PORE WATERS EXTRACTED FROM COMPACTED BENTONITE SUBJECTED TO SIMULTANEOUS HEATING AND HYDRATION

A compacted clay block of montmorillonite clay has been simultaneously subjected to heating and hydration by parallel and opposite fronts, i n order to determine the physico-chemical effects of the thermohydraul ic process on the clay and on its pore water. The pore waters of the c lay have been extracted at ambient temperature after the thermal-hydra tion treatment by a compaction at high pressure (60 MPa) technique. Th ey have been analyzed, and the chemistry has been evaluated by using t he speciation program EQ3NR. The movement of salts towards hot areas h as been observed as a result of the thermo-hydraulic gradients, but it is conditioned by anionic retention processes, which mainly affect th e mobility of SO42- anions. The distribution of the exchangeable catio ns is modified by the thermal gradient. (C) 1997 Elsevier Science Ltd.