Sustainable usage of calcium carbide residue for stabilization of clays

Chemical stabilization is commonly used to improve engineering properties of problematic soils. This study investigates the possibility of using calcium carbide residue (CCR), a by-product of the acetylene production process, to improve engineering properties of clays. For this purpose, an array of unconfined compressive strength (UCS) and consolidation tests is performed on green bentonite (with predominantly montmorillonite mineralogy) and white kaolin (with predominantly kaolinite mineralogy) to assess strength and compressibility of the stabilized clays with different CCR dosages and at various curing times. Furthermore, a suite of microlevel tests characterizes the microstructural properties of the stabilized clay matrices to provide further insight into the mechanism of strength development. Microlevel assessments are performed using field emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), particle size analysis (PSA), and nitrogen-based Brunauer-Emmett-Teller (N2-BET) surface-area analysis tests. The experimental results suggest that CCR can significantly improve the strength and compressibility characteristics of the tested clays. The highest strength improvements are attained with 9 and 12% of CCR for the tested bentonite and kaolin, respectively. Furthermore, the UCS values from the current study are compared with those reported in the literature for the same clays stabilized with several traditional and nontraditional additives. Microlevel observations delineate the formation of new cementing materials that result from chemical reactions between CCR and clay minerals. Less-porous and denser soil fabrics are seen on the surface of clay particles. Findings of this study confirm the potential of CCR as a sustainable alternative to traditional stabilizers for soil improvement purposes in civil engineering applications