|FHWA > HfL > 557.2101 16 - Field Cast Joints Between Precast Concrete Units|
557.2101 16 - Field Cast Joints Between Precast Concrete Units
PDF Version ( 0.02 mb)
This specification covers field casting of joints for the precast concrete units, including batching, transportation, casting and curing.
Ultra High Performance Concrete (UHPC)
The material shall be Ultra High Performance Concrete consisting of the following components all supplied by one manufacturer: Fine aggregate Cementitious material Super plasticizer Accelerator Steel Fibers, specifically made for steel reinforcement 14 mm x 0.185 mm, 2200 MPa yield minimum, deformed
Water shall meet the requirements of §712-01.
Qualification Testing: Note: qualification testing will be waived if the same material from the same supplier has already been tested according to this standard. The Contractor shall complete the testing of the UHPC a minimum of three months before placement of the joint. The testing sequence will include the submission of a plan for casting and testing procedures to the DCES for review and approval followed by casting and testing according to the approved plan.
Casting and testing must include the following:
Contractor shall use the same mixing equipment intended to mix the UHPC for the joint.
A minimum of 64 cubes 50 mm on a side shall be cast in steel molds.
All cubes shall be moist cured for 4 days and shall be kept sheltered in open air after 4 days. 4 cubes shall be tested each testing day. Testing days are at 4 days, 7 days, 14 days, and 28 days. The compressive strength shall be measured by ASTM C39 and shall meet 100 MPa minimum at 4 days and 150 MPa minimum at 28 days. Only a concrete mix design that passes these tests may be used to form the joint.
Construct 3 joints, 2.4 meters long, with the same dimensions and geometry as the joint between precast units. The contractor shall prepare to cast each joint by making two precast concrete slabs 2.4 meters long, 1.0 meter wide, and 200 mm deep, with the same shear key and equivalent reinforcement as the precast beams. Prior to placing the joint, prepare the existing surfaces of the precast slabs according to 584-3. The shear key shall be on the long side of the slab. The two concrete slabs shall be held rigidly in place while the UHPC joint is being cast and for four days thereafter.
The contractor will then ship the specimens to Turner Fairbanks Laboratory for testing.
9 cylinders 305 mm diameter and 190 mm deep. Each cylinder shall have one 800 mm long epoxy-coated reinforcing bar cast in the center of the circular face. The axis of the bar shall be perpendicular to the formed surface. 3 of the bars shall be #19 bars embedded 125 mm deep, 3 of the bars shall be #16 bars embedded 100 mm deep, and 3 of the bars shall be #13 bars embedded 75 mm deep. These cylinders will be kept wet for four days then delivered to the Materials Bureau for testing according to Test Method No. NY 701-14 E. Contact the Materials Bureau prior to casting for specific instructions on preparing the test specimens. The test will be performed as soon as practical after the corresponding samples reach 100 MPa.
This test is a pullout test. The samples pass if the bars yield, then fail without the concrete failing and without the bars pulling out of the concrete. If the samples do not pass, consult the DCES for further action to be taken. The joint cannot be poured until the DCES addresses the failure. The DCES may order the pour to take place using the mix design without making changes, or may change the reinforcement pattern.
Pre-Pour Meeting: Prior to the initial placement of the UHPC, the contractor shall arrange for an on site meeting with the UHPC representative. The contractor's staff and the NYSDOT Engineer and Inspectors shall attend the site meeting. The objective of the meeting will be to clearly outline the procedures for mixing, transporting, finishing and curing of the UHPC material.
The contractor shall arrange for a representative of the UHPC supplier to be on site during the placement of the joints. The representative shall be knowledgeable in the supply, mixing, delivery, placement, and curing of the UHPC material.
Storage: The contractor shall assure the proper storage of premix, fibers and additives as required by the supplier's specifications in order to protect materials against loss of physical and mechanical properties.
Form Work, Batching and Curing
The design and fabrication of forms shall follow approved installation drawings and shall follow the recommendations of the manufacturer. All the forms for UHPC shall be constructed from plywood.
The contractor shall follow the batching sequence as specified by the supplier and approved by the DCES. The surface of the UHPC field joints shall be filled flush with the precast panels to within a tolerance of plus or minus 2 mm.
The concrete in the form shall be cured according to Manufacturer's recommendations four days at minimum temperature of 16ºC to attain the design strength.
The contractor shall take four sets of compressive strength test samples for each day of placement. Each set consists of 3 cylinders 75 mm x 150 mm. All sets shall be moist cured for 4 days and shall be kept sheltered in open air after 4 days.
The following tests shall be performed: Concrete compressive strengths shall be according to ASTM C 39. The first set is to be tested at 4 days. The second set shall be tested at 28 days. The third set will be sent to the Materials Bureau between the 4th day and the 14th day. The fourth set shall be treated as a reserve set.
MEASUREMENT FOR PAYMENT
Measurement will be by length of UHPC joints placed in meters. The length of in-place UHPC shall be calculated to the nearest 0.1 m.
BASIS OF PAYMENT
Payment at the contract price for the above item shall be full compensation for all labor, equipment, and material to do the work, including sample construction, shipping, and testing.