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Group moderated by Tom Saad. Long-term performance benefits can be achieved in highway structures when high performance concrete (HPC) is properly used in the structural system. The main benefits for utilizing high strength concrete (HSC) in bridge elements is to extend span lengths of bridges with commonly fabricated girder types, reduce the depth of superstructures, and eliminate girder lines to offer cost-efficiency. The vast majority of bridges in the United States are constructed with concretes with compressive strengths less than 10 ksi. From the structural engineer’s viewpoint, the major impediment to deploying HPC has been the limited validation of design provisions for HSC. It provides a synthesis of information on the mechanical properties of HSC and offers guidance to structural engineers regarding the use of HSC. The information presented is based on the state-of-the-art of HSC and may not be included in the AASHTO bridge design specifications. The AASHTO Standard Specifications limit the compressive strength of prestressed concrete to 5 ksi. In the AASHTO Load and Resistance Factor Design (LRFD) Specifications the limit has been increased to 10 ksi. Both specifications allow, at the discretion of the Engineer, the use of higher strengths if tests are conducted to establish various mechanical properties of concrete. Furthermore, the LRFD specification prohibits the use of concrete with strengths below 2.4 ksi at 28 days.
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