International Concrete Abstracts Portal

SP-228CD This CD-ROM of Special Publication 228 contains the papers presented at the Seventh International Symposium on the Utilization of High-Strength/High- Performance Concrete that was held in Washington, D.C., USA, June 20-24, 2005. The symposium continued the success of previous symposia held in Stavanger, Norway, (1987); Berkeley, California (1990); Lillehammer, Norway, (1993); Paris, France, (1996); Sandefjord, Norway, (1999); and Leipzig, Germany, (2002). The symposium brought together engineers and material scientists from around the world to discuss topics ranging from the latest applications to the most recent research on high-strength and high-performance concrete. In the years since the first symposium was held in Stavanger, there has been worldwide growth in the use of both high-strength and high-performance concrete. In addition to more research and applications of traditional types of high-performance concrete, the use of self-consolidating concrete and ultra-high-performance concrete has moved from the laboratory to practical applications. This publication offers the opportunity to learn the latest about these developments.

The Federal Highway Administration (FHWA) encourages the use of high performance concrete (HPC) to improve the long-term performance of the nation’s infrastructure at lower life-cycle costs. For its purposes, the FHWA uses 11 performance criteria to define high performance concrete, and it designates three levels of performance for each criterion, with Grade 3 being the most stringent. For FHWA projects, the specifier is expected to select the criteria necessary for a given element, and then select an appropriate performance grade. It’s not necessary or desirable to specify the same performance grade for all characteristics. Guide Specification for High Performance Concrete for Bridge Elements provides mandatory language that the specifier can cut and paste into project specifications, as well as guidance on what characteristics should be specified in a given case, and what criterion is needed to ensure satisfactory performance. It includes commentary that tells how to obtain the desired performance for each characteristic. In cases where two performance criteria are in conflict, the commentary advices the user how to balance conflicting requirements.

The Concrete Pavement Technology Program (CPTP) is a national program of research, development, and technology transfer sponsored by the Federal Highway Administration. The focus of the program is on implementing improved methods of designing, constructing, evaluating, maintaining, and rehabilitating portland cement concrete (PCC) pavements in order to promote cost-effective designs and long-term performance for federal-aid highways. Research is conducted to address State highway agency, FHWA, industry, and academia needs. Innovative designs and improved methods are evaluated through demonstrations and field trials of high performance concrete pavements by the various State highway agencies. An extensive implementation effort is included to encourage early adoption of promising research results.

Development of high performance concrete has increased the span length of given size precast prestressed girders up to 40 percent. While the designer’s main concerns were the safety and stability of the bridge once construction was completed, attention should also be given to the temporary stresses and stability of these precast girders during handling, erection and construction. This research investigated long-span girder stability during handling and erection along with girder stability during bridge deck construction. Bulb-tee, NU (developed by the University of Nebraska) and AASHTO sections were considered. The effects of intermediate diaphragms on the behavior of long span prestressed high performance concrete girder bridges were evaluated using finite element analysis. The limit on diaphragm spacing as stated in AASHTO was found to be conservative. Different methods to improve the lifting spans of long high performance concrete girders were also recommended. The outcome of this research will expedite and help assure safety in the construction of high performance concrete long-span girders.

Partial prestressing, unbonded tendons and high-strength concrete have become commonly used techniques and materials in the prestressed concrete industry. The effect of their application on the non-linear behaviour of continuous post-tensioned beams was studied in an experimental program at the Magnel Laboratory for Concrete Research of Ghent University. It was found that post-tensioned continuous concrete beams with higher strength concrete had limited moment redistribution and rotation capacity. In a further study it was investigated whether this effect can possibly be modified by the addition of regular steel fibres and micro steel fibres in high-strength concrete. The effect of regular steel fibres seemed rather limited. The addition of micro steel fibres improved the rotation capacity of high strength concrete beams.