The Strategic Highway Research Program (SHRP) awarded a contract to North Carolina State University (NCSU) to investigate the use of high-performance concrete (HPC) in highway pavements and bridge structures. The goals of the project were threefold. First, a number of HPC mixtures were developed for highway applications. Second, laboratory testing of the HPC mixtures was conducted. Finally, a number of field test sites were constructed and monitored. Three different classes of HPC were established for this research. These are very early-strength (VES), high-early-strength (HES), and very high-strength (VHS) concrete. Two types of VES and VHS concrete were developed. The VES mixture was developed for use primarily as a rapid repair material where time is critical and cost is a lesser concern. The HES mixture was developed for bridge deck construction where deterioration due to freezing and thawing and steel corrosion is a major problem. The HES mixture can also be used for repair where cost is important and time is a lesser concern. The VHS mixture was developed for use in bridge structures where high-long-term strength is needed rather than rapid strength gain characteristics. Paper summarizes the development of the mixture proportions for the three classes of HPC. Included in the paper are the strength and serviceability requirements for the mixtures. Recommendations are made for adapting the HPC mixtures for local conditions.

In recent years, moment-resisting frames built using high-strength concrete have been used for high-rise buildings, primarily for economic reasons. When such high-rise buildings are subjected to severe earthquakes, cyclic horizontal and axial loading can be imposed on the exterior columns. The ductile behavior of such columns needs to be insured. In this study, improvement of the flexural ductility of high-strength concrete columns under high axial compressive load is attempted by arranging longitudinal bars with mixed steel grades. The basic concept of this method is to achieve the gradual attainment of yield of longitudinal bars, from low- to high-strength steel, as the column deflection increases, and thus to delay the column reaching the maximum moment capacity until the column deflection attains the required level. To verify the adequacy of the preceding design concept, six cantilever columns with 400-mm-square cross section have been constructed and tested under simulated severe seismic lateral loading with axial compressive load of either 0.3 f' c or 0.6 f' cA g. The compressive strength of concrete f' c was 65.7 MPa on average, and steels with yield strengths of 442 and 1033 MPa were used for longitudinal reinforcing bars. The adequacy of the preceding design concept was verified from the test results, and it was found that the New Zealand concrete design code could provide a good guideline for its application to design.

Presents the results obtained from tests on high-performance concrete columns. Twenty-four columns were tested. The test parameters included shape and size of cross section, longitudinal reinforcement ratio, load eccentricity, and concrete compressive strength. Analytical methods to predict the behavior and strength of columns are also presented. Good correlation between test and analytical results is found.

Presents the results of an investigation on the long-term deformation of steel fiber reinforced concrete containing silica fume. The influence of loading ages on the creep and ages of curing on the shrinkage of specimens was investigated. The volume fraction of steel fibers used in concrete is 0, 1, and 2 percent. The addition of silica fume is 0, 5, and 10 percent by weight of cement. Test results indicate that the combined effect of fibers and silica fume reduces the creep and shrinkage and enhances the development of compressive strength of concrete. At specific silica fume content (10 percent), the effect of increasing fiber content to reduce creep and shrinkage decreases gradually as the fiber content increases. This phenomena is similar to the addition of silica fume in concrete with 1 percent volume fraction of steel fibers.

The twin 450-m Petronas Towers under construction in Kuala Lumpur City Centre, Malaysia, are discussed. These world's tallest buildings use concrete columns, ring beams and a core of 40- to 80-MPa cube strength concrete, and steel long-span floor beams. Benefits of high-strength concrete are discussed, including occupant comfort achieved using mass-to-length building period and high inherent damping to reduce building response, high lateral stiffness, simple monolithic cast in situ connections, reasonable member sizes, local labor use, and light erection equipment. Special design features include deep barrette foundations acting in friction, temperature control measures for a massive mat pour, treatments at stepped and sloping columns, and use of haunched beams to accommodate mechanical ducts. The construction approach to creep and shrinkage is also discussed.