Production and quality control of high-performance concrete in Texas bridge structures.

摘要

To demonstrate the suitability of HPC for use in highway structures, the FHWA initiated a series of projects in 1993 that includes the complete incorporation of HPC from design to long-term monitoring of the bridges in service. This dissertation focuses on the design and construction of the first two of these projects in the United States which are the Louetta Road Overpass in Houston, Texas and the North Concho River Overpass in San Angelo, Texas. The Louetta Road Overpass project included the use of pretensioned precast U-beams while the North Concho River Overpass project included the use of pretensioned precast AASHTO standard Type IV beams. These beams required very high initial prestressing forces and the use of 15.2-mm (0.6-in.) prestressing strands to take full advantage of the high performance concrete. The high initial prestressing forces required high early release strengths of 74.5 MPa (10,800 psi) and 56 day design strengths of 101.4 MPa (14,700 psi). The designers (TxDOT) also required a high modulus of elasticity at release and long-term 41.4 GPa (6,000 ksi) to meet serviceability requirements for the structures. Each bridge component had specific durability and or mechanical property requirements similar to the precast beams. HPC mix designs were developed and optimized in the laboratory using locally available materials to produce the most economical mix designs for use in the various high performance concrete components associated with the two bridge projects. The dissertation investigates aspects involving concrete properties, mix design, applicability of current design requirements, applicability of current construction practices, predictability of short- and long-term performance, and the requirements for quality control and quality assurance testing and inspection. The performance related test results of both mechanical and material (durability) testing of over 40,000 specimens from laboratory and plant produced concrete is presented including the statistical analysis. Related research studies conducted including the early-age curing aspects of the prestressed/precast beams, the use of maturity method for cast-in-place decks, microstructure performance of HPC, and a high performance concrete permeability correlation study (AASHTO T259 and AASHTO T277) are also presented.