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.

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.

Ductility is an important factor in design of high strength concrete (HSC) members under flexure. A number of eight HSC beams with different percentage of ??& ???were cast and incrementally loaded under bending. During the test, the strain on the concrete middle faces and on the tension and compression bars and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior and especially the ductility of the HCS members are more deeply reviewed. Also a comparison between theoretical and experimental results are reported here.

This paper describes the first experience of using self-consolidating concrete for pretressed concrete bridge girders in North Carolina. Under construction in eastern North Carolina is a multi-span bridge which will use one hundred thirty AASHTO Type III girders, each 54.8 ft (16.7 m) long. To demonstrate the full-scale field production of self-consolidating concrete, and for comparative purposes, three girders from one production line of five girders were selected for the experimentation. Two of the girders were cast with self-consolidating concrete and one with normal concrete as control. The plastic and hardened properties of both the self-consolidating concrete and the normal concrete were monitored and measured. The plastic properties of self-consolidating concrete included unit weight, air content, slump flow, visual stability index (VSI), and passing ability measured by J-ring and L-box. Hardened properties of the two concretes included temperature development during curing, compressive strength, elastic modulus, and flexural tensile strength. The prestressing force was monitored by load cells. The transfer lengths of prestressing strands were determined by embedded strain gauges, and from the measured strand end-slips. Finally, the three girders were tested in flexure up to the design service load to determine and compare their load-deformation characteristics.