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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.

The object of this study is to investigate the possibility of improving ductility of high-strength concrete columns with the lateral reinforcement. Eight column specimens confined by lateral reinforcements having 328.4 and 792.3 MPa in yield strength were tested under reversed cyclic lateral loads with constant axial compressive load levels from 0.254 to 0.629. The concrete compressive strengths were 85.7 and 115.8 MPa, respectively. Volumetric ratio of lateral reinforcement was 1.6 percent in all specimens. Test results indicated that the very large ductility could be achieved by using high yield strength lateral reinforcement, even for such high-strength concrete columns. Modifications of previously proposed stress-strain models on confined concrete were also made for applying them extensively into the calculation of moment-section curvature relationships of high-strength concrete columns with lateral confining reinforcement.

Two bridges, the Joigny and Pertuiset, have recently been built in France using high-strength concrete. It was necessary to measure the shrinkage and creep deformation of the concretes for their design. Two series of samples were taken, corresponding to the two kinds of concretes (one with and one without silica fume). The specimens were loaded at different levels and ages (including early ages). Some cylinders were carefully sealed to avoid any drying. Besides the mathematical equations deduced from these trials and detailed in the paper, the following results were discovered: the nonsilica fume high-strength concrete (HSC) is quite comparable to the normal strength concrete (NSC); during the setting, the silica fume HSC exhibits a certain autogenous shrinkage which is higher than that of the NSC concrete; for the silica fume HSC, the magnitude of the creep deformation is highly dependent on the age of concrete at loading, compared with elastic strains, so that the creep is much lower than for NSC (except when loading occurs at a very early age); regarding NSC, the theory of superposition applies fairly to the creep of high-strength concrete for nondecreasing loadings; and, finally, the desiccation creep is reduced for nonsilica fume HSC and entirely cancelled for silica fume HSC, meaning that creep does not depend on size for these materials. Some physical models are proposed at the paper's conclusion to explain these phenomena.

Heat of hydration of a selection of high-strength concretes has been investigated by means of a so-called semiadiabatic calorimeter test. The temperature development within a hardening specimen enclosed in an insulated container is used as basis for a simulation of the adiabatic temperature increase and the specific heat development of the cement. The results indicate that the heat of hydration can be affected within a relatively wide range by the utilization of traditional mix design parameters. Heat of hydration is affected not only by the cement content but also by the water/cementitious ratio {w/(c + s)} and the silica fume content. The heat of hydration per cement unit decreases approximately 9 percent when the w(c + s) is reduced form 0.36 to 0.27. At w(c + s) 0.50, the replacement of cement by silica fume on a 1:1 basis induces a significant increase in the heat evolved per cement unit. The increase corresponds approximately to the reduction in cement content. Hence, the temperature rise in the concrete is not significantly affected. The ability of the silica fume to increase the heat evolvement of the cement decreases with decreasing w(c + s), and is negligible at w(c + s) 0.27. Hence, a replacement of cement by silica fume on a 1:1 basis at this w(c + s) leads to a lower temperature rise of the concrete.