Geosynthetics, materials that are broadly used in civil engineering and en-vironmental protection, have certain initial characteristics, which are obtained while testing new products. However, with time, these values change as a result of the influence of degrading factors. Getting to know the scope of these changes enables improving products or designing structures with the appropriate safety factor.Power industry in Poland uses mainly hard and brown coal in processes of energy generation. Fly ashes raised by the exhaust fumes and separated by elec-trofilters and ash-slag removed from furnace chamber are combustion by-products. Nowadays, the ash-slag mixtures are valuable anthropogenic soils, used for building embankments, where the geotextiles are also built in.The taken up research aimed at the determination of the influence of the ash-slag chemistry on the changes of chosen strength parameters of geotextiles. The main degrading agent in the period of the research, which could influence the structure and thus the strength of geotextiles, was pH of the ash-slag. The mixture was taken from the dumping ground of the Steelworks Arcelor Mittal Poland S.A. in Kraków, from several places of the holding pond of the surface of 15 ha, from depths 0.5 to 2.0 m. The carried out chemical tests ...
