Stabilization of expansive soils using pumice, lime, and marble

Abstract

Expansive soils widely exist in barren and semi-barren areas and cause severe engineering problems because they tend to shrink when dry and expand when wet. For this purpose, the efficiency of using lime, pumice, and marble to stabilize an expansive soil, which is classified according to Unified Soil Classification System (USCS) as high plasticity soil (CH), was investigated. Several experiments were performed to determine the properties of swelling soil such as wet sieve analysis, hydrometer analysis, Atterberg limits, specific gravity, permeability, compaction, one-dimensional swelling test, and unconfined compressive strength. In addition, differential thermal analysis (DTA) and X-ray diffraction analysis were conducted to determine the mineralogical properties of the soil. In this study, pumice was used at a range of 0-25% with increments of 5%, whereas lime was utilized at ratios of 0%, 3%, 5%, 6%, and 8%. In addition, marble was used at ratios of 0%, 5%, 7%, 12%, and 15%. The effects of using each of these additives alone on the consistency limits were examined. Afterwards, in the first stage, the Taguchi method for optimization was implemented to analyse the effects of the mixtures of all additives together with soil on the consistency limits. In the second stage by the Taguchi method, the best ratios for each additive were determined and their effects on swelling parameters, unconfined compressive strength, and compaction parameters were studied. Based on the obtained results, the SP25L6M15 mixture decreased the plasticity index and swelling pressure by 86.34% and 96.91%, respectively, while the SP20L8M15 mixture decreased the liquid limit by 51.04%. Furthermore, the SP25L8M12 mixture enhanced the strength of soil by 93.45%, 428.20%, and 1252.9% for curing times of 1, 7, and 28 days, respectively. In addition, the SP25L8M12 mixture decreased the swell percentage by 99.18%.