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A 5-year National Research Project on advanced concrete buildings with high-strength and high-quality materials has been in progress in Japan since 1988. A High-Strength Concrete Committee was organized to establish guidelines to be used in applying the high-strength concrete of 30 to 120 MPa to reinforced concrete buildings; it has started to investigate the following items: development of cements, aggregates, chemical admixtures, mineral admixtures of high-strength concrete and establishing of the quality standards of these materials and the design method of mix proportion; establishing the evaluation method for properties of fresh concrete required in construction; establishing of evaluation methods for compressive strength and other properties of hardened concrete; and establishing of the quality control procedure and evaluation method for concrete strength in structures. Paper describes the problems of production, transportation, and placement when high-strength concrete is applied to reinforced concrete buildings standing in seismic zones and urban areas such as Tokyo. The results obtained from the preliminary studies and experiments by the high-strength concrete committee will also be briefly described.

During the 1980s, the use of high-strength concrete gained wide acceptance. The materials and mix proportions for making high-strength concrete are selected empirically by extensive laboratory testing since there are no accepted procedures, such as the ACI method of proportioning normal concrete mixtures. For someone who, for the first time, would like to make high-strength concrete from local materials, the problem is complicated by the fact that a variety of newly developed chemical and mineral admixtures may have to be incorporated simultaneously into the concrete mixture. The published literature has enough information on the new admixtures, but is essentially of little help in selecting the type and optimum dosage of these admixtures. In this paper, the authors have attempted to address the problem of selection of materials and mix proportions for high strength from a microstructural standpoint. Principles underlying the strength of brittle solids are discussed and important features of concrete microstructure, which influence the strength, are described. Microstructural considerations are used as a basis for the selection of materials and for establishing guidelines that are helpful in the development of a simple procedure for concrete mix proportioning.

Discusses the need and requirements for a method of proportioning high-strength concrete mixes. The development of the method, which is based on a well-established method used for conventional concrete, is described. Design charts are given for various stone sizes, and an example of such a chart is illustrated. Because the method is based on easily determined aggregate properties, it is suitable for any type of aggregate: crushed or naturally occurring stone and sand, and graded or single-sized stone.

The objective of this paper is to show that the use of high-strength concrete (HSC) (especially concrete with silica fume) can notably reduce the long-term deformations of reinforced concrete (RC) slabs. This may be achieved by reducing creep deformation, increasing the elastic modulus, the tensile strength, and the steel-concrete bond properties. Moreover, this paper shows that the CEB (Comite Euro-International du Beton) moment-curvature relationship established for ordinary concrete is still valid for HSC. A procedure for the nonlinear finite element analysis of RC beams and slabs is briefly described. The proposed procedure is based on the nonlinear CEB moment-curvature relationship incorporated into an iterative secant stiffness algorithm. Predicted deflections from the proposed procedure are compared with experimental results from slabs made with ordinary or HSC.

When high-strength concretes are used in high-rise buildings, long-span bridges, and offshore structures, special attention must be given to the dimensional changes that occur in the concrete members. For design purposes, the length changes are usually considered to consist of instantaneous shortening, shrinkage, and creep. Instantaneous shortening depends on stress level, cross-sectional dimensions of the member, and modulus of elasticity of steel and concrete at the age when the load is applied. Shrinkage deformations generally depend on type and proportions of concrete materials, quantity of water in the mix, size of member, amount of reinforcement, and environmental conditions. Creep deformations depend on concrete stress, size of member, amount of reinforcement, creep properties of concrete at different ages, and environmental conditions. In recent years, questions have been raised about the validity of methods for calculating deformations in high-strength concrete members and the in-place properties of high-strength concrete members. These properties include compressive strength, modulus of elasticity, shrinkage, and creep. This paper reviews existing state-of-the-art technology concerning instantaneous shortening, shrinkage, and creep of high-strength concrete members.