Long term performance of cement-bentonite cut-offs in saline and acidic solutions

The paper presents the results of a research aimed at evaluating and predicting the long term performance of CB mixtures in terms of hydraulic conductivity, k. A low k value is the necessary (even if not sufficient) requirement for a cut-off wall to isolate polluted sites. Aqueous sulphate solutions of different nature (acidic, saline) and concentrations were used as permeants in column tests performed for long time (one year or more) in order that full effects of physical and chemical reactions may occur. Results of these tests are here analysed mainly with the aim to find a criterion to predict how long a cement-bentonite cut-off wall can keep a proper hydraulic performance.