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Three types of cements and three types of fine aggregates, viz seashore sand, crushed stone and a blend of the two were utilized for this study. The water-to-cement ratio by weight ranged from 0.40 to 0.50. All mixes were made at a slump of 10-cm (4-in.) and air content of 4 percent. The blended cement concrete with fly ash showed the lowest shrinkage among the three cement concretes. The creep tests showed similar results. Good workability, high strength, low shrinkage and creep could be achieved using fly ash concretes.

Concretes containing both portland cement and fly ash were evaluated to determine the effect of fly ash on air-void stability. Ten fly ashes were used, they have a wide range of chemical and physical properties as well as geographical origins. Air contents of plastic concretes were determined, and both air content and air-void parameters were measured in hardened con-cretes cast at four time intervals after initial mixing. These tests indicate that air contents of concretes containing Class C fly ash appear to be more stable than those in concretes containing Class F fly ash. The higher the organic matter content of a fly ash, the higher will be the air-entraining admixture requirement for concrete in which the admixture is used. In addition, the higher the air-entraining admixture requirement, the greater is the air loss on extended mixing. Even though the air volume is reduced the spacing factor, specific surface, and number of voids are little affected. A "Foam Index" was determined for each of the ten fly ash-Portland cement combinations. Air-entraining admixture requirements of actual concretes containing both portland cement and fly ash were compared to the "Foam Index" test results. These tests indicate that the "Foam Index" could be especially useful to concrete pro-ducers as a quality control test for checking the air-entraining admixture requirements for different sources or lots of fly ash.

The paper describes commercial use of concretes containing fly ash in Australia. comparison is made between fly ash and other concrete types, mainly on the basis of equal 28 day strength. Setting times, Bleeding, Workability, Air Entrainment, Rate of Strength Gain, Elastic Properties, Flexural and Indirect Tensile Strength, Heat of Hydration, Shrinkage Creep, Sulphate Resistance, Carbonation, Abrasion Resistance, Alkali Aggregate Reactivity are discussed. Field observations of concrete structures containing fly ash after prolonged environmental exposure are also included.

The paper describes investigations undertaken to develop a suitable fly ash blended Portland cement for concrete used in two large water dam projects in Yugoslavia, which have recently been completed. The fly ash selected for this purpose is produced at a power station using brown coal with combustion temperatures 1550-1600°C, as compared to other Yugoslavian power stations using lignite coal with combustion temperatures generally in the range of lOOO-12OO°C. It was shown that the combustion temperature is the single most important factor in controlling the quality of fly ash, with excellent physical and pozzolanic properties being produced at higher temperatures. A fly ash content (F) of 50% in Portland cement (C), i.e. F/(F+C) = 0.50, was selected for these projects, as it was shown to be the most suitable blend with regard to the heat of hydration, setting time, consistency and soundness properties. A concrete mix with 225 kg/m3 of this fly ash blended Portland cement and aggregate of maximum size 63 mm (24 in) was adopted and both the laboratory and site tests showed this mix to possess good properties in the fresh and hardened states. A comparison of these results was made with the comparable concrete prepared with commercially available Portland cement and slag cement, and the use of fly ash blended Portland cement was found to be advantageous.

There are several federal and state specifications being used in the United States involving the use of fly ash in portalnd cement concrete. The American Society for testing and Materials establichwed a stancdard on fly ash in 1954 and several foreign specifications that followed had similar formats. However, for use by all agencies in that particular country. In recent years there have been a few other proposed unique classification systems. In the United States, the classificaiton of fly ash by reference to the type of coal has been questioned, as well as some of the specification limits. The many new "Western" fly ashes have caused concern for some properties not presently covered, such as free lime and sulfate resistance. Also, due to poor correlation between laboratory pozzolanic activity tests and field performance, there is a need for a system in terms of parameters controlling performance. A review of the various specifications will be presented, and will include a disussion of the similarities as well as items that are unique to a particular specification. An attempt will be made to present a universal specification scheme for fly ashes.