Containment techniques are amongst the most common methods of remediating land contaminated by previous industrial use. An important part of the containment process is the placing of vertical in-ground barriers to minimise the movement of contamination from site. Self hardening slurry trench cut-off walls of cement--bentonite are barriers that are increasingly being used in the United Kingdom. The use of cement--bentonite slurry trench cut-off walls, particularly in highly aggressive environments, raises concerns over durability and long-term performance. The relatively recent use of such barriers means that there is little information on their long-term performance. This paper describes research being undertaken to investigate the properties of cement--bentonite cut-off walls and to examine potential durability problems. Laboratory immersion tests have been used to assess the chemical resistance of typical cement--bentonite mixes containing ordinary Portland cement, ground granulated blast-furnace slag and pulverised fuel ash. These mixes showed varying degrees of resistance to chemical attack with pulverised fuel ash mixes more resistant than those with ground granulated blast-furnace slag. The advantages and limitations of such tests arc discussed.
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