The development of new polymer materials with fly ash offers new scientific and technological perspectives due to the specific interesting physical properties of these materials. These properties derive either from their reduced grain size or from the structure and properties of the grain boundaries, which constitute a significant volume fraction. Polymer concrete realized of epoxy resin, fly ash and crushed fine and coarse aggregates has been prepared for assessing the influence of fly ash and resin dosage on the microstructure and density, for different combinations. In the paper are presented fly ash characterization and microstructure of polymer concrete obtained for mixes studied in the experimental program.