Use of Secondary Waste Minerals as a Novel Low –CostCementitious Landfill Liner

Conventional liners have been made with clay and HDPE membranes, supporting packed aggregate layers. When cementitious materials are used for the containment of waste they act in two different, and sometimes conflicting, ways. The first is physical and the second is chemical containment in which the leachate passing through the barrier is buffered to high pH thereby substantially reducing the solubility of many harmful species and promoting sorption onto the matrix. Chemical barriers have been extensively researched for nuclear waste containment and this paper reports on the development of chemical barriers for the nonnuclear waste management using a novel alternative technology in which low-cost concrete liners may be constructed, making use of materials, which are considered to be wastes by their primary producers. It focuses on the ability of a cementitious barrier to chemically condition liquid leachates, neutralising organic acids and reducing the solubility of priority pollutants. This is similar to the way in which cement suppresses actinide leaching in the disposal of nuclear wastes. In this paper the required properties of cementitious mixes for this purpose are discussed. The results of an extensive investigation into potential mixes using various mineral wastes are presented and the measured properties are compared with those, which are required. All of the mixes, which have been investigated, contain large amounts of secondary materials. If these materials which have the potential for use either as binder or as aggregate materials for concrete, were treated as wastes their disposal costs would be high, so the mixes may be designated as "negative cost mixes". The results indicate that many of these mixes are well suited to this application