Compacted clay liner formed with beach sand, Na-bentonite and waste materials

Abstract

Waste materials can be used to optimize bentonite content in compacted clay liners, which can also provide enhanced performance. In this research, the use of sewage sludge & slag- clinker dust and brick dust as replacement for Na bentonite was evaluated. The main composition of the liner mix design was set as beach sand and Na bentonite with a mixing ratio of 3 to 1, respectively, to satisfy the minimum requirements of commonly accepted regulations for liner materials. Waste materials were added as 3%, 6% and 12% by dry weight of the beach sand and bentonite mix. Physicochemical properties, compaction characteristics, compressive strength, volume change behavior and hydraulic conductivity were measured through a series of laboratory tests. The effect of curing was assessed after 1, 7, and 28 days. In addition, microstructural interactions were observed directly and indirectly through Scanning Electron Microscopy, X-ray Diffraction, X-ray Fluorescence and Fourier-transform infrared spectroscopy tests. Results showed that the waste materials have enhanced the mechanical behavior of sand bentonite mixture. The presence of pozzolanic materials provided formation of additional bonds affecting pore volume, decreasing swell potential and hydraulic conductivity even below desired levels. The unconfined compressive strength of all mixture groups significantly increased during early stages of curing time. Overall, the use of waste materials in compacted liners offers an alternative and sustainable solution for recycling and reducing waste and shows their potential as stabilizer materials in landfill applications.