Biopolymer and Gypsum Added Na Bentonite for a More Effective Clay Liner

Bentonite soil is frequently utilized as a compacted clay liner, which is a critical component of municipal waste landfill systems. This study aims to investigate the feasibility of treating sodium bentonite (NAB) with natural biopolymers to obtain an effective clay liner. The NAB was treated with three biopolymers: sodium alginate (SA), agar gum (A), and xanthan gum (X), at different replacement percentages (2%, 4%, 6%, and 8%). Additionally, an investigation was conducted to determine the extent to which replacing 50% of these additives with gypsum (G) would improve the biopolymer treatments. Fourier-transform infrared spectroscopy (FTIR), pH, one-dimensional swelling, and unconfined compressive strength (UCS) were carried out in this study. The FTIR results indicated the presence of intermolecular hydrogen bonding when NAB was treated with biopolymers and gypsum, which is crucial for enhancing the UCS. Furthermore, the thermal treatment of biopolymers significantly contributes to improving the UCS. Among the various biopolymers tested, agar gum demonstrated the most significant improvement, specifically, replacing 8% of the NAB with agar gum resulted in a 55% increase in UCS. Volume change behavior was most influenced by replacement of NAB with gypsum by 8%, which reduced the vertical swelling to 21% as opposed to 79% for the untreated NAB. The use of SA conversely resulted in an increased vertical swelling of 91%.