International Concrete Abstracts Portal

Many recent innovations in advanced concrete materials technology have made it possible to produce concrete with exceptional performance characteristics. High Performance Concrete (HPC) is defined as concrete which meets special performance and uniformity requirements that cannot always be achieved by using only the conventional materials and normal mixing, placing and curing practices. The performance requirements may involve enhancements of: placement and compaction without segregation, long-term mechanical properties, early-age strength, toughness, volume stability, or service life in servere environments. International Workshop on High Performance Concrete addresses technical papers presented during the workshop. A total of 32 papers are included and cover subjects including: * Self-compactable high-performance concrete in Japan * Durability of DSP mortars exposed to conditions of wetting and drying * Ferrocement: Applications for urban environment * Studies of high-performance concrete structural members * High performance and durability through design * United States government's role in high-performance materials for infrastructure * Tensile properties of high-performance concrete * High-performance concretes for highway applications * Bending properties of high early strength fiber reinforced concrete * High-strength concrete research for buildings and bridges Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP159

Concrete for the twenty first century can be much stronger, more durable and at the same time cost and energy efficient. However, this will not be possible unless we understand this material better. In spite of its wide spread use, compared to other structural materials there is very little well organized expenditure on research and development of concrete. One critical gap in our understanding is relating microstructure with macroscopic properties, and relating what happens at the ionic level to the response of concrete structures. Integrating the understanding of microstructure with processing and engineering properties is one of the major goals of our Science and Technology Center for Advanced Cement-Based Materials in the United States, established in 1989. Interactions with Industry have flourished due to the coordinated multidisciplinary and multi-institutional approach of the center. The Industrial Affiliates Program has eighteen members representing a wide range of internationally active corporations who provide invaluable input regarding the commercial significance of the Center's research. An overview of some of our new research results will be presented. The center has made significant progress in (1) characterizing pore structure, (2) developing experimental tools and computer models to relate evolving pore structure with permeability and conductivity, (3) understanding rheology, (4) designing a new class of organo-silicate composites, (5) untlerstanding fracture process zone, and (6) high performance fiber reinforced composites.

Fly ash, a by-product from the coal-burning power generation process, is often used, for its pozzolanic properties and its fineness, to enhance the strength and durability of concrete and high-strength concrete. The quality assurance of fly ash is frequently questioned since its properties tend to vary depending on the source of coal, type of boiler, pulverizing equipment, and the removal efficiency of the air pollution control devices. Since fly ash is cornmonly used as one of the main components in the development of high-performance concrete, a closer look at the effects of fly ash on the properties of high-performance concrete is critical. In this study, two types of fly ash, dry and wet bottom ashes of different particle size distributions, were used. Physical and chemical properties of these fly ashes were tested and compared with the original feed fly ashes received directly from the utility. The effects of these fly ashes on the strength of concrete were studied when used as 15, 25, 35, and 50 percent cement replacement by weight of cement. The results show that fly ash, when proportioned properly, can enhance the properties of concrete. The chemical composition of fly ash of different particle size distributions varies slightly. For the same type of fly ash, the finer the particle, the higher the specific gravity. The smaller fly ash particle has a faster reactivity rate than the coarser one. The compressive strengths of several selected mixes of fly ash concrete are equal to, or higher than, the control concrete before the age of 28 days. For fly ash with large particle size distribution, the fly ash concrete reaches only 85 percent of the control concrete strength at the age of 180 days. It was also found that fly ash concrete exhibits excellent acid resistance when compared to conventional concrete.

This paper discusses recent research on high performance concrete with a focus on cemenentitious materials designed for durability. A major key to suchp erformance originates with the concrete microstructure. Recent advances in optimizing cement and concrete materials by using calculated packing diagrams offer the promise of superior products achieved by increased packing efficiency. A high packing density coupled with adequate processing and cement binder characteristics makes possible the formation of a fine microstructure. In turn, this fine microstructure results in a low permeability and therefore provides a resistance to aggressive forces from the environment, which together enhance its long term durability. The favorable interaction among physical and chemical phenomena gives rise to better long term performance, whether the application is structural, or chemical, such as in waste management.

Australia is a dry warm continent. The major population centres are located close to the coastline. This paper examines the predictions for future building and construction activity in Australia. Based on the physical situation, for example climate and geography, and the anticipated needs for HPC arising from the forecast trends in construction activity it tries to forecast the research needs for HPC in Australia. It also endeavours to assign priorities for these research needs in terms of the size of the market likely to be affected.