Mathew Royce, New York State Department of Transportation
The Route 52 bridge over the Wallkill River is located in the village of Walden, NY, 50 miles (80 km) north of New York City. This new bridge was completed in 2005, replacing a 176-ft (53.6-m) long steel truss bridge built in 1934.
The main span of the bridge consists of two cast-in-place concrete arches with a clear span of 148.8 ft (45.4 m). The arches support precast concrete spandrel columns, cap beams, and prestressed concrete adjacent box beams, with a cast-in-place concrete composite deck slab. Precast and cast-in-place components were efficiently combined in the bridge to build an aesthetically pleasing structure within a reasonable cost. The bridge is expected to have a service life of 75 years with low maintenance.
The cast-in-place concrete elements for the bridge were made using conventional concrete. The precast elements contained self-consolidating, high performance concrete (SCHPC). This was the first use of SCHPC in precast concrete components by the New York State Department of Transportation. The SCHPC resulted in improved production efficiency with minimal repairs to the components after removal from the forms. The surface textures of the components were significantly better than those of components made using conventional concrete. No treatment for filling ‘bug holes’ was necessary.
SCHPC Specifications
The concrete mix requirements for the SCHPC included the following:
Entrained air content ≥ 3%
Silica fume content ≥ 5% of the total cementitious material
Water-cementitious materials ratio < 0.40
Calcium nitrite corrosion inhibitor at a dosage rate of 25 L/m3 (4.04 gal/yd3)
Concrete spread of 560 to 760 mm (22 to 30 in.)
Visual stability index ≤ 2
Only materials from the NYSDOT approved list to be used
The hardened concrete performance criteria were as follows:
Concrete compressive strength (f’c) at 56 days per AASHTO T 22 ≥ 70 MPa (10,150 psi)
Modulus of elasticity per ASTM C469 ≥ 30 GPa (4351 ksi) when f’c ≥ 70 MPa (10,150 psi)
Shrinkage after 56 days of drying per AASHTO T 160 < 600 millionths
Specific creep at 56 days per ASTM C512 ≤ 60 millionths/MPa (0.41 millionths/psi)
Freeze-thaw durability per AASHTO T 161 Proc. A ≥ 80%
Scaling resistance per ASTM C672 ≤ Rating of 3
Chloride penetration per AASHTO T 259 modified < 0.025% at 25 mm (1 in.)
In addition to the above requirements, reinforcement in the substructure components was epoxy-coated and the precast components and top surface of the concrete deck were coated with a penetrating sealer to prevent chloride and water ingress. Uncoated reinforcement was used in the prestressed concrete beams.
Cost of SCHPC
NYSDOT did not incur any additional cost for the use of SCHPC for the precast components. Based on the feedback from the precaster, cost savings in fabrication labor offset the additional material costs associated with use of SCHPC. Improved appearance of the components and reduction in repair needs were added benefits.
Conclusion
In general, the use of SCHPC concrete bridge components for the Route 52 bridge over the Wallkill River has been a remarkable success. Based on the current specifications, producers are now free to choose SCHPC or conventional HPC for bridge components. Due to the labor savings associated with SCHPC, more and more producers are now opting for SCHPC.
Further Information
A more detailed description of this bridge is provided in the article titled “Wallkill River Arch Bridge” published in the PCI Journal, July-August 2008, pp. 44-50.