Application of high performance concrete to long-span prestressed bridge girders

This paper presents results of an investigation regarding the mechanical properties and durability of high performance concrete (HPC) and its applications to long-span prestressed bridge girders. Tests were conducted on approximately 7000 concrete specimens to investigate strength gain with time, compressive strength, tensile strength, stiffness, indirect permeability and freeze-thaw durability of high performance concrete. Parameters investigated included: cementitious material content, aggregate type, and curing conditions. The main factor affecting the mechanical properties and durability of HPC was the aggregate type. Two long-span prestressed bridge girders were fabricated using HPC and large diameter strand Information including transfer lengths, prestress losses over time, cracking loads, and behavior under repeated loads was obtained. Transfer lengths of large diameter stand in HPC were conservatively predicted by current design practice. There was no stiffness degradation observed through three million cycles of service loads. Initial shrinkage cracks that occurred in one of the girders were found to affect the camber, prestress losses and cracking load due to the geometric effect of crack closure subsequent to strand release.