Implementation of High Strength-High Performance Concrete in Two Texas Highway Overpass Structures: Critical Comparison

Abstract

Two prestressed concrete highway overpass structures, the Louetta Road Overpass and the North Concho River Overpass, were recently constructed in Texas. The structures were built with high strength–high performance concrete (HS-HPC) with nominal strengths of up to 61 MPa (8,800 psi) at release of prestress and 97 MPa (14,000 psi) at 56 days. The use of HS-HPC, in addition to the use of prestressing strands that measured 15 mm (0.6 in.) in diameter, allowed for the accommodation of longer spans and larger girder spacing than are typical for similar designs with conventional concrete. As a result, the structural designs were extremely efficient when compared with the conventional designs. In addition, use of HPC in bridge decks is expected to result in reduced maintenance requirements and a longer service life for each bridge, thereby reducing life-cycle costs. Although HPC is used in both structures to increase structural efficiency and reduce projected life-cycle costs, the structures are quite different and represent unique applications of HPC. Both structures were instrumented as part of an extensive research program, and data were collected on prestress losses, camber and deflections, concrete strains, and concrete temperatures in several actual bridge girders. These data, in combination with observations regarding practical issues such as fabrication, handling, and overall construction costs, are used to compare and contrast the use of HPC in the two bridges. A brief set of recommendations for the use of HPC in future highway bridge projects is also presented.