In this paper the fly ash, which is the finest residue of the lignite combustion entrapped by electrostatic filters at Ptolemais electrical power station, is examined, in order to determine the possibility of its usage in the production of concrete. It is implemented by testing concrete models in actual scale. Mineralogical, petrographical and chemical analyses of the fly ash as well as of the produced concrete are presented. The concrete that was produced by cement, sand, water, aggregates and fly ash (in various percentages) showed micro-cracks in its structure, due to the reduced interconnection of the fly ash with the aggregates. Nevertheless, the fly ash may act as adhesive material, as well as the material that fills the cracks of the concrete. Tests of the strength on models made by this concrete have shown comparable results in strength with reference concrete produced without as. It is concluded that the mixing of fly ash in concrete does not affect its strength and sometimes it fills the cracks of the concrete mass..

Keywords: fly ash, lignite, concrete, mineralogy, Greece