SECTION 505 – PRECAST AND PRESTRESSED STRUCTURAL CONCRETE
505.01 Description
This Section describes the requirements for manufacturing, furnishing, and erecting prestressed members, precast reinforced concrete culverts, and precast concrete arch structures.
505.02 Materials
505.02.01 Materials
Provide materials as specified: Coarse Aggregate (No. 57) ................................ ................................ ................................ ........................... 901.03 Concrete ................................ ................................ ................................ ................................ ...................... 903.03 Non-Shrink Grout ................................ ................................ ................................ ................................ 903.08.02.A Structural Precast Concrete ................................ ................................ ................................ ........................... 904.03 Prestressed Concrete ................................ ................................ ................................ ................................ .... 904.04 Reinforcement Steel ................................ ................................ ................................ ................................ ..... 905.01 Dowels................................ ................................ ................................ ................................ ..................... 905.01.05 Post-Tensioning Reinforcement ................................ ................................ ................................ ................ 905.02.03 Bearing Pads ................................ ................................ ................................ ................................ ................ 907.03 Anchor Bolts ................................ ................................ ................................ ................................ ............ 908.01.03 Epoxy Waterproofing ................................ ................................ ................................ ............................... 912.02.02 Preformed Joint Filler ................................ ................................ ................................ ................................ ... 914.01 Subsurface Drainage Geotextile................................ ................................ ................................ ..................... 919.01 Water ................................ ................................ ................................ ................................ ............................ 919.08 Provide post-tensioning grout that complies with the requirements for Class B or C grout according to Section 10 of the AASHTO LRFD Bridge Construction Specifications.
505.02.02 Equipment
Provide grouting equipment according to the AASHTO LRFD Bridge Construction Specifications. For each tensioning jack, provide the RE with jack calibrations charts certified by a testing laboratory approved by the Department to show the relationship between the dial gauge and the force delivered. Ensure that jacks and the gauges are calibrated as a unit, and are recalibrated every 6 months.
505.03 Construction
505.03.01 Pretensioned Prestressed Concrete Beam and Prestressed Concrete Beam
A.Working Drawings. Submit working drawings for certification that include the class of concrete, the pattern and schedule for releasing strands before detensioning, detensioning concrete strength, and tensioning and detensioning patterns. If the design requires post-tensioning, include end blocks in the design. In the case of multiple span structures, if the design of beams of any 1 span requires end blocks, include end blocks for all spans of the fascia beams.
B.Shipping and Storing. Notify the RE at least 5 days before shipping. Transport and store precast girders and slabs in an upright position, and ensure that the points of support and directions of the reactions with respect to the member are approximately the same during transportation and storage as when the member is in its final position. Obtain RE approval to transport or store precast units in a position other than upright. When shipping members that are pre-tensioned, ensure that no creep occurs.
C.Erection Plan. Submit working drawings for certification regarding the plan of operations to the RE at least 30 days before the pre-erection meeting. Include, at a minimum, the following in the plan:
1.Number and type of manpower and equipment.
2.Shipping procedures.
3.Lifting procedures.
4.Erecting sequence.
5.Temporary bracing.
6.Manufacturer’s recommendations.
7.Procedures for employee safety.
8.Traffic control and protection.
9.Method of post-tensioning and determining friction loss.
10.Anchorage details and design calculations, signed and sealed by a Professional Engineer.
D.Erecting. Notify the RE to schedule a pre -erection meeting at least 20 days before the start of erection. Before erecting prestressed concrete beams, follow t he loading requirements for substructure members as specified in
504.03.02 J. Place the embankment backfill behind the abutment walls to at least 50 percent of their height before
erection, unless otherwise approved. Set bearing pads according to the manufacturer’s recommendation. Set structural bearing assemblies or reinforced elastomeric bearing assemblies as specified in 506.03.02.C. Anchor prestressed concrete voided slabs and box beams to abutments and piers using dowels as anchors.
E.Post-Tensioning of Prestressed Slabs and Box Beams. Do not splice strands unless approved by the RE. Install post-tensioning reinforcement through preformed ducts before grouting the longitudinal keyways. Tension the rods and strands to the value shown on the Plans. Continuously monitor the tension being applied during the tensioning process. After tensioning the post-tensioning reinforcement, remove the exposed ends at the fascia members so that no part of the post -tensioning reinforcement or end fi ttings extend beyond a point 1 inch inside the exterior face of the prestressed concrete member. Do not flame -cut the post -tensioning reinforcement. Permanently protect exposed strand or rod ends at end fittings from corrosion using a method approved by the RE. Fill the recessed pockets at the fascia with mortar matching the concrete surface.
F.Grouting.
1.Concrete Beams. Grout according to Section 10 of the AASHTO LRFD Bridge Construction Specifications.
2.Concrete Box Beams and Concrete Slab Beams. Sandblast the keyway surface clean to ensure bonding before erection. The Contractor may sandblast at the fabrication plant if shown on the certified working drawings. The Contractor may substitute waterblasting for sandblasting. Immediately before grouting, clean the keyway by waterblasting. Ensure that the water does not puddle. After cleaning, seal the keyway with closed cell foam backer rod at least 1/4 inch below the keyway bottom. Seal the ends of the keyway to prevent grout loss. Do not grout the keyway before the RE’s inspection and approval. Mix and place non -shrink grout according to the manufacturer’s recommendations. Begin the grouting operation at one end of the keyway and proceed continuously to the opposite end without interruption. Fill only 1 keyway with grout at a time. Consolidate the grout as it is placed in the keyway, and finish the grout flush with the top of the keyway. Ensure that the ambient temperature is between 40 and 85 °F when placing grout. When the ambient temperature is expected to fall below 40 °F, provide measures to maintain the concrete surface temperature between 40 and 85 °F. Provide curing blankets and place over the grout no later than 1 hour after the grout placement. Keep the curing blankets on the grouted keyways for at least 48 hours. Allow the grout in the keyways to cure at least 72 hours before allowing traffic or equipment on the bridge.
505.03.02 Precast Concrete Culvert
A.Working Drawings. Submit working drawings for approval that show plan, elevation, and sections as well as details for all appurtenances such as headwalls, cutoff walls, wingwalls, and aprons. In addition, include details of the neoprene gasket between the precast concrete culvert units as well as all threaded inserts, bar extensions, waterproofing, and end anchorage details for the post-tensioning reinforcement. Provide erection details including handling points, neoprene gasket details, the method for pulling the culvert boxes together, section lengths, and the method of installing the units.
B.Shipping and Storing. Notify the RE at least 5 days before shipping. Ship and store precast units according to the manufacturer’s recommendations.
C.Erection Plan. Submit a plan of operations as specified in 505.03.01.C.
D.Erecting. Notify the RE to schedule a pre-erection meeting at least 20 days before the start of erection. Construct a minimum 2 foot thick, coarse aggregate layer that extends 12 inches past each side of the precast culvert. Compact the coarse aggregate layer using the directed method as specified in 203.03.02.B.3. Tie the precast units together with a minimum of 4 longitudinal rods or strands to ensure an adequate seal and to provide continuity and concrete shear transfer between the precast units. Provide a flexible, watertight, neoprene gasket according to ASTM D 1056 at the joint between the precast units. Ensure that the gasket is continuous around the circumference of the joint and has only 1 splice. Before backfilling, place a 2 foot wide strip of subsurface drainage geotextile over the top and side transverse joints. If precast concrete culvert units are used in parallel for multicell installations, fill the space between the units with non-shrink grout or Class A concrete.
E.Post-Tensioning. Place a longitudinal rod or strand through a preformed hole located in each corner of the units and stressed to a tension of 30,000 pounds e ach. After tensioning, cut the exposed end of the post -tensioning reinforcement to 1 inch below the surface of the anchorage pocket. Do not flame cut the post -tensioning reinforcement. Galvanize all hardware associated with the end anchorage system. Apply 2 coats of bituminous paint to the exposed parts of the end fittings.
F.Grouting. Fill hand hole pockets, post-tensioning reinforcement sleeves, and lifting lugs with non-shrink grout after the joints are sealed and the post-tensioning reinforcement are tensioned. Apply 1 coat of an epoxy waterproofing to all top slab hand hole pockets or lifting holes that are grouted in the field after the grout has properly cured.
G.Backfilling. Backfill and compact around the culvert as specified in 203.03.
505.03.03 Precast Concrete Arch Structure
A.Working Drawings. Submit working drawings for approval that include the following:
1.Concrete compressive strength value.
2.When the earth cover over the precast concrete arch unit is less than 24 inches, provide corrosion protected reinforcement in the outside mat of reinforcement.
3.Plan, elevation, and sections as well as details for all appurtenances, such as headwalls, cutoff walls, wingwalls, and aprons.
4.Details of the neoprene gasket between the precast concrete arch units as well as all threaded inserts, bar extensions, waterproofing, backfilling and loading requirements, and end anchor age details for the post-tensioning reinforcement.
5.Profiles and dimensions of all precast concrete arch structures, lifting loads of all components, and reinforcement steel layout.
6.Erection details of the joint seal between the precast concrete arch structures, joint seal details, section lengths, and the method of installing the units.
B.Shipping and Storing. Notify the RE at least 5 days before shipping the precast concrete arch units. Ship precast units according to the manufacturer’s recommendations. Store the precast concrete arch units according to the manufacturer’s requirements. To prevent cracking of the structures, support the precast concrete arch units with timber members.
C.Erection Plan. Submit a plan of operations as specified in 505.03.01.C.
D.Erecting. Notify the RE to schedule a pre-erection meeting at least 20 days before the start of erection. Construct footings using Class B concrete. Ensure that the surface of the footing does not vary more than 1/4 inch in 10 feet. Provide a float finish to the footing. Ensure that the concrete reaches a compressive strength of 3 ,000 pounds per square inch, as determined from test cylinders cast during placing of the concrete, before installing the preca st concrete arch structure. Install precast concrete arch units on footings according to the manufacturer’s erection instructions. Connect the foundations for the precast concrete arch units and other appurtenances with reinforcement or suitable mechanica l connections to form one monolithic body. Fill the footing keyway and lifting points with non-shrink grout.
E.Joints. Seal and cover the butt joint made by 2 adjoining precast concrete arch units, the joint between the end unit and the headwall, and the joint between the end unit and wingwall according to the manufacturer’s recommendations. Ensure that the joint surface is clean before the sealing operations. Cover the joint continuously from the bottom of a precast concrete arch unit section leg across the top of the arch and to the opposite arch unit section leg. Ensure that all laps that result in the joint wrap are a minimum of 6 inches long with the overlap running downhill.
F.Backfilling. After the RE has approved the precast arch structure, place I -9 soil aggregate in 8 inch lifts or less. When placing backfill, ensure that the difference between the heights of the backfill on the opposite sides of the arch structure does not exceed 12 inches. Use mechanical tampers to compact the backfill adjacent to each side of the arch units and over the top of the arch units until they are covered to a minimum depth of 12 inches. Do not operate heavy equipment (weighing in excess of 12 tons) over the structure until a depth of backfill has been placed that will support the equipment.
505.04 Measurement and Payment
The Department will measure and make payment for Items as follows: Item Pay Unit PRETENSIONED PRESTRESSED CONCRETE BEAM, ___" LINEAR FOOT
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Source: Standard Specifications for Road and Bridge Construction, 2019 (rev. 2022-12-21) Edition. Pages 273–276 of 651. View official source ↗