Investigation of the functional lifetime of TRISOPLASTr in relation to chemical compositions of pore water solutions in barriers

Trisoplastr is a mixture of sand, bentonite and a polymer, used amongst others as landfill cover as well as barriers. Its permeability is generally lower than 1-2 x 10-11 m/s. Trisoplast keeps its functionality even in contact with different kinds of liquids, is not susceptible to cyclic drying and rewetting, and the permeability hardly depends on its dry bulk density. Tests with 10¿iaxial strain show only a slight increase in permeability. The functional lifetime of Trisoplast is governed by exchange of adsorbed sodium ions against dissolved calcium ions. This process depends on the composition of the pore water solution in the soil layers directly in contact with Trisoplast and the displacement rate of dissolved calcium ions either by convectiveor diffusive transport phenomena. The functional lifetime of Trisoplast even under relatively extreme conditions is at least 100 years and scores clearly better than the reference sand-bentonite barrier.