Abstract
This dissertation, stemming from a substantial research endeavor funded by the U.S. National Science Foundation (Award #1928813), stands as an essential exploration of Engineered Water Repellency (EWR) in mitigating frost heave. Combining laboratory experiments, field investigations, and numerical analyses, this interdisciplinary study aims to disentangle the impact of matric and osmotic potentials on this phenomenon, marking a significant leap in our comprehension of frost heave mechanisms. Frost-susceptible soils (FSS) present challenges in construction due to their dynamic thermal and mechanical properties. The detrimental effects of frost heave on infrastructure, particularly road pavements, prompt immense costs—over two billion US dollars annually—attributed to recurrent maintenance and structural damage. Extensive research, from as early as the 17th century, has grappled with the complexities of frost heaving, highlighting the transport of moisture to freezing fronts as a key factor. While prevailing studies have centered on matric effects, the influence of solutes on ice lensing has been noted, underscoring the need for further investigation. Engineered Water Repellency (EWR) emerges as a promising solution. By treating soils with environmentally compatible polymers, the transport of water through frost-susceptible soils can be limited, offering a viable alternative to combat frost action. Experimental assessments revealed that increasing EWR treatment led to higher hydrophobicity, with contact angles surpassing 110° and Water Drop Penetration Test times exceeding 3600 seconds. However, optimal treatment concentrations varied by organosilane, demonstrating plateauing trends in hydrophobicity. Exploration of grain size effects on water-repellent soils showcased reduced contact angles with increasing grain size, influencing the effectiveness of treatment. This indicated the necessity of considering soil properties for successful implementation in infrastructure. Further analyses unveiled the impact of salt concentrations on EWR treatment efficacy. Salts, common in cold regions for road maintenance, proved to diminish the water-repellent properties, requiring careful consideration in treatment strategies. The interplay between water repellency and hygroscopicity highlighted treatment dosage, drying conditions, and soil properties as crucial factors. While silanes and siloxanes limit moisture absorption, they don’t eradicate it, emphasizing the complexity of soil performance. Evaluation of breakthrough pressure in water-repellent soils offered insights for using these materials as moisture barriers in construction. Automated tests indicated that treated soils could sustain hydrostatic heads of up to 36kPa. Frost heave mitigation, using EWR treatment, was proven effective even after multiple freeze-thaw cycles. A systematic exploration of osmotic potential in freezing soils paved the way for a refined understanding of freezing soil processes, shedding light on factors influencing water migration and frost heave. This dissertation serves as a milestone in comprehending frost heave mechanisms and the potential of EWR treatment in geotechnical applications. The comprehensive exploration of soil treatment, the impact of soil properties, and the complexities of water repellency underpin a promising avenue for addressing frost heave challenges in construction and infrastructure.