An overview of opportunities and concerns on the use of fly ash as a pozzolan in hydraulic cement concrete in constructing highways and other transportation facilities is presented. It is derived primarily from more detailed information given in nchrp synthesis of highway practice 127. Some of the early concerns related to the loss ofentrained air in fly ash concrete, shipment-to-shipment uniformity of fly ash, and more careful selection of by-products marketed as pozzolans. Significant differences between the by-products from burning bituminous coal and subbituminous coal have been identified, and more fundamental information is being developed. The need to use a more rational method of proportioning ingredients for concretes containing fly ash based on performance characteristics is discussed. A more rational approach can provide opportunities for more efficient utilization of fly ash as a pozzolan in hydraulic cement concrete. This paper appears in transportation research board record no. 1284, Cement, admixtures, and concrete 1990.
Samenvatting