The durability of building composites with polymer matrix, such as polymer concretes, is considered high or excellent. However, very few studies are available that show the properties of such composites tested long after the specimens' preparation, especially composites with fillers other than traditional rock aggregates. The paper presents the long-term compressive strength of polymer concrete containing common and alternative fine fillers, including quartz powder (ground sand) and by-products of the combustion of Polish fossil fuels (coal and lignite), tested nine or 9.5 years after preparation. The results were compiled with the data for respective specimens tested after 14 days, as well as 1.5 and 7 years. Data analysis confirmed the excellent durability of concrete-like composites with various fillers in terms of compressive strength. Density measurements of selected composites showed that the increase in strength was accompanied by an increase in volumetric density. This showed that the opinion that the development of the strength of composites with polymer matrices taking place within a few to several days was not always justified. In the case of a group of tested concrete-like composites with vinyl-ester matrices saturated with fly ashes of various origins, there was a further significant increase in strength over time.
Keywords: durability; fly ash; fossil fuel combustion by-products; long-term compressive strength; mineral fillers; polymer composites; polymer concrete.