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Highlights the importance of insuring uniformity of in-place concrete for quality assurance in construction. The functional requirements of strength, serviceability, and durability can be assured by quality assurance in design, specification, choice of materials, and workmanship. Steps to insure uniformity of cement received in an irrigation project from different sources are described. Tests to establish uniformity of concrete in dam construction and shotcrete for tunnel lining are highlighted with the help of case studies.

Roller compacted concrete (RCC) became an accepted method for dam construction during the latter half of the 1980s and during the early 1990s there has been a very rapid growth in this form of dam. High dams up to 200 m in height and containing several million m 3 of concrete are now being designed. Paper describes the development of RCC dams over the last decade and shows how there has been a move away from the early RCC dams that contained a relatively low cementitious content toward a dam that contains higher cementitious contents, usually with a high proportion of pozzolan. Although a number of different pozzolans have been used, the significant majority of RCC dams have contained low-lime fly ash. The in-situ properties that have been achieved in RCC dams already in service for a number of years have been found to be suitable for gravity dams more than 200 m high. Arch-gravity RCC dams have been completed with heights approaching 80 m, together with a thick-arch RCC dam of a comparable height. It is considered that the traditional concrete dam will be superseded within the not-too-distant future by the RCC method of construction, and on a number of sites where rock-fill dams were originally planned, RCC dams will eventually be constructed.

Recent literature suggests that there is considerable potential for reduction in the emission of CO 2 to the environment through the manufacture of new types of cement that do not rely on the calcination of limestone (and accompanying release of CO 2). The 1988 1-billion metric t worldwide production of cement accounted for 1 billion metric t of CO 2 release, i.e., 5 percent of the 1988 world CO 2 emission (human activity only). This is equivalent to the CO 2 emission of all Japanese activity. The use of lesser amounts of calcium-based cements could be achieved through their partial replacement by alkali-activated alumino-silicate materials, which do not release large quantities of CO 2 in their manufacture. The fostering of low-CO 2 high-alkali-based cements will mean a dramatic change in the research and development presently carried out in the USA and other countries. Alkalies are generally thought of as the cause of deleterious alkali-aggregate reaction. As a result, the tendency has been to avoid any addition of alkali portland cement products, often requiring cement manufacturers to supply low-alkali cements. The use of MANSMR spectrography for the determination of composition of alkali-activated cements, in combination with ASTM C 227 bar expansion, allows the prediction of potential for alkali-aggregate reaction. A preliminary study involving Al and Si MANSMR spectroscopy revealed that the alkali-activated alumino-silicate cements are the synthetic analogues of natural pozzolans that are known to effectively suppress alkali-aggregate reaction. These cements, even with alkali contents as high as 9.2 percent, do not generate any deleterious alkali-aggregate reaction, according to the ASTM C 227 bar expansion test. Industrial experience based on the use of alkali-activated slags in Eastern Europe since 1964, associated with the commercially produced alkali-activated cements in the US since 1988, suggest that high-alkali cements will ultimately improve the concrete used in buildings and highways, and also serve global need by reducing emission of CO 2 and reducing energy consumption during cement manufacturing. In terms of a 5 percent growth scenario, the predicted business as usual (BaU) world cement production for the year 2015 equals 3500 million metric t. Based on an amount of blended portland cement production on the order of 1850 million metric t (1000 portland + 560 slag + 290 fly ash) in the 21st century, the need for novel alkali-activated cementitious materials could be in the range of 1650 million metric t.

The future of the concrete industry appears to be bright from projections based on current trends in population growth, and increasing industrialization and urbanization. However, this optimism must be tempered with changing attitudes in society on ecological issues such as conservation of natural resources, durability of engineering materials, and environmental pollution. Due to increasing public concern with durability of concrete as a construction material, this subject is discussed in detail with reference to deficiencies in the science of concrete durability, methods of testing for quality assurance and service-life prediction, and education in concrete technology.

In the August, 1971 issue of the ACI Journal, the report of the ACI Board Committee on "Concrete--Year 2000" was published. That committee concluded that looking ahead 30 years in 1971 was as difficult as it was in 1900 to look ahead 70 years to 1970 because of the accelerating rate of change. That acceleration has not altered. It is believed that the least amount of progress has occurred in the area of cooperation under what, in 1971, the committee termed "advancements in attitude." It seems that there is more rather than less conflict and litigation among participants in concrete technology. One of the most significant improvements waiting to be made is in the area that some are calling "conflict resolution." In the 21st century, concrete technology will be alive and well, and continuing to make progress in some ways that cannot now be predicted.