151 Introduction 1511 Historical Development

Since the 1990s, the expression high-performance concrete and the acronym HPC have become very popular and very fashionable in civil engineering. At a first glance, it sounds like advertising a new product but, in most respects, HPC is not fundamentally different from the concrete that we have been using all along, as it does not contain any new ingredient and does not involve new practices on site.

No single person invented HPC, and no single country pioneered its use. The development of HPC materials in use today was an incremental and combined effort involving many individuals, companies, government agencies, and countries, particularly in Asia, Europe, and North America.

The full development of HPC took quite a long time. Initially, HPC was mainly related to high-strength concrete. Specified concrete strength for buildings steadily increased from 35 MPa in the 1950s to 100 MPa by the end of the 1980s. During this period, the term "high-strength concrete'' was frequently used. However, when the high range water reducer or superplastizer was invented and began to be used to decrease the water/cement (w/c) or water/binder (w/b) ratios rather than being exclusively used as fluid modifiers for normal-strength concretes, it was found that in addition to improvement in strength, concretes with very low w/c or w/b ratios also demonstrated other improved characteristics, such as higher fluidity, higher elastic modulus, higher flexural strength, lower permeability, improved abrasion resistance, and better durability. Today, the definition of HPC has expanded to encompass both durability and strength.

The term "high-performance concrete'' originally comes from French. It was coined in 1980 by Roger Lacroix and Yves Malier [1]. In 1986, the French project "New Ways for Concrete'' brought together 36 researchers from France, Switzerland, and Canada. The research, findings, and field applications of all the members of this group formed the contents of the first book published that was solely devoted to HPC [2].

By the end of 1988, Pierre-Claude A'itcin, assisted by Denis Mitchell and Michael Collins, wrote the successful proposal for the Network of Centres of Excellence on High Performance Concrete, funded under the Federal Government "Centres of Excellence Programme.'' This research program started in 1990, and in its second phase, starting in 1994, the Network became known as Concrete Canada. The researchers who comprised Concrete Canada were not the only Canadians researching and using HPC; however, they were the preeminent and most active group in this field. By virtue of many publications in scientific journals, a Newsletter sent to 7000 persons world-wide, the organization of technology transfer days and seminars, and the construction of demonstration projects, Concrete Canada played the major role in establishing HPC as a widely accepted construction material in Canada.

In the United States, starting from 1989, a 4-year investigation on the mechanical behavior of HPC was initiated by the researchers at North Carolina State University under the support of the Strategic Highway Research Program (SHRP) [3]. The research complied most of the publications in the HPC area and provided very useful information for HPC studies.

Since the publication of these two documents, there has been a phenomenal increase in the development and use of HPC. So a need exists to update the earlier documents and summarize the significant developments during the past several years. This volume is a sequel to the earlier state-of-the-art report and covers the 6-year period from 1989 to 1994. A second annotated bibliography containing 776 references for the 6-year period has also been compiled by the authors as a separate document [3].

In the decade 1990-2000, numerous research programs have been carried out in many countries in Europe, Asia, Australasia, Japan, and North America. Meanwhile, thousands of papers on HPC have also been published [4]. At present, the use of HPC has spread throughout the world.

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