Integrated recycling of geopolymerized quarry dust and bagasse ash with facemasks for the balanced amelioration of the fat clay: a multi-waste solution

This study proposes a novel approach by integrating geopolymerized bagasse ash (GBA) and geopolymerized quarry dust (GQD) along with shredded facemasks (FM) for the balanced amelioration of fat clay. Extensive geotechnical testing and mineralogical and microstructural analyses were conducted to assess the performance of the proposed multi-waste fat clay stabilizer. GBA and GQD were found to reduce the liquid limit (w_L) and plasticity index (I_P) of fat clay up to 12% and 30% of their weight by soil, respectively, based on which composite binary additive (CBA) was devised for which optimum binary additive (OBA) was found at 20% of CBA. The strength characteristics, i.e., unconfined compressive strength (q_u), CBR value, and yield stress (σ_y) of soil treated with OBA were observed to be significantly higher than that of untreated soil. Meanwhile, the combination of OBA and FM increased the strength more than OBA up to 0.2% of FM, after which a slight decrease was observed. The stress–strain curve, brittleness index (I_B), and ductility index (I_D) of the OBA-treated fat clay showed a brittle failure response, which was transformed into a ductile response as FM increased in OBA cum FM stabilizer. Microstructural analysis showed the formation of flocculation, reticulation, and cementitious gel in the treated soil. Mineralogical and elemental analyses confirmed the formation of (N, C)–A–S–H gel in the fat clay, primarily responsible for the strength gain of the treated soil. The microstructural analysis also evidenced the FM strings in the microstructure responsible for maintaining the ductility of soil. Also, the proposed multi-waste recycling has significant implications for waste management, as its implementation for the construction of a two-lane subgrade covering a distance of 1 km may enable the repurposing of 1188.58 tons of assorted solid waste.