425Precast Prestressed Concrete Structural Members

2.1 Prestressing Hardware. Furnish prestressing hardware in conformance with the manufacturer’s

specifications.

2.2 Concrete. Furnish concrete of the class shown on the plans.

2.3 Prestressing Steel . Furnish prestressing steel conforming to one of the following types:

 seven- wire steel strand meeting DMS -4500 , “Steel Strand, Uncoated Seven- Wire Low -Relaxation for Prestressed Concrete,”  alloy bars meeting ASTM A722, or  steel wire meeting ASTM A 421. Use seven -wire steel strand produced by a prequalified manufacturer on the Department’s MPL. The Department may take samples in accordance with Tex -710-I to verify compliance with specification requirements. Assign an individual lot number to all bars from each size and heat, all wire from each coil, and all strand from each reel, and tag the material for accurate identification at the jobsite. Identify each lot of anchorage assemblies and couplers in a similar manner. Unidentified prestressing steel, anchorage assemblies, or couplers received at the project site will be rejected. Loss of positive identification of these items at any time will be cause for rejection.

2.4 Post -Tensioning System . Furnish post -tensioning system as required by Item 426 and as shown on the

plans. 583 3. CONSTRUCTION Fabricate precast prestressed concrete members in accordance with Item 424, “Precast Concrete Structural Members (Fabrication).” Fabricate railroad structures in accordance with the AREMA Manual for Railway Engineering and Item 424. In the case of a conflict between the AREMA manual and Item 424, the more stringent requirements apply.

3.1 Handling, Storing, Hauling, and Erection of Precast Prestressed Concrete Members. Properly handle,

store, haul, and erect all members so that they are placed in the structure in a manner to avoid excessive bending stresses and without damage. Lift members with approved lifting devices as shown on the shop drawings or as approved. Maintain beams in an upright position at all times, and raise and support them near the ends to prevent torsion unless approved on shop or erection drawings. Do not move members from the casting yard until all requirements of the pertinent Items have been met. Haul beams to the project site after at least 7 days have elapsed since casting, unless otherwise approved. The storage area must be clean and well drained. Prevent excessive or differential settlement of members by storing on:  stable ground and  dunnage of sufficient size, shape, and strength to prevent crushing. Place dunnage a distance no more than 3% of the beam length from the beam ends. When approved, cantilever beams may be supported at locations other than near the ends. Support concrete box beams and U-beams under the solid end block area during handling, storage, hauling, and erection. Separate members with blocking arranged in vertical planes that will not crush under load when members are stacked. Stack members so lifting devices are accessible and undamaged. Use dunnage or blocking material that will not damage or stain the required finis h. Rearrange improperly stored members and inspect them for damage. Members that are improperly stored and become cracked, warped, or otherwise damaged in storage may be rejected. Securely tie or brace all beams during erection in conformance with minimum erection and bracing standards. Protect traffic against falling objects during the erection of diaphragms and other structural members, during the placing of cast -in-place concrete, and during the erection and dismantling of forms when railroad or roadway traffic must be maintained beneath beams already placed. Protect traffic with nets or flooring with openings not larger than 1 in. or as approved. Fit mating surfaces to prevent excessive grout leakage when erecting precast prestressed concrete bridge deck panels. Fill the joint with grout or seal it with an acceptable caulking compound before placing the cast- in-place portion of the slab if such fit is not provided. Finish surfaces of beams or other members after slab placement in accordance with Section 4 20.4.13., “Ordinary Surface Finish,” and Item 427. Correct beam discrepancies including, but not limited to horizontal misalignment or variations in vertical camber, to achieve a satisfactory completed structure at no additional expense to the Department. Correction may require replacement of the member.

3.2 Packaging, Storing, and Handling of Prestressing Steel . Protect prestressing steel against physical

damage and rust or other results of corrosion, from manufacture to grouting or encasing in concrete. Prest ressing steel with physical damage will be rejected. Replace any reel containing broken wires. Provide wire that is bright and uniformly colored, without foreign matter or pitting on the surface. 584 Package prestressing steel in containers or shipping forms for protection from physical damage and corrosion during shipping and storage. A corrosion inhibitor must be:  placed in the package or form,  incorporated in a corrosion inhibitor carrier type packaging material, or  applied directly to the steel when permitt ed. The corrosion inhibitor must not have deleterious effect on the steel, concrete, or bond strength of steel to concrete. Inhibitor carrier- type packaging material must conform to the provisions of federal specification MIL-PRF-3420 G. Immediately replace damaged packaging or forms, or restore them to original condition. Have the shipping package or form clearly marked with the corrosion inhibitor type, packaging date, and a statement that the package contains high-strength prestressing steel. Handle prestressing steel carefully to avoid abrading, nicking, or kinking the strand, bar, or wire. Protect prestressing steel from damage and corrosion by storing it above the ground on platforms, skids, or other approved supports. Any pitting or tightly adhering rust on prestressing steel will be cause for rejection of the steel. Do not weld or torch- cut near any prestressing steel, so that it is not exposed to weld spatter, direct heat, or short -circuited current flow. When prestressing steel for post -tensioning is installed in the ducts, any rust that forms during the first 14 days after installation will not be cause for rejection of the steel.