450PRECAST PRESTRESSED CONCRETE CONSTRUCTION

450-1 Description.

Fabricate, store, transport and erect precast/prestressed concrete members prestressed by the pretensioning method. Pretensioned precast prestressed concrete products are products prestressed by the pretensioning method. In this method, steel or fiber rein forced polymer (FRP) components are stressed and anchored; the concrete for the product is then cast and cured, and finally the stress in the steel or FRP components is released from the anchorages to the concrete through bond, after the concrete has attai ned its specified release strength. A precast prestressed concrete plant, hereinafter called plant, is an independent operating facility capable of performing all the operations necessary to fabricate precast/prestressed concrete products. Obtain precast /prestressed products from a plant that is currently on the Department’s Production Facility Listing. Producers seeking inclusion on the list shall meet the requirements of Section 105. When the Producer’s Quality Control Program is suspended, accept resp onsibility of either obtaining precast/prestressed products from a precast/prestressed concrete plant with an accepted Quality Control Program, or await re -approval of the Producer Quality Control Program. The Engineer will not allow changes in Contract Ti me or completion dates as a result of the concrete plant’s Quality Control Program suspension. Accept responsibility for all delay costs or other costs associated with the plant’s Quality Control Program suspension.

450-2 Quality Control Program.

450-2.1 General: Develop a Producer Quality Control Program as specified in

Section 105. Meet the requirements of the accepted Quality Control Program, Contract Documents, and Precast/Prestressed Concrete Institute (PCI) Manual for Quality Control for Plants and Production of Structural Precast Concrete Products (MNL -116). The requirements of the Contract Documents will govern, when there is a discrepancy between the PCI Manual and the Contract Documents. Accept responsibility for performing daily Quality Contr ol (QC) inspections of all phases of work ensuring all materials and workmanship incorporated into the product meet the requirements of the Contract Documents. Also, maintain a daily activity report detailing the results of the daily Quality Control Progra m activities. Ensure these daily reports and minutes of the weekly meetings with the Engineer and the plant’s production personnel are maintained at the plant. During the weekly meetings, discuss the results of the QC inspections. Ensure a QC inspector i s present during concrete placements and performs inspection during all fabrication of precast prestressed concrete products, including the inspection of the operations before, during and after the placement of concrete.

450-2.2 Plant: Ensure each plant h as an onsite QC Manager or designee meeting the

requirements of Section 105 at all times during fabrication.

450-2.3 Tolerances:

Inspect all prestressed concrete products within five working days of detensioning to ensure their dimensions (other than sweep and camber) conform to the specified tolerances and to determine if there are any deficiencies. FY 2023-24 Return to Table of Contents Inspect the product for conformance with the product dimension tolerances shown in Appendix B of PCI Manual MNL -116, except as modified herein. Apply the tolerances with respect to the theoretical positions and dimensions shown in the Plans. Apply the same tolerances for U -Beams as those specified for I -Beams, when inspecting the product for conformance with dimension tolerances. For Florida U -Beam diaphragms, the tolerances are:

450-2.4 Product Certification: Ensure the QC inspector inspects all completed products

at the plant not less than 24 hours before shipment to verify that all Contract Documents requirements are met. Upon verification that all Contract Document requirements have been met and all necessary repairs have been satisfactorily completed, the product will be stamped with the approved QC Manager stamp identified in the Producer QC Plan. With each monthly request submitted for payment, attach a certification stating that the listed precast prestressed products have been produced under the Producer QC Plan and meet the Contract Document requirements. Ensure the certification is signed by a lega lly responsible person of the plant and is submitted on the plant’s letterhead.

450-2.5 Documentation: Ensure that a system of records is maintained in each plant

which will provide all information regarding the certification and testing of prestressing s teel, FRP prestressing strands, reinforcing steel, FRP reinforcing, concrete materials and concrete, curing materials, embedded items, tensioning, concrete proportioning, pre -placement, placement, post-placement inspections, curing, and disposition of prod ucts. Include in the record keeping all the deficiencies found as a result of the inspection and testing. Keep certified test reports for all materials incorporated into the production of precast prestressed concrete products. Ensure that the record of t ensioning operations is maintained and reflects the identification of the bed, type of fabricated products, the complete Financial Project Identification Number, jack identification number, date prestressing strands were stressed, temperature at the time o f stressing, and signature of the qualified tensioning machine operator. Ensure the proposed method and format for documenting required information is included in the Producer QC Plan. Maintain records until all the precast prestressed products for a p roject have been fabricated then submit required records to the Engineer. Ensure records are available at all times for the Engineer’s inspection.

450-2.6 Quality Assurance Inspection and Testing: The Engineer will perform

periodic inspections, sampling, and testing to ensure of the quality and acceptability of the materials, methods, techniques, procedures and processes being utilized in the fabrication of precast prestressed concrete products.

450-3 Materials.

450-3.1 General: Meet the following requirements:

Concrete ................................ .............................. Section 346 Steel Strands* ................................ ...................... Section 933 Carbon Fiber Reinforcing Polymer (CFRP) Strands*................................ .............................. Section 933 Steel Prestressing Bars ................................ ........Section 933 Steel Accessories ................................ ................ Section 933 Steel Spirals ................................ ........................ Section 931 Reinforcing Steel an d Metal Welded Wire Reinforcement ................................ ..... Sections 415 and 931 FRP Reinforcing ................................ . Sections 415 and 93 2 FRP Spirals** ................................ ..................... Section 932 Embedded Ducts ................................ ................. Section 960 Membrane Curing compounds*** ...................... Section 925 Epoxy Resin Compounds ................................ ....Section 926 Burlap ................................ ................................ ..Section 925 FY 2023-24 Return to Table of Contents Curing Blanket ................................ ........................... 400-16 Penetrant sealer*** ................................ .............Section 413 Methacrylate ................................ ....................... Section 413 Epoxy Injection of Cracks ................................ ..Section 411 * Do not use strands from more than one source in any individual prestressed element, with the exception of the partially tensioned strands (dormant strands ). ** The FRP spirals cannot be used in combination with steel prestressing strand . *** Use membrane curing compounds and sealers that are compatible with coating or other materials that are applied to concrete surface. Use inserts in accordance with the recommendations of the manufacturers and within their certified capacities and application qualifications. Do not use aluminum inserts. Use draped strand devices of sufficient rigidity having adequate support to retain the position of the strand unchanged under the induced load. Do not allow the devices to induce friction to the tendons such that the required jacking force and elongation cannot be attained.

450-3.2 Strand Chucks and Splice Chucks: For pretensioning, use str and chucks that

are capable of anchoring the strands without slippage after seating and ensure against strand failure within the grips at loads less than 95% of ultimate tensile strength of the prestressing strand. Submit manufacturer’s certification tha t splice chucks used to transmit the prestressing force from one prestressing tendon to another are capable to hold at least 95% of the ultimate tensile strength of the prestressing strand. Do not use wedges that become worn, cracked, deformed, or that a llow dead end seating in excess of 3/8 inch. Use components from the same manufacturer to make up chucks and to provide proper wedge fit. Use chucks as complete units. Clean, inspect, and lubricate the chucks between each use. Use wedges and housing that are compatible and made for the specific type and size of prestressing strand used. Ensure proper fit and proper seating of wedges on the strands. The Engineer will allow one splice per strand subject to the following:

450-4 Material Acceptance and Testing.

450-4.1 Concrete: Perform the QC sampling and testing of concrete in accordance with

the requirements of Section 346.

450-4.2 Reinforcing , Welded Wire Rein forcement and Prestressing St rand for

Pretensioning:

450-4.2 1 General: Identify all reinforcing steel, welded wire reinforcement and

prestressing st rand for pretensioning by LOTs. A LOT of reinforcing steel or welded wire is a shipment of material from the same manufacturer and heat. A LOT of prestressing steel is a shipment of material of the same size, production grade and heat from the same manufacturer. A LOT of FRP reinforcing bars or prestressing strands is a shipment of material of the same size, fiber lot and resin batch from the same manufacturer. Acceptance of reinforcing bars, welded wire reinforcement and prestressing steel for pretensioning is based on manufacturer’s certification and the Department’s FY 2023-24 Return to Table of Contents verification tests. The sampling for v erification testing will be performed by the Department at each plant, on at least two LOTs per year . Additional samples may be taken at the manufacturing source of reinforcing bars, welded wire reinforcement and prestressing strands. When products cont ain the material that has failed to meet the requirements of 450 -3, reject the unused material of the failed LOT. The Engineer may require an engineering analysis of the products which contain the failed material, in accordance with Section 6.

450-4.2 2 Steel Reinforcing and Welded Wire Reinforcement : Obtain and

maintain for each LOT a certified mill analysis, physical property test report and the manufacturer’s assigned LOT number with the heat of the material represented. Verify that the report represents the steel received and that the steel meets th e Contract Documents requirements. Reject all unidentified reinforcing steel or welded wire reinforcement received at the plant or job site. Submit the manufacturer’s certified mill analysis and provide three, 7 foot long, randomly selected samples from the designated LOT of reinforcing steel and three randomly selected samples from the designated LOT of welded wire reinforcement when requested by Engineer. Ensure each sample of welded wire reinforcement covers an area of four intersections of transverse and longitudinal bars. Ensure the transverse wires of each piece of welded wire reinforcement extend approximately 6 inches to both sides.

450-4.2 3 Fiber Reinforced Polymer (FRP) Reinforcing: Meet the requirements

of 932-3.

450-4.2 4 Steel Prestressi ng Strand for Pretensioning: Obtain and maintain for

each LOT of material received, the manufacturer’s assigned LOT number, certified test values for specified material properties together with a representative load -elongation curve and the modulus of elas ticity value based upon strand nominal area. Submit and support by records maintained by the strand manufacturer, production tolerances applied in selection of the reported strand modulus. Verify that documents submitted represent the shipment received and meets the Contract Documents requirements. Reject all unidentified prestressing steel received at the plant or job site. Submit the manufacturer’s certified mill analysis and provide three, 5 foot long randomly selected samples from the designated L OT of material when requested by the Engineer.

450-4.2 5 Fiber Reinforced Polymer (FRP) Prestressing Strand for

Pretensioning: Meet the requirements of 933 -5.2.2.

450-4.2 6 Strand Chucks and Splice Chucks: Obtain and maintain certified test

results cer tifying that the material meets the requirements of 450 -3.

450-4.2 7 Steel Accessories: Use only steel accessories meeting the requirements

of 450-3.

450-4.2 8 Ducts: Obtain and maintain certified test results certifying that the

material meets the req uirements of 450 -3.

450-5 Shop Drawings.

Submit shop drawings for all pretensioned prestressed concrete products containing FRP bars, FRP strands, or stainless steel strands. Submit shop drawings for all other pretensioned prestressed concrete products wh en the Contract Documents do not contain all the detailed information necessary to fabricate and erect the pretensioned prestressed concrete product. Ensure the submitted shop drawings meet the requirements of the Contract Documents. FY 2023-24 Return to Table of Contents Obtain prior approval of any adjustments to the shop drawings which will result in a net change of prestressing force within the product. Shop drawings are not required to depict negligible, supplemental reinforcement used to facilitate fabrication of products if the additions do not affect the performance of the product. In lieu of shop drawings, submit the following to the Engineer:

450-6 Forms.

450-6.1 General: Use metal side and bottom forms, unless otherwise specified in the

Contract Docume nts. For members with special shapes such as corner sheet piles, wood forms are permitted. Slab beams, slab units and sheet piles may be cast on concrete surfaces meeting the profile dimensional tolerances of 450 -6.3. Apply release agents in accordance wit h the manufacturer’s recommendations. Liquid membrane curing compounds may be used to prevent bonding of slab products and sheet piles to the existing concrete surface, when applied in two or more coatings. Ensure the last application of liquid membrane is applied immediately before placement of the slab or sheet pile. For all beam members, use side forms designed to be removed without damaging the top flange of the beam. Remove the forms horizontally away from the beam by a method that prevents any conta ct of the form with the top flange after release of the form. Do not subject the top flange to any vertical force at any time. Include the form details and method of removal in the Producer QC Plan. For all Florida I-Beams, use forms that do not have more than two horizontal joints. Use void forms of a type for which service adequacy has been demonstrated, having sufficient strength to provide stability during handling and placing and to withstand FY 2023-24 Return to Table of Contents hydrostatic pressures and other forces imposed upon t hem during concrete placement. Use form material that is neutral with respect to the generation of products harmful to the physical and structural properties of the concrete. Ensure that the presence of the form materials does not cause any detrimental eff ect to the concrete or other materials within the member. Positively vent all voids to the outside of the member. For end headers and inside forms, other materials capable of resisting the pressure from concrete are permitted , except that end headers used with CFRP strands must be either timber headers or steel headers with rubber grommets to protect the CFRP strands from damage . Use end headers so designed that they can be placed and maintained in correct position between the side forms. Hold the headers in place with devices capable of being removed or loosened after the concrete has attained its initial set allowing free form expansion during curing methods that involve heat. Use end headers with openings conforming to the prestressing st rand pattern to permit passage of the prestressing st rand. Locate the openings accurately within 1/8 inch of planned location of prestressing st rand elements. Construct circular openings for strands a maximum of 1/4 inch larger than the nominal strand diameter. Constru ct square or rectangular openings a maximum of 1/4 inch larger, horizontally and vertically, than the nominal strand diameter. Ensure that all headers are mortar tight.

450-6.2 Supports: Use forms of sufficient thickness, with adequate external bracing an d

stiffeners, which are anchored to withstand the forces due to placement and vibration of concrete. Ensure that joints in forms are mortar tight. Support bottom forms on concrete pallets with metal stiffeners, wales or shims. Do not use timber elements be tween the bottom metal form and concrete pallets.

450-6.3 Alignment: Make and maintain during their use, forms and centering true to the

shapes and dimensions for the product being produced. Plumb, align, and secure forms for each product in position befo re each reuse. Apply the following tolerances to form alignment and pallets or beds used in prestressed construction:

450-6.4 End Header Locations:

450-6.4 1 General: Provide a minimum of 18 inches of exposed strands from the

end header to the stressing anchorage for all products. Provide a minimum of 18 inches of exposed strands between adjacent ends of all products except 24 -inch square and smaller piles. Provide a minimum of 6 inches of exposed strands between adjacent ends of 24 -inch square and smaller piles.

450-6.4 2 Cold Weather: Provide a distance of at lea st 5 feet from the end header

to the stressing anchorage, when the ambient temperature is expected to be below 55ºF between the time of tensioning and detensioning. When the ambient temperature is expected to be below 55ºF between the time of tensioning an d detensioning and the product's exposed strands between the stressing anchorages are not protected, maintain a 25 foot minimum free length of stressed strands, between the end header and the stressing anchorage at each end of a bed line. When cold FY 2023-24 Return to Table of Contents weather concrete conditions as specified in 450 -10.1 are in effect, protect all exposed strands between stressing anchorages regardless of length. When the products and strands between stressing anchorages are protected, provide protection adequate to maintain th e ambient temperature of the air around the strands at or greater than 55ºF until the products are detensioned or 24 hours after placing concrete, whichever is less.

450-6.5 Surface Conditions: Use clean, rust free form surfaces against which concrete is

to be cast. Inspect forms and, if necessary, recondition them.

450-6.6 Form Ties: Ensure that no form wires or metal pieces are left within 2 inches of

the surface of the finished concrete.

450-6.7 Corners, Angles and Joints: Ensure corners and angles ar e chamfered, mitered,

or rounded with a radius of 3/4 inch, unless otherwise specified or shown in the Plans. Provide smooth mortar tight joints between panel forms within the alignment tolerances.

450-6.8 Form Release Agent: Before placing concrete, trea t the facing of all forms with

a form release agent in accordance with the manufacturer’s requirements. Ensure the application of form release agents does not contaminate prestressing strands and/or reinforcing steel.

450-7 Protection and Placement of Pres tressing St rand.

450-7.1 Protection of Prestressing St rand: Maintain and store prestressing steel above

the ground surface on platforms, skids, or other supports, to prevent contamination from below, and protect them from mechanical injury. Do not use any packaging or wrapping material that retains moisture at the bottom of the reel. Clean contaminated prestressing st rand before use or otherwise reject it. Handle prestressing st rand carefully to prevent nicks or kinks . Do not expose steel prestressing strand to temperatures greater than 165ºF at any time. Do not ex pose CRFP prestressing strand to temperatures greater than 120°F at any time. Do not use arc welding equipment, including welding electrode lines, within 2 feet of prestressing st rand. Do not perform welding on forms that have been set in place after the p restressing st rand is placed in the bed. Reject prestressing st rand that has sustained any physical damage at any time.

450-7.2 Placing Prestressing St rand: Use care during placement of prestressing st rand

to avoid physical damage and contamination. Rejec t damaged strands. Do not use prestressing strand containing nicks, kinks, or former chuck grip marks. Do not use prestressing strand showing evidence of scale formation or which has become pitted. Remove and replace any damaged prestressing st rand in the bed.

450-7.3 Cleanliness of Prestressing St rand: Inspect the prestressing st rand for any

evidence of contamination. Use st rand that is free of deleterious materials such as grease, oil, wax, dirt, paint (except that used for marking identification) or oth er similar contaminants. Remove any contaminants detected from the st rand before proceeding with fabrication activities. Rust on prestressing steel that can be removed by light rubbing is acceptable. Streaks or spots which may remain after rust removal are acceptable if no pitting is present.

450-7.4 Debonded Strands: Install debonding material (sheathing) according to the

prestressing strand locations and lengths shown in the Plans, and manufacturer’s instructions, except as modified herein. Do not instal l sheathing over the full length of a product. Extend the sheathing through the header. T ape and tie the sheathing at the terminus located at the inside of the member. The tape must be strong enough to hold the sheathing closed . Use non-slit tubular or two -part sheathing that is high -density plastic. The sheathing must have a minimum wall thickness of 0.025 inch, and an inside diameter exceeding the maximum outside diameter of the strand by 0.02 0 inch to 0.1 50 inch. Tape the entir e length FY 2023-24 Return to Table of Contents of seams to ensure mortar tightness when using two -part sheathing. The sheathing and tape must not react with concrete, coating, steel, or FRP components . Slit tubular sheathing may be used to repair minor defects such as breakages or punctures in non-slit tubular sheathing, rectifying an improperly debonded strand, or incorrect debonded length of a strand. Tape the entire length of the slit tubular sheathing seam and tie the ends to ensure mortar tightness.

450-8 Tensioning Equipment and Operati ons.

450-8.1 Equipment: Use a hydraulic jacking system that is adjustable to the automatic

application and sustaining of a predetermined load, together with a pressure transducer or load cell built into the hydraulic system. Connect such pressure gage or transducer to a dial or digital readout and printer (manual recording of the tensioning operations is permitted) which will provide an instantaneous readout and record of the applied load in pounds. Use a jacking system with the capacity to induce the requ ired load. Base the use of this system on demonstrated accuracy and repeatability of plus or minus 2% of anticipated load verified through comparison with loads indicated by an independent load cell. Calibrate all jacking systems before using and repeat calibration at intervals not exceeding 12 months. Calibrate and recalibrate in accordance with the equipment manufacturer’s recommendations, by qualified calibration agency or by plant personnel under the supervision of a Specialty Engineer. Calibrate ga ges, jacks and pumps as a system in the same manner they are used in tensioning operations with the cylinder extension in the approximate position that it will be in actual use at final jacking force. In multi -strand tensioning systems, gages may be calibr ated against a master gage of known accuracy, provided that the other units of the system are calibrated against the same master gage. Ensure calibrations cover the load ranges that will be used during production. Verify the accuracy setting of the automat ic cutoff valves by running the desired cutoff load. Ensure a certified calibration curve accompanies each tensioning system. Load readings can be used directly if the calibration determines a reading is within plus or minus 2% tolerance of anticipated loa d. Ensure calibration of load cells or proving rings used to calibrate jacking systems are on compression force testing equipment that has been calibrated in accordance with ASTM E74. When any jack or gage appears to be giving erratic results, or if the jack force and elongation do not compare within specified limits and differences cannot be justified while work is in progress, recalibrate the equipment. Also verify the accuracy of the equipment after internal jacking system repairs or when gage and jack ing units are switched. Calibrate or recalibrate in accordance with ASTM E4 using equipment that is calibrated in accordance with ASTM E74. After calibration or recalibration is completed, prepare a certificate and have it signed by the person responsibl e for the verifications as outlined in ASTM E4 and ASTM E74. Ensure that the calibration report includes, the serial number of the equipment that is calibrated, calibration chart in a graph or tabular form, calibration date, temperature, full range of read ings before and after calibration, National Institute of Standards and Technology’s (NIST’s) traceable number of calibration device, method of calibration, calibration agency, and laboratory or Engineer supervising the calibration. Verify the accuracy of the jacking and recording system a minimum of once each week during tensioning operations by either an independently calibrated load cell, or by comparison with calculated strand elongation. When weekly verification is to be performed by comparison with c alculated strand elongation, check a minimum of ten strands and the difference FY 2023-24 Return to Table of Contents in the indicated load and the load determined from the elongation must agree within 5% of the computed theoretical load values. If the differences are greater than 5%, suspend t he tensioning operation, evaluate the tensioning operation by qualified personnel , and correct any deficiencies before proceeding. When weekly verification is done by load cell, perform a minimum of five spot checks to the maximum anticipated load. Use a load cell or proving ring calibrated in accordance with ASTM E74 and the accuracy of the force must be traceable to NIST. Maintain records of readings obtained from the force recording system and verifying standard. Ensure the weekly verification record i ncludes the serial number of the equipment, verification date, verification agency, NIST traceable number of calibration standard, and name of the person making the spot checks. The load reading from the recording system must agree within plus or minus 2% of the anticipated load indicated by the load cell or proving ring that are calibrated annually.

450-8.2 Operations:

450-8.2 1 General: The tensioning operations consist of the application of the

final force or load required by the Plans and with adjust ments for abutment rotation, bed shortening, anchorage header movement, live end seating, dead end seating, splice chuck seating, friction in the jacking system and any other elements as applicable for the type of bed and anchorage used. Also, adjust the f orce when the temperature differential between the ambient temperature at time of stressing and the expected concrete temperature at time of placement is greater than 25ºF. Increase the force at the rate of 1% for each 10ºF increment that the ambient temperature at time of stressing is below the expected concrete temperature at time of placing. Decrease the force at the rate of 1% for each 10ºF that the ambient temperature at time of stressing is above the expected concrete temperature at the time of placin g. Do not allow the stress in the steel prestressing st rand to exceed 80% of the specified tensile strength of the strand, after seating. Do not allow the stress in the CFRP prestressing strand to exceed 70% of the specified tensile strength of the strand, after seating. During each tensioning operation, for the verification of the live and dead end seating, check the seating of at least 4 strands or a minimum of 10% of the total number of strands, whichever is greater. Maintain a record of the tensioning operation. Compensation for temperature differential and abutment rotation are not required for self -stressing beds. However, adjust the final load for the effects of bed shortening due to the load from all the strands. If the placement of concrete is delayed for more than seven calendar days after the completion of the stressing operation, check and adjust the final strand load as necessary before placement of concrete and maintain a record of the stressing operation. Accomplish tensioni ng by either single strand tensioning or multiple strand tensioning, and ensure that it is symmetrical about the vertical axis of the product. Tensioning methods, in general, consist of tensioning to the required loads indicated by the jacking system, or t ensioning to the required load while monitoring the elongation of the prestressing st rand. Production personnel will p erform tensioning operations under supervision of a QC Inspector/Technician in accordance with Section 105 for prestressed concrete pla nt quality control personnel, or certified personnel may perform tensioning operations directly .

450-8.2 2 Single Straight Strand Tensioning: Apply an initial force of 5% to

25% of the final force to eliminate slack in the system. When single straight st rand tensioning is FY 2023-24 Return to Table of Contents used, tension the prestressing st rand until the required final force is attained. Measure and record the force and elongation.

450-8.2 3 Multiple Straight Strand Tensioning: Apply the initial uniform

tensioning load to each individual strand before the application of full tensioning load to the group of strands. The amount of the initial load will be influenced by the length of the casting bed and the size of strands in the g roup to be tensioned. The minimum initial tensioning load will be 5% of the required final load. Increase the magnitude of this load if deemed necessary but do not allow it to exceed 25% of the required final load. Then tension the strands by multiple stra nd tensioning to final load by pulling to elongation and checking against the jack load. Allow the required elongation to control the tensioning. The actual jack load must agree within 5% of the required load. For uniform application of load to strands, the face of anchorage at final load must be in a plane parallel to its position under initial load. Verify this by measurement of movement on opposite sides of the anchorage and check its plumb position before and after application of the final load. Duri ng tensioning, allow the anchorage to move without restraint.

450-8.2 4 Draped Strand Tensioning: Tension draped strands by either partial

tensioning and subsequent strains or by final tensioning in draped position. Partial stressing and subsequent st rains applies when the strands are tensioned through a combination of applied jack loads and strand uplift. To verify the final force, place a load cell between the tensioning anchorage and anchor chucks at the dead end on at least two draped strands. Othe r methods as approved by the Engineer may be used to verify the final force in the dead end. Apply an initial force of 5% to 25% of the final force to eliminate slack in the system . After application of the initial force, establish reference marks for meas uring elongation. Apply a pre -calculated jacking force and measure elongations on a minimum of four strands. The average measured elongation must agree within 5% of the theoretical elongation for strand force measured by jack load, or the factors contribut ing to the difference must be identified and corrected before proceeding. Allow the load indicated by the jacking system to control the tensioning for the pre -calculated load. Obtain the required final force by lifting or depressing the strand simultaneous ly at all pickup or hold down points or in an approved sequence as shown on the shop drawings. On each different bed setup, after lifting or depressing the strands to their final position, check the final force at the dead end of at least two strands on the bed. If the load is below the required tensioning force by more than 5%, adjust it to the final load. When the final stressing is performed in the draped position, apply the tensioning load in two increments with the tendons being held in their draped positions. To verify the final force, place a load cell between the tensioning anchorage and anchor chucks at the dead end on at least two draped strands. Other methods as approved by the Engineer may be used to verify the final force in the dead end. Bri ng each strand to an initial tension of 5% to 25% of the final load before the application of the required final load. After application of the initial load, establish reference marks for measuring elongation. Then tension the strands to final load and measure the elongation. Allow the load indicated by the jacking system to control the tensioning for the initial and final loads. The measured elongation must agree within 5% of the theoretical elongation for the strand force measured by jack load, or the fac tors contributing to the difference must be identified and corrected before proceeding. When the jacking is performed at one end of the bed, check the applied load on two draped strands at the other end of FY 2023-24 Return to Table of Contents the bed. If the load on the end opposite the jacki ng end is below the required value by more than 5%, adjust the load to the required final load.

450-8.2 5 Wire Breakage:

450-8.2 5.1 Steel Prestressing Strand: Limit wire breakage to 2% of the

total area of the strands in any product and verify that b reakage is not indicative of a more extensive distress condition, otherwise reject the defective strand . Replace individual strands with more than one wire failure.

450-8.2 5.2 Fiber Reinforced Polymer (FRP) Prestressing Strand:

Replace individual stran ds with any wire failure.

450-8.2 6 Position of Prestressing St rand: Position prestressing st rand as shown

in the Plans within the tolerances allowed in 450 -2.3. Fix the required vertical and horizontal position of each prestressing strand at the ends of each product and at intervals within each product not exceeding 30 feet. Use the method of fixing the prestressing st rand shown in the Producer QC Plan. When blocks are to be used for supporting prestressing st rand, use those cast from concrete of the sam e mix design as used in the prestressed product. Stagger the location of blocks with an offset of 12 inches or greater and do not stack them.

450-9 Placement of Reinforcing Bars and Other Embedded Materials.

450-9.1 Reinforcing Bars and Supports : Tie and/or support in position all reinforcing

steel in each product with other reinforcing bars in a manner that will accurately position the reinforcing bars throughout the fabrication process. Use types of ties and methods of tying recommended by the CRSI, including lacing. Do not tie reinforcing bars to debonded prestressing st rands within the limits of the sheathing material. Tie or lace beam stirrup bars at a minimum of three points. Tie reinforcing bars, other than stirrup bars in beam ends, a t a minimum of every other intersection. Either tie or lace spirals in piling at all four corners in the 1 inch pitch area, at the top corners and bottom center in the 3 inch pitch area, and at the top corners in the center area. Tie the bottom center in the pile center area as necessary to maintain concrete cover. Bend all tie s away from the form surface to provide maximum concrete cover. When shown in the Plans, weld reinforcing steel in accordance with the requirements of AWS Structural Welding Code D 1.4. Do not weld in the prestressing bed.

450-9.2 Other Embedded Materials:

450-9.2 1 Inserts and Lifting Devices:

450-9.2 1.1 Placement: Locate inserts and lifting devices in accordance

with the tolerances listed in 450 -2.3. For stainless -steel or FRP reinforc ed products, use only non - metallic or stainless -steel (Type 304 or 316) inserts and lifting devices.

450-9.2 1.2 Corrosion Protection: Provide corrosion protection for

embedded metal lifting devices that would remain exposed after lifting operations ar e complete as indicated below:

450-9.2 2 Placement of Bearing Assemblies: Set bearing assemblies designed to

transmit reaction forces to the concrete in the position shown in the Plans. Place bearing plate assemblies or shoes which are to be cast in a product within appropriate tolerances as provided in

450-2.3 Check the assem blies for position after stripping from the forms.

450-10 Concrete Operations.

450-10.1 Temperature Restrictions:

450-10.1 1 Cold Weather Concreting: When the temperature of the surrounding

air is expected to be below 40ºF within 24 hours after placing concrete, the temperature of the plastic concrete as placed must be 55ºF or greater. Maintain the temperature of the concrete after placement at or above 55ºF for the first 24 hours or until detensioning, whichever occurs first. For piles and other members with a minimum section dimension of 12 inches or more, maintain the temperature of the concrete after placement at or above 50 F for the first 24 hours or until detensioning, whichever occurs first. Make arrangements for heating, covering, insulating or housing the concrete work in advance of placement and maintain the required temperature without adversely affecting the concrete due to concentration of heat. Do not use direct fired heaters during the first 24 hours after concrete placement, unless actions are taken to prevent exposure of the concrete to exhaust gases which contain carbon dioxide. Continuously monitor the temperature of the concrete or the ambient air around the product until the product is detensioned. Monitor by the use of thermocouples l ocated in the product cross -section or temperature recording devices located under the enclosure. Provide one thermocouple or temperature recording device for each 200 feet of bed length or part thereof. Locate the thermocouples within the products cross -section as shown in the Producer QC Plan or as approved by the Engineer. Record the monitored temperatures determined by each thermocouple. Review the recorded temperatures to ensure that they are within the specified limits. Initially calibrate recording d evices or thermocouples and recalibrate them at least annually in accordance with the manufacturer’s recommendations.

450-10.1 2 Hot Weather Concreting : Meet the requirements of Section 346 for

temperature requirements and special measures for mixing con crete in hot weather. Apply mist of water to prestressing strands, steel reinforcing , FRP reinforcing, and steel forms just before placing the concrete when the hot weather concreting special measures are in effect and the temperature of steel forms or reinforcing steel is greater than 120ºF.

450-10.2 Protection of Concrete from Adverse Conditions or Weather: Have

protection materials available before the concrete placement begins to cover the products in the event of rain or other adverse conditions during the placement of concrete. Protection materials may be tarps, curing blankets, or other impervious m aterial that will not puncture when placed over protruding reinforcing and/or form elements. Include the method and materials for protection in the Producer QC Plan.

450-10.3 Concrete Placement:

FY 2023-24 Return to Table of Contents

450-10.3 1 General: Check forms, reinforcing bars, prestressing strand, vent

pipes, anchorages and other embedded items for compliance with the Contract Documents before placing concrete. Place concrete in accordance with 400 -7, except as modified herein. For concrete operations conducted at night, provide eno ugh lighting to allow visual inspection of the interior of the forms during the complete concrete placement operation. Convey concrete by the use of buckets, conveyors, pumps, troughs, or other equipment specifically designed for concrete conveyance, pr ovided the placement method consistently produces quality concrete with no segregation or separation of the mix. Locate the concrete conveyance equipment within 12 inches of the top of the forms or surface of the concrete to minimize the free fall of the c oncrete. Multiple placements may be used within a bedline, provided compliance with 450-11.1 is maintained.

450-10.3 2 Requirements for Successive Layers: Except for self -consolidating

concrete (SCC), place concrete as described in 450 -10.3.2.1 throug h 450-10.3.2.5 as shown in the Producer QC Plan or as approved in writing by the Engineer. In any progressive concrete placement operation, do not allow the time between successive placements onto previously placed concrete to exceed 20 minutes, unless the previously placed concrete has not yet stiffened, as evidenced by the continued effective use of vibration.

450-10.3 2.1 AASHTO Type II, Florida I -Beam 36 and Double T -

Beams, Piling , Slab Beams and Precast Slab Units (Except Voided Piling and Slabs) : Place concrete in one or more layers or lifts. If more than one layer is used for Double T -Beams, end the first layer such that the top of the concrete is slightly below the bottom of the flange. end the first layer such that the top of the concrete is slightly below the bottom of the flange.

450-10.3 2.2 AASHTO Type III, Type IV and Florida I-Beams 45 and

54 and Voided Units (Slabs and Piling): Place concrete in a minimum of two horizontal layers. The thickness of the first layer will be such that th e top of the concrete is just above the top of the bottom flange. In voided units, end the first layer slightly above the middle height of the void.

450-10.3 2.3 All Beams 63 Inches or Deeper: Place concrete in a

minimum of three horizontal layers. The thickness of the first layer will be such that the top of the concrete is slightly above the top of the bottom flange. The thickness of the second layer will be such that the top of the concrete is slightly above the bottom of the top flange.

450-10.3 2.4 Pretensioned I -Beams Containing Longitudinal Post -

Tensioning Ducts: Place concrete in one continuous lift beginning in the end block zone and progressing to the other end. Do not allow the progression of the concrete placement to proceed until previously placed concrete is properly consolidated, and the rate of advancemen t equals the ability to fill the forms. In progression of the placement, deposit concrete within the forms on the surface of previously placed concrete.

450-10.3 2.5 Florida U -Beams: Place the concrete in Florida U -Beams in

a minimum of two horizontal l ayers. The thickness of the first layer shall be such that the top of the concrete is above the top of the bottom flange.

450-10.4 Vibration of Concrete: Except for SCC, consolidate concrete in steel

reinforced p roducts by internal or external vibration, or combination of these methods. For SCC, meet the requirements of Section 8.4 of the Materials Manual for production batch verification. FY 2023-24 Return to Table of Contents For CFRP strand reinforced p roducts, use SCC without the use of vibration. If further consolidation is needed, manual rodding is permitted. Design external form vibrators for the specific use. Design forms used in conjunction with external vibration and build them to effectively transmit vibration to the concrete mass. Mount and operate form vibrators in compliance with the vibrator manufacturer’s recommendations, a copy of which must be on file at the plant. Secure vibrators to the form mounts by positive locking devices so that maximum vibration is transmitted into the form. Modify or replace external form vibrator sys tems that are demonstrated to be ineffective. Operate vibrators at each mount location for the time necessary for complete concrete consolidation. Do not allow progressive points of vibration to exceed twice the visually effective radius of vibration. Keep forms equipped with external vibrators clean, and free of any buildup of hardened concrete. Ensure internal vibrators are available before concrete placement is started. Use an internal vibrator with a head of such size that proper vibration of the conc rete will be secured without causing movement of the prestressing st rand or reinforcing bars. The vibrating frequency range must be 8,000 to 15,000 impulses per minute. Have at least one standby vibrator available on-site. Insert the vibrator in the concre te at points spaced to ensure uniform vibration of the entire mass of the concrete. Do not allow points of insertions to be further apart than the radius over which the vibrator is visibly effective. Allow the vibrator to sink into the concrete by its own weight and penetrate into the underlying layers sufficiently so that the layers are thoroughly consolidated . After the concrete is thoroughly consolidated, slowly withdraw the vibrator to avoid formation of holes. Revise the existing placement and consol idation procedure to improve the consolidation of the concrete, if the existing placement and consolidation procedure ha s produced unacceptable surface defects such as honeycombing, aggregate or mortar pockets, or excessive air bubbles.

450-10.5 Finishing :

450-10.5 1 General: When concrete incorporating silica fume is used, screed and

finish with a continuous water fog mist maintained above the concrete. Do not apply the mist directly toward the concrete. A monomolecular finishing aid approved by the Engineer may be applied in accordance with the manufacturer’s recommendation.

450-10.5 2 Beams: Rough float the top surface of the beam and then scrub it

transversely with a coarse brush or metal tine to produce a roughened surface for bonding. For the other external surfaces of prestressed beams, unless otherwise specified, apply a General Surface Finish in accordance with 400 -15.1. Remove mortar leakage and stains to produce beams with a uniform appearance.

450-10.5 3 Piling: Unless a Class 5 Applied Finish Coating is specified, apply a

general surface finish as specified in Section 400 to pile surfaces, except that pointing with mortar will not be required for chips and bug holes with a depth less than 1/4 inch and a diameter of less than 3/4 inch. All other genera l surface finish requirements will apply, including the pointing of material form tie cavities with mortar. Surface finish deficiencies that meet the definition of noncomplying prestressed products must be corrected in accordance with 450 -12. Miter or roun d the top corners similar to the corner radius of the pile forms. Surfaces exposed during casting must have a steel trowel finish.

450-10.5 4 Slabs and Double -T Beams: When the Plans show the top surface of

prestress slab units, slab beams, or Double T -Beams units to be the riding surface, apply a Class FY 2023-24 Return to Table of Contents 4 floor finish in accordance with Section 400. When the Plans show the surface to be overlaid with asphalt or concrete, rough float the top surface and then scrub it transversely with a coarse brush to rem ove all laitance and to produce a roughened surface for bonding. For the other external surfaces of slabs and Double T -beams, unless otherwise specified, apply a General Surface Finish in accordance with 400 -15.1.

450-10.6 Curing: Cure prestressed concret e for a minimum duration of 72 hours. If

forms are loosened upon setting of concrete and/or removed before the 72 hour curing period is complete, expand the curing to cover the newly exposed surfaces by either coating with curing compound or extending the continuous moist cure area. Maintain concrete surface moisture at all times until curing is begun. If a water sheen is not present, apply supplemental moisture by misting or prevent water sheen loss on flat work by use of an evaporation retarder. After the finishing operations have been completed and as soon as the concrete has hardened sufficiently to permit the application of curing material without marring the exposed surface, cover the exposed surfaces of all prestressed concrete products by one of th e following procedures or other alternate curing methods. Alternate curing methods must be approved by the Engineer. Base alternate curing methods upon a demonstrated ability to retain surface moisture of the concrete and to control curing temperatures wit hin acceptable limits. Discontinue use of any alternate curing method other than those included herein upon any indication of noncompliance with this Specification.

450-10.6 1 Continuous Moisture: Place burlap on the surface and keep it

continuously satu rated for the curing period by means of soil soakers, leaking pipes, or automatic sprinklers. Do not apply moisture manually. If side forms are removed during the curing period, extend the burlap to completely shield the sides of the product. Water flow ma y be metered to cycle repetitively for five minutes on and five minutes off during the 72 hour curing period. When it is not practical to apply moisture or curing compound inside the voided piles, cover their ends with wet burlap to prevent moisture loss.

450-10.6 2 Membrane Curing Compound: Apply a Type 2 white pigmented

curing compound to all surfaces in a single -coat, continuous operation, at a uniform coverage as recommended by the manufacturer but not less than 1 gallon per 150 square feet. Apply the curing compound on the concrete surfaces that are still damp but have no free standing water. Allow surfaces covered by the membrane curing compound to remain undisturbed for the curing period. Recoat any cracks or other defects in the membrane seal which are detected during the curing period upon discovery . If side forms are loosened during the curing period, remove them at that time and immediately coat the formed surfaces with either a Type 1 clear, or Type 2 white pigmented membrane curing compound . Maintain the surface seal for the remainder of the curing period. Bottom surfaces must be similarly coated after removal of the forms. Remove membrane curing compound to applied surfaces of concrete products to which other concrete is to be bonded by sand blasting or water -blasting until all traces of membrane curing compound are removed. When the curing compound is applied by spraying, use a compressor driven sprayer of sufficient size to provide uniform spray at the nozzle. Keep all nozzles clean to ensure a uniform application of compound. For compressor driven sprayers, provide a calibrated reservoir which will allow the quantity of applied materials to be accurately determined. Maintain standby equipment in case of mechanical failure. If a mechanical failure occurs, a hand held pump -up sprayer may be used to apply curing compound to the remainder of the products FY 2023-24 Return to Table of Contents cast in the day’s production. Suspend additional concrete placements until the mechanical sprayer is functioning properly.

450-10.6 3 Curin g Blankets: Curing blankets may be used for curing the top

surfaces of products. Do not use curing blankets which are torn or punctured. Securely fasten edges to provide as tight a seal as practical. Allow curing blankets to remain in place for the curing period. Should the system fail to maintain a moist condition on the concrete surface, discontinue the use of curing blankets and take immediate corrective action to prevent further loss of concrete moisture.

450-10.7 Accelerated Curing:

450-10.7 1 General: Use low-pressure steam curing, radiant heat curing or

continuous moisture and heat curing. Submit steam and/or radiant heat curing procedures for CFRP strand products for approval . If accelerated curing is completed before the curing pe riod has elapsed, continue curing for the remaining part of the curing period in accordance with one of the curing methods above. If accelerated curing is used, furnish and use temperature recording devices that will provide accurate, continuous, and pe rmanent records of the time and temperature relationship of the enclosure and concrete throughout the entire curing period. Place the temperature recording sensors at a minimum of two locations, spaced approximately at or near the third point of bed length , to measure the temperatures of the enclosure and concrete. Initially calibrate recording thermometers and recalibrate them at least annually in accordance with manufacturer’s recommendations. Place the sensors at the center of gravity of the bottom flanges for beams. Place the sensors at the center of gravity of the cross sections perpendicular to the length for solid piles or poles, and at the midpoint of the wall thickness for voided piles or poles. When the ambient air temperature is equal to or hig her than 50ºF, start the accelerated curing by supplying or retaining moisture and the application of the heat, following the initial set period of concrete. Determine the initial set time in accordance with ASTM C403. During the application of heat, do no t allow the temperature rise in the concrete product to exceed 36ºF per hour. The maximum curing temperature of the enclosure or concrete must not exceed 150ºF. Maintain the maximum curing temperature uniform throughout the enclosure, with variation of not more than 20ºF from the maximum peak temperature until concrete reaches the required release strength. Allow the concrete element to cool gradually at the maximum cooling rate of 50ºF per hour and continue the cooling at this rate until the concrete tempe rature is 40ºF or less above the ambient temperature outside the curing enclosure. When the ambient air temperature is below 50ºF cure the concrete in two stages. Start the accelerated curing of the first stage during the preset period by applying heat to increase the temperature of concrete at the maximum rate of 10ºF per hour. The total temperature gain of concrete during the initial set period cannot exceed 40ºF higher than the placement temperature, or 104ºF, whichever is less. Upon obtaining the ini tial set, continue curing as stated above for ambient temperature of 50ºF or higher. To prevent moisture loss on exposed surfaces during the preheating period, cover products as soon as possible after casting or keep the exposed surfaces wet by misting or wet blankets. Use enclosures for heat curing that allow free circulation of heat about the product and that are constructed to contain the heat with minimum moisture loss. The use of tarpaulins or similar flexible covers may be used provided they are kept in good repair and secured in such a manner to prevent the loss of heat and moisture. Use enclosures that cover the entire bed from stressing abutment to stressing abutment, including all FY 2023-24 Return to Table of Contents exposed stranding, except when using CFRP strands. When using CFRP s trands, follow the manufacturer’s instructions.

450-10.7 2 Low -Pressure Steam: The steam must be in a saturated condition. Do

not allow steam jets to impinge directly on the concrete, test cylinders, or forms. Cover control cylinders to prevent moisture loss and place them in a location where the temperature is representative of the average temperature of the enclosure.

450-10.7 3 Curing with Radiant Heat: Apply radiant heat by means of pipe

circulating steam, hot oil or hot water, or by electric heatin g elements. To prevent moisture loss during curing, keep the exposed surfaces wet by misting or wet blankets.

450-10.7 4 Continuous Moisture and Heat: This method consists of heating the

casting beds in combination with the continuous moisture method des cribed above. Do not allow the heating elements to come in direct contact with the concrete or the forms. The initial covering of burlap and the continuous application of moisture will be as described in 450 -10.6.1. An auxiliary cover in addition to the bu rlap for retention of the heat will be required over the entire casting bed. Support this cover a sufficient distance above the product being cured to allow circulation of the heat.

450-10.8 Curing Requirements for Silica Fume Concrete: Use either a 72 hour

continuous moisture curing or a (12 -24) hour low-pressure steam curing in accordance with

450-10.7 Upon completion of the low -pressure steam curing, continue curing for the remaining

part of the 72 hour curing period by application of the curing compou nd, continuous moisture curing, or use of the curing blankets. If 72 hour continuous moisture is used, begin curing silica fume concrete immediately after the finishing operation is complete and keep a film of water on the surface by misting until the cu ring blankets are in place. No substitution of alternative methods nor reduction in the time period is allowed. After completion of the 72 hour curing period, apply a membrane curing compound to all concrete surfaces. Apply curing compound according to

450-10 6.

450-10.9 Form Removal: Do not remove forms sooner than six hours after casting and

not until the concrete strength is sufficient to avoid structural damage. For AASHTO Type V, Type VI, Florida I-Beams, and Bulb I-Beams, do not remove the forms supp orting the top flange concrete sooner than 12 hours after casting unless the release strength has been reached.

450-11 Detensioning.

450-11.1 General: The required concrete strength at which the prestressing force may be

transferred to the concrete in a p roduct will be a minimum of 4,000 psi, unless specified otherwise in the Plans. Verify the release strength by compressive strength cylinder tests or other approved means, no later than 24 hours after casting and every 24 hours thereafter until release strength is developed. In lieu of every 24 hour testing, estimate the strength development of concrete using the maturity method in accordance with ASTM C1074, the pulse velocity method in accordance with ASTM C597, or any other nondestructive test method acceptable to the Engineer, until the time of the detensioning. Before detensioning, verify the concrete release strength by testing the compressive strength test cylinders. Make a minimum of two compressive strength release test cylinders daily f or each individual mix or for each LOT, or fraction thereof, of a given concrete mix design where the daily consumption exceeds this volume or when non -continuous batching or dissimilar curing is used. The release strength test, representing the LOT, is th e average FY 2023-24 Return to Table of Contents compressive strength of two test cylinders, cured under conditions similar to the product or match-cured test specimens, which are match cured until the time of release. For products cured using accelerated curing, release the prestressing forc e immediately after terminating the accelerated curing process. After the detensioning operation is completed, continue to 72 hour curing period using one of the methods listed in 450 -10.6. For products cured using methods other than accelerated curing, re lease the prestressing force within a detensioning time limit, not to exceed five calendar days after the verification of release strength by compressive strength cylinder test or other approved strength gain monitoring system. For all products in a cast ing line, use the same test method for determining their release strengths. Ensure the detensioning time limit is included in the Producer QC Plan. Cure concrete cylinders used for detensioning strength tests in the same manner and location as the prestressed concrete products they represent . For I-Beams, when side forms are loosened upon setting of concrete or removed before the 72 hour curing period is complete, the top flange dormant strands may be released after the concrete reaches a compressive stre ngth of 2,000 psi. Perform detensioning operations under the supervision of personnel possessing a certificate of completion of PCI Quality Control Personnel Certification Level II, and

450-11.2 Method of Stress Tr ansfer: In all detensioning operations, keep the

prestressing forces nearly symmetrical about the vertical axis of the product and apply them in a manner that will minimize sudden shock or loading. Remove or loosen forms, ties, inserts, or other devices th at would restrict longitudinal movement of the products along the bed. Release hold-downs for products with draped strands in a sequence as shown in the Plans or Producer QC Plan. Cut dormant strands (partially tensioned strands) before releasing any fully tensioned strands. Release fully bonded strands next, beginning with the lowest row and moving upwards, followed progressively by strands having the minimum length of tubular sheathing through to those strands having the maximum length of tubular sheathin g. Transfer prestressing forces to the concrete by either single strand release or multiple strand release.

450-11.3 Single Strand Detensioning: Detension the strand by using a low -oxygen

flame in accordance with a pattern and schedule provided in the a pproved shop drawings, or Producer QC Plan, or described in 450 -5. Heat with a low -oxygen flame played along the strand for a minimum of 5 inches. Heat strands in such a manner that the failure of the first wire in each strand will occur after the torch ha s been applied for a minimum of five seconds. Release strands in all prestressed products simultaneously and symmetrically about the vertical axis at both ends of the bed and at all intermediate points between products to minimize sliding of products. Strands in piles, sheet piles, slabs, and AASHTO Type II Beams may be detensioned at the intermediate areas after detensioning both ends. For CFRP strands coupled with steel strands, detension the steel strands first using the flame cutting process describ ed above. At intermediate locations where CFRP strands are continuous between adjacent precast components, flame or shear cutting of the strands is not allowed.

450-11.4 Multiple Strand Detensioning: In this method, detension all strands

simultaneously by hydraulic dejacking. The total force is taken from the header by the jack, then released gradually. Do not allow the overstress required to loosen the anchoring devices at the FY 2023-24 Return to Table of Contents header to exceed the force in the strand by 5%. After detensioning, strands at all points may be cut progressively from one end of the bed to the other using equipment and methods described above.

450-11.5 Cutting Strands and Bars: Upon completion of the detensioning operation,

cut steel strands to required length, using an oxygen flame or mechanical cutting device. Do not use electric arc welders to cut bars or steel strands. Upon completion of the detensioning operation, cut CFRP strands to the required length using a mechanical cutting device. Do not use flame or shear cutting to cut CFRP strands.

450-11.5 1 Beams: For beam ends that will be permanently encased in concrete

diaphragms, cut strands to 2.5 inches plus or minus 0.5 inch beyond the end of the product or as specified in the Plans. For beams with ends that will not be encased in permanent concrete diaphragms, mechanically cut strands a minimum of 1/8 inch below the concrete surface.

450-11.5 2 Piles: Mechanically cut strands flush with the concrete surface. For

top (head) of fender piles and pile ends not embedded under final conditions, burn the strands a minimum of 1 inch below the concrete surface and clearly mark the pile to identify the top (head) end.

450-11.5 3 Poles: Mechanically cut strands to a minimum of 1/8 inch below the

concrete surface.

450-11.6 Protecting Ends of Strands: Prepare the concrete surfaces and apply Type F-1

epoxy in accordance with the manufacturer’s recommendations.

450-11.6 1 Beam Ends that will not be Permanently Encased in Concrete

Diaphragms:

450-11.6 2 Beam Ends that will be Permanently Encased in Concrete

Diaphragms:

450-11.6 3 Piles: Apply epoxy patches to all recessed strands.

450-11.6 4 Poles: Coat entire face of tip (top) and butt (bottom) ends with epoxy.

450-12 Noncomplying Prestressed Products.

450-12.1 General: When a precast prestressed concrete product does not co mply with

the requirements of this Section or is damaged, use the following provisions for evaluating and dispositioning of deficiencies. However, when precast prestressed concrete products have been installed, the disposition of concrete cracks shall be i n accordance with Section 400. Apply these provisions in all cases that clearly fall under the circumstances described in Section 400. Consider situations not covered by these specific circumstances on their individual merits. Consider and apply the follow ing where practical. Make all major repairs that require a repair proposal under the observation and the satisfaction of the QC Manager or designee.

450-12.2 Identification of Defects: The QC Manager, or QC inspectors under direction

of the QC Manager , will examine all deficiencies within the time limit specified in 450-2.3 and

450-2 4, to determine the applicable provisions and requirements of this Article and which

course of action is appropriate.

450-12.3 Common Defects in Precast Prestressed Concrete Products:

450-12.3 1 Surface Deficiencies: Surface deficiencies are defined below and

include spalls, chips, bug holes, surface porosities, honeycombs , and shallow surface cracks . Regardless of the types of deficiencies, when the total surface area of all deficiencies within a single product exceeds 1.0% of the product’s area that will be exposed to the environment, the deficiencies are considered major. FY 2023-24 Return to Table of Contents

450-12.3 1.1 Bug Hole: A bug hole is a void caused by air that is

entrapped against the form and that has an area up to 3.0 square inches and a depth up to 1.5 inches. Treat any bug hole with a dimension exceeding either of these dimensions as a honeycomb. The Engineer will not require repair of any bug hole with a depth less than 0.25 inch and less than 0.75 inch in diameter , unless otherwise indicated in the Plans or Specifications.

450-12.3 1.2 Spall: A spall is a depression resulting when a fragment is

detached from a larger mass by impact, action of weather, by pressure or by expansion within the larger mass. A cosmetic spall is a circular or oval depression not greater than 1.0 inch in depth nor greater than 3.0 square inches in area, and must be repaired in accordance with 450-13.2. With the exception of spalls in the bearing areas and edge s of the top flange, a minor spall is defined as a spall not larger than 2.0 square feet and no deeper than one inch plus the sum of the concrete cover and the diameter of the bar in the first layer of reinforcing. Repair minor spalls in accordance with 450 -13.4. Spalls located at the edges of the top flange are considered minor spalls as follows:

450-12.3 1.3 Chip: A chip is the local breaking of the corners or edges of

the concrete with the resulting voi d containing angular surfaces. Cosmetic chips are chips where the sum of the two lateral dimensions perpendicular to the length does not exceed 2.0 inches. Regardless of length, it is not necessary to repair cosmetic chips except for visually exposed r einforcing steel, prestressing strand, insert, or weldments surfaces, which may require repair in accordance with 450 -13.5. Minor chips are chips where the sum of the two lateral dimensions perpendicular to the length exceeds 2.0 inches, but does not e xceed 4.0 inches, and with a length of no more than 12.0 inches. Repair minor chips in accordance with 450 -13.5. Major chips are any chips larger than minor chips. Major chips require engineering evaluation and disposition in accordance with 450 -12.

450-12.3 1.4 Surface Porosity: Surface porosity is considered a minor

defect and is the localized porosity of a formed surface due to medium scaling. Medium scaling is defined as the loss of surface mortar up to 3/8 inch in depth and exposure of concrete aggregate. Repair surface porosity in accordance with 450 -13.3.

450-12.3 1.5 Honeycombing: Honeycombing is voids in the concrete,

loss of fines or other material from between the aggregate particles, the inclusion of air pockets FY 2023-24 Return to Table of Contents between aggregate partic les, or larger volumes of lost material. Remove honeycombing in its entirety to sound concrete before establishing the classification of the defect. Minor honeycombing is a void no deeper than concrete cover and no larger than 2.0 square feet in area af ter the removal of unsound material. Repair minor honeycombing in accordance with 450 -13.6. Major honeycombing is a void deeper than concrete cover regardless of the surface area, or shallower but with a surface area greater than 2.0 square feet that re sults after the removal of unsound material.

450-12.3 1.6 Shallow Surface Cracks: Shallow surface cracks are

considered a minor defect, and are defined as the separation of the formed or finished surface up to 0.25 inch in depth. Remove the affected material and repair the surface in accordance with 450-13.3.

450-12.3 2 Segregated Appearance in Hardened Concrete: Segregation of

hardened concrete is considered a major defect. When hardened concrete segregation is evident, evaluate in accordance with FM 5-617.

450-12.3 3 Cold Joints: A cold joint is a plane of weakness in concrete caused by

a batch of concrete setting before the next batch is added, so that the two batches fail to bond. A cold joint is considered a major defect and requires an EAR.

450-12.3 4 Formed Surface Misshaping: Formed surface misshaping is the

visual and measurable deficiency or excess of material from the specified tolerance on any surface of a product.

450-13.7 Any deficiency exceeding the specified minus ( -) tolerance or twice the specified plus

(+) tolerance will be considered maj or.

450-12.3 5 Bearing Area Flaws: Consider the bearing area to extend from the

end of the product to 3 inches beyond the edge of the bearing contact area for the full product width. Do not allow the bearing plate or bearing area plane of precast prestressed concrete beam and slab unit s to deviate from a true plane by more than 1/8 inch when tested in all directions with a steel straightedge. In the event that a 100% true plane is not achieved, the Engineer will accept a surface having not less than 80% of its area in a true plane provi ded the deviations are evenly distributed. Remove minor convex projections by grinding with an abrasive stone. The Engineer will accept minor depressions, provided that they amount to not more than 20% of the bearing area, are evenly distributed over the e ntire bearing area, and are not deeper than 1/8 inch.

450-12.3 6 Cracks: A crack may appear before or after detensioning and may or

may not cause separation throughout the product thickness or depth. Identify cracks by the FY 2023-24 Return to Table of Contents classifications and locations described below and subject them to the disposition re quired by the identified crack. If the total surface length of all cracks within a single product, regardless of their width and depth, located between the end zones exceeds one -quarter of the product’s length, the cracks are considered major. Establish crack sizes subseque nt to release of all pretensioning forces. The Engineer will reject any pile that is cracked to the point that a transverse or longitudinal crack extends through the pile, shows failure of the concrete as indicated by spalling of concrete on the main bo dy of the pile adjacent to the crack, or which in the opinion of the Engineer will not withstand driving stresses. Occasional hairline surface cracking caused by shrinkage or tensile stress in the concrete from handling will not be cause for rejection.

450-12.3 6.1 Locations of Cracks: Regardless of cause and for the

purposes of this Specification, cracks will be identified as occurring in either critical or non - critical locations of the product in accordance with the following criteria and conditions:

450-12.3 6.1.1 Critical Location Cracks: Critical locations of

cracks are any locations in which a crack would tend to open under stresses occurring at any time during the service life of the structure, or which may reduce the ultimate capacity or fatig ue life of the product. Specifically, critical locations of cracks are any locations in a product not defined and not included in 450 -12.3.6.1.2 as non-critical. Cracks in critical locations require engineering evaluation and disposition in accordance with 450-12.

450-12.3 6.1.2 Non-Critical Location Cracks: Non-critical

locations of cracks are defined by the position within a product ’s length, the position within a product’s depth, and the orientation of the crack.

450-12.3 6.2 Classification and Treatment o f Cracks: Cracks in precast

prestressed components, excluding piling, will be identified according to their width, and surface appearance , and classified as follows : FY 2023-24 Return to Table of Contents

450-12.3 6.2.1 Cosmetic Cracks: Cracks located in non -critical

locations on product which are less than 0.006 inch wide. Based on the environmental classification of the site where the product will be located, treat cosmetic cracks as follows:

450-12.3 6.2.2 Minor Cracks: Cracks located in non -critical

locations on products which are between 0.006 and 0.012 inch wide, inclusive. Based on the environmental classification of the site where the product will be located and the final elevation of the product on the site, treat minor cracks as follows:

450-12.3 6.2.3 Major Cracks: Cracks, regardless of

environmental classification, located in critical locations on products or cracks in non -critical locations of the product that are greater than 0.012 inch wide. Major cracks are considered major defects and require an EAR in accordance with Section 6 to determine the disposition of the affected product

450-12.3 6.2.4 Cracks in the Riding Surface: Repair cosmetic

and minor cracks in the top surface of components which will become the riding surface (with no overlays), once in service, rega rdless of the environmental classification as follows:

450-13 Repair Methods and Materials.

450-13.1 General: Before beginning the repairs of bug holes, spalls, chips, surface

porosity, and honeycomb, remove all laitance, loose material, form oil, curing compound and any other deleterious matter from the repair area. Repair cosmetic or minor deficiencies by methods specified herein. Submit alternative repair methods as needed. For each proj ect, maintain the record of deficiencies and their repair methods. Ensure the record includes information about product description, unit serial number, date cast, FY 2023-24 Return to Table of Contents defect description including dimensions, repair method and materials, defect discovery date, and signature of producer’s QC Manager indicating concurrence with the information. Cure repaired surfaces for the full 72 hour curing time or for the curing time as recommended by the manufacturer of the repair material. Ensure the repaired surfaces ha ve a surface texture, finish and color which matches the appearance of the unaffected surrounding area of the product.

450-13.1 1 Product Acceptance on the Project: Use only materials listed on the

Approved Product List (APL) ,in accordance with the following Sections : Epoxy Compounds (Type F) ……………….. Section 926 Materials for Concrete Repair………………. Section 930 Non-shrink Grout…………………………… Section 934

450-13.2 Cosmetic Surface Filling: Repair areas to be filled with an approved non -

shrink grout or material for concrete repair . Mix, apply , and cure the material in accordance with the manufacturer’s recommendations. Coating of the prepared surface with epoxy compound before placement is not required.

450-13.3 Surface Restoration: Maintain the surface continuously wet for a minimum of

three hours before applicati on of repair material. Repair areas to be restored with a mortar mix consisting by volume of one part cement, 2.5 parts sand that will pass a No. 16 sieve, and sufficient water to produce a viscous slurry mix or repair areas to be restored with an approved non-shrink grout or material for concrete repair . Mix, apply , and cure the material in accordance with the manufacturer’s recommendations. Cure areas repaired with a mortar mix in accordance with 450-10.6. Coating of the prepared surface with epoxy compound before placement is not required.

450-13.4 Cutting and Filling: Carefully cut all feathered edges of the area to be repaired

back perpendicular to (or slightly undercut from) the surface and to the depth of sound concrete or to a minimum depth of 1/2 inch, whichever is deeper. Coat the prepared surface with an approved epoxy bonding compound applied in accordance with the manufacturer’s recommendations. Fill the cutout area with an approved non -shrink grout , material for concrete repair, or epoxy mortar . Mix, apply, and cure in accordance with the manufacturer’s recommendations. Firmly consolidate the material in the cutout area.

450-13.5 Restoration of Surfaces and Edges: When reinforc ement is exposed, remove

concrete from around the items to provide a 1-inch clearance all around. When less than one -half the reinforcement diameter is exposed, a positive connection utilizing anchor screws may be proposed in lieu of 1 -inch clearance all around. Do not damage the reinforcement. Form surfaces and edges to t he original dimensions and shape of the product. Coat the prepared surface with an approved epoxy bonding compound applied in accordance with the manufacturer’s recommendations. Restore surfaces and edges with an approved non -shrink grout , material for concrete repair, or epoxy mortar. Mix, apply, and cure in accordance with the manufacturer’s recommendations. Firmly consolidate the material in the area to be repaired. Restore surfaces and edges to the original dimensions and shape of the product.

450-13.6 Removal and Restoration of Unsound Concrete: Carefully cut the area of

unsound concrete to be repaired back perpendicular to (or slightly undercut from) the surface and to the depth of sound concrete or to a minimum depth of 1 inch, whichever is deeper. W hen reinforcement is exposed, remove the concrete from around the items to provide a 1 -inch clearance all around. When less than one -half the reinforcement diameter is exposed, a positive connection utilizing anchor screws may be proposed in lieu of 1 -inch clearance all around. Do FY 2023-24 Return to Table of Contents not damage the reinforcement. Coat the prepared surface with an approved epoxy bonding compound applied in accordance with the manufacturer’s recommendations . Fill the area to be repaired with an approved non -shrink grout , concrete repair material, or epoxy mortar. Mix, apply, and cure in accordance with the manufacture’s recommendations. Firmly consolidate the material in the area to be repaired. Restore surfaces and edges to the original dimensions and shape of the product.

450-13.7 Surface Grinding: Grind off misshaped formed surfaces with an abrasive

stone. Apply two coats of penetrant sealer in accordance with the requirements of Section 413, to any surfaces which are not subsequently encased in concrete, immediately after gri nding has been accepted. Do not apply a penetrant sealer to any surfaces to be subsequently encased in concrete.

450-13.8 Treatment of Cracks: Treat cracks in accordance with 450 -12.3.6.

450-14 Handling, Storage, Shipping and Erection.

450-14.1 Handling: All products which are pretensioned may only be handled after

transfer of the prestressing force. For products that are prestressed by a combination of pretensioning and post -tensioning do not handle before sufficient prestress has been applied t o sustain all forces and bending moments due to handling. Exercise care in handling to prevent damage to products. Lift and move products so as to minimize stresses due to sudden changes in momentum. Calculate pick up and dunnage points. Pick up products only at points designated as pickup points as shown on the Plans or shop drawings. Maintain all beams in an upright position at all times. Evaluate the temporary stresses and stability of beams during their handling. The temporary stresses induced into the products during handling must be within the acceptable stresses at release listed in the Department’s Structures Design Guidelines. Take appropriate action to increase the stability of products during handling when the factor of safety against lateral buckling instability is below 2.0. Include the expected fabrication tolerance for sweep in the analysis. The analysis procedure provided by the PCI or similar procedures may be used for the stability evaluation. Verify lifting devices for capacity in lif ting and handling products, taking into account various positions during handling. Keep multiple component lifting devices matched to avoid non -compatible use. When a product has multiple lifting devices, use lifting equipment capable of distributing the l oad at each device uniformly to maintain the stability of the product. When the lifting devices are grouped in multiples at one location, align them for equal lifting. Take appropriate steps to prevent the occurrence of cracking. When cracking occurs dur ing handling and transportation, revise handling and transporting equipment and procedures as necessary to prevent cracking for subsequent products.

450-14.2 Storage: Store precast prestressed beams, Double T -Beams, slab beams and

slab units on only two p oints of support located within 18 inches of the end of the product or as calculated. Support skewed beams, Double T -Beams, slab beams or slab units within 18 inches of the end of the full product section or as calculated. Do not support slab beams on the outer 6 inches of the product width. Support other products on an adequate number of supports so as to keep stresses in the products within the allowable stresses at release listed in the Department's Structures Design Guidelines. Locate multiple supports (more than two) within 1/2 inch of a horizontal plane through the top surface of the supports. Adequately brace beams as necessary to maintain stability. FY 2023-24 Return to Table of Contents All supports must be level and on adequate foundation material that will prevent shifting or differe ntial settlement which may cause twisting or rotation of products. Immediately pick up products in storage that have rotated or twisted and adjust the supports to provide level and uniform support for the product. Support prestressed products that are st acked by dunnage placed across the full width of each bearing point and aligned vertically over lower supports. Move dunnage points in accordance with 450 -2.3 with the approval of the QC Manager. Do not use stored products as a storage area for either shor ter or longer products or heavy equipment. Where feasible, base the selection of storage sites, storage conditions and orientation upon consideration of minimizing the thermal and time -dependent creep and shrinkage effects on the camber and/or sweep of t he precast pretensioned products. Continuous application of water during the initial 72 hour moist curing period may be interrupted for a maximum of one hour to allow relocation of precast prestressed concrete elements within the manufacturing facility. Keep the moist burlap in place during relocation of the element.

450-14.3 Shipping: Do not ship precast prestressed concrete products to the project site

prior to the completion of the 72 hour curing period and attainment of the required 28 -day strength. Verification of the shipping strength test, before 28 days, is permitted by testing compressive strength cylinders that are cured under the conditions similar to the product or by testing temperature match cured cylinders. The use of maturity method, AST M C1074, pulse velocity method in accordance with ASTM C597, or any other nondestructive test method acceptable to Engineer, is permitted to estimate the strength before its verification by test cylinders. The shipping strength test is the average compress ive strength of two test cylinders. Do not ship products until accepted and stamped by the QC Manager or the inspectors under the direct observation of the QC Manager or designee. In the case of elements repaired due to major defects, notify the Engineer at least 72 hours in advance of shipping to verify compliance with the Specification. At the beginning of each project, provide a notarized statement to the Engineer from a responsible company representative certifying that the plant will manufacture th e products in accordance with the requirements set forth in the Contract Documents and Producer QC Plan. The QC Manager’s stamp on each product indicates certification that the product was fabricated in conformance with the Producer QC Plan, the Contract, and the Specifications . Ensure that each shipment of prestressed concrete products to the project site is accompanied with a signed or stamped delivery ticket providing the description and the list of the products. Evaluate the temporary stresses and stability of all products during shipping and locate supports, generally within 18 inches from the beam end, in such a manner as to maintain stresses within acceptable levels. Include impact loadings in the evaluation. Do not support slab beams on the outer 6 inches of the product width.

450-14.4 Erection: Erect precast prestressed products without damage. Meet the

handling and storage requirements of 450-14.1 and 450 -14.2 for field operations. Before casting diaphragms and the deck slab, do not allow the horizontal alignment of prestressed concrete beams to deviate from a straight line connecting similar points of beam ends by more than the sweep tolerances specified in 450 -2.3. Adequately brace beams as necessary to maintain stability. FY 2023-24 Return to Table of Contents

450-15 Measurement and Payment.

450-15.1 General: The work specified in this Section will be measured and paid for as

shown be low for the particular item involved. Precast prestressed concrete members are acceptable to the Department for full payment when all requirements of the Contract Documents have been met. No partial payments will be made for precast prestressed concrete me mbers until the 28-day strength requirement, along with other applicable Specification requirements, have been met.

450-15.2 Prestressed Concrete Piling: Payment will be made at the Contract unit price

per foot for the particular type of piling, measured and paid for as specified in Section 455, including the provisions for cutoffs and splices.

450-15.3 Prestressed Concrete Beams: Payment will be made at the Contract unit price

per foot for Prestressed Beams, complete in place and accepted. Final pay lengths will be plan quantity based on casting lengths, as detailed in the Plans, subject to the provisions of 9 -3.2.

450-15.4 Prestressed Concrete Slab Unit s and Slab Beams : Payment will be made at

the Contract unit price per foot for the units, complete in place and accepted. Final pay lengths will be plan quantity based on casting lengths, as detailed in the Plans, subject to the provisions of 9-3.2.

450-16 Basis of Payment.

Price and payment will be full compensation for all work and materials specified in this Section, including reinforcement, pretensioning strand, embedded ducts, hardware, inserts and other materials as required, to fabricate, transport and place the product into its permanent position in the structure. Payment for the items will be made under the following: Item No. 450 - 1- Prestressed Beams - per foot. Item No. 450 - 2- Prestressed Beams: Florida I -Beams - per foot. Item No. 450 - 3- Prestressed Slab Units - per foot. Item No. 450 - 4- Prestressed Beam U -Beams - per foot. Item No. 450 - 8 Prestressed Beams: Florida Slab Beam – per foot. Item No. 450 - 88- Prestressed Slab Units Transversely Post -Tensioned - per square foot. FY 2023-24 Return to Table of Contents SECTION 451 PRESTRESSED SOIL ANCHORS

451-1 Description.

Construct prestressed soil anchors consisting of a high strength steel tendon anchored to the retaining wall on one end and to the soil on the other end through a bulb of pressure injected portland cement concrete grout. Test each anchor by prestressing to the load indicated in the Contract Documents before locking off to the retaining wall. Select the prestressed soil anchor type and the installation method, and determine the bond length a nd anchor diameter. Assume responsibility for installing prestressed soil anchors that develop the load -carrying capacity indicated in the Plans in accordance with 451 -7. Provide corrosion protection for permanent prestressed soil anchors. The Engineer will not require corrosion protection for temporary prestressed soil anchors. Protect anchor tendons from corrosion as shown in the Plans in accordance with 451 -8.

451-2 Definitions.