
2.Supply a certificate of conformance stating the manufacturer’s minimum guaranteed ultimate tensile strengths and actual ultimate strengths with each reel or heat of prestressing steel wires, bars, or strands. Refer to this Section, Article 2.2.
3.Samples for prestressing steel testing
a.Provide samples to the Department for verification testing from each manufactured reel of prestressing steel strand, from each size and each heat of prestressing bars, from each coil of prestressing wire, and from each lot of anchorage assemblies and bar couplers to be used. 1) Provide three 5 ft long samples of each size from each reel for strand. 2) Provide three 7 ft long samples from each heat or reel for wire or bars.
E.Post-Tensioning Anchorages
1.Submit a test report and certificate of conformance provided by an independent testing laboratory for review which indicates that the anchorages meet the testing requirements in Section 10.3.2.3 of the AASHTO LRFD Bridge Construction Specifications.
a.Indicate that anchorages satisfy the requirements stated in this Section, Article 2.3, paragraph A.
F.Stressing Jacks
1.Refer to this Section, A rticle 3.4, paragraph B.
2.Furnish calibration charts certified by an independent laboratory with each jack and associated gauge or load cell used on the project.
a.Calibrate j ack and its gauge or load cell as a unit with the cylinder extension in the approximate position that it will be at final jacking force. Post-Tensioning Concrete
b.Provide certification for accuracy of the jack and associated gauge or load cell at the start of the work, after repair or adjustment, and every 180 days thereafter or as requested by the Department.
c.Provide pressure gauge calibration charts that are done while the jack is in the identical configuration as will be used on site including same length of hydraulic lines.
G.Duct Pressure Field T est Records
1.Submit a copy of the duct pressure field test records speci fied in this Section, Article 3.3, paragraph B for information.
H.Elongation Records Record elongations of each tendon at time of stressing along with jacking force and target elongation. Refer to this Section, Article 3.4.
1.Submit record of elongation of each tendon at time of stressing along with jacking force, gauge pressure, and target elongation for information within five days of completed tendon installation. Refer to this Section, A rticle 3.4, paragraph D.
I.Stressing Operation Records
1.Submit a copy of the stressing operation records specified in this Section, Article 3.4, paragraph A5 for information.
J.Post-Tensioning Grout Test Reports
1.Submit c ertified test reports for review from an independent Laboratory , Cement Concrete Reference Laboratory (CCRL) approved, which show that the post -tensioning grout material meets the requirements specified in this Section, Article 2.6.
K.Grouting O peration Reports
1.Submit for information:
a.Progress of grouting operations for each duct signed by grouting operation supervisor in control of the work for information within five calendar days after grouting
b.Information per duct indicating dates of t endon installation and grouting
c.Copy of the grouting operation records specif ied in this Section, Article 3.5, paragraph E11
1.6 Supervi Sor Requirements
A.PT system manufacturer’s representative must:
1.Be certified as a PTI Level 2 Bonded PT Field Specialist
2.Attend the preconstruction meeting Post-Tensioning Concrete
3.Be present at all times during installation of PT system components to:
a.Inspect and approve i nstallation of hardware, including ducts
b.Provide i nstructions to the Contractor regarding concrete placement around the ducts, end-anchorage assemblies, and other appurtenances
4.Provide close observation and control of:
a.Duct pressure field test
b.Stressing and anchoring of tendons
c.Post-grout inspections and repairs
d.Record keeping, certification of stressing results, and approval of elongations
5.Be present for grouting operations
6.Review and sign:
a.Duct pressure field tests records
b.Elongation records
c.Stressing operation records
7.More than one representative is required when multiple PT operations are occurring simultaneously.
B.Grouting operation supervisor must:
1.Be certified as either an ASBI Certified Grouting Technician or a PTI Lev el 2 Bonded PT Field Specialist
2.Attend the preconstruction meeting
3.Provide close observation and control of grouting operations, including:
a.Mixing and placing
b.Field trial tests
c.Field mockup tests
d.Production tests
4.Review and sign:
a.Grouting Procedures
b.Safety Procedures
c.Grouting operation reports
Part 2 — Products
2.1 General
A.Store materials in a weatherproof building, shed, covering, or container until time of use.
B.Equipment for oil -free and water -free compressed air.
1.Refer to ASTM D 4285. Post-Tensioning Concrete
2.2 Prestressing Steel
A.Materials:
1.Strand
a.Uncoated, Grade 270, low -relaxation, 7- wire st rand conforming to AASHTO M 203
2.Bar
a.Uncoated deformed (Type II) conforming to AASHTO M 275
3.Wire
a.Uncoated, low-relaxation conforming to AASHTO M 204
B.Attach tags for strand from each manufactured reel, bars of each size from each mill heat, wire from each coil, anchorage assemblies, PT system components and bar couplers to be shipped to the site.
1.Assign the individual lot number and tag in such a manner that each lot can be accurately identified at the job site.
2.Unidentified prestressing steel, anchorage assemblies, or bar couplers received at the site will be rejected if there is a loss of positive identification of these items at any time.
C.Use bar couplers only at the locations shown .
1.Use mechanical couplers that develop at least 96 percent of the actual ultimate strength of the bar, tested in an unbonded state, without exceeding anticipated set.
2.Use couplers for bars that do not reduce the elongation at rupture below the anticipated elongation of an uncoupled bar.
D.Protect prestressing steel against physical damage and rust or other results of corrosion at all times from manufacture to grouting or encasing in concrete.
1.Do not use prestressing steel that has sustained physical damage .
2.Remove and discard lengths of strand containing broken wire.
3.Use wire that is bright and uniformly colored, having no foreign matter or pitting on its surface.
4.Package prestressing steel in containers or shipping forms to protect the steel against physical damage and corrosion during shipping and storage.
a.Use a corrosion inhibitor which prevents rust or other results of corrosion, placed in the package or form, 1) Use a corrosion inhibitor either placed in the package form, or applied directly to the steel that has no deleterious effect on the steel, grout , concrete or bond strength of steel to grout . 2) Use inhibitor carrier type packaging material that conforms to the provisions of Federal Specification MIL-PRF-3420. Post-Tensioning Concrete
b.Immediately rejuvenate or replace the corrosion inhibitor if its useful life expires.
5.Use shipping package or form that is clearly marked with a statement that the package contains high- strength prestressing steel, care to be used in handling, the type, kind, and amount of corrosion inhibitor used including the date when placed, safety orders, and instructions for use.
a.Immediately replace damaged packaging or forms or restore to original condition.
2.3 Post -Tensioning Anchorages
A.Use anchoring devices that develop at least 96 percent of the actual ultimate tensile strength of the prestressing steel, tested in an unbonded state, without exceeding the anticipated set.
2.4 Ducts
A.General
1.Use corrugated galvanized metal ducts, corrugated plastic ducts, rigid steel pipe ducts or smooth plastic ducts.
a.Use ducts that are mortar tight, and capable of withstanding concrete pressures without deforming or permitting the entrance of cement paste during the placing of concrete.
b.Use ducts that can be accurately bent and placed at the locations shown.
2.Minimum internal dimensions for:
a.Multi-strand tendons : cross -sectional area 2 ½ times the cross- sectional area of the prestressing steel
b.Prestressing bars : diameter ½ inches larger than bar outside diameter, measured across deformations
c.Prestressing bars with couplers : diameter ½ inches larger than largest dimension of the largest enclosed element 1) Enclose bar couplers and coupler components in housings long enough to permit the necessary movements
3.Use ducts that have properties compatible with the assumed design values shown.
4.Use ducts that can be bent as shown without crimping or flattening and have sufficient strength to maintain their correct alignment during placing of concrete.
5.Use d uct splices at joints between precast segments that are capable of positively preventing t he entrance of cement paste and water from concrete .
a.Use d uct splices that do not cause electrolytic action or deteriorate. Post-Tensioning Concrete
6.Provide reference marks on rigid ducts to facilitate orientation during placement.
7.Provide hold down ties to the forms when the buoyancy of the ducts in the fluid concrete would lift the reinforcing steel.
B.Metal Ducts:
1.Fabricate corrugated semi -rigid ducts from ASTM A 653 galvanized sheet steel, coating designation G90.
a.Use a minimum wall thickness of: 1) 26 gauge for semi -rigid ducts less than or eq ual to
2.625 inches in diameter
2) 24 gauge for semi -rigid ducts greater than 2.625 inches in diameter 3) 31 gauge w hen bar tendons are pre assembled with semi -rigid ducts
b.Fabricate with either welded or interlocked seams. 1) Galvaniz e welded seams.
2.Fabricate rigid steel pipe ducts from galvanized ASTM A 53 Grade B schedule 40 steel pipe.
a.Use pipe with smooth inner walls capable of being curved to the proper configuration without crimping or flattening.
3.Provide j oints between sections of ducts that have positive metallic connections which do not result in angle changes at the joints.
C.Plastic Ducts
1.Refer to Section 10.8.3 of the AASHTO LRFD Bridge Construction Specifications for the fabrication and testing requirements of corrugated plastic ducts.
a.Use seamless fabrication methods to manufacture corrugated plastic duct.
2.Use rigid smooth black polyethylene ducts manufactured from 100 percent virgin polyethylene resin meeting the requirements of ASTM D 3350 with a minimum cell class of 445574C where the tendon is not embedded in concrete .
a.Use a resin containing antioxidant(s) with a minimum oxidation induction time (OIT) according to ASTM D 3895 of not less than 40 minutes .
b.Manufacture s mooth duct with a dimensional ratio (D/R) of
17.0 as established by either ASTM D 3035 or ASTM F 714
as appropriate for the manufacturing process used.
c.Use duct meeting the minimum pressure rating of 100 psi. Post-Tensioning Concrete
D.Exceptions
1.Use plastic ducts that are leak tight, vapor tight and impermeable where special corrosion protection is required, such as in bridge decks, external tendons, and bridge elements subjected to corrosive environments.
2.Use plastic ducts where stray electrical currents may cause corrosion damage to tendon materials.
3.Do not use plastic ducts when the radius of curvature of the tendon is less than 30 ft.
E.Splices, Joints, Couplings, Connections, and Inlet and Outlet Pipes
1.Use stainless steel, nylon, or polyolefin materials.
a.Stainless steel products other than bolts, conform to ASTM A 240 Type 316. 1) ASTM F593 Type 316 for bolts
b.Nylon products, use one of the following cell classes according to ASTM D 5989: 1) S-PA0141 (weather resistant) 2) S-PA-0231 (heat stabilized) 3) S-PA0401 (ultimate strength not less than 10,000 psi with UV stabilizers added)
c.Polyolefin products, conform to the following: 1) Contains antioxidants with a minimum induction time of 20 minutes according to ASTM D 3895 2) Remolded finished polyolefin material has a stress crack resistance minimum failure time of 3 hours at an applied stress of 348 psi using ASTM F 2136
2.Make splices, joints, couplings, and connection to duct and anchorage with devices or methods (mechanical couplers, plastic sleeves, heat -shrink sleeves) producing a smooth interior alignment with no lips or kinks.
a.Provide connections and fittings that are airtight and watertight.
b.Tape sealed connections or repairs are not permitted
c.Heat-shrink sleeves requirements, refer to PTI M50.3, Section 4.3.7.
d.Provide connections that are external to the concrete with a minimum pressure rating of 100 psi.
3.Plastic components, including fasteners, must be free of water soluble chlorides and not react with the concrete or enhance corrosion of the prestressing steel. Post-Tensioning Concrete
4.Use inlet and outlet pipes that are ¾ inch minimum inside diameter for strand tendons, or ⅜ inch for single bar tendons.
a.Use inlet and outlet pipes that are fitted with positive mechanical shut -off valves or plugs . 1) Design and test inlets, outlets, valves, and plugs to resist a minimum pressure of 150 psi .
b.Extend pipes a sufficient distance out of the concrete member to allow for proper closing of the valves
2.5 Reinforcing Steel
A.Use coated reinforcing steel according to Section 03211.
2.6 Pt Grout
A.Use a commercial, prepackaged, anti -bleed, post -tensioning grout conforming to the requirements for a Class C grout as defined by PTI M55.1.
1.Furnish grout capable of meeting the vertical rise requirements for the project tendons.
2.Deliver grout in plastic lined or coated moisture proof containers, stamped with the application type, date of manufacture, lot number and mixing and pumping instructions.
a.Use grout within 6 months of manufacture.
3.Use water that is potable, clean, and free of injurious quantities of substances known to be harmful to Portland cement or prestressing steel.
2.7 Epoxy Grout
A.Refer to Table 1 for properties Table 1 Epoxy Grout Properties Property Test Method Requirements Compressive Strength (7 day) ASTM C 579 Method B , 2 inch cubes , Load Rate II > 10,000 psi Tensile Strength (7 day) ASTM C 307 > 2,000 psi Slant Shear Bond Strength ASTM C 882 > 1,500 psi Linear Shrinkage ASTM C 531 0.025 % Post-Tensioning Concrete
2.8 Permanent Grout Cap
A.Use permanent grout caps made of one of the following:
1.Fiber reinforced polymers using nylon, Acrylonitrile Butadiene Styrene (ABS), or polyester resins :
a.Use one of the following cell classes for products made from nylon: 1) S-PA0401 (weather resistant) 2) S-PA0231 3) S-PA0401 (ultimate strength not less than 10,000 psi with ultraviolet stabilizer added) according to A STM D 5989
2.ASTM A 240 Type 316L stainless steel
B.Use caps rated for a minimum pressure of 150 psi.
C.Seal caps against the anchor bearing plate with neoprene “O” -ring seals and ASTM F 593 Type 316 stainless steel bolts.
D.Provide an inlet port at the top of the cap or front of cap as appropriate.
2.9 Epoxy Com Pound
A.Comply with ASTM C 881 Type IV.
Part 3 — Execution
3.1 Anchorage Installation
A.Arrange the anchorage so that the prestressing force in the tendon can be verified before removal of the stressing equipment.
B.Set anchorage devices or block -out templates for anchorages in a plane normal to the axis of the tendons s o that anchor plates are normal in all directions of the tendon and bear uniform ly on the concrete.
C.Recess the anchoring devices so that the ends of the prestressing steel and parts of anchoring devices including permanent grout caps are embedded at least 2 inches inside the end surface of the element.
D.Locate anchorages within plus or minus ¼ inch of the desired position laterally and plus or minus 1 inch along the tendon.
1.Maintain minimum cover requirements. Post-Tensioning Concrete
E.Verify entrance and exit angles of tendon paths at anchorages and at faces of concrete so they are within plus or minus 3 degrees of desired angle measured in any direction, and deviations in the alignment are accomplished with smooth transitions without kinks.
3.2 Duct Installation
A.Securely tie ducts in position, inspect, and repair before concrete placement is started.
1.Use s upplementary support bars where needed to maintain proper alignment of the duct .
B.Securely fasten internal ducts to avoid displacing or damaging the ducts during concrete placement.
1.Support p olyethylene duct and m etal duct for longitudinal PT in the flanges at intervals not to exceed 2 ft.
2.Tie p olyethylene duct in webs for longitudinal PT to stirrups at intervals not to exceed 2ft.
3.Support flat ducts for transverse PT at intervals of not more than 12 inches.
4.Tie m etal duct for longitudinal PT in webs to stirrups at intervals not to exceed 4 ft.
C.Verify final position of PT duct is within the tolerances shown in Table 10.4.1.1- 1 of the AASHTO LRFD Construction Specifications.
1.Position the duct as shown and adjust the reinforcement as determined by the Engineer if conflicts exist between the reinforcement and post -tensioning duct .
D.Provide inlet/outlet ports at the following locations:
1.Anchorage areas of tendon
2.The high points of the duct, when there is more than a 20 inch variation in the vertical position of the duct
a.Locate additional outlet ports 3 f t to either side of the high point
3.Low points of the duct. Verify outlet port is free draining
4.Major changes in the cross section of the duct, such as coupler locations
5.Locations as shown
E.Verify that ducts, anchorage blockouts, openings, inlets, and outlets are kept clean and free of debris, fuel, oils, other contaminants, and site trash.
1.Seal the ends of ducts after installation in the forms.
2.Leave low point outlets open. Post-Tensioning Concrete
F.Verify angle changes at duct joints are within plus or minus 3 degrees of desired angle measured in any direction, and deviations in the alignment are accomplished with smooth transitions without kinks .
G.Use mandrels as stiffeners in each duct during concrete placement for precast segments .
1.Extend mandrel throughout the length of the segment being cast and at least 2 f t into the corresponding duct of the previously cast segment.
2.Provide mandrels of sufficient rigidity to maintain the duct geometry with the tolerances shown in this Section.
3.3 Tendon Installation
A.Verify that ducts are unobstructed, undamaged, and free of water and debri s after completion of concrete placement and before installing the prestressing steel .
1.Prove that the ducts are clear of obstructions or damage by passing a suitably sized torpedo through the ducts.
a.Size the torpedo ¼ inch smaller than the clear, inside dimensions of the duct, with rounded ends.
b.Use a 2 ft long torpedo for straight ducts .
c.Size the torpedo, for sharply curved ducts , such that when both ends touch the outermost wall, the torpedo is at least ¼ inch clear of the inside wall.
d.The member will be rejected if the torpedo will not easily travel completely through the duct.
e.Using a torpedo to verify that ducts are clear is not required for four strand tendons in flat ducts used for transverse PT of segmental box -girders placed before concrete casting. 1) Prove PT ducts are free and clear of obstructions or damage by moving the group of strands back and forth in duct for a minimum distance of 1 f t in each direction. 2) Move strands easily, by hand, without resorting to excessive effort or mechanical assistance.
2.Flush ducts with oil -free and water -free compressed air or water as required to remove unwanted material from inside of ducts.
a.Ducts subjected to contamination with chlorides, water used for flushing ducts may contain slack lime (calcium hydroxide) or quicklime (calcium oxide) in the amount of 0.1 lb/gal. 1) Test for presence of chlorides and oils in discharged water before placing tendons. 2) Continue to flush if chloride levels in flush water outflow exceeded 300 ppm until chloride level in flush water outflow is below 250 ppm. Post-Tensioning Concrete
b.Blow all water out of the duct with oil -free compressed air and swab dry after flushing.
B.Conduct duct pressure field tests before installing the internal or external prestressing steel .
1.Install grout caps, inlet and outlet port caps, and other components necessary to seal ducts.
2.Pressurize duct to 5 0 psi using oil -free and water -free compressed air.
a.Only one duct per web or girder may be tested at a time.
3.Lock off the outside air source.
4.Record pressure loss for 1 minute.
a.Locate the leak, repair, and retest i f the pressure loss exceeds 15.0 psi for tendons greater than 150 f t long, or
25.0 psi for tendons less than or equal to 150 f t long .
5.Include location and method of repair in duct air test records if repairs are required.
6.Do not load strand until all pressure tests are successful.
C.Strands in an individual tendon may be pushed or pulled through the duct individually, or may be pulled through the duct as a unit.
1.Protect the strand which is being advanced into the duct from contact with abrasive materials such as steel or concrete and contaminants such as grease, oil, and dirt at all times.
a.Round off ends of strands and wires that are pushed, or fit advancing end with smooth protective cap.
b.Use pulling lines with a capacity of at least 2.5 times the dead weight of the tendons when used for essentially horizontal tendon installation.
c.Do not use pushing wheels made from metal.
d.Do not intentionally rotate strands or wires during installation.
e.Use a special steel wire sock or other device attached to advancing end if a tendon is pulled through the duct .
f.Do not install permanent tendons before completion of testing as required by this Section.
3.4 Stressing Tendons
A.General
1.Do not apply PT forces until the concrete has attained the required compressive strength as shown.
a.Do not apply PT forces to cast -in-place concrete structures other than segmentally constructed bridges until 10 days after the last concrete has been placed in the member. Post-Tensioning Concrete
b.Make t est cylinders for determining strength of the same concrete and cured under the same conditions as the member.
2.Stress all strands in each tendon simultaneously with a multi -strand jack except for those in flat ducts with not more than four strands .
3.Furnish equipment for tensioning the tendons from the manufacturer of the PT system.
4.Sequence the stressing of post -tension cast -in-place bridge such that no more than one tendon is stressed per web before stressing a tendon in another web.
a.Do not apply an eccentric force about the centerline of the structure that exceeds 1/6 of the total post -tensioning force at any time during the prestressing.
5.Keep stressing operation records that include the following for each tendon installed:
a.Project Pin, Name, and number
b.Contractor and subcontractor
c.Tendon location, size and type
d.Date tendon was first installed in ducts
e.Coil and reel number for strands or wires and heat number for bars and wire
f.Assumed and actual cross -sectional area
g.Assumed and actual modulus of elasticity
h.Date stressed
i.Jack and gauge numbers per end of tendon
j.Required jacking force
k.Gauge pressures
l.Elongations (theoretical and actual)
m.Anchor sets (theoretical and actual)
n.Stressing sequence ( for example tendons before and after this tendon)
o.Stressing mode (one end or two ends or simultaneous)
p.Witnesses to stressing operation (Contractor, m anufacturer’s representative, and Inspector)
q.Date grouted, days from stressing to grouting, grouting pressure applied, and injection end
r.Other relevant information
B.Stressing Jacks
1.Use hydraulic jacks to stress tendons that are capable of providing and sustaining the necessary forces. Equip each jack with either:
a.A pressure gauge with an accurately reading dial at least 6 inches in diameter . Post-Tensioning Concrete
b.A load cell with indicator by means of which the prestressing force in the tendon may be determined. 1) Do not use the lower 10 percent of the Manufacturer’s rated capacity when determining the jacking stress.
2.Use a jacking system that provides an independent means of measuring the tendon elongation.
C.Tensioning Operations 1. Tension prestressing steel so that the force of the prestressing steel will not be less than the value shown on the authorized shop drawings.
a.Do not exceed 80 percent of the g uaranteed ultimate tensile strength of the prestressing steel during the stressing of the tendons. 1) Replace tendons stressed past 80 percent of the guaranteed ultimate tensile strength.
b.Anchor the prestressing steel at initial stresses that will result in the long term retention of permanent forces of not less than those shown on the approved shop drawings.
c.Do not allow the initial stress at the anchorage to exceed 70 percent of guaranteed ultimate tensile strength after anchor set.
2.Remove and replace strand due to wire failure or slipping during stressing if any of the following conditions are met:
a.Member cross section has a final effective PT force less than 98 percent of the design total PT force based on the recorded jacking force or liftoff force, whichever is smaller .
b.PT force across a mating joint is less than 98 percent of PT force required by the contract drawings for that mating joint for that stage of construction. 1) This requirement applies to segmental construction, or similar construction that has members post - tensioned together across a common joint face at any stage of construction.
c.Any single tendon has more than a 5 percent reduction in cross- sectional area or post -tensioning steel due to wire failure.
3.Follow stressing sequence shown in authorized shop drawings.
D.Elongations
1.Conduct the tensioning process such that tension being applied and the elongation of the post -tensioning steel can be measured at all times.
2.Keep a permanent record of gauge pressures and tendon elongations for each tendon.
3.Measure elongations to the nearest 1/16 inch. Post-Tensioning Concrete
4.Preload tendons to 20 percent of their final jacking force before beginning elongation readings to eliminate take -up in the tensioning system.
5.Mark e ach strand before final stressing to permit measurement of elongation and to verify that all anchor wedges set properly.
6.The measured elongation must agree within 7 percent of the theoretical elongation for the post -tensioned elements to verify the required tendon force, or the entire operation must be checked and the source of the error determined and remedied to the satisfaction of the Department before proceeding with the work .
a.Do not overstress the tendon to achieve the theoretical elongation.
b.Acceptance may be achieved by force verification lift -off tests demonstrating that the measured force is within minus 1 percent and plus 5 percent of the required force as shown if the measured elongations fall outside of the acceptable tolerance.
7.Do not cut off the stressing tails of the tendons until the elongations have been approved by the PT system manufacturer’s representative. Within 4 hours of approval:
a.Cut prestressing steel using an abrasive saw or plasma torch to within ¾ inch to 1½ inch from anchorage. 1) Flame cutting of PT steel is not permitted.
b.Clean rust and other debris from metal surfaces which will be covered by the grout cap
c.Place grout cap, including a seal, over the wedge place until the tendon is grouted.
E.Protection of Steel After Installation
1.Minor rust which may form on the surface of the prestressing steel within 10 calendar days after protective packaging has been opened will not be cause for rejection.
2.Prestressing steel installed, tensioned, and grouted within 10 calendar days will not require the use of corrosion inhibitor in the duct following installation of the prestressing steel.
a.Blow a vapor phase corrosion inhibitor powder conforming to MIL-PRF-3420 into ducts containing prestressing steel if prestressing steel is anticipated to be removed from protective packaging for 10 days or more before grouting.
3.Do not exceed 15 calendar days between removal of prestressing steel from protective packaging and grouting operations.
a.Failure to begin grouting operations will result in stoppage of work. Post-Tensioning Concrete
3.5 Grouting
A.General
1.Begin grout ing operations to fill the void space between the duct and the tendons as soon as possible after all the prestressing steel has been tensioned, anchored and approved by the PT system manufacturer’s representative.
2.Flush the inside of the duct with water under pressure to remove all traces of the corrosion inhibitor used to protect the prestressing steel if a vapor phase corrosion inhibitor has been blown into ducts before grouting.
a.Continue flushing operations until the discharge water is free of traces of the corrosion inhibitor.
b.Blow all water out of the duct with oil -free compressed air and swab dry after flushing.
3.Eliminate vibration from all sources under the contractor’s control within 300 f t of the member being grouted for the duration of the grouting procedure and 4 hours after completion.
4.Conduct a joint meeting of the Contractor, grouting crew and the Engineer before grouting operations begin .
a.Discuss the grouting operation plan, required testing, corrective procedures, and other relevant issues at the meeting.
B.Temperature
1.Keep PT grout below 90 degrees F during mixing or pumping.
a.Cool the mixing water if necessary.
2.Keep ducts free of water to avoid damage due to freezing in temperatures below 32 degrees F.
3.Keep accurate temperature records covering maximum and minimum air temperatures, and temperatures of the concrete adjacent to the ducts to be grouted when ambient temperature m ay be expected to fall below 40 degrees F .
4.Do not use any material in which frost or ice is present, and keep the ducts and equipment free of frost and ice.
5.Postpone grouting operations if frost is expected within 48 hours of start.
6.Maintain a temperature of at least 35 degrees in the grout in the ducts for the duration of the grouting and the longer of 72 hours after completion or until job- cured 2 inch cubes of PT grout reach a minimum compressive strength of 800 psi when low temperatures are expected and grouting cannot be postponed. Post-Tensioning Concrete
C.Equipment
1.Use equipment which meets the requirements in Section 10.11.3 of the AASHTO LRFD Bridge Construction Specifications.
2.Provide flushing equipment with an independent power source on site, capable of developing a pressure of 250 psi and of sufficient capacity to flush out partially grouted ducts as required due to blockage or breakdown of equipment.
a.Do not exceed the allowable grouting pressures when flushing. Refer to this Section, article 3.5 E7.
D.Mixing
1.Mix PT grout according to the manufacturer’s recommendations.
a.Continue mixing grout until a uniform, thoroughly blended grout is obtained, without excessive temperature increase.
2.Agitate the grout continuously u ntil it is pumped.
3.Do not begin grouting operations until the field trial tests specified in PTI M55.1, Section 4.7.1 have been satisfactorily performed.
a.Do not add water to increase grout flowability that has been decreased by delayed use of the grout.
4.Perform field mockup test specifi ed in PTI M55.1, Section 4.7.2, when required by the E ngineer.
5.Do not exceed a water -cement ratio of 0.45.
E.Grout ing Operations
1.Blow oil- free and water -free compressed air through the ducts checking all inlet and outlet pipes to verify they are capable of accepting injection of the PT grout immediately before grouting.
2.Open all inlet and outlet ports before grouting starts.
3.Obtain target flow rates as a function of mixer type used and ambient temperatures from the PT grout manufacturer.
a.Verify the grouting rate is slow enough to avoid air entrapment and segregation of the grout and verify complete filling of the duct.
4.Maintain a continuous, one- way flow of PT grout in a generally uphill direction.
a.Inject PT grout from near the lowest end of tendons.
b.Grout each tendon in one operation.
c.Flush the grout out of the duct with water immediately when one-way flow of grout cannot be maintained or grouting is interrupted.
5.Refer to PTI M55.1 , Section 4.7.3 for production test requirements of production grout.
6.Perform normal operations at approximately 75 psi.
7.Do not exceed a pumping pressure at the tendon inlet of:
a.145 psi for internal polyethylene ducts
b.245 psi for internal circular steel ducts Post-Tensioning Concrete
c.145 psi for external HDPE pipe
d.Close the inlet and inject the PT grout at the next outlet (which now becomes an inlet) which has just been, or is ready to be closed, as long as a one- way flow is maintained if the actual grouting pressure exceeds the maximum allowed . 1) Fit the outlet that is to be used for injection with a positive shutoff . 2) Do not inject grout into a succeeding outlet from which grout has not yet fl owed.
8.Waste grout through the first outlet after the inlet pipe until residual water or entrapped air has been removed,
a.Cap or otherwise close outlet when the consistency of the ejected grout is the same as the injected grout.
b.Close following remaining outlets in the same manner, except at high points where the outlets a short distance downstream to the high point are closed before the high point outlet.
c.Discharge at least 2 gallons of grout through the final outlet pipe before sealing.
9.Provide a standpipe at the upper end of the duct for vertical or nearly vertical tendons.
a.Design the standpipe to collect and store bleed water and allow it to be removed from the grout.
b.Locate the standpipe so that the level of the grout can be brought to an elevation so that bleeding will not cause the level of the grout to drop below the highest point of the upper anchorage device.
c.Remove the standpipe after the grout has hardened.
10.Do not remove or open plugs, caps, or valves until the PT grout has set.
a.Remove ends of inlet/outlet pipes at least 2 inches below the concrete surface after the grout has set.
b.Fill the void with epoxy grout within 4 hours of inlet and outlet removal .
c.Remove all miscellaneous material used for sealing grout caps before carrying our further work to protect anchorages .
d.Permanently seal all outlet and inlet openings for external tendons .
11.Keep grouting operation records that include the following for each duct:
a.Names of personnel performing the grouting activity
b.Identification of tendon
c.Date grouted
d.Number of days from tendon installation to grouting
e.Quanti ties and types of material used Post-Tensioning Concrete
f.The maximu m pumping pressure at the inlet
g.Temperature measurements of air, water, prepackaged material, mixture grout, and concrete member in the duct 1) Note if temperatures are within acceptable limits.
h.Summary of tests performed and the results, inc luding post-grouting inspection
i.Volume of grout pumped and capacity of duct accounting for reduction for area of prestressing steel 1) Include ratio of actual grout used to anticipated quantity of grout used.
j.Time from beginning grouting operation to sealing all inlet and outlet pipes
k.Discussions of problems encountered during grouting and steps taken to resolve them
F.Post-Grouting Inspection
1.Randomly inspect 10 percent of the inlet and outlet pipes at anchorage and at high points for voids by drilling and inspecting with a borescope.
a.Inspect ducts between 24 and 72 hours after grouting.
b.Use drilling equipment that will automatically shut off when steel is encountered to prevent damaging the prestressing steel and anchorages.
c.All anchorages and high points will be inspected if a void exposing prestressing steel is found by random drilling.
d.Fill drilled holes not indicating voids with epoxy compound within 4 hours of completion of inspections. 1) Use an injection tube to fill drilled hole from the base.
e.Use vacuum grouting to fill voids that expose prestressing steel. 1) Perform vacuum grouting operations under the direct supervision of a crew foreman who has been trained and has experience in the use of vacuum grouting equipment and procedures.
3.6 Protection of End Anchorage
A.Protect PT strand, wire, and bar anchorages as soon as practical, but not to exceed 10 days after grouting is completed .
B.Cap inlets and outlets with plastic or stainless steel threaded plugs. Post-Tensioning Concrete
C.Construct anchorage pour -backs with epoxy grout according to manufacturer’s recommendations.
1.Mechanically clean and abrasive blast clean the surface of concrete in anchorage recesses until clean aggregate is exposed. a) Flush surface with water and blow dry.
2.Do not damage reinforcing steel coatings.
3.Test substrate at pour-back locations using ASTM C 1583 and develop a minimum of 175 psi tension.
D.Construct pour -backs using tight fitting forms that can be installed and held in place securely against the previously placed concrete.
1.Fill recess with epoxy grout and finish flush.
Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 945–968 of 1,331.