SECTION 904 – PRECAST AND PRESTRESSED CONCRETE
904.01 Non-Structural Precast Concrete
904.01.01 Component Materials
Provide materials as specified: Concrete ................................ ................................ ................................ ................................ ...................... 903.03 Self-Consolidating Concrete (SCC) ................................ ................................ ................................ .......... 903.06.02 Mortar................................ ................................ ................................ ................................ ...................... 903.08.01 Curing Materials ................................ ................................ ................................ ................................ .......... 903.10 Reinforcement Steel ................................ ................................ ................................ ................................ .... 905.01 Welded steel wire fabric used for reinforcement need not be galvanized. For Precast Concrete, the minimum cement content specified in Table 903.03.06-3 is not required for Class A or Class B concrete.
904.01.02 Fabrication
Fabricate precast concrete at a plant as specified in 1011.01 and listed on the QPL.
1.Placing Reinforcement Steel. Before placing the concrete, place reinforcement steel in position as shown on the approved working drawings and as specified in 504.03.01. Firmly tie the reinforcement to prevent displacement during placing of the concrete.
2.Placing Concrete. Place concrete as specified in 504.03.02.B, 504.03.02.C, 504.03.02.D and 504.03.02.E. Before placing concrete, ensure that reinforcement steel and any other embedded materials are free of loose rust, frost, d irt, oil, or contaminants that may prevent a bond with the concrete. Consolidate concrete with internal vibrators. The fabricator may use external vibration to supplement internal vibration. If using SCC, minimize or eliminate the use of vibrators to prevent segregation.
904.01.03 Curing
Cure according to the PCI MNL-116, except for steam curing. Do not strip forms until the piece has attained a stripping strength of 2,000 pounds per square inch. If steam curing, delay the application of steam within the enclosure for 4 hours or until the concrete has attained an initial set as determined according to ASTM C 403. Maintain an ambient temperature between 50 °F and 90 °F during the delay. Ensure that the maximum rate of temperature increase in the enclosure is 40 °F per hour. Monitor the temperature in the enclosure using recording thermometers placed at a minimum of 2 locations. Ensure that the enclosure temperature is maintained between 90 °F and 150 °F until 2 concrete test cylinders, field cured according to AASHTO T 23, have attained the stripping strength.
904.01.04 Removing Forms and Finishing
Ensure that items remain in forms for the duration of the curing operation. Remove forms when concrete has attained the stripping strength. If handling devices are used, remove and fill the holes with concrete or mortar. Provide a Class 1 finish as specified in 504.03.02.H.1. Complete surface finishing operations before placing the piece in storage.
904.01.05 Shipping and Handling
Store, stack, and transport the pieces using methods that do not cause the development of cracks or other damage. Do not ship pieces until the class design strength as specified in Table 903.03.06-3 has been attained.
904.01.06 Quality Control and Acceptance Requirements
Notify the ME, in writing, at least 21 days before start of production. For quality control, keep applicable records according to PCI Division 1, Quality Control, or NPCA requirements, and supply copies of these records to the ME as requested. Ensure that the quality control technician performing all tests is certified as an ACI Field Testing Technician, Grade 1. Submit Quality Control Plan to ME for review and approval. Follow the Department approved Buy America Compliance Plan. Provide documentation of compliance when requested by the ME. Submit certification of compliance as specified in 106.07. If the concrete piece is spalled, honeycombed, chipped, or otherwise defective, the ME or RE will reject the piece.
904.02 Precast Concrete Retaining Walls
904.02.01 Component Materials
Provide materials as specified: Concrete ................................ ................................ ................................ ................................ ...................... 903.03 Self-Consolidating Concrete (SCC) ................................ ................................ ................................ .......... 903.06.02 Mortar ................................ ................................ ................................ ................................ ..................... 903.08.01 Curing Materials ................................ ................................ ................................ ................................ ........... 903.10 Reinforcement Steel ................................ ................................ ................................ ................................ ..... 905.01 Welded steel wire fabric used for reinforcement need not be galvanized. For Precast Concrete, the minimum cement content specified in Table 903.03.06-3 is not required for Class A or Class B concrete.
904.02.02 Fabrication
Use a system listed on the QPL to fabricate prefabricated modular walls or mechanically stabilized earth walls. Fabricate precast concrete at a plant as specified in 1011.01 and listed on the QPL.
1.Placing Reinforcement Steel. Place reinforcement steel as specified in 504.03.01. Before placing the concrete, place reinforcement in position as shown on the approved working drawings, and firmly tie the reinforcement to prevent displacement during placing of the concrete.
2.Forms. Cast the units in steel forms to ensure the production of uniform units. Place the forms on a flat surface with the front face of the form down.
3.Placing Concrete. Place concrete as specified in 504.03.02.C, 504.03.02.D, and 504.03.02.E. Before placing concrete, ensure that reinforcement steel and other embedded materials are free of loose rust, frost, dirt, oil, or contaminants that may prevent a bond with the concrete. Consolidate concrete with internal vibrators. The fabricator may use external vibration to supplement internal vibration. If using SCC, minimize the use of vibrators to prevent segregation.
4.Fabrication Requirements. Fabricate posts and panels free of honeycombing or voids and true to the size and dimensions specified in Table 904.02.02-1. Clearly mark the name of manufacturer, name of contract, date of manufacture, mark numbers, and type of unit, as shown on the approved working drawings, in the inside or back face of each unit. Table 904.02.02-1 Dimensional Tolerances For MSE Walls All Panel Dimensions ±1/4 inch Deviation from Vertical 1/8 inch per 5 feet For Modular Walls Length and Height of Face ±3/16 inch Deviation from Square for Units < 10 feet wide1 5/16 inch maximum Deviation from Square for Units ≥ 10 feet wide1 3/4 inch maximum
1.Measure deviation from square on the diagonal.
904.02.03 Curing
Cure as specified in 904.01.03, except that the required stripping strength is 3,000 pounds per square inch.
904.02.04 Form Removal and Finishing
Remove forms and finish concrete as specified in 904.01.04.
904.02.05 Shipping and Handling
Handle and ship as specified in 904.01.05.
904.02.06 Quality Control and Acceptance Requirements
Notify the ME in writing at least 21 days before start of production. For quality control, keep applicable records according to PCI Division 1, Quality Control, or NPCA requirements, and supply copies of these records to the ME as requested. Ensure that the quality control technician performing all tests is certified as an ACI Field Testing Technician, Grade 1. Submit Quality Control Plan to ME for review and approval. Follow the Department approved Buy America Compliance Plan. Provide documentation of compliance when requested by the ME. During production, the ME will inspect the quality of materials and the process of manufacture. The ME will accept the concrete as specified in 903.03.05 and will inspect the finished pieces before shipping for dimensional tolerances and damage. The ME will reject units for any of the following:
1.Variations in the exposed face that substantially deviate in appearance.
2.Dimensions not conforming to the tolerances specified in Table 904.02.02-1.
3.Honeycombed or open texture not properly repaired.
4.Defects that would affect the structural integrity of the unit.
5.Stained front face due to excess form oil or other reasons.
6.Broken or cracked corners.
904.03 Structural Precast Concrete
904.03.01 Component Materials
Provide materials as specified: Concrete ................................ ................................ ................................ ................................ ....................... 903.03 Self-Consolidating Concrete (SCC) ................................ ................................ ................................ .......... 903.06.02 Mortar ................................ ................................ ................................ ................................ ..................... 903.08.01 Curing Materials ................................ ................................ ................................ ................................ ........... 903.10 Reinforcement Steel ................................ ................................ ................................ ................................ ...... 905.01 Bolts and Bolting Materials ................................ ................................ ................................ ........................... 908.01 Epoxy Waterproofing ................................ ................................ ................................ ............................... 912.02.02 For Precast Concrete, the minimum cement content specified in Table 903.03.06-3 is not required for Class A or Class B concrete.
904.03.02 Fabrication
Fabricate precast concrete at a plant as specified in 1011.01 and listed on the QPL. Provide an office for the ME as specified in 1011.03.
1.Placing Reinforcement Steel. Before placing the concrete, place all reinforcement steel in position as shown on the approved working drawings and as specified in 504.03.01. Firmly tie the reinforcement steel to avoid displacement during placing of the concrete. For longitudinal distribution reinforcement steel, the fabricator may use welded wire fabric or deformed billet steel bars. Ensure that welded wire fabric is shipped in mats. In precast concrete box culverts, the ME will allow lifting devices in each precast unit for the purpose of handling and erection. If using lifting hooks or lugs, galvanize the devices according to ASTM A 153.
2.Placing Concrete. Place concrete as specified in 504.03.02.B, 504.03.02.C, 504.03.02.D, and 504.03.02.E. Before placing concrete, ensure that reinforcement and any other embedded material are free of loose rust, frost, dirt, oil, or contaminants that ma y prevent a bond with the concrete. Consolidate concrete with internal vibrators. The fabricator may use external vibration to supplement internal vibration. If using SCC, minimize the use of vibrators to prevent segregation.
3.Fabrication Requirements. Identify each precast concrete unit with a permanent marking. Manufacture the precast concrete units in steel forms. For precast culverts, ensure that units conform to the requirements specified in Table 904.03.02-1. Provide 2 rows of threaded inserts or bar extensions in the last precast culvert section for the cast -in-place end section and the wingwall attachment and for the headwall attachment, if necessary. Table 904.03.02-1 Fabrication Requirements for Culverts Wall Thickness 8 inches minimum Top and Bottom Slab Thickness 10 inches minimum Concrete Cover for Walls and Bottom Slab 1 1/2 inches minimum Concrete Cover for Top Slab 2 inches minimum For precast concrete arch structures, ensure that units comply with Table 904.03.02-2. Table 904.03.02-2 Fabrication Requirements for Precast Concrete Arch Structures Concrete Cover Outside Face 2 inches minimum Concrete Cover Inside Face 1.5 inches minimum Internal Dimension Tolerance ±1% or ±2 inches, whichever is less Wall Thickness Tolerance1 −5% or −1/2 inch, whichever is more Difference in Side Lengths2 ±3/4 inch
1.The ME will not reject structures having thicknesses that exceed that shown in the approved working drawing.
2.Requirement waived for skewed ends for laying curves.
904.03.03 Curing
Cure as specified in 904.01.03, except that the required stripping strength is 4,000 pounds per square inch.
904.03.04 Removing Forms and Finishing
Ensure that units remain in their steel forms for the duration of the curing operation. Upon removal of the forms, provide a Class 1 finish as specified in 504.03.02.H.1 to the entire precast concrete culvert unit, including exterior, interior, and lap surfaces. For culverts, af ter approval of the Class 1 finish, apply 1 coat of an epoxy waterproofing on the exterior of the roof slab. Apply this coating in the precaster’s plant not earlier than 72 hours after fabrication, and after the concrete compressive strength has reached 4,000 pounds per square inch. Ensure that the concrete surfaces of the precast units are dry during application of the epoxy waterproofing. Apply the epoxy waterproofing according to the product manufacturer’s recommendations.
904.03.05 Shipping and Handling
Handle and ship as specified in 904.01.05.
904.03.06 Quality Control and Acceptance Requirements
Notify the ME in writing at least 21 days before start of production. For quality control, keep applicable records according to PCI Division 1, Quality Control, or NPCA requireme nts, and supply copies of these records to the ME as requested. Ensure that the quality control technician performing all tests is certified as an ACI Field Testing Technician, Grade 1. Submit Quality Control Plan to ME for review and approval. Follow the Department approved Buy America Compliance Plan. Provide documentation of compliance when requested by the ME. During production, the ME will inspect the quality of materials and the process of manufacture. The ME will accept the concrete as specified in 903.03.05 and will inspect the finished pieces prior to shipping for dimensional tolerances and damage. If the concrete piece is spalled, honeycombed, chipped, or otherwise defective, the ME may reject the piece or approve repairs. If the ME does not inspect the precast concrete item, submit certifications of compliance as specified in 106.07.
904.04 Prestressed Concrete
904.04.01 Component Materials
Provide materials as specified: Concrete ................................ ................................ ................................ ................................ ..................... 903.03 Mortar................................ ................................ ................................ ................................ ...................... 903.08.01 Curing Materials ................................ ................................ ................................ ................................ .......... 903.10 Reinforcement Steel ................................ ................................ ................................ ................................ ..... 905.01 Prestressing Reinforcement ................................ ................................ ................................ .......................... 905.02 Bolts and Bolting Materials ................................ ................................ ................................ .......................... 908.01 Epoxy Waterproofing ................................ ................................ ................................ ............................... 912.02.02 Epoxy Bonding Compound ................................ ................................ ................................ .......................... 919.07 In the construction of prestressed concrete I-beams or prestressed concrete slab and box beams, when the use of galvanized reinforcement steel is planned for the deck construction, galvanize all reinforcement steel that will provide composite action. For prestressed concrete piles in a marine environment, use grit impregnated epoxy -coated prestressing steel st rands as specified in 905.02. When storing, cover the strands with an opaque polyethylene sheeting or other suitable protective material to protect the reinforcement from exposure to sunlight, sal t spray, and weather. For stacked bundles, drape the protective covering around the perimeter of the stack. Adequately secure the covering; however, allow air circulation to prevent condensation under the covering. Do not store epoxy-coated prestressing steel within 1,000 feet of ocean or tidal water for more than 2 months.
904.04.02 Fabrication
Fabricate prestressed concrete at a plant as specified in 1011.02 and listed on the QPL. Provide an office for the ME as specified in 1011.03.
1.Placing Reinforcement and Prestressing Steel. Store reinforcement above ground, and cover strand packs when not in use. Place reinforcement steel as specified in 504.03.01 and as shown in the working drawings. Position or loosely tie reinforcement steel until prestressing strands have been positioned. After pre-stressing, firmly tie the reinforcement prior to placing concrete. If using an anti-bonding agent on the forms to facilitate their removal, protect the prestressing strands agains t contamination by the anti-bonding agent. Use supports, spaced a maximum of 10 feet apart, to support bottom strands and side reinforcement steel. If necessary, provide horizontal and vertical spacers to hold the wires in place in the enclosures.
2.Prestressing. Provide protection, for the ME inspecting the prestressing operation, adequate to stop a flying strand. Use shields, placed at both ends of the bed, made of steel, reinforced concrete, heavy timbers, or other material to provide protection acceptable to the ME. Apply stress to each cable as shown on the working drawings using either the single strand or the multi-strand jacking method. If performing prestressing by the multi-strand jacking method, bring the individual strands to a uniform initial tension before applying the full pretensioning. Measure the initial tension of each strand using a dynamometer, a gauge, or other such means. After the initial tensioning, stress the strands until the specified elongation and jacking pressure are attained. If performing prestressing by the single strand jacking method, do not construct more than 1 splice per strand. When multi-strand jacking is used, either splice all strands or splice no more than 10 percent of the strands. Ensure that spliced strands are similar in physical properties, are from the same source, and have the same twist or lay. Position splices outside of the prestressed members. Do not torch cut the ends of the strand lengths to be spliced. For prestressing draped strands, apply stress by either partially jacking at the end of the bed, followed by raising or lowering the strands to their final position, or entirely by the jacking operation. Regardless of the method of prestressing, use low-friction devices at all points of slope ch ange in the strand trajectory. If the strands are tensioned in their draped position, support the strands using lubricated rollers with bronze bushings or roller bearings at all hold-up points, and low-friction, free-turning rollers at all hold-down points. When strands are deflected after partial tensioning, simultaneously raise or depress the strands at all points or in an approved specified sequence. Replace broken strands if the allowable number of wire breaks specified in Table 904.04.02-1 is exceeded. Locate and tie wire breaks directly to the strand to prevent raveling during the vibration of the concrete. Table 904.04.02-1 Maximum Allowable Wire Breaks Number of Strands Maximum Allowable Wire Breaks Less than 20 strands 0 20 to 39 strands 1 40 to 59 strands1 2 60 and more strands1 3
1.Replace the strand if more than 1 break occurs in an individual strand. If concrete is not placed within 72 hours of prestressing, the ME may require the bed to be checked for proper stresses before placement of concrete. After final stressing, position strands and uniformly distribute the stress in the strands throughout the bed length.
3.Placing Concrete. Before placing concrete, ensure that the prestressing is acceptable to the ME and that reinforcement and any other embedded materials are free of loose rust, frost, dirt, oil, or contaminants that may prevent a bond with the concrete. Place concrete as specified in 504.03.02.B, 504.03.02.C, 504.03.02.D, and
504.03.02 E. Consolidate concrete with internal vibrators. The fabricator may use external vibration to
supplement internal vibration. Only place concrete in the presence of, or as directed by, the ME. For prestressed concrete box beams, place voids in the forms after the ME has inspected the concrete poured to encase the strands in the bottom portion of the beam.
4.Fabrication Requirements. Fabricate the prestressed concrete members to plan dimensions wit hin the tolerances specified in applicable sections of PCI MNL-116. The ME will reject members having dimensions outside the tolerance limits, unless the Contractor performs corrective measures. Obtain approval from the Department before taking any corre ctive measures. Adhere to beam camber tolerances so that preformed transverse tie holes for prestressed box and slab beams line up correctly during erection, facilitating the placement of transverse ties. Cast a permanent, unique, identification mark and the date of the casting in the top of members. Upon removal of the forms, mark the ends of members with the same identification marking.
5.Detensioning. Do not detension the bridge members until the strength tests indicate that the concrete has reached a compressive strength of at least 4,000 pounds per square inch for Class P, 4 ,500 pounds per square inch for Class P-1, and 5,000 pounds per square inch for Class P-2 concrete. Before detensioning, submit to the ME a plan for the pattern and schedule for releasing the strands. Strip or loosen forms that may tend to restrict the horizontal or vertical movement of the member. For detensioning, use either the multiple strand release method or the single strand release method. If the multiple strand method of release is used, gradually and simultaneously release all of the strands or a symmetrical group of strands. Transfer the load on the strands from the anchorage to the jacking system. Gradually release the jack or jacks until the strands are relaxed. For the single strand release method, detension the strands in the sequence of the pattern and schedule of release by slow-heat cutting. Use a low -oxygen flame applied along the strand for a minimum of 5 inches until the metal gradually loses its strength. Apply the heat at a rate to induce failure of the first wire in the strand at least 5 seconds after the heat is applied. The ME will reject pieces if the fabricator fails to follow the detensioning procedure.
904.04.03 Curing
Cure as specified in 904.01.03, except that the required str ipping strength is 4 ,000 pounds per square inch for Class P, 4,500 pounds per square inch for Class P-1, and 5,000 pounds per square inch for Class P-2 concrete. In addition, when the ambient air temperature is above 100 °F, initiate a water cure or other approved method as soon as the concrete is able to receive the water without physical damage to its surface. The fabricator may discontinue this cure upon introduction of steam, provided that a relative humidity of 100 percent is maintained.
904.04.04 Removing Forms and Finishing
Do not remove side forms until the strength of 2 cylinders, similarly cured as the member, achieves at least 2,500 pounds per square inch. Do not move the member from the bottom forms before detensioning. Upon the removal of forms, the ME may reject any member that has 1 prestressing strand exposed for a length in excess of 24 diameters, or 2 or more strands visually exposed. In addition, the ME may reject any unit that is honeycombed to such an extent that chipping away from honeycombed concrete results in the conditions described for exposed strands. If the ME determines that the defective areas can be repaired, submit a repair procedure to the ME for approval. Perform approved patching before detensioning. Provide a Class 1 finish, as spec ified in 504.03.02.H.1, on formed surfaces of the concrete members. For surfaces of concrete exposed to view in the finished structure, perform additional finishing by rubbing mortar on the surface using burlap. Ensure that the rubbing produces a smooth surface of uniform color and texture. Transversely score the top surface of members using a stiff wire brush. After the removal of hold -down devices from the bottom of the beams, coat the resulting holes with an epoxy bonding compound, and plug the holes with mortar while the epoxy bonding compound is still tacky. If the epoxy bonding compound dries out before the placement of the mortar, sandblast the area and reapply the bonding compound. Patch vent holes for box beams upon removal from forms after the internal void drains are opened. Treat portions of prestressed concrete beams as shown on the Plans with an epoxy waterproofing. Do not apply the epoxy waterproofing to the top surface of a beam. Use an epoxy waterproofing that closely mat ches the color of the concrete. Do not apply the epoxy waterproofing sooner than 72 hours after detensioning. Ensure that the concrete surface is dry and clean of oil, grease, and dirt before applying the coating. Apply the epoxy waterproofing by brush only, unless otherwise approved by the ME. Ensure that the epoxy waterproofing is applied uniformly and provides adequate coverage.
904.04.05 Shipping and Handling
The fabricator may handle members immediately after completion of detensioning. Before placing members in storage, ensure that surface finishing operations are completed and the member is approved by the ME. Do not remove a girder from the bed unless the differential between girder and air temperature is less than 80 °F. Before box and slab beams are moved to storage, inspect nonmetallic draining devices and open to provide for passage of water. Notify the ME at least 2 days before shipping. Do not ship until the class design strength as spe cified in Table 903.03.06-3 has been attained and a minimum of 72 hours have elapsed following detensioning. Determine shipping strength by testing a complete set of cylinders that represent the lot of concrete and were cured with the item. Transport girders in an upright position. Ensure that the points of support and directions of the reactions with respect to the girder are approximately the same during transportation and storage as in its final erection position. Request the Department’s approval for transportation or storage of girders in any other position.
904.04.06 Quality Control, Quality Assurance, and Acceptance Requirements
Notify the ME in writing at least 21 days before start of production. For quality control, keep applicable records in conformance with PCI Division 1, Quality Control, or NPCA requirements, and supply copies of these records to the ME as requested. Ensure that the quality control technician performing all tests is certified as an ACI Field Testing Technician, Grade 1. Submit Quality Control Plan to ME for review and approval. Follow the Department approved Buy America Compliance Plan. Provide documentation of compliance when requested by the ME. During production, the ME will inspect the quality of materials and the process of manufacture. The ME will accept the concrete as specified in 903.03.05 and will inspect the finished pieces prior to shipping for dimensional tolerances and damage. If concrete is placed on the same bed at different times in the day, the ME will split the day’s production into separate lots. If the concrete member is spalled, honeycombed, chipped, or otherwise defective, the ME may reject the piece or approve repairs. If the ME does not inspect the precast concrete item, submit certifications of compliance as specified in 106.07.
Referenced in this section
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Source: Standard Specifications for Road and Bridge Construction, 2019 (rev. 2022-12-21) Edition. Pages 489–496 of 651. View official source ↗