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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.

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.

Basic studies were conducted to develop high-performance concrete, with low-heat and high-strength characteristics under low-temperature environments, using blast furnace slag. The purpose of this study was to clarify the effects of slag fineness, slag content, gypsum content, limestone-powder content, and high-range water-reducing admixtures (HRWRA) on the strength development, adiabatic temperature rise, porosity, amount of Ca(OH) 2, and carbonation of concrete; and the effect of curing temperature on concrete strength development. As a result of this study, it was found that it is possible to produce high-performance concrete with low heat and high strength under low-temperature environments, by properly combining, and taking into consideration, their respective properties, granulated blast furnace slag, HRWRA, and other admixtures.

The time-dependent properties of high-strength concrete subjected to tensile and compressive loading have been studied experimentally and have been compared with those of normal concrete. Two kinds of load application were used during this investigation: loading with a constant strain rate and sustained loading. The range of strain rates is chosen between the so-called static and the creep strain rate limits. The ratio of adopted stress to 28-day prismatic strength in the sustained loading tests was chosen at 0.15, 0.35, 0.50, 0.75, 0.85, and 0.95. The research program mainly focused on the influence of the type of load application on the behavior of high-strength concrete in compression and tension. The phenomena observed in the experiments are interpreted by referring to a basic mechanism of rate sensitivity of concrete. The differences of the material structure between high-strength concrete and normal strength concrete are emphasized. In general, it is found that some properties of high-strength concrete in compression, such as strength and deformation characteristics, are more sensitive to the strain rate than those of normal strength concrete, whereas in tension, this tendency is less pronounced. On the basis of the test results, the long-term strength of high-strength concrete is defined.

The shear friction analogy is a valuable and simple tool that can be used to estimate the maximum shear force transmitted across a cracked plane in a concrete member. The expressions to determine the shear friction capacity up to now have been based on experiments on concretes with cylinder strengths of at most f' c = 60 N/mm 2. In such concretes, the aggregate particles normally do not break at the formation of cracks through the concrete. In high-strength concrete, however, the cement matrix is strong enough to cause fracture of the aggregate particles. As a result, the crack faces are relatively smooth, so that the shear friction capacity is expected to be reduced. In this paper, shear friction tests are described on concrete with a cylinder strength of f' c = 100 N/mm 2. The experiments are carried out on cracks in plain concrete and on reinforced cracks. It is shown that the reduction in shear friction capacity due to aggregate fracture is considerable.