Geotechnical Characterization of Carbide Lime

Abstract

Carbide lime is a calcium hydroxide-rich by-product generated during the production of acetylene gas from the reaction of calcium carbide with water. This study characterized carbide lime to evaluate its suitability for geotechnical and engineering applications through chemical and laboratory geotechnical analyses. The chemical composition revealed that the material is predominantly composed of CaO and Ca(OH)₂, with relatively low concentrations of SiO₂, Al₂O₃, and Fe₂O₃. The combined percentage of SiO₂, Al₂O₃, and Fe₂O₃ was below the minimum requirement specified by ASTM C618 for pozzolanic materials, indicating that the carbide lime is not a pozzolan but a highly reactive calcium-rich binder. Geotechnical characterization classified the material as A-7-6 according to the AASHTO classification system, indicating a clayey soil with fair to poor subgrade quality and a group index of 6. The California Bearing Ratio (CBR) of 92% under unsoaked conditions demonstrated high load-bearing capacity. Compaction tests produced a maximum dry density of 1.041 g/cm³ at an optimum moisture content of 18.40%. Atterberg limit tests yielded a liquid limit of 42.01%, plastic limit of 22.22%, and plasticity index of 19.79%, indicating moderate plasticity. The liquidity index (-0.20) and consistency index (1.20) showed that the material exists in a stiff to semi-solid state, while the activity value (0.27), flow index (0.54), and toughness index (0.37) indicated low clay activity and relatively low resistance to deformation. Overall, the findings demonstrate that carbide lime possesses favorable engineering characteristics that make it suitable as a soil stabilizing agent and a partial substitute for commercial hydrated lime.