Novel composite landfill liners

This paper presents results of a study into alternative landfill liner technology, in which a large proportion of the materials used in construction are considered to be wastes by their primary producers. A composite barrier comprising concrete-clay-concrete layers is described, in which two concretes have been developed using waste materials. These include an alkali activated blast furnace slag and a novel binder based on a zinc oxide-sodium borate slag. The aggregates used in these concretes are either slags from the metals processing industry (such as ferrosilicates or chrome alumina) or spent foundry sands. Studies of the leaching properties of many of these materials show them to be relatively unreactive in both landfill leachates and in the chemical environment prevailing in cement pore solutions. Accelerated leach testing of these materials, using high pressure flow cells, suggests that they are mutually compatible with each other and with the clay hydraulic barrier in the liner system.