Describes the development of a new type of high-performance concrete incorporating large volumes of ASTM Class F fly ash. Briefly, this concrete incorporates about 56 percent fly ash by weight of cement, and has a water-to-cementitious materials ratio of about 0.32. The portland cement and fly ash contents are of the order of 155 and 215 kg/m 3 of concrete, respectively. The flow slumps are achieved by the use of large dosages of superplasticizers. Because of the low cement content, the temperature rise in this concrete is low, and this concrete is ideally suited for concrete structures where excessive temperature rise is a concern. Also, the high-volume fly ash concrete has all the attributes of a high-performance concrete. It has excellent mechanical properties and demonstrates superior resistance to freezing and thawing cycling, chloride-ion penetration, sulfate attack, carbonation, and marine environment. Also, it has low permeability, and shows excellent performance in reducing potential expansion due to alkali-aggregate reaction.

The Hibernia offshore concrete platform is being constructed in Newfoundland, Canada, and will be used in hydrocarbon production on the Grand Banks off the east coast of Canada. The 111-m tall concrete structure will contain approximately 165,000 m 3 of high-strength concrete. Construction of the concrete platform through 1993 consisted of a 108-m-diameter base slab that rested on a series of precast and cast-in-place concrete skirts. Specified 28-day compressive strengths (cylinder) for the skirts and base slab were 49 and 69 MPa, respectively. Actual average compressive strengths achieved were73.8 and 81.7 MPa, respectively. The remaining construction will be completed by 1996. The use of two different concrete production systems and their results are described.

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.

A high-performance concrete may posses satisfactory performance in many aspects other than compressive strength. In the context of in situ strength development, the performance of concrete at an early age is important. The temperature development, resistance to thermal cracking, early age engineering properties, and in situ strength development may all play a significant role in insuring satisfactory long-term performance. Describes the engineering properties of some very high-strength and high-performance concretes containing blast furnace slag with compressive strengths in excess of 80 Mpa under simulated "in situ" conditions of restricted moist curing and high-hydration temperatures. The influence of blast furnace slag content and the implications of the in situ development of engineering properties on performance are discussed.

Bond reinforcing bars and concrete under impact loading were studied for both plain and steel fiber reinforced concretes. Experiments consisted of both pullout tests and push-in tests. The design compressive strengths of the concrete were 40 MPa (normal strength) and 75 MPa (high strength) at 28 days. The impact loading induced bond stress rates ranging from 0.5 x 10 -4 to 0.5 x 10 -2 MPa/sec. The bond under stress rates ranging from 0.5 x 10 -8 to 0.5 x 10 -4 MPa/sec was also studied for comparison. Each reinforcing bar was instrumented with five pairs of strain gages to monitor the actual strains during the bond-slip process. All test data were collected by a high-speed data acquisition system at a sampling rate of 200 sec. Stress distributions in both the steel and concrete, bond stresses and slips, bond stress-slip relationships, fracture energy in bond failure, and internal crack development were investigated. It was found that compressive strengths increased the bond-resistance capacity and fracture energy in bond failure, and therefore had a great influence on bond stress-versus-slip relationship. This effect was increased by high loading rates and steel fiber additions, especially for the push-in loading mode.