The use of lime and Nano CaCo₃ to controlling on collapsibility of gypsiferous soils

Abstract Gypsiferous soils, or gypsic minerals, are soils with a high proportion of sulfate calcium sulphate, typically form in areas with high rates of evaporation and little to no rainfall. These soils are distinguished by a gypsiferous deposit of over 5% in the top meter of the soil profile, thick surface crust, salinity, and sodality. The term “gypseous soil” refers to the predominant calcium-sulfate compound in soil composition. The research’s soil samples came from two locations of Karbala governorate at the Ain Al-Tamr area and at Shabas Salman area. These soils had gypsum content of 51% and 2% respectively. In this research, an experimental investigation is performed on the influence of two different additions to the gypseous soil in order to reduce the collapse potential of the these soil using the Single Odometer Test (SOT) method. This study’s additives were lime and a mixture of lime and CaCo3 nanoparticles. The percentages of lime were 4% and 8%, but the percentage of CaCO 3 nanoparticles replaced each of the stated ratios of lime by 0.25, 0.5, and 1% of CaCO 3 nanoparticles. Testing was also done on the soils in their natural form to see how additions affected them. Although the primitive proportions of these additives contributed to reducing the collapse potential of these soils, they remained within the unsafe classification until reaching the optimal ratio of treatment according to the treatments used in this research, where they were (3% lime + 1% CaCO 3 nano) or (7.5% lime + 0.5% CaCO 3 nano) for soil I. As for soil II, the optimal treatment ratios were (3.5% lime + 0.5% CaCO 3 nano), (3% lime + 1 CaCO 3 nano), (7.25% lime + 0.25 CaCO3 nano), or (7% lime + 1% CaCO3 nano). To a certain extent, the treatment becomes useless and can result in a reverse process, that is, the probability of collapse returning to increase again.