Pyrolysis of asphalt in the presence and absence of water

The bitumen used for the embedding of nuclear wastes has been pyrolysed in confined and hydrous systems, in order to evaluate while an elevation of th e temperature in the deep geological repository could induce chemical trans formations of the bitumen matrix, which could influence its confining prope rties. The pyrolysates have been extracted in chloroform and the extract ha s been separated in aliphatic aid aromatic hydrocarbons, resins and asphalt enes. These different fractions have been analyzed by GC-MS and mu -IRTF. F ew modifications of the bitumen structure are observed up to 300 degreesC. Above this temperature, the pyrolysis of the bitumen generates light hydroc arbons and ai aromatic and condensed insoluble residue. The use of the time -temperature index allows to estimate the temperatures which have to be rea ched in the repository in order to observe the first transformations of the bitumen. (C) 2001 Elsevier Science B.V. All rights reserved.