The article contains results of tests of geotechnical properties of fly ashes from the Skawina Power Plant. Samples of the ashes were taken from three discharge hoppers with electrostatic precipitators, marked as dedusting zones I, II and III. The research included determination of parameters characterising the particle size distribution, compactibility, capillarity, loss on ignition, water permeability and shear strength. The analysis of the results of the tests was carried out in the context of the use of the ashes in road building. It was found that the tested ashes from different dedusting zones have relatively small differences in physical characteristics and mechanical properties. The ashes do not meet the requirements for materials used in road building. It was pointed out that the improvement of the geotechnical properties of the fly ashes could be obtained by using mixtures thereof with other industrial wastes of coarser graining or by stabilisation with binding agents. Low values of permeability coefficient result in the classification of the tested ashes as suitable for sealing for example levees or landfills.

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