IOSIF LINGVAY, ELENA RADU, ALINA CARAMITU, DELIA PATROI, GABRIELA OPRINA, LADISLAU RADERMACHER, SORINA MITREA BITUMINOS INSULATIONS DURABILITY OF UNDERGROUND METALLIC PIPELINES II. LABORATORY STUDY ON THE AGING OF BITUMINOUS MATERIAL The structural and physicochemical changes that lead to the aging of the bituminous insulation of underground metallic pipelines were determined through various investigations (XRD, dielectric spectroscopy and thermal analysis – coupled techniques TG + DTA + DTG). The resistance to moulds of the bituminous insulation was evaluated by using specific microbiological methods and the dominant microbiological species found in the soil where the investigated bituminous material was exposed for 19 years were identified. The measurements carried out on samples taken from site showed that the bituminous material used in the anti-corrosive isolation of steel pipes has a very low resistance to microorganisms; thus, the dielectric qualities of bitumen deteriorate substantially (tgä increases 3-4 times). The exposure of the bituminous insulation to different climatic conditions and to solar radiation (UV-IR) leads to a decrease in the dielectric losses in the insulation and to an increase in crystallinity and thermo oxidative reactivity of bitumen, thus leading to a significant decrease in the material’s resistance to the action of fungi.