Macro and microscopic characteristics of soft soil stabilized by Portland cement-soda residue under dry-wet cycling

The durability of soft soil stabilized by Portland cement-soda residue (PC-SR) subjected to dry-wet cycles remains relatively unclear now despite previous studies have extensively examined the engineering attributes of soft soil stabilized by PC-SR. Therefore, this study delineates the impacts of dry-wet cycles on the macro and micro features of soft soil stabilized by PC-SR. Based on the orthogonal test design, the unconfined compressive tests, X-ray diffraction test, scanning electron microscopy, and mercury intrusion porosimetry tests were conducted to analyze the impact of dry-wet cycles on the strength, mineral components and microstructural characteristics of stabilized soil cured for 28 days. The experimental findings revealed that the strength of soil stabilized by PC-SR initially ascends and subsequently declines after dry-wet cycles. At the microscale, the tests showed that the dry-wet cycles transform the microstructure of stabilized soil by damaging the cementation among soil particles, expanding the pore diameter, and forming macropores and fissures. Combined with macro and micro results, it is shown that in the initial stage of the dry-wet cycle, the continuous hydration reaction promotes the increase of the microstructure density of solidified soil. However, under the continuous influence of the dry-wet cycle, the dissolution and expansion of mineral components lead to the degradation of the microstructure, which leads to the decline of the macro strength of the stabilized soil, further revealing the mechanism of the macro strength of the stabilized soil rising first and then decreasing. This study showed that Portland cement-soda residue treatment was efficient to prevent the deterioration from the dry-wet cycles.