This dissertation presents an in-depth investigation into the performance of Engineered Water Repellent (EWR) soils for mitigating frost action, particularly in pavement subgrade applications. EWR involves the permanent bonding of soil particles with organosilanes (OS), a silica-based-organic_coupling agent that modifies the soil surface without forming bonding properties. This modification is achieved by replacing the -OH groups, which absorb water, with a stable alkyl siloxane. The study evaluates the ability of EWR-treated soils to withstand hydrostatic pressure, both-in_laboratory breakthrough tests and in the field through capillary rise from high water table. The research bridges the gap between laboratory tests and field applications by optimizing OS concentrations, EWR penetration and placement depth, and its water resistance for creating capillary breaks. Field evaluations were conducted at the MnROAD facility in Minnesota, where two test sections were constructed and monitored. In addition to performance testing, the research includes a comprehensive Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) of frost-resistant gravel road treatments and flexible pavements in Minnesota. The breakthrough pressure (BP) was measured using a modified water-ponding method combined with a triaxial setup and FlowTRAC system for precise volume and pressure control. BP was defined as the pressure at which 0.02 cc of water permeated the soil within one minute. The study evaluates the effects of sustained water pressure and key factors such as density, water-repellent treatment dosage concentration, confining pressure, loading rate, and duration on the water resistance behavior of EWR-treated samples. The impact of extreme environmental conditions, including repetitive loading, repeat wetting-drying, and inundation, on the durability and resistance of hydrophobic soils was assessed. Furthermore, six different soil types were analyzed using various approaches, including mixing at optimum moisture content (OMC) for compacted EWR lifts, and simulated field spraying (at 0.55, 0.33, and 0.22 OS liters/m² on untreated soils). The results were then used to design a capillary barrier system. A physics-based model was used to calculate the most effective EWR placement depth, positioned between the frost depth and the water table. Contact Angle (CA) tests were performed to determine the optimal OS dosage required for each soil. The study also evaluates the performance of EWR-treated samples under various environmental conditions, including air drying, cyclic wet-dry (W-D) cycles, and prolonged immersion, by assessing their unconfined compressive strength (UCS). X-ray scans were used to analyze porosity changes and internal pore structures after exposure to drastic environmental conditions. Two field test sections were constructed and instrumented at the MnROAD facility in Otsego, MN, where a commercially available organosilane was sprayed at three different depths at predetermined rates. These test cells were instrumented to monitor soil volumetric water content, temperature, suction, frost heave-thaw settlement, and pavement quality. The study also evaluated typical gravel roads (2-lane, 1-mile) and four frost-resistant alternatives using Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA). The scenarios included standard gravel (regraded), gravel with a macadam base, chemically stabilized roadstone, and two EWR treatments (spray and compacted). Primary data were collected from the County Engineering Office, with LCA modeling performed using the FHWA LCA PAVE tool, and economic impact was assessed via Net Present Value (NPV) following ISO 15686-5 standards. A similar study was conducted for the MnROAD test sections, evaluating the environmental and economic impacts of typical flexible pavement structures used in Minnesota, as well as three EWR-treated variants. The LCCA was performed using MnDOT's tool to calculate NPV, following ISO 15686-5 standards. The study revealed that soil densification and molding moisture content play significant roles in enhancing BP, increasing from 7.4 kPa to 21.25 kPa (a threefold increase) when comparing loosely (13.2 kN/m³) to densely (14.69 kN/m³) compacted soils. Additionally, as the fine content decreased from 100% to 63%, BP values dropped threefold. Confining pressure also significantly influenced BP, indicating changes in hydraulic conductivity and interparticle voids. The curing period was crucial, with BP increasing over seven days. The results showed that increasing the loading rate reduced BP, while increasing the time interval between loading steps significantly improved the soil’s resistance to water infiltration. After durability testing, BP values decreased due to microstructural changes and unused OS. UCS results showed that OS treatment reduced the optimum moisture content (OMC) while having minimal impact on maximum dry density (MDD). However, mechanical strength decreased as OS concentration increased, likely due to the organic moiety of the OS molecule (siloxane bond formation), which reduced compressive strength. Despite this, EWR-treated soils maintained structural integrity during extended immersion, with higher OS concentrations offering better resistance to W-D cycles. Over 120 days of soaking, both soils experienced strength reductions of up to 98% due to increased porosity and excess unbound OS. X-ray analysis confirmed volumetric changes correlated with water infiltration and pore expansion. While EWR enhanced moisture resistance, a reduction in mechanical strength was observed. CA test results showed that lower OS concentrations decreased CA values, but they remained above 90° (hydrophobic) for most soils at a 1:40 (OS: Soil) ratio. Sprayed CA tests showed penetration depths were generally limited to less than 2 mm for soils at OMC but increased to 4.2 mm for air-dried and 4.7 mm for oven-dried samples, indicating that drier conditions enhance OS penetration. BP testing, simulating field water pressures, revealed that higher OS concentrations (0.55 liters/m²) provided the greatest water resistance. However, limitations in penetration depth and molding solution volume pose challenges for field applications. The study concludes that while laboratory tests provide valuable insights into OS application efficiency, real-world conditions require adjustments to OS concentrations and application methods to achieve optimal hydrophobic performance. Field simulations showed that a 50% reduction in frost heave was achieved at a placement depth of 1.2 meters. Preliminary results indicated that treated sections experienced settlement and maintained consistent volumetric water content, while control sections showed measurable heave and full saturation. The study presents a methodology for utilizing EWR as an engineering solution for moisture migration mitigation within pavement structures alongside relevant field performance assessments. Gravel roads treated with chemical stabilizers emerged as the most sustainable and cost-effective option, with regrade being 45% more expensive and generating 47% more emissions. OS-related activities in EWR-treated gravel roads accounted for 13-20% of emissions and 34-49% of total costs. In the flexible pavement LCCA and LCA evaluation, the MnDOT Soil Replacement Method (SRM) with EWR showed a 23% reduction in global warming potential (GWP) compared to traditional SRM methods. OS-related activities accounted for 10% of the total emissions in EWR variants and 14% of the total costs, including excavation and granular material. For field applications, several questions remain, including optimizing OS to improve efficiency and reduce costs. Although OS-treated soils are expected to be non-leachable, further testing should include leaching experiments before and after activation. Drying time optimization for field applications should also be explored to ensure effective EWR treatment. Future studies should investigate combining EWR with other methods, such as wicking fabrics, to manage near-surface moisture content more effectively. Additional field tests across different soil types and environmental conditions are necessary to further validate the performance and application of EWR treatments.