Hydraulic Binder Stabilised Near-Surface Soils Exposed to Cold Curing Climate and Freeze-Thaw Cycles

摘要

Fine-grained soils are normally not suitable as subbase in road, railway, and other largescale constructions due to their compressibility, low shear strength, and/or frost susceptibility. Common procedures to improve the subbase are soil replacement, lightweight fill, or insulation. The engineering properties of fine-grained soils can also be improved in situ by mixing them with hydraulic binders. A SWOT analysis based on literature study indicates that near-surface soil stabilisation has opportunities as a method. However, one major weakness of the method of near-surface soil stabilisation is the question of strength reduction as a consequence of freeze-thaw cycles. It is unclear how near zero curing temperature followed by freeze-thaw cycles, representing conditions in northern countries, might influence the curing as well as the ultimate strength of the stabilised soil. The impact of freeze-thaw cycles on the engineering properties of stabilised soils was investigated with focus on the reduction of strength. In these laboratory investigations, curing took place at temperatures of +4℃ with freeze-thaw cycles interrupting the curing period. Variations in the laboratory set up contained different soil types, binders, binder contents, and curing times before the freeze-thaw cycles. The results show, that the strength increases with curing time in spite of the near zero temperature; but for one binder, a strength-over-time development with decrease after 90 days has been observed in the cold curing conditions in the experiments. In general, the strength gained during curing was reduced by freeze-thaw cycles. However, strength was regained during curing afterwards, and reached a higher level of strength than the original soil before stabilisation.