This research explores the innovative resilience and self-healing properties of engineered cementitious composites (ECC) reinforced with shape memory alloy (SMA) fibers, tailored for environments susceptible to saltinduced freeze-thaw damage from deicing salts, seawater, and saline soils. The study examines ECC composites enhanced with varying SMA fiber volumes 0 %, 0.5 %, 0.75 %, and 1 % and three fiber shapes linear, indented, and hook-shaped, with an additional sandblasting surface treatment. Systematic analyses of monotonic and cyclic flexural behavior, as well as self-healing efficacy, were performed across four distinct freeze-thaw cycles (0, 50, 100, and 150) within environments of fresh water and a 3.5 % NaCl solution. Digital Image Correlation (DIC) was employed to precisely monitor the self-healing performance. The results highlight substantial enhancements in SMA-ECC, particularly improved flexural strength by up to 35 %, 30 %, and 17 % for hook, indented, and linear fibers respectively in freshwater. These gains were slightly reduced under saltwater conditions to 32 %, 26 %, and 15 % respectively. Additionally, crack-closure efficiencies in significant self-healing with improvements of 45 %, 38 %, and 27 % for hook, indented, and linear fibers respectively. The Weibull probability distribution model was used to establish the damage evolution equation of the SMA-ECC in two freeze-thaw environments. The results of this study can serve as a reference for the development of freeze-thawresistant designs for SMA-ECC structures in future applications.

Extensive research has demonstrated that cement is one of the most effective materials for improving soil properties. Researchers have investigated cement-stabilized soil techniques from various perspectives, including microstructural evolution and mechanical performance. However, studies on cement-stabilized soils in seasonal frozen regions remain limited. This study thus explored the application of cement-stabilized soil in these regions, specifically examining the effects of freeze-thaw cycles on its microstructure and shear strength through scanning electron microscopy (SEM) and direct shear tests. The findings indicate that freeze-thaw cycles induce noticeable microcracks and pores, significantly increasing particle breakage and decomposition, which leads to a loose structure and severely compromises the soil's mechanical properties. Incorporating cement generates hydration products that form cementitious bonds between soil particles, significantly enhancing structural density and overall stability. This cement stabilization effectively mitigates the damage caused by freeze-thaw cycles, enabling the soil to maintain good shear strength even after such cycles. These findings underscore the importance of cement stabilization in improving soil performance under freeze-thaw conditions, providing a theoretical basis and technical support for foundation improvement in cold regions.

Weak soils pose significant challenges for civil engineering projects, particularly in cold regions. Stabilizing such soils with additives is a common practice to enhance their geotechnical properties. This research aimed to evaluate the durability of clayey soils stabilized by alkaline-activated kaolin at 10, 25, and 50 %, along with 10 % recycled cement kiln dust (CKD). The stabilization process involved curing the soils at different temperatures (40, 60, and 80 degrees C) for varying durations (1, 7, 14, and 28 days). The stabilized soils underwent 5, 10, and 20 freezethaw(F-T) cycles to evaluate their durability. The results indicated F-T cycling led to a reduction in the unconfined compressive strength (UCS) of unstabilized soils, with a more pronounced impact as the number of F-T cycles increased. However, this adverse effect was mitigated by additive stabilization. The improvement in UCS in stabilized soils was directly linked to the additive content, curing duration, and temperature. Both additives demonstrated superior resistance to F-T cycling, with CKD outperforming kaolin. Study findings provided guidelines for utilizing kaolin and CKD for earthwork applications in cold regions with economic and sustainability advantages.

Improving soft clay soil's mechanical properties and durability has been the subject of intense research. In this context, traditional stabilizers such as cement and lime have been introduced as the most widely used materials. However, the utilization of these conventional additives poses several challenges due to recent global concerns regarding the reduction of greenhouse gas emissions. Therefore, international research is shifting toward using environmentally friendly soil-stabilizing waste materials. This study, for the first time, evaluates the stabilization of kaolin clay soil using lime kiln dust (LKD) as a high CaO content waste pozzolan and volcanic ash (VA) as a natural pozzolan with considerable SiO2 2 and Al2O3 2 O 3 contents. In general, the research aims to demonstrate the effective performance of these two inexpensive and environmentally friendly additives in improving the mechanical characteristics and durability of kaolin clay soil, thereby providing the essential groundwork for the practical application of this method in stabilizing soft clay soil. This study included preparing samples with LKD at 3%, 5%, 7%, and 10% of the dry weight of clay and replacing LKD with VA at 0%, 25%, 75%, and 100%. The specimens were cured for 3, 7, and 28 days. Following the curing process, the optimal sample was subjected to varying numbers of freeze-thaw (F-T) cycles. The samples were examined by conducting a series of standard compaction, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) tests at different stages of adding stabilizers, as well as before and after exposure of F-T cycles. The findings revealed that adding LKD and VA increased the UCS by accelerating and improving the pozzolanic and hydration reactions. Also, the combination of LKD and VA in kaolin soil enhanced F-T durability, resulting in less strength deterioration even after 10 cycles, when compared to the untreated control sample. In particular, the optimal mixture containing 5% LKD and 25% VA replacement improved 11 times in UCS compared to untreated kaolin clay and showed a slight reduction of only 7% after 10 F-T cycles. Overall, the incorporation of LKD and VA enhanced the mechanical properties and F-T durability of kaolin clay soil, making it a low-cost, sustainable, and eco-friendly option for soil improvement.