Sustainable usage of calcium carbide residue for stabilisation of expansive soils: strength and microstructure analysis

This study examines the effectiveness of using calcium carbide residue (C.C.R.) to stabilize black cotton soil (B.C.S.). It includes soil characterization, mechanical testing, and microstructural analysis to thoroughly examine the effects of C.C.R. on B.C.S.‘s engineering properties.

Soil samples were collected from Nashik, India, and classified as high plasticity (C.H.) with low swelling behavior. C.C.R. was used as a stabilizing agent, which contains high calcium oxide (CaO) and other pozzolanic materials such as silicon dioxide (SiO₂) and aluminum oxide (Al₂O₃). XRD analysis confirmed the presence of approximately 96% calcium hydroxide (Ca(OH)₂) in C.C.R., indicating its potential for pozzolanic reactions and cementitious material formation. Mechanical testing, including unconfined compressive strength (U.C.S.) tests and one-dimensional consolidation tests, demonstrated significant improvements in soil strength and stiffness with the addition of C.C.R. At low C.C.R. contents, ductile behavior was observed, transitioning to brittle behavior at higher C.C.R. contents, akin to highly structured natural soils. The addition of C.C.R. altered the compaction characteristics of the soil, leading to reduced soil densification and increased moisture content.

Microstructural analysis through scanning electron microscopy (S.E.M.) revealed the development of reticular fabric and soil-CCR clusters, particularly with prolonged curing periods. X.R.D. analysis showcased mineralogical transformations, including the formation of cementitious products such as calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-S-H), indicative of pozzolanic reactions and enhanced soil stability.

The observed mechanical, mineralogical, and microstructural changes highlight the feasibility of utilizing industrial byproducts for soil stabilization in similar geological and environmental contexts.