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The durability, which refers to the ability of earthen structures to ensure their functionality over time while maintaining their required mechanical performance, is a key issue in evaluating the effectiveness of lime treatment. In this study, the effect of wetting-drying cycles on the compressibility and the microstructure was investigated with lime-treated/untreated samples considering the wetting fluid and the maximum aggregate size (S0.4, Dmax = 0.4 mm; S5, Dmax = 5 mm) effects. Results showed that the wetting-drying cycles caused an increase of void ratio and changed the bi-modal porosity to tri-modal characteristics for the untreated samples, while it led to a reversible variation of void ratio and an unchanged bi-modal pore size distribution characteristics for lime-treated samples, indicating the soil improvement by lime treatment. Thereby, the wetting-drying cycles made the compression curve of untreated samples change from convex to linear shape, while their effect was visible but not significant for the lime-treated soil. Higher decrease of macro-pore void ratio with loading was obtained on the lime-treated samples under wetting-drying cycles compared to the as-compacted samples, indicating a slight softening of soil structure by the wetting-drying cycles. Regarding the effect of wetting fluid nature, synthetic seawater resulted in a higher compressibility than deionised water. This was attributed to the presence of higher quantity of macro-pores in the samples wetted by synthetic seawater induced by the shrinkage of clay fraction. The aggregate size had slight effect on the compressibility of as-compacted samples due to their similar production of cementitious compounds and matric suction. Nevertheless, after wetting-drying cycles, the lime-treated samples S5 had lower decrease of macro-pore void ratio than the lime-treated samples S0.4, due to the significant reduction of macro-pore population with wetting-drying cycles.
•Lime treatment increased the soil resistance to wetting-drying (W/D) cycles.•The volume change with loading was related to the collapse of macro-pores.•W/D cycles led to higher reduction of macro-pores.•Synthetic seawater induced higher compressibility than deionised water.•After W/D cycles, specimens S0.4 had higher decrease of macro-pores than S5.