Mechanical characteristics and microstructure study of saline soil stabilized by quicklime after curing and freeze-thaw cycle

Quicklime is widely utilized in stabilizing special soils, and the curing condition, as well as freeze-thaw cycles (FTCs), can significantly affect the engineering properties of lime-stabilized soil. In this study, quicklime is adopted to stabilize the saline soil in cold regions. The effects of curing time, numbers of freeze-thaw cycles, and constraint conditions (three-dimensional constraint, radial constraint, and no constraint) on mechanical and microstructure characteristics are investigated by performing a series of unconfined compression tests (UCT), Xray diffraction (XRD) and scanning electron microscope (SEM) tests. The UCT results indicate that specimens obtain the highest unconfined compression strength (UCS) under three-dimensional constraint and the lowest UCSs under no constraint. XRD and SEM tests reveal that pozzolanic reaction and carbonation play an important role during curing. UCSs of specimens cured for 7 days increase with the increase of FTCs while those of specimens cured for 28 days decrease in the early stage of FTCs but increase after 10 FTCs. FTCs destroy the original structure of stabilized soil and break the aggregates. Small particles of free quicklime and broken aggregates fill the pores. In addition, cementitious materials bond these particles together which resulted in a denser microstructure and an increase of UCS after 10 FTCs.

Automated summary

This study investigates the effects of curing time, numbers of freeze-thaw cycles, and constraint conditions on the engineering properties of lime-stabilized saline soil in cold regions. The results show that three-dimensional constraint leads to the highest unconfined compression strength (UCS), while no constraint results in the lowest UCS. Curing for longer periods and increasing freeze-thaw cycles generally improve the UCS, although there is a decrease in UCS after initial freeze-thaw cycles for specimens cured for 28 days. The microstructure analysis reveals the role of pozzolanic reaction and carbonation in the curing process.