[en] Not-irradiated concrete samples from biological shielding of three different research reactors were taken and all were irradiated inside the concrete body of TRIGA reactor in Ljubljana. The samples originated from ASTRA research reactor in Seibersdorf, from TRIGA Mark II research reactor at Atominstitut in Vienna (TRIGA Wien) and from TRIGA Mark II research reactor at Jozef Stefan Institute in Ljubljana (TRIGA Ljubljana). Long-lived activation studies and depth distribution of activation studies were performed on these samples at Jozef Stefan Institute in Ljubljana. Besides activation studies chemical analyses of all these samples were performed and calcium and barium contents were determined. The results of measurements show that the long-lived isotope of barium dominates in all samples. Other important long-lived isotopes are europium and cobalt. One notable observation of these experiments is that the specific barium activation in all samples from three different reactors is practically identical. The concrete from ASTRA has lowest europium content and the concrete from TRIGA Wien has lowest cobalt content. The final purpose of presented measurements is estimation of the activated concrete volume, which has to be treated as radioactive material. (author)