Problems with fineness testing of coal fly ash for use in concrete
Poole, Toy S.
Miscellaneous PaperAbstract: The specification governing use of coal fly ash in concrete (ASTM C 618) includes a fineness uniformity requirement. This requirement is frequently exceeded. The relationship between product variation and the probability of exceeding this requirement was developed. It was found that a product standard deviation in fineness (including testing error) of less than or equal to 2.38 percent would be required to ensure that a material would meet the uniformity requirement in 95 percent of samples. Product standard deviation is strongly dependent on sampling techniques. Many apparently good fly ashes fail to meet the C 618 level of uniformity when sampled by grab samples, but more meet the requirement when analysis is done on composite samples. An error in the calibration of sieves used in the testing of fly ash fineness and a corrective action has been published. In this work, CCRL data collected on two very coarse samples were used to evaluate the improvement in testing error associated with the change. The between-laboratory standard deviation for the existing test method were found to be 4.6 percent. It was reduced to 2.4 percent when the new procedure was applied.
Structures Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Coal fly ash; Concrete; Fineness; Concrete additives; Particle size determination
Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; SL-93-9.
Approved for public release; distribution is unlimited.