The strength of concrete used in routine bridge construction has increased gradually over the past 20 years. The use of high strength concrete is especially promising in the precast concrete industry, where quality control is more easily monitored. The purpose of the research described herein was to develop a high strength concrete mix design, investigate its material properties, and evaluate the cost effectiveness of its use in prestressed, pretensioned bridge girder design. A mix design yielding 11,460 psi (79 MPa) compressive strength at 28 days is presented. The material properties of this mix, including 18-hour compressive strength, modulus of elasticity, and modulus of rupture, are described. Span increases, made possible by the use of high strength concrete, are shown for several AASHTO girder shapes. A cost comparison, performed for span lengths ranging from 40 to 140ft (12 to 43 m), shows that as much as 66 $1ft (216 $/m) of bridge length could be saved with the use of high strength concrete girders in place of normal strength concrete girders.
