03251Post-Tensioning Concrete

POST-TENSIONING CONCRETE

PART 1 GENERAL

1.1SECTION INCLUDES

concrete elements.

but not limited to ducts, anchorage assemblies, supplementary reinforcing bars, and grout used for pressure grouting ducts.

1.2RELATED SECTIONS

1.3REFERENCES

Reinforcement

Concrete

Concrete

Seamless

Sheet, and Strip for Pressure Vessels and General Applications

Coated (Galvannealed) by the Hot-Dip Process

Post-Tensioning Concrete

Monolithic Surfacings

Chemical-Resistant Mortars, Grouts, Monolithic Surfacings, and Polymer Concretes

Grouts, Monolithic Surfacings, and Polymer Concretes

Concrete by Slant Shear

Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-Off Method)

Controlled Outside Diameter

Scanning Calorimetry

(PA)

Diameter

Determine Slow-Crack-Growth Resistance of HDPE Resins or HDPE Corrugated Pipe

Opaque

Post-Tensioning Post-Tensioning Concrete

Post-Tensioned Structures

1.4DEFINITIONS

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 ejection of materials from inside the ducts.

occurrence of losses, including the anchor set loss.

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, friction, 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.

ducts. Used to prove that installed ducts have not been blocked or damaged during the concrete pour.

1.5SUBMITTALS

following:

grillage reinforcement

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

set Post-Tensioning Concrete

grout cap

LRFD Bridge Design Specifications

after friction and anchor set losses based upon expected actual coefficients and values for the PT system to be used.

concrete reinforcing at locations where duct or anchorage passes through grids of reinforcing steel, such as at anchorage zones, diaphragms, bents, and other highly congested areas.

revisions to concrete dimensions from that shown.

approval.

scheduled grouting operations for review.

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 grouting, 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 pressure 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.

a test report including the following:

for use

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.

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.

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.

this Section, Article 2.3, paragraph A.

with each jack and associated gauge or load cell used on the project.

cylinder extension in the approximate position that it will be at final jacking force.

Post-Tensioning Concrete

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.

while the jack is in the identical configuration as will be used on site including same length of hydraulic lines.

this Section, Article 3.3, paragraph B for information.

stressing along with jacking force and target elongation. Refer to this Section, Article 3.4.

along with jacking force, gauge pressure, and target elongation for information within five days of completed tendon installation. Refer to this Section, Article 3.4, paragraph D.

Section, Article 3.4, paragraph A5 for information.

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.

grouting operation supervisor in control of the work for information within five calendar days after grouting

and grouting

Section, Article 3.5, paragraph E11

1.6SUPERVISOR REQUIREMENTS

Post-Tensioning Concrete

to:

placement around the ducts, end-anchorage assemblies, and other appurtenances

approval of elongations

operations are occurring simultaneously.

PTI Level 2 Bonded PT Field Specialist

including:

PART 2 PRODUCTS

2.1GENERAL

until time of use.

Post-Tensioning Concrete

2.2PRESTRESSING STEEL

conforming to AASHTO M 203

each mill heat, wire from each coil, anchorage assemblies, PT system components and bar couplers to be shipped to the site.

each lot can be accurately identified at the job site.

couplers received at the site will be rejected if there is a loss of positive identification of these items at any time.

actual ultimate strength of the bar, tested in an unbonded state, without exceeding anticipated set.

below the anticipated elongation of an uncoupled bar.

results of corrosion at all times from manufacture to grouting or encasing in concrete.

matter or pitting on its surface.

protect the steel against physical damage and corrosion during shipping and storage.

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

useful life expires.

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.

to original condition.

2.3POST-TENSIONING ANCHORAGES

ultimate tensile strength of the prestressing steel, tested in an unbonded state, without exceeding the anticipated set.

2.4DUCTS

rigid steel pipe ducts or smooth plastic ducts.

concrete pressures without deforming or permitting the entrance of cement paste during the placing of concrete.

locations shown.

cross-sectional area of the prestressing steel

diameter, measured across deformations

than largest dimension of the largest enclosed element 1) Enclose bar couplers and coupler components in housings long enough to permit the necessary movements

values shown.

and have sufficient strength to maintain their correct alignment during placing of concrete.

capable of positively preventing the entrance of cement paste and water from concrete.

deteriorate. Post-Tensioning Concrete

during placement.

in the fluid concrete would lift the reinforcing steel.

sheet steel, coating designation G90.

1) 26 gauge for semi-rigid ducts less than or equal to 2.625 inches in diameter 2) 24 gauge for semi-rigid ducts greater than 2.625 inches in diameter 3) 31 gauge when bar tendons are preassembled with semi-rigid ducts

1) Galvanize welded seams.

Grade B schedule 40 steel pipe.

the proper configuration without crimping or flattening.

connections which do not result in angle changes at the joints.

Specifications for the fabrication and testing requirements of corrugated plastic ducts.

corrugated plastic duct.

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.

oxidation induction time (OIT) according to ASTM D 3895 of not less than 40 minutes.

17.0 as established by either ASTM D 3035 or ASTM F 714 as appropriate for the manufacturing process used.

Post-Tensioning Concrete

where special corrosion protection is required, such as in bridge decks, external tendons, and bridge elements subjected to corrosive environments.

corrosion damage to tendon materials.

is less than 30 ft.

A 240 Type 316. 1) ASTM F593 Type 316 for bolts

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)

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

anchorage with devices or methods (mechanical couplers, plastic sleeves, heat-shrink sleeves) producing a smooth interior alignment with no lips or kinks.

watertight.

Section 4.3.7.

minimum pressure rating of 100 psi.

soluble chlorides and not react with the concrete or enhance corrosion of the prestressing steel.

Post-Tensioning Concrete

for strand tendons, or ⅜ inch for single bar tendons.

mechanical shut-off valves or plugs. 1) Design and test inlets, outlets, valves, and plugs to resist a minimum pressure of 150 psi.

member to allow for proper closing of the valves

2.5REINFORCING STEEL

2.6PT GROUT

conforming to the requirements for a Class C grout as defined by PTI M55.1.

the project tendons.

stamped with the application type, date of manufacture, lot number and mixing and pumping instructions.

substances known to be harmful to Portland cement or prestressing steel.

2.7EPOXY GROUT

Table 1 Epoxy Grout Properties Property Test Method Requirements ASTM C 579 Compressive Strength Method B, 2 inch > 10,000 psi (7 day) cubes, Load Rate II 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

2.8PERMANENT GROUT CAP

Styrene (ABS), or polyester resins:

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 ASTM D 5989

and ASTM F 593 Type 316 stainless steel bolts.

2.9EPOXY COMPOUND

PART 3 EXECUTION

3.1ANCHORAGE INSTALLATION

verified before removal of the stressing equipment.

normal to the axis of the tendons so that anchor plates are normal in all directions of the tendon and bear uniformly on the concrete.

and parts of anchoring devices including permanent grout caps are embedded at least 2 inches inside the end surface of the element.

laterally and plus or minus 1 inch along the tendon.

Post-Tensioning Concrete

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.

3.2DUCT INSTALLATION

placement is started.

alignment of the duct.

during concrete placement.

flanges at intervals not to exceed 2 ft.

intervals not to exceed 2ft.

inches.

to exceed 4 ft.

10.4.1.1-1 of the AASHTO LRFD Construction Specifications.

determined by the Engineer if conflicts exist between the reinforcement and post-tensioning duct.

variation in the vertical position of the duct

point

locations

kept clean and free of debris, fuel, oils, other contaminants, and site trash.

Post-Tensioning Concrete

desired angle measured in any direction, and deviations in the alignment are accomplished with smooth transitions without kinks.

precast segments.

and at least 2 ft into the corresponding duct of the previously cast segment.

with the tolerances shown in this Section.

3.3TENDON INSTALLATION

debris after completion of concrete placement and before installing the prestressing steel.

a suitably sized torpedo through the ducts.

dimensions of the duct, with rounded ends.

both ends touch the outermost wall, the torpedo is at least ¼ inch clear of the inside wall.

travel completely through the duct.

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 ft in each direction. 2) Move strands easily, by hand, without resorting to excessive effort or mechanical assistance.

required to remove unwanted material from inside of ducts.

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

and swab dry after flushing.

prestressing steel.

necessary to seal ducts.

air.

exceeds 15.0 psi for tendons greater than 150 ft long, or 25.0 psi for tendons less than or equal to 150 ft long.

repairs are required.

individually, or may be pulled through the duct as a unit.

contact with abrasive materials such as steel or concrete and contaminants such as grease, oil, and dirt at all times.

advancing end with smooth protective cap.

dead weight of the tendons when used for essentially horizontal tendon installation.

installation.

advancing end if a tendon is pulled through the duct.

testing as required by this Section.

3.4STRESSING TENDONS

compressive strength as shown.

other than segmentally constructed bridges until 10 days after the last concrete has been placed in the member.

Post-Tensioning Concrete

concrete and cured under the same conditions as the member.

jack except for those in flat ducts with not more than four strands.

manufacturer of the PT system.

that no more than one tendon is stressed per web before stressing a tendon in another web.

structure that exceeds 1/6 of the total post-tensioning force at any time during the prestressing.

tendon installed:

for bars and wire

this tendon)

representative, and Inspector)

pressure applied, and injection end

and sustaining the necessary forces. Equip each jack with either:

6 inches in diameter.

Post-Tensioning Concrete

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.

measuring the tendon elongation.

steel will not be less than the value shown on the authorized shop drawings.

strength of the prestressing steel during the stressing of the tendons. 1) Replace tendons stressed past 80 percent of the guaranteed ultimate tensile strength.

in the long term retention of permanent forces of not less than those shown on the approved shop drawings.

percent of guaranteed ultimate tensile strength after anchor set.

stressing if any of the following conditions are met:

98 percent of the design total PT force based on the recorded jacking force or liftoff force, whichever is smaller.

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.

cross-sectional area or post-tensioning steel due to wire failure.

and the elongation of the post-tensioning steel can be measured at all times.

elongations for each tendon.

Post-Tensioning Concrete

beginning elongation readings to eliminate take-up in the tensioning system.

elongation and to verify that all anchor wedges set properly.

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.

elongation.

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.

have been approved by the PT system manufacturer’s representative. Within 4 hours of approval:

torch to within ¾ inch to 1½ inch from anchorage. 1) Flame cutting of PT steel is not permitted.

be covered by the grout cap

the tendon is grouted.

within 10 calendar days after protective packaging has been opened will not be cause for rejection.

calendar days will not require the use of corrosion inhibitor in the duct following installation of the prestressing steel.

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.

steel from protective packaging and grouting operations.

work.

Post-Tensioning Concrete

3.5GROUTING

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.

traces of the corrosion inhibitor used to protect the prestressing steel if a vapor phase corrosion inhibitor has been blown into ducts before grouting.

of traces of the corrosion inhibitor.

and swab dry after flushing.

within 300 ft of the member being grouted for the duration of the grouting procedure and 4 hours after completion.

Engineer before grouting operations begin.

corrective procedures, and other relevant issues at the meeting.

temperatures below 32 degrees F.

minimum air temperatures, and temperatures of the concrete adjacent to the ducts to be grouted when ambient temperature may be expected to fall below 40 degrees F.

the ducts and equipment free of frost and ice.

start.

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

the AASHTO LRFD Bridge Construction Specifications.

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.

flushing. Refer to this Section, article 3.5 E7.

grout is obtained, without excessive temperature increase.

PTI M55.1, Section 4.7.1 have been satisfactorily performed.

decreased by delayed use of the grout.

when required by the Engineer.

checking all inlet and outlet pipes to verify they are capable of accepting injection of the PT grout immediately before grouting.

ambient temperatures from the PT grout manufacturer.

entrapment and segregation of the grout and verify complete filling of the duct.

uphill direction.

one-way flow of grout cannot be maintained or grouting is interrupted.

of production grout.

Post-Tensioning Concrete

(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 flowed.

water or entrapped air has been removed,

ejected grout is the same as the injected grout.

except at high points where the outlets a short distance downstream to the high point are closed before the high point outlet.

pipe before sealing.

nearly vertical tendons.

allow it to be removed from the grout.

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.

set.

concrete surface after the grout has set.

removal.

caps before carrying our further work to protect anchorages.

tendons.

duct:

Post-Tensioning Concrete

material, mixture grout, and concrete member in the duct 1) Note if temperatures are within acceptable limits.

post-grouting inspection

reduction for area of prestressing steel 1) Include ratio of actual grout used to anticipated quantity of grout used.

and outlet pipes

steps taken to resolve them

anchorage and at high points for voids by drilling and inspecting with a borescope.

steel is encountered to prevent damaging the prestressing steel and anchorages.

exposing prestressing steel is found by random drilling.

within 4 hours of completion of inspections. 1) Use an injection tube to fill drilled hole from the base.

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.

3.6PROTECTION OF END ANCHORAGE

to exceed 10 days after grouting is completed.

Post-Tensioning Concrete

manufacturer’s recommendations.

in anchorage recesses until clean aggregate is exposed.

develop a minimum of 175 psi tension.

held in place securely against the previously placed concrete.

END OF SECTION

Post-Tensioning Concrete