Experimental study on the strength, collapsibility, and microstructure of cement and micro-silica-stabilized saline soil under freeze-thaw cycles

Saline soil is characterized by high concentrations of soluble salts, which can pose hazards such as frost heaving, uneven thaw settlement, and concrete erosion, especially subjected to freeze-thaw (F-T) cycles in the seasonal frozen and frost regions. This study aims at investigating the cement and micro-silica treatments effect on the changes in microstructure, strength property and durability of compacted saline soil, and evaluating the suitability of micro-silica as potential industrial waste materials for altering the mechanical behaviors of saline soil in comparison with the use of cement as traditional binder. Unconfined compression tests, oedometer tests, and freeze-thaw cycle tests were conducted on the untreated and treated saline soil stabilized by cement alone, micro-silica alone, and mixtures binders with cement-micro-silica (CMS). Furthermore, the microscopic characteristics were analyzed by scanning electron microscope and X-ray diffraction test. Tested results indicates that the cement is committed to improving the strength of saline soil, and the micro-silica contributes to improve the F-T cycle durability. The performance of CMS-treated saline soil with unconfined compressive strength of 1.763 MPa and coefficient of collapsibility of 0.056 is superior to that of cemented and micro-silica-treated saline soil alone. Besides, the stabilization with CMS achieved promising results with 3% cement and 4% micro-silica admixture, achieving the purpose of recycling micro-silica and exhibiting the excellent durability with strength loss of 50% due to F-T cycles. The formation of cementitious compounds originated from pozzolanic reactions between cement and micro-silica can effectively improve the behaviors of saline soil.