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.

Four one-bay and one-story high-strength concrete frames were made and tested under reversed cyclic lateral force while subjected to high axial compression. Test results have indicated that confinement of high-strength concrete columns in frame by steel tube in stead of conventional hoop and use of high-strength steels as longitudinal rebars of the frame members could not only assure ductile seismic performance to the frame under high axial compression, but also reduce the residual story deformation to acceptable level. The damages in hoop-confined reinforced concrete beam were also significantly mitigated. In addition, a design formula was proposed to evaluate the ultimate lateral load capacity of the confined high-strength concrete frame. Good agreement between the theoretical ultimate lateral loads and the measured results verified validity of the proposed formula.

Three series of tests were carried out to investigate the behavior and strength of high and normal strength concrete spiral columns under uniaxial compressive loading. Five columns with normal strength and fourteen high strength spiral columns were tested. Normal strength and high strength steel were used as spiral reinforcement. The main variables investigated were; (a) volumetric ratio (varied from 0.008 to 0.038) and spacing of spiral reinforcement, (b) ratio of gross to core area (varied between 1.05 and 1.45), and (c) strength of spiral reinforcement. Strength increase and ductility due to the presence of spiral reinforcement were investigated. When high strength concrete is used, the minimum spiral reinforcement required by ACI 318-02 results in extremely small spacing as the ratio of the gross to core area increases. Spacing of the spiral reinforcement can be increased to reasonable values if higher strength steel is used. During the tests it was observed that the columns having high strength spiral reinforcement behaved well, and had adequate ductility.

In geopolymer concrete, a by-product material rich in silicon and aluminium (low calcium fly ash) is chemically activated by a high alkaline solution to form a paste that binds the loose coarse and fine aggregates, as well as other un-reacted materials in the mixture. This paper presents the results of an experimental study on the behaviour and the strength of twelve geopolymer concrete slender columns under equal load eccentricities. The primary variables of the test series were concrete compressive strength, longitudinal reinforcement ratio, and load eccentricity. The test results gathered included the deflection and the load capacity of the columns. The test failure loads were compared with the values calculated by the methods currently available for Ordinary Portland Cement (OPC) concrete. Excellent correlation between experimental and analytical results is found.

Pure bending loading with a constant moment is frequently used as a loading method in experiments on lap splices. However, the stress state of the concrete around the lap splices must approximate that of the actual reinforced concrete members. This paper discusses the mechanical properties of lap splices based on results from combined flexure and shear loading tests conducted on high-strength concrete (70-MPa grade) and normal-strength concrete (30-MPa grade) beams with all lapped splices in a critical section with high stress. The results revealed differences in concrete strength in terms of the splice characteristics under flexure and shear stress. For example, the maximum flexural crack width in the high-strength concrete specimens under service loading is smaller than that of normal-strength concrete specimens. The expansion of the yield zone of the main reinforcement in lap splices was greater than that in the normal-strength concrete specimens. Furthermore, the ratio of ultimate bond strength, which was obtained from the equation for bond splitting strength, to bond strength at the time of yield was small in the high-strength concrete specimens.