Abstract
This article focuses on the evaluation of concrete substructures of 10 road bridges in eastern Slovakia, built between 1960 and 1970, based on core sampling and compressive strength testing performed in accordance with current European procedures for in-situ strength assessment. The results confirm that the concrete was predominantly site-batched, characterized by a large aggregate size and significant strength variability. Although all tested specimens meet the design requirements valid at the time of construction, only about half of the bridges achieve the prescribed characteristic strength when assessed according to present-day European standards. Despite their age of 60–70 years, the substructures (abutments and piers) remain in very good condition. In contrast, the superstructures show extensive deterioration, dominated by reinforcement corrosion and alkali–silica reaction, which will require costly rehabilitation or replacement in the near future.