Valorization of industrial wastes as alternative liner materials: A review

Clays and geosynthetics are the main materials for hydraulic barriers due to low conductivity for environmental protection. However, high costs and lack of disponibility generate the need for alternatives. Therefore, linked to immediate action regarding reducing the amount of waste generated and developing strategies for preventing contamination, industrial waste has emerged as alternative liner materials. They seem to represent a potential resource of geotechnically applicable materials to substitute, or as amendment, for clays and geosynthetics. Many disposed materials have been studied as geomaterial and showed promising results, although an evaluation of the properties must be carried out. Thus, this work reviews industrial by-products acting as liner materials, their geotechnical properties, treatment needed, compaction energy, compressibility, shear resistance, chemical and mineralogical composition, methodological approaches, lack of research and opportunities for future investigations. The selected sources were waterworks sludges (WS), vegetal-based biomass ashes (BA), mining wastes (MW), and steel slags (SS) by-products, most of the literature achieved hydraulic conductivity of 10^-9 m/s when dealing with those wastes and treating biogeochemically. It is possible to reach the best ratios mixing with soils of up to 20 % for WS and BA, 50 % for SS and even 100 % of MW, creating a wide range of waste-based geocomposites. The reviews comprise recent literature on alternative materials providing insights into future investigation looking to develop sustainable practices and new waste-based materials.