attachment-2-bid-193-25.pdf

SECTION 528

2016 NHDOT

Description

1.1 This work shall consist of manufacturing, storing, transporting, and erecting, precast, pre-tensioned, concrete I-girders, bulb-tee girders, box beams, butted deck beams, and deck panels herein referred to as “ members”, in accordance with the Contract plans. The relevant provisions of the AASHTO LRFD

Bridge Construction Specifications shall be adhered to unless such provisions are in conflict with this specification. This specification includes provisions for high performance concrete and alkali-silica reactivity.

Materials

2.1 Cement. Portland cement shall be Type II or III conforming to AASHTO M 85 or M 240, as appropriate.

2.1.1 All cement used in the manufacture of the members in any one structure shall be the same brand, type and color, unless otherwise permitted.

2.2 Aggregate. Aggregate shall conform to the requirements of 520.2.2. The coarse aggregate gradation shall be as specified for Concrete Class AA in Section 520.

2.3 Admixtures. Admixtures shall conform to the requirements of 520.2.3.

2.4 Prestressing Steel.

2.4.1 Prestressing steel shall be uncoated, seven-wire strand, conforming to the requirements of

AASHTO M 203 Grade 270 low-relaxation.

2.4.2 The Fabricator shall furnish certified copies of a representative load-elongation curve test report for each size and grade of strand, for lots of 10 tons or fraction thereof.

2.4.3 The Fabricator shall furnish a certified mill test report for each heat and coil of wire used in the production of the strand.

2.4.4 Each manufactured reel of prestressing steel strand to be shipped shall be assigned an individual lot number and clearly tagged for accurate identification. Such identification shall not be removed from the reel or strand until the reel is entirely used or until end-use fabrication has been completed.

2.5 Reinforcing steel. Reinforcing steel shall conform to the requirements of 544.2.

2.6 Wire Fabric. Welded deformed steel wire fabric shall conform to the requirements of AASHTO M

221M.

2.7 Storage of concrete materials shall conform to the requirements of 520.2.10.

2.8 Concrete.

2.8.1 Concrete shall be controlled, mixed, and handled as specified in the pertinent portions of Section

520 unless otherwise specified herein.

2.8.2 Mix Design. The Fabricator shall design and submit for approval the proportions and test results for a concrete mix which shall attain the following: a minimum design compressive strength as detailed on the plans for test cylinders sampled in accordance with the requirements of AASHTO T 141, molded and cured in accordance with the requirements of AASHTO T 23, and tested in accordance with the requirements of AASHTO T 22; a surface resistivity greater than 15 kilohm-centimeter (kΩ-cm) at 56 days using AASHTO TP 95. The minimum average compressive strength of the proposed mix shall be determined using the procedures in Appendix D. Air entrainment shall be targeted at a value of 6.0 percent +/-1.5 percent. Testing shall be in accordance with AASHTO T 119 and T 152.

2.8.2.1 Thirty (30) days prior to the start of member fabrication, the mix design shall be submitted to the

Bureau of Materials and Research for approval. No concrete shall be placed within the forms until the concrete mix design is approved.

2.8.2.2 The Fabricator shall supply laboratory test reports that contain data on the mineralogy and potential reactivity for all aggregates being used in the concrete mix. All aggregates shall be tested in accordance with the requirements of AASHTO T 303 to determine alkali-silica reactivity. The laboratory supplying the test results shall provide evidence that the laboratory is properly equipped and qualified to perform the test methods. All test results submitted for alkali-silica reactivity shall be from tests conducted within one calendar year from the date the mix design is submitted to the Department.

2.8.2.3 Mix designs using potentially alkali reactive aggregates shall include mitigation for reactivity and shall be submitted to the Department for approval. Mitigation of potentially reactive aggregates shall consist of one or more of the following methods: use of low alkali cement (less than 0.6 percent Na2O equivalent); use of a mineral admixture; or use of a chemical admixture. The proposed mitigation method will be accepted for use after the NHDOT Bureau of Materials and Research reviews test results supplied by the Contractor that show the effectiveness of the mitigation. An effective mitigation technique should reduce the mean expansion to below 0.10% for alkali-silica reactivity when tested in accordance with AASHTO T303.

2.8.2.4 Should a change in sources of material be made, a new mix design shall be established and approved prior to incorporating the new material. When unsatisfactory results or other conditions make it necessary, the Engineer will require a new mix design.

2.8.3 All concrete used in precast prestressed members shall contain corrosion inhibitor as shown on the

Qualified Products

List, Section 520. Corrosion inhibitor shall be used at the rate recommended by the manufacturer.

Construction Requirements

3.1 General.

3.1.1 Design stresses are closely controlled, however, the behavior in service depends upon the specified concrete being properly placed in forms of the correct dimensions around accurately positioned prestressed strand.

3.1.2 Specifications. Fabrication, transportation and erection of prestressed concrete members shall conform to the requirements of the AASHTO LRFD Bridge Construction Specifications, Section 8-

Concrete Structures and Section 10-Prestressing, and PCI MNL-116, Manual for Quality Control for

Plants and Production of Precast and Prestressed Concrete Products, except as modified by this special provision. In the case of conflicting specifications, the most stringent shall apply.

3.1.3 Approval. Prior to performing any work under 528, the Contractor must have received approval for all shop drawings and any special Contract requirements.

3.1.4 Special Contract Requirements.

3.1.4.1 Pre-Placement Meeting. A pre-placement meeting may be requested by the Engineer and shall be scheduled to review the specification, the schedule, and discuss any special requirements. The meeting will be held at least forty-five (45) days prior to the scheduled casting of any member or test section. The Bureau of Bridge Maintenance shall schedule the meeting and invite representatives of the

Fabricator and Materials and Research, along with any other party the Engineer deems appropriate.

3.1.4.2 Sure Cure System. The Fabricator shall utilize the Sure Cure Cylinder Mould System, or approved equivalent system, to temperature match cure test cylinders sampled in accordance with AASHTO T 141, molded in accordance with AASHTO T 23 and tested in accordance with AASHTO T 22 for use in verifying concrete compressive strength at release (f’ci), design compressive strength (f’c) for acceptance and concrete permeability in all member types. Verification that the system is operating properly shall be supplied to the Department once every 12 months. Documentation shall confirm that the system heats the molds only when they are colder than the internal girder temperature.

3.1.4.2.1 Match cured cylinders shall be produced using the sure cure system. The cylinders shall be connected to the system’s temperature matching controller for the initial curing period. Once the members are stripped and detensioned or the test section stripped, the cylinders shall be subsequently stripped from their molds and stored alongside the member or the test section until they are scheduled to be tested.

3.1.4.2.2 The system’s reference thermocouple shall be located in the center of the bottom bulb. of the girder section, or as otherwise directed by the Engineer in other member types. The thermocouple extension wire shall protrude up out of the member and shall be connected to the system’s temperature matching controller. Thermocouples shall be placed as follows:

• For members longer than 50 ft. in length, one thermocouple shall be placed in each member cast.

• For members less than 50 ft. in length, one thermocouple shall be placed in each 12 cy. of product (i.e.

3 thermocouples shall be installed for a placement with 30 cy. of concrete). A minimum of 1 thermocouple shall be placed in each bed cast.

3.1.4.3 Test Section.

3.1.4.3.1 At least thirty (30) days prior to member fabrication, a test placement [10 ft. in length] of the actual member section (unreinforced) shall be poured utilizing the proposed methods of concrete placement and curing. The air entrainment target value of 5 percent shall be held as an absolute minimum value for the test section. Concrete not meeting the air content target value shall not be incorporated into the test placement. Slump as required per 2.8.2 shall be maintained.

3.1.4.3.2 The Fabricator shall submit to the Bureau of Materials & Research results of temperature match cured cylinders(a set of two, averaged to comprise one strength test) tested for strength at the following intervals as a minimum (15 hours, 24 hours, 3 days, 7 days, and 28 days) for determination of a strength versus time plot for the test placement section.

3.1.4.3.3 The Fabricator shall obtain two cores in accordance with AASHTO T 24 from the web of the girder test section, or other location determined by the Engineer, and test them for design compressive strength at 28 days (or other time interval to attain design compressive strength as detailed on the plans) to verify the in place concrete strength of the test section. The cores shall be taken no earlier than two days prior to conducting the actual test. Results of the core strength tests shall be submitted to the

Bureau of Materials & Research.

3.1.4.3.4 Surface Resistivity testing may be completed by the Bureau of Materials & Research in accordance with AASHTO TP 95 at an age of 56 days or later. The Fabricator shall obtain one additional core from the web of the girder test section and submit the cores to the Bureau of Materials & Research for permeability testing. The Fabricator shall also submit one additional match cured cylinder from the test placement to the Bureau of Materials & Research for permeability testing.

3.1.4.3.5 Approval to proceed to member fabrication will be provided by the Bureau of Materials &

Research and shall be contingent on successfully achieving the minimum design compressive strength in each of the match cured cylinders and cores tested at 28 days. If unsatisfactory results occur or conditions arise to hinder the outcome of the tests, the Engineer will require a new test section placement, with modifications as deemed necessary, to be poured and successfully tested.

3.1.4.3.6 Test Section Exemption. Fabricators having proven experience with the mix design submitted for use, in precast/prestressed bridge member applications, shall be exempt from the test section placement, as approved by the Department. Proven experience will be determined by the Bureau of

Materials and Research based on submission of satisfactory test resultsusing a particular mix design that meets or exceeds the following criteria in a similar fabricated bridge member or a similar 10 foot long bridge member test section:

Compressive Strength (as specified in 3.1.4.3.5)

Surface Resistivity (as specified in 2.8.2)

Air content (as specified in 3.1.4.3.1 or higher)

Slump of the concrete (as specified in 2.8.2)

Approval to proceed to member fabrication will be provided by the Bureau of Materials and Research and shall be contingent on review and approval of the submitted test results.

3.1.4.4 The fabrication schedule shall account for phased construction and the durations between the construction phases as shown on the plans.

3.1.5 Member Concrete Strength Testing.

3.1.5.1 The Fabricator shall submit to the Bureau of Materials & Research results of temperature match cured cylinders (a set of two, averaged to comprise one strength test) tested for compressive strength at release and design compressive strength at 28 days (or other time interval to attain design compressive strength detailed) for each bed cast.

3.1.5.2 Each member cast shall have a minimum of two additional match cured cylinders for each thermocouple used available for testing by the Department at 28 days (or other time interval to attain design compressive strength detailed) for quality assurance. Acceptance of the concrete within each member will be based on successfully achieving a minimum average design compressive strength for two match cured quality assurance cylinders.

3.1.6 Member Concrete Permeability Testing.

3.1.6.1 Surface Resistivity testing may be completed on all member types by the Bureau of Materials &

Research in accordance with AASHTO TP 95 at an age of 56 days or later. The Fabricator shall submit one match cured cylinder from each bed cast to the Bureau of Materials & Research for permeability testing.

3.1.6.2 Acceptance of the concrete within each bed cast will be based on successfully achieving the minimum average surface resistivity value of 15 kΩ-cm at 56 days for one match cured quality assurance cylinder.

3.2 Qualification of the Fabricator.

3.2.1 Minimum Requirements. All plants/shops fabricating material for the Department shall satisfy the following minimum requirements:

3.2.1.1 Certification. The precast concrete manufacturing plant shall be certified by the Prestressed

Concrete Institute Plant Certification Program. The Fabricator shall submit proof of certification prior to the start of production.

Certification shall be as follows:

For deck panels, certification shall be category B2 or higher.

For straight strand members, certification shall be category B3 or higher.

For draped strand members, certification shall be in category B4.

3.2.1.2 Engineering/Drafting. The Fabricator shall have trained, knowledgeable, and experienced drafting personnel available who can produce and check legible, complete, and accurate shop detail drawings.

3.2.1.3 Specifications. The Fabricator shall have available in the shop all pertinent specifications governing the work.

3.2.1.4 Technician. The Fabricator shall provide a technician having at least 5 years continuous experience in the manufacture of prestressed members, who shall supervise the work.

3.2.2 Quality Control. The Fabricator shall perform quality control functions to ensure that the product is fabricated in accordance with Contract documents and specifications.

3.3 Alternate Strand Patterns.

The use of alternate strand patterns are subject to the approval of the Bureau of Bridge Maintenance.

The design of debonded strand patterns are subject to the requirements listed in Appendix C of this specification.

3.3.1 Changes to the eccentricity of the prestressing force at any location within the member shall have the following additional requirements. Upon approval, plans with details showing the proposed changes shall be submitted for inclusion into the Plans on file in the Bridge Maintenance office. The plans shall include the State's standard border and title box and shall be on archival quality, 22” x 34” double matte

Mylar. The plans shall include member sections and strand eccentricities at appropriate locations, a member elevation showing proposed changes (draping, debonding, mild reinforcement, etc.) and other pertinent information resulting from changes in the design. The plans shall be stamped by a Licensed

Professional Engineer licensed in the State of NH. The design calculations and load rating form (Form 4) shall be submitted for documentation and stamped by a Licensed Professional Engineer licensed in the

State of NH.

3.4 Shop Drawings.

3.4.1 The Contractor shall prepare and submit shop details, and all other necessary working drawings for approval in accordance with the requirements of 105.02. The Contractor shall submit six copies of the shop drawings for approval.

3.4.1.1 Beam camber monitoring and camber restraining procedures shall be included on the shop drawings.

3.4.2 Fabrication shall not begin until written approval of the submitted shop drawings has been received from the Engineer.

3.4.3 Deviation from the approved shop drawings will not be permitted without written order or approval of the Engineer.

3.4.4 Tracings. Original tracings of all corrected shop drawings shall be delivered to the Department before final payment will be made.

3.5 Shop Inspection.

3.5.1 Inspection. A Department Representative will inspect the fabrication of the members for quality assurance. This inspection will include the examination of materials, work procedures, and the final fabricated product.

3.5.1.1 Fabrication shall only be done in the presence of an authorized inspector representing the

Department. The Department’s authorized quality assurance inspector is herein referred to as the “

Inspector”.

3.5.2 Notice. At least fourteen (14) days prior to the scheduled start of casting on any member or test section, the Fabricator shall contact the Department's Bureau of Materials and Research to provide notice of the scheduled start date. The Bureau of Materials and Research will assign an Inspector to the scheduled work to provide quality assurance testing. The Inspector will coordinate directly with the

Fabricator to determine the casting schedule.

3.5.2.1 In addition to the requirements of 3.5.2, the Fabricator shall contact the Bureau of Materials and

Research at least two(2) days before the actual work begins to allow scheduling of independent assurance testing by the Bureau.

3.5.3 Authority. The Inspector shall have the authority to reject any material or workmanship that does not meet the requirements of the Contract documents.

3.5.3.1 Inspection at the shop is intended as a means of facilitating the work and avoiding errors. It does not constitute final approval and will not relieve the Contractor from any responsibility in regard to imperfect material or workmanship and the necessity for replacing same.

3.5.4 Acceptance. The Inspector shall affix an acceptance stamp to members ready for shipment. This mark shall be made by paint or ink stamp in a location that will not be visible when the structure is completed.

3.5.4.1 The Fabricator shall present the Inspector with a copy of the shipping invoice to be stamped for verification of inspection and approval prior to shipment.

3.5.4.2 The Inspector’s acceptance implies that, in the opinion of the Inspector, the members were fabricated from accepted materials and processes and loaded for shipment in accordance with the

Contract requirements. The Inspector's stamp of acceptance for shipment does not imply that the members will not be rejected by the Engineer if subsequently found to be defective.

3.5.5 Cooperation. The Fabricator shall fully cooperate with the Inspector in the inspection of the work in progress.

3.5.5.1 The Fabricator shall allow the Inspector unrestricted access to the necessary areas of the shop during work hours. Work done while the Inspector has been refused access shall be automatically rejected.

3.6 Stressing Equipment.

3.6.1 Prestressing shall be done with approved hydraulic jacking equipment.

3.6.2 Hydraulic jacks shall be equipped with accurately reading pressure gauges. The combination of jack and gauge shall be calibrated and a certified graph or table showing the calibration shall be submitted to the Engineer. The calibration date shall be within a 12-month period immediately prior to the start of work.

3.7 Placement and Stressing of Strands.

3.7.1 Prestressing strands shall be accurately placed to achieve the center of gravity of the strand as shown on the approved shop drawings. Strands shall be protected against corrosion and free of nicks, kinks, dirt, rust, oil, grease, and other deleterious substances.

3.7.2 Layers of strands shall be separated by steel supports in accordance with the Concrete Reinforcing

Steel Institute Manual of Standard Practice and shall be of approved shape and dimension. Suitable horizontal and vertical spacers shall be provided, if required, to keep the strands in true position in the forms. Hold-down devices used at all points of change in slope of the strands shall be of approved low-friction type.

3.7.3 Prior to stressing, the Fabricator shall submit for approval the computations of the proposed gauge pressure, elongations of the prestressing strands (allowing for losses), and the sequence of operations. A record shall be kept of the gauge pressure and the elongation produced thereby for each strand.

Complete and accurate records of each stressing operation shall be submitted to the Engineer.

3.7.4 The mild reinforcing steel shall be placed in position after the stressing is performed unless otherwise approved.

3.7.5 Each strand shall be stretched initially to a minimum gauge pull to eliminate all slack and equalize the stresses in the strands as determined by the Engineer before starting elongation measurements. All strands shall be in position before the stressing operation is begun.

3.7.6 Stressing shall be performed by either simultaneous or individual application of tension to the strands. The amount of stress to be applied to each strand and the sequence of stressing shall be as shown on the plans and approved shop drawings. Stressing shall be performed only in the presence of the Inspector.

3.7.7 Safety Measures. Safety measures must be taken by the Fabricator to prevent accidents due to possible breaking of the prestressing strand or the slipping of the grips during the prestressing process.

3.7.8 Several members may be cast in a continuous line and stressed at one time. Sufficient space shall be maintained between ends of members to permit access for cutting strands after the concrete has attained the required strength.

3.8 Debonding of the prestressing strands, if required, shall be accomplished by the use of sheathing.

Sheaths shall be of an approved material which is watertight, has sufficient strength to withstand concrete placement and does not react with concrete or steel. Sheaths shall be properly sealed to prevent intrusion of cement paste during concrete placement.

3.9 Forms.

3.9.1 Forms shall be subject to the approval of the Engineer.

3.9.2 Forms shall be made and maintained true to the shapes and dimensions shown on the plans.

3.9.3 The surface of forms shall be smooth, and if necessary, joints shall be treated so that a minimum of joint marks are evident in the finished member.

3.9.4 Forms shall be constructed and end bearing plates placed so as to allow for any shortening of the member due to compressive stresses resulting from transfer of stress and from shrinkage.

3.9.5 Side forms shall be of steel and shall be supported without resort to ties or spreaders within the body of the member. They shall be braced and stiffened so that no deflection or curvature occurs during concrete placement.

3.9.6 Forms shall be cleaned before each use.

3.10 Mixing of Concrete.

3.10.1 Proportioning and batching of concrete shall conform to 520..3.1 or as ordered.

3.11 Placement of Concrete.

3.11.1 Concrete shall not be deposited in the forms until the Inspector has approved the placement of the reinforcing and prestressing strands. Concrete shall be deposited only in the presence of the

Inspector and in accordance with 520.3.5.

3.11.1.1 Cold Weather. When the average daily temperature falls below 35 °F for more than 1 day, protective measures shall be taken to prevent damage to the concrete by freezing. The protective measures shall be included on the shop drawings as required.

3.11.2 All reinforcing and strands shall be free of dirt, rust, oil, grease, and other deleterious substances.

3.11.3 All items encased in the concrete shall be accurately placed in the position shown on the plans and firmly held during the placing and setting of the concrete. Clearance from the forms shall be maintained by supports, spacers, or hangers in accordance with 544.3.4 and shall be of approved shape and dimension.

3.11.4 The details of all inserts, anchors, and any other items required to be cast into the members

(whether detailed on the Contract drawings or provided for the Contractor's convenience) shall be shown on the shop drawings. Members shall not be fired or drilled into for attachment purposes. All hardware shall be galvanized except as otherwise noted.

3.11.5 The temperature of the concrete shall not exceed 90 °F when placed in the forms.

3.11.6 Placement of concrete in stages to facilitate box beam fabrication will be allowed. Interval times between concrete placement stages shall be limited to 45 minutes to ensure that a cold joint has not formed between the two placement stages. Placement plans requiring interval times longer than 45 minutes shall be approved prior to use. Interval times extending beyond 45 minutes without prior approval are cause for rejection of the member.

3.12 Consolidation of Concrete.

3.12.1 Consolidation of concrete shall conform to 520.3.5.4 or as ordered.

3.12.2 The vibrating shall be done with care and in such manner as to avoid displacement of reinforcing, strands, shoes, or other inserts.

3.12.3 The size of the vibrator spud shall be proper for the size of the openings available.

3.12.4 External vibration will be permitted.

3.13 Roughness of Top Surface of Member.

3.13.1 The top surface of all members shall be finished true by striking off at the top of the forms. A flattened area of sufficient size (4” by 4” +/-) shall be provided at the centerline of bearing and tenth points on tops of all the girders to facilitate taking elevations for measuring camber and deflection.

These areas shall be steel trowel finished with a maximum difference in elevation between the high to low spots being less than 1/8”.

3.13.2 As soon as conditions permit, before the concrete has fully hardened, all dirt, laitance, and loose aggregate shall be removed from the top surface. The top surface shall be finished as shown on the plans.

3.13.2.1 The top surface of precast prestressed deck panels shall be roughened with a broom finish.

3.14 Curing.

3.14.1 General. The Contractor shall indicate on the shop drawings, for approval, the method of cure and a complete outline of the proposed procedure. The Contractor may choose one of the following curing methods:

a. Saturated Cover. Each unit shall be immediately covered with heavy, water saturated burlap, or other material acceptable to the Inspector. The burlap shall be kept saturated, and the concrete surface temperature shall not drop below 68 °F. These conditions shall be maintained for a minimum of three days or until the concrete has reached release strength.

b. Low Pressure Steam. Live steam shall be introduced into the enclosure through a series of steam jets which shall be evenly spaced within the enclosure. The initial set of the concrete shall take place before steam is introduced. The enclosure shall be at 100% relative humidity to prevent loss of moisture to ensure proper hydration of the cement. The steam curing cycle shall include a gradual heating and cooling period during which the rate of change in temperature shall not exceed 68 °F per hour. The maximum temperature inside the enclosure shall not exceed 160 °F. After the concrete has reached specified release strength, the temperature within the curing enclosure shall be decreased at an average rate not exceeding 68 °F per hour until the temperature within the curing enclosure is within 50 °F of the ambient temperature of the storage area.

3.14.1.1 The maximum concrete temperature within the member shall be less than 160 °F.

3.14.2 Record of Curing Time and Temperature. The Fabricator shall provide one (1) automatic temperature recorder for every 100 ft. of member. The recorder shall continuously record curing temperatures while the member is curing. The sensors shall be carefully placed to ensure that ambient conditions are measured. Recorder accuracy shall be certified once every 12 months and the certificate displayed with each recorder. In addition, random temperature checks of each recorder shall be made by the Inspector.Each chart shall indicate the casting bed, date of casting, time of commencing, graphic plot and the units that are represented by the chart. The start of artificial heat (if steam cured) and the transfer of prestress shall be indicated on each graphic record.When curing is complete, the charts shall be properly marked and given to the Quality Assurance Inspector. Temperatures recorded on the charts shall be considered as verification of whether the units have been cured in accordance with the approved shop drawings.

3.15 Release of Prestress.

3.15.1 A detensioning sequence shall be submitted with the shop drawings on a separate 8 1/2” x 11” sheet. The proposed sequence is for informational purposes and will be used only as a reference for the inspector during fabrication.

3.15.2 Detensioning shall not commence until the concrete has attained a compressive strength of at least 4000 psi (or the release strength indicated on the plans) as shown by match cured test cylinders.

Detensioning shall be done at approximately equal concrete strengths for all members. The temperature of match cured cylinders used for determination of adequate release strength shall be controlled by a thermocouple located in the last member cast in each bed.

3.15.3 Detensioning shall be accomplished by a gradual release of jack pressure, or by cutting individual strands in an approved sequence. If detensioning is accomplished by single strand release, each strand shall be cut by gradually heating the strand at both ends of the member simultaneously. A minimum length of 5” of strand shall be heated to prevent any shock or snap when the strand is finally severed.

Each strand shall be cut at all spaces between members when cast continuously before starting detensioning on the following strand in the sequence. All detensioning shall be performed in the presence of the Inspector.

3.15.4 If the concrete has been heat-cured, detensioning shall be performed immediately following the curing period while the concrete is still warm and moist.

3.15.5 Detensioning shall be kept symmetrical about the axes of the member and in the sequence submitted as part of the shop drawings.

3.15.6 Forms, or any device which restricts either horizontal or vertical movement of the member, shall be stripped or loosened prior to detensioning.

3.16 Stripping Forms and Finish of Member.

3.16.1 No forms shall be removed without approval. Proper care and precautions shall be exercised in removing forms so that no damage results to finished surfaces.

3.16.2 The member shall receive a Class 1, Ordinary Finish in accordance with 520.3.12 except patching shall be in accordance with 3.18.

3.16.3 The shear key joints at the sides of butted beams shall be abrasive blast-cleaned prior to shipping.

3.16.4 Finish of Strands. At the ends of simple span members and the free ends of members made continuous, all strands shall be recessed. Each recess shall be 1 1/2” square and 3/4” deep. Projecting strands shall be burned out unless specified otherwise on the plans and the recess cleaned prior to patching with an approved material. The entire end cross-section shall then be coated with an approved bitumastic material.

3.16.5 Finish of Strands for Deck Panels. At the ends of deck panels strands shall have a minimum extension of 4” beyond each end of the panel.

3.17 Damage/Cracking. The PCI New England Region Bridge Member Repair Guidelines, Report Number

PCINER-01-BMRG shall be used in conjunction with this specification to help identify damage, determine the potential cause and appropriate repair procedure if warranted.

3.17.1 Precast Concrete Deck Panels. Detensioning procedures causing member cracking shall be revised before detensioning the next bed. A revised detensioning sequence shall be submitted for review as in

3.15.1.

3.17.1.1 Rejection. Any of the following conditions will be cause for rejection of prestressed deck panels:

1. Any crack transverse or diagonal to the strand pattern and crossing more than one strand

2. Any crack parallel to a strand and longer than 1/3 of the panel length

3. Cracks shorter than 1/3 of the panel length and present at more than 12% of the total number of strands in the panel

4. Voids or honeycombed areas with exposed strands

Deck Panels with cracks or with damage less severe than the conditions stated above shall be repaired by the Contractor using an approved procedure, at no cost to the Department.

3.17.2 Other Members. Detensioning procedures causing web splitting or other member cracking shall be revised before detensioning the next bed. A revised detensioning sequence shall be submitted as in

3.15.1. Cracks less than 0.01” in width shall be sealed by an approved method. Cracks in excess of 0.01” may be cause for rejection. Cracked members shall be repaired or replaced by the Contractor at the

Department's direction at no cost to the Department.

3.18 Patching.

3.18.1 Patching of any surface irregularities, especially those resulting from honey-combing, shall be done only after inspection for determination as to whether or not the work is acceptable.

3.18.2 When patching is allowed, it shall be done within 24 hours after stripping, and the patching shall be damp-cured for not less than a 3-day period and kept from freezing for the following 3 days.

3.18.3 Patching of damaged members in lieu of required replacement will not be permitted.

3.19 Dimensional Tolerances.

3.19.1 All tolerances not specified otherwise, shall be in accordance with PCI MNL -116 “ Manual for

Quality Control for

Plants and Production of Precast and Prestressed Concrete Products” except as modified herein.

3.19.2 Centerline camber of all members shall be measured at the same time within the first 24 hours after release of the prestress strands. Beams fabricated more than 30 days in advance of the projected over pour shall have their camber monitored at regular time intervals with a frequency sufficient to allow for camber growth to be restrained should it be projected to exceed contract plan estimated mid span camber plus ¾”. These measurements shall be provided to the engineer for review.

3.20 Handling and Storing.

3.20.1 Members damaged during handling and storage will be repaired or replaced at the Department’s direction at no cost to the Department.

3.20.2 Members shall be lifted at the designated points by approved lifting devices embedded in the concrete and proper hoisting procedures.

3.20.3 The points of support and the direction of the reactions with respect to the member during handling and storage shall be approximately the same as when the member is in its final position.

Members shall be stored plumb.

3.20.4 Storage areas shall be smooth and well compacted to prevent damage due to differential settlement. Stacks of members may be supported on the ground by means of continuous blocking located perpendicular to the strands at the ends. Intermediate blocking between members shall be located directly over the blocking below.

3.20.4.1 Members shall be protected from freezing temperatures 32 °F, for 5 days or until attaining design compressive strength detailed on the plans, whichever comes first.

3.20.5 Members may be loaded on a trailer as described above. Shock-absorbing cushioning material shall be used at all bearing points during transportation of the members. Tie-down straps shall be located at the lines of blocking only.

3.20.6 The members shall not be subject to damaging torsional or impact stresses.

3.20.7 Panels stored prior to shipment shall be inspected by the Contractor prior to being delivered to the site to identify damage that would be cause for repair or rejection. The Contractor shall ensure that sufficient acceptable panels are available for anticipated placement so that unacceptable delays to the project completion can be avoided.

3.21 Shipping.

3.12.1 A member shall not be transported from the casting yard until the minimum 28 day compressive strength stated in 3.1.5 has been attained as shown by test cylinders cured according to 3.1.4.2, and a minimum of 7 days has elapsed from casting of the member.

3.22 Erection of Prestressed Concrete Members.

3.22.1 Delivery and Field Inspection. Material, workmanship and condition after shipment will be inspected after delivery to the construction site, with this and any previous inspections constituting only partial acceptance.