Stabilization of swelling soil by lime, fly ash, and calcium carbide residue

This study aimed to compare the swelling and strength parameters of weak and swellable soils with calcium carbide residue remaining from acetylene industrial production with lime and fly ash. For this purpose, bentonite and river sand were mixed as a 75–25% bentonite–sand mixture to obtain the pure test sample. Five percent, 10%, and 15% by weight of calcium carbide residue, lime, and fly ash were added to pure sample. All test samples were prepared at the optimum water content of each mixture. The prepared samples were left to cure for 1, 7, 14, 21, and 28 days and then undergo liquid limit, plastic limit, compaction test, unconfined compression test, direct shear box test, and swelling pressure tests which were performed on the samples at the mixing ratios determined for all additives on each curing day. The soil improvement performances of these additives were evaluated considering the curing times. Results revealed that the calcium carbide residue significantly improved the unconfined compressive strength, cohesion, internal friction angle, and swelling pressure value of the pure sample. When evaluated together with other additives used in the study, it was observed that calcium carbide residue was within acceptable limits. In addition, the samples were exposed to XRD test for each mixing ratio on the 7th and 30th days. The mineralogical structures of the samples were examined, and the effect of the additives on the mineralogical structure of the mixture was discussed.