International Concrete Abstracts Portal

In Japan high strength concrete was first achieved as early as the 1930s. Yoshida reported in 1930 that high strength concrete with 28-day compressive strength of 102 MPa was obtained. This result was obtained by a combination of pressing and vibrating processes without the use of any chemical and mineral admixtures. This method has been applied for production of high strength segments. In the 196Os, superplasticizers were developed in Japan and West Germany which were very effective chemical admixtures to decrease the water content in concrete. With the use of superplasticizers, it became possible to decrease the water to cement ratio while maintaining the workability of the concrete. This technique was applied very widely and many bridges, high-rise buildings, precast concrete members have been produced. In the 197Os, the combined use of superplasticizers and ultra-fine materials such as silica fume, finely ground blast furnace slag or anhydrous gypsum based additives were studied and has been applied to concrete structures until today. Finally, super high strength concrete greater than 120 MPa in compressive strength was achieved with selected materials and special techniques and this kind of concrete has been applied in other industries instead of in the construction industry. This paper summarizes the history and progress of the development of high strength concrete in Japan.

High strength concrete (HSC) is defined by FIP/CEB as “concrete with a cylinder strength above 60 MPa (-87OOpsi) and up to 130 MPa (-18900 psi), the practical upper limit for concretes with ordinary aggregates. It also includes lightweight aggregate concrete with a cement paste of similar properties “. FIP/CEB similarly regards high performance concrete as material with water-binder ratio (w/b) less than 0.40 According to these definitions all concrete installations built in Norway in the 1990s for the oil and gas-fields in the North Sea and most highway structures are built with HSC/HPC. This amounts to about 20 - 25 % of our total domestic concrete production. Norway was the first nation in the world to have HSC with characteristic cube strengths up to 105 MPa (~ 15300 psi) incorporated in its code of design, NS 3473, in 1989. This paper describes the main Norwegian experience by using these qualities in full scale. The presentation is supplemented by some case studies illustrating some typical applications. The main lesson from some 15 years experience is that the introduction of these “hi-tech” concrete grades should be accompanied by a proper upgrading of the workforce’s competence on all levels to ensure the intended quality.

Following is a brief overview of the techniques employed in developing the first generation of High Performance Concrete (from 50 to 130 Mpa/l9 000 psi), then the second generation and, most recently, the generation of Reactive Powder Concrete (from 200 to 800 Mpa/120 000 psi), the authors highlight the originality of the French approach as it has evolved, within the construction industry, over the past ten years. The basic principles underlying this originality are focused on : - high performance rather than high strengh, since improvements in other mechanical, physical and chemical properties have become, for many structural applications, crucial in the choice of construction materials, - application beyond sophisticated structures exclusively to encompass more basic construction uses or even many small, pre-fabricated structural elements, - a global analysis (design, development, maintenance) and a << systems B approach to construction that serves to emphasize the economic considerations behind High Performance C o n c r e t e . The second, and most detailed, part of this paper provides specific examples of the French approach through a discussion of not only : bridges and tunnels sized for heavy loads, major building projects, industrial structural framework (nuclear plant, offshore platform, oil tanker, etc), but also : short and medium-span bridges, small-scale, prefabricated components used in construction and public works, foundation work and structural repairs, etc. The third part, based on ten years of experience acquired through rather varied applications from French industry, provides an outlook on future development prospects and suggests new domains, both within or outside the field of construction.

This paper reports on the latest application of high-strength concrete / high-performance concrete in Germany. High-strength concrete has been used especially for the construction of high-rise buildings. The increased application of high-strength concrete led to the DAfStb guideline for the technology and dimensional design of high-strength concrete in Germany. Special attention is focused on the improvement of ductility of high-strength concrete.

In order to enable rational and safe design with high performance concrete recommendations for this material are necessary. In the Netherlands an extended research program has been carried out focusing on aspects like behaviour in compression at various loading rates, shear friction in cracks, in-plane loading of cracked reinforced elements, splitting effects in the anchorage zone of prestressing strands, joints between precast columns, and creep. Furthermore trial casts have been carried out in order to get more experience with HPC at the building site. A four storey office building was completely built in HPC. During construction the temperature of the hardening concrete was measured at many locations, in order to investigate the development of temperature stresses and to get indications of the cracking probability. More-over a section of a box girder bridge was cast as an exercise for the construction of a 160 m span bridge in 1996. Both the labora-tory experiments and the site trials raised the confidence in suc-cessful applications of high performance concrete.