Building structures located in saline soil areas are more vulnerable to damage due to the combined effects of loading and sulfate erosion. Polypropylene fibers lithium slag concrete (PFLSC) exhibits good corrosion resistance, which can mitigate damage to building structures in saline soil areas. However, the eccentric compression behavior of PFLSC columns under sulfate erosion and external loading remains unclear. Therefore, in this study, an eccentric compression test was conducted on 10 PFLSC columns after exposure to combined sulfate erosion and external loading, with corrosion time and stress ratio as the research variables. The failure modes, load-displacement curves, failure loads, and strains of rebars were investigated. The results indicate that polypropylene fibers and lithium slag can effectively inhibit the corrosive effects of sulfates and significantly enhance the ductility and ultimate axial capacity of the specimens. Additionally, taking into account the prior load levels and the damage caused by sulfates to the concrete, a damage factor has been introduced to determine the strength of the concrete after undergoing loads and sulfate exposure. Ultimately, a model has been proposed to calculate the ultimate axial capacity of PFLSC columns under the coupled effects of loads and sulfuric acid. The calculated results showed excellent agreement with the corresponding experimental results. It provides reliable guidance for the durability design of PFLSC columns.

Freeze-thaw cycling is a critical issue in cold-climate engineering because these cycles impact the mechanical properties of soils due to the translocation of water and ice at temperatures near 0 degrees C. Reinforcement methods have been developed to decrease these adverse effects, including the use of polypropylene (PP) fibers. However, few macrostructural investigations have been able to demonstrate the underlying physical basis for their effectiveness. This study used computed tomography (CT) images of clay samples reinforced with 2% PP fibers and subjected to unconfined compression and Brazilian tests before and after up to 10 closed-system freeze-thaw cycles (FTCs). Significant effects of the FTCs on soil structure include a reduction in macropores and an increase in mesopores. The addition of PP fibers reduces this change in the number of macropores from 28% to 18% following 10 FTCs. Unreinforced samples also show more localized propagation of shear/tensile cracks during tests than reinforced samples as a result of having a higher failure strength and ductility. The bridging effect of fibers, deviation of the failure path, and formation of microcracks around fibers are clearly illustrated in the CT images. This study provides significant insights relevant to engineering design in cold regions.

Adding fibers into cement to form fiber-reinforced soil cement material can effectively enhance its physical and mechanical properties. In order to investigate the effect of fiber type and dosage on the strength of fiber-reinforced soil cement, polypropylene fibers (PPFs), polyvinyl alcohol fibers (PVAFs), and glass fibers (GFs) were blended according to the mass fraction of the mixture of cement and dry soil (0.5%, 1%, 1.5%, and 2%). Unconfined compressive strength tests, split tensile strength tests, scanning electron microscopy (SEM) tests, and mercury intrusion porosimetry (MIP) pore structure analysis tests were conducted. The results indicated that the unconfined compressive strength of the three types of fiber-reinforced soil cement peaked at a fiber dosage of 0.5%, registering 26.72 MPa, 27.49 MPa, and 27.67 MPa, respectively. The split tensile strength of all three fiber-reinforced soil cement variants reached their maximum at a 1.5% fiber dosage, recording 2.29 MPa, 2.34 MPa, and 2.27 MPa, respectively. The predominant pore sizes in all three fiber-reinforced soil cement specimens ranged from 10 nm to 100 nm. Furthermore, analysis from the perspective of energy evolution revealed that a moderate fiber dosage can minimize energy loss. This paper demonstrates that the unconfined compressive strength test, split tensile strength test, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) pore structure analysis offer theoretical underpinnings for the utilization of fiber-reinforced soil cement in helical pile core stiffening and broader engineering applications.