Organosilane (OS) treatment has shown promise for mitigating geotechnical hazards such as frost heave by inducing hydrophobicity. However, its effectiveness under field-relevant in situ conditions, especially the influence of treatment method, is insufficiently understood. Motivated by a field implementation at the MnROAD Research Facility, where a spray application was adopted, this work investigates three soils when subjected to a spray treatment under laboratory conditions. Hydrophobicity was characterized by contact angle (CA) at varying depths within the soil profile and breakthrough pressure (BP) tests. Results showed that spray application led to hydrophobicity being confined to a finite near surface zone. Drying after treatment enhanced the measured CA response. Spray treatment led to relatively low BP values with the soil having the highest fine content, indicating that its fine pore structure restricted OS penetration and development of a hydrophobic barrier. Comparison with treatment where soils were compacted with OS showed that the latter had higher BP values. In this case, the soil with the largest fine content had the highest BP, indicating that once OS was distributed more uniformly, the fine pore structure became effective at restricting water entry. These findings demonstrate that the performance of hydrophobic soils depends strongly on treatment method and cannot be solely assessed based on surface properties.

The persistent degradation of soil stiffness and strength due to moisture fluctuations can be mitigated through Engineered Water Repellency (EWR). This technique alters the wettability of soils using organosilane (OS), modifying the soil surface without forming cementitious bonds. This study evaluates the performance of EWRtreated soils under varying environmental conditions, including air drying, wet-dry cycles, and prolonged immersion, by assessing the unconfined compressive strength (UCS) of two EWR-treated soils. The soils were treated with different OS concentrations and subjected to up to 120 days of immersion and 21 wet-dry cycles. The UCS of treated samples was measured as the hydrophobicity of the EWR soils developed during drying. X-ray CT scans were used to analyze porosity changes and internal pore structures post-exposure to the varying environmental conditions. The results showed that OS treatment reduced the optimum moisture content while having minimal impact on maximum dry unit weight. However, mechanical strength decreased as OS concentration increased, attributed to the organic moiety of the OS molecule siloxane bond formation, which reduced compressive strength. However, EWR-treated soils maintained their structural integrity during extended water immersion, with higher OS concentrations offering better resistance to wet-dry cycles. Over 120 days of soaking, EWR-treated soils experienced strength reductions due to increased porosity and excess unbound OS. These findings contribute to a deeper understanding of hydrophobic soils, providing valuable insights into the mechanical strength of EWR soils and enhancing the feasibility of applying this technology for subgrade modification.

Silane can be effective in limiting freeze-thaw impact on pavement systems as it creates water-repellent properties in the substrate and can limit the water ingression to subgrade soil. While primary frost heave stems from the phase change of pore water to ice, secondary frost heave is induced by continuous water flow from the vadose zone towards growing ice lenses. Consequently, limiting the influx of water from the vadose zone could be the most efficient approach to mitigate the detrimental effects of freeze-thaw cycles on subgrade soils. This study aims to minimize the freeze-thaw effects by treating subgrade soils with silanes. Two frost susceptible soils from Iowa (IA-PC and IA-KC) were sprayed with two different dosages (1.6 L/m2 and 3.2 L/m2) of silanes, and spraying was employed at multiple depths within the specimens. One-dimensional frost heave tests were conducted, and frost heave potential was measured in terms of water intake, total frost heave, heave rate, and soil water content. The silane treatment resulted in a reduction in frost heave, ranging between 57 % and 80 %. The heave rate for the untreated IA-PC specimen was 4.3 mm/day, which decreased to 0.4 mm/day with a two-layer spray treatment using a silane concentration of 1.6 L/m2. Increasing the number of silane-sprayed layers was more effective than increasing the silane concentration to limit water ingress and enhance the freeze-thaw resistance of the subgrade soil.

Engineered water repellency (EWR) using organosilanes provides a promising approach for mitigating frost heave by preventing ice lens formation. This study evaluates the environmental and economic impacts of typical flexible pavement structures used in Minnesota, as well as three EWR-treated variants. Primary data for the life cycle assessment (LCA) were collected from the Minnesota Department of Transportation (MnDOT) and Minnesota Road Research Facility and analyzed with the Federal Highway Administration LCA PAVE tool. The life cycle cost analysis (LCCA) was performed with the MnDOT tool to calculate the net present value per the ISO 15686-5 standard. The MnDOT soil replacement method (SRM) with EWR emerged as the most sustainable and cost-effective, showing a 23% reduction in global warming potential compared with the traditional SRM. The primary sources of emissions and expenses were hot mix asphalt activities, accounting for 58%–71% of the total. The LCA contributed less than 8% to the overall integrated cost, underscoring the predominance of LCCA in decision-making. Further field evaluations are recommended to confirm the long-term performance of EWR technologies and to optimize their integration into pavement design.

Freeze–thaw cycles significantly affect soil behavior, leading to pavement failures and infrastructure damage, especially in seasonally freezing regions. The application of road salt for deicing operations introduces high salt concentrations into soils, which can alter their physical properties. Salt in soils affects their freezing point, moisture migration, and overall freeze–thaw behavior. This study investigates the effects of varying sodium chloride (NaCl) concentrations on sandy soil using both the ASTM and low-temperature-gradient methods to simulate different freezing protocols. The methodology involved subjecting soil specimens with 0%, 0.2%, 1%, and 5% salt concentrations to freeze–thaw cycles and measuring parameters such as heave rate, maximum heave, water intake, moisture content, and salt migration. The results revealed that increasing salt concentration leads to a reduction in the freezing point, with the 5% NaCl concentration showing the most significant depression at 2.96°C. The heave rate and maximum heave decreased with higher salt concentrations: the 5% NaCl concentration reduced the heave rate to 11.3 mm/day (ASTM method) and 1.5 mm/day (low-temperature-gradient method) from 22.5 mm/day (ASTM method) and 17.2 mm/day (low-temperature-gradient method) in control. Salt migration analysis indicated more variability in salt distribution within the soil profile under the low-temperature-gradient method, especially at higher salt concentrations. This variability is linked to osmotic suction effects, which retain more water within the soil matrix during freeze–thaw cycles. The study highlights the importance of considering both salinity and freezing protocols in understanding soil behavior under freeze–thaw conditions.

Engineered water repellency (EWR) is a soil improvement method that involves intentionally modifying natural soil to become hydrophobic. Potential applications of EWR include landfill covers, frost mitigation, and moisture control in pavement systems. Designing with EWR requires knowledge of water entry pressure (WEP) and its relationship to pore size and contact angle for a given soil. In this study, a commercial grade organosilane (OS) was examined using a new methodology to establish the WEP. Soil specimens were placed in a triaxial-type cell and tested with a step-wise pressure profile from 0.7 to 117 kPa. The results indicate that for a given dosage, a relatively higher density yields the least water infiltration and a larger WEP. The maximum dry density (e.g., 95% of standard proctor effort) should be specified for field application.

Expansive soils, characterized by large deformations due to clay mineral swelling, pose persistent challenges for geotechnical and foundation engineers. These movements can continue for years, raising concerns for project owners. Moisture control is vital, as moisture triggers swelling and shrinkage in these soils. To address this issue, engineered water repellency (EWR) is proposed as an innovative solution. EWR involves making soils hydrophobic using organosilanes (OS), which keeps the soil at a stable moisture content year-round. In this study, a highly expansive clay was treated with OS at a 1:10 ratio (OS:soil by weight). The treatment significantly reduced expansive properties (soil plasticity and swelling), and a 75% increase in unconfined compressive strength after seven days. This approach offers a promising alternative for mitigating expansive soil issues, providing engineers and designers with an effective tool to address this challenging geotechnical problem.

The recurring challenge of soil stiffness and strength reduction, arising from fluctuations in soil moisture, finds a promising solution in engineered water repellency (EWR). Engineered water repellency involves the transformation of in situ soil into a hydrophobic state, using organosilane (OS), which modifies the soil surface without creating cementitious bonding. This study delves into the mechanical strength of two distinct EWR-treated soil samples, subjected to wet-dry cycles simulating moisture variations. Strength determination was carried out using unconfined compressive strength (UCS) testing at a 1% per minute strain rate. A comparative evaluation was also conducted on untreated soil samples with varying moisture content. The results showed that EWR-treated samples exhibited minimal water absorption, averaging less than 4 g per cycle, and endured only a 38% decline in unconfined compressive strength after 12 cycles. In contrast, untreated samples experienced substantial strength fluctuations, reaching 73%, owing to the inherent variability in moisture levels.

The extent to which hydrophobic soils can be used in geotechnical engineering practice depends upon a commensurately increased understanding of how fundamental relationships apply in hydrophobic systems, such as moisture-density. This research is to determine the compaction characteristics of organo-silane (OS) treated soils using conventional geotechnical laboratory equipment. The intrinsic difficulty in lubricating hydrophobic soils, which would allow for rearrangement of particles and subsequent compaction, arises from their inherent low surface energy. This work describes a method for compacting OS treated soils that leverages the necessary conditions such as reaction time and drying conditions for achieving hydrophobicity. Procedural steps for compacting OS treated soils are detailed by making use of a water-soluble hydrophobizing agent added to a fine-grained soil. Based on the critical dosage ratio of 1:100 (hydrophobizing agent: soil) identified, a molding water content is defined constituting of a fraction of the hydrophobizing agent. Soil water content and dry density curves are developed using the standard Proctor and Harvard miniature to contrast the resulting effect of OS. Compared to the untreated soil, a decrease in optimum water content was observed with the OS treated soil regardless of compaction technique used. For the standard Proctor test, a decrease in optimum water content from 12.0 to 9.2 % was observed, whereas compaction with the Harvard miniature showed a marginal decrease from 9.3 to 9.0 %. With the untreated soil, a relatively larger maximum dry density (2.17 g/cm3) was obtained with the standard Proctor compared to the Harvard miniature (2.05 g/cm3). The protocol defined to compact OS treated soils has shown to induce hydrophobicity spatially within the sample depth. These results suggest that engineered water repellency can be implemented in so far as treatment and compaction are largely synchronous and prior to reaction and hydrophobization.

The occurrence of freeze-thaw cycles within the soil can result in adverse consequences such as frost heaving and a reduction in stiffness during thawing. The freezing behavior and subsequent thaw-weakening of soils can be influenced by the salt concentration in soils, which is affected due to road deicing operations during the winter. The presence of salt concentrations in soils induces a phenomenon known as freezing point depression, resulting in a decrease in the formation of ice within the soil. Concurrently, an elevated concentration of salt triggers osmotic suction as a result of the expulsion of ions towards the freezing front during the process of ice formation. These two phenomena can potentially result in either a decrease or an increase in the vulnerability of soils to frost action. The present study aims to examine the influence of varying salt concentrations on the freeze-thaw susceptibility of soil. The soil samples were treated with various salt concentrations, including 0.2%, 1%, and 5% NaCl solutions, as well as a control prepared with deionized water. The experiment involved determining the freezing point depression resulting from the presence of salt, and it was observed that the degree of depression increased in proportion to the concentration of salt. The specimens underwent a freeze-thaw test in a one-dimensional manner. During the experiment, measurements were taken for heave, temperature, and water intake. Additionally, the moisture content of the specimen was determined at various depths following the freeze-thaw test. In order to comprehend the distribution of salt within the specimen following a freeze-thaw cycle, the salt concentration of the specimens was assessed at various depths. This was achieved by measuring the electrical conductivity of pore water using a 1:5 soil-to-water extraction method. The findings indicated that the freezing point depression exerted a greater influence compared to osmotic suction, resulting in a decrease in the formation of ice within soils. The specimens treated with salt exhibited a reduction in the heave of up to 31% when compared to the control prepared with deionized water, due to lower ice segregation. Large variations in moisture content and salt concentration were observed between different specimens and along the specimen height after the freeze-thaw test. It can be concluded that freezing point depression has a greater influence over osmotic suction at above salt concentrations during freeze-thaw. Hence, the presence of salt can aid in the mitigation of freeze-thaw damage in soils.

Frost action in soils causes a significant effect on the performance of roadways. This effect is more pronounced in the regions that are experiencing seasonal subfreezing temperatures as the soil undergoes multiple freeze-thaw cycles. Apart from the subfreezing temperature, the frost action is also affected by the soil type as the void ratio and hydraulic conductivity of soils control the presence and movement of water for the growth of ice lenses. Frost heave is mainly attributed to silty soils, but significant frost heave can also occur in clay and sandy soils under favorable environmental conditions. For the present study, frost heave and thaw settlement of clayey and sandy soils, subjected to a one-dimensional freeze-thaw cycle, is investigated to determine how the frost action varies with soil types. Soil specimens were subjected to ten freeze-thaw cycles. Total heaving, heave rate, and water intake were measured as a function of time during testing. The moisture content of the soils after ten freeze-thaw cycles was also measured. The amount of pore water and external water supply affects the total heave during freeze-thaw cycles. Therefore, the effect of moisture availability during the freeze-thaw cycles was also investigated by comparing the results of specimens with or without an external water supply. Results of the study suggested that significant frost heave occurred in both clay and sandy soils. In addition, the application of ten freeze-thaw cycles provided a better estimation of the total heave than that observed with two freeze-thaw cycles (typical/standard numbers of freeze-thaw cycles). The maximum heave (40.9 mm) and heave rate (5.01 mm/day) were found to be higher in clay soil. The presence of an external water supply contributed to the frost action, and total heave was seven times higher in soils with an external water source. Soil with a free water supply showed 1.1-1.7 times higher moisture content after ten cycles compared to the soils with no external water supply. These results were used in estimating the frost heave potential of soils in different environmental conditions.

In cold regions, the soil temperature gradient and depth of frost penetration can significantly affect roadway performance because of frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil index properties, temperature, and availability of water. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous flow of water from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration toward the freezing front, where ice nucleates, coalesces into lenses, and grows. This study evaluates the frost heave potential of frost-susceptible soils from Iowa (IA-PC) and North Carolina (NC-BO) under different temperature gradients. One-dimensional frost heave tests were conducted with a free water supply under three different temperature gradients of 0.26°C/cm, 0.52°C/cm, and 0.78°C/cm. Time-dependent measurements of frost penetration, water intake, and frost heave were carried out. Results of the study suggested that frost heave and water intake are functions of the temperature gradient within the soil. A lower temperature gradient of 0.26°C/cm leads to the maximum total heave of 18.28 mm (IA-PC) and 38.27 mm (NC-BO) for extended periods of freezing. The maximum frost penetration rate of 16.47 mm/hour was observed for a higher temperature gradient of 0.78°C/cm and soil with higher thermal diffusivity of 0.684 mm2/s. The results of this study can be used to validate numerical models and develop engineered solutions that prevent frost damage.

In this work, the mechanical properties of three frost susceptible soils are investigated after treatment with organosilanes (OS). Compaction and strength characteristics tests are carried out on treated and untreated samples by means of a Harvard miniature compaction apparatus and a pocket penetrometer, respectively. The soils were treated with TerraSil, initially diluted at a ratio of 1:100 (OS:water) batched gravimetrically. It was determined that there was an overall decrease in optimum moisture content (from 1.07% to 2.26%) with samples treated with TerraSil. The influence on density varied with soil type, with modest increases (from 1,776 kg/m3 to 1,808 kg/m3) for one soil (Keokuk County) with a measurable plasticity index. The penetrometer results showed similar trends for the treated and untreated samples. The treated samples had slightly lower compressive strength overall. The most significant strength decrease (from untreated to treated for the same moisture content) for Ashe County was from 5 kg/cm2 to 3.167 kg/cm2, Hanover from 5 kg/cm2 to 4.5 kg/cm2, and Keokuk County from 2.75 kg/cm2 to 2 kg/cm2. These results are expected to be useful for engineering applications of TerraSil.

Airport pavements are subjected to high-impact loads, and conventional design wisdom prescribes pavement thicknesses utilizing the lowest modulus obtainable for subgrade soil over a given wet-dry cycle. This is due to variations in strain, stress, deformation, and reduction in strength when subjected to moisture changes. By engineering water repellency in pavement soils, moisture conditions can be kept fairly uniform, allowing for easier design, reducing speculation of performance, and saving material and construction costs. Temperature and water content measurements were obtained from soil obtained from the Charlotte Douglas International Airport treated with organosilane and compared with untreated soil under varying moisture conditions. Results show a reduction in moisture content as well as variations in the treated soil sample compared to the untreated sample. Samples were exposed to two winter storm events, and a maximum heave of similar to 6 mm was measured for the untreated soil, while the treated soil sample did not heave.

Frost heave creates systemic failures in roadways, buried pipelines, and cold storage facilities across the United States and around the world. Significant frost heaving may occur when the following three conditions are met: (1) there are sustained freezing conditions, (2) the soil is frost-susceptible (typically silt-sized), and (3) there is access to water. Under these conditions and depending on the temperature gradient pore water freezes into ice lenses that grow in the direction of heat loss, causing heave. When the temperature increases during the spring season, the ice melts inducing thaw settlement and causing a reduction in soil strength. The nature and extent of frost heave vary according to the availability of water, pore fluid composition, rate of heat loss, and soil type. Similarly, soil properties influence the rate at which water is attracted to a growing ice lens and the temperature at which ice formation occurs. Laboratory tests can discern the significance of freezing intensity and duration as well as soil properties, including mineralogy, grainsize distribution, and pore fluid. As part of a larger nationwide project, the current study evaluates the frost heave potential of soils collected from Alaska, Iowa, and North Carolina. Cylindrical soil samples were given free access to water and subjected to two freeze-thaw cycles. Total heaving, heave rate, temperature profile, frost penetration depth, and its rate were measured as a function of time. Water intake during testing was also measured. The results of the study showed that amount of silt and clay content in the soil have a direct effect on the frost heave phenomenon. Soils that have higher silt content and less clay content had higher heaving. It was determined that all the soils were highly frost susceptible and had high-heave rates up to 28.4 mm/day. The maximum frost penetration depth and frost penetration rate were 114 mm and 260 mm/day, respectively.

Frost action (heaving and thawing) is a perennial problem encountered in the design, construction, and management of civil engineering structures, particularly road pavements in cold regions and areas that experience seasonal sub-freezing temperatures. This paper reviews the existing methods for frost heave mitigation and proposes an innovative approach through engineered water repellency. Soil was collected from a test plot at the Charlotte Douglas International Airport and treated with a commercially available organosilane. Preliminary results indicate an increase in the maximum dry density from 17.54 kN/m(3) to 17.66 kN/m(3) and a decrease in the optimum moisture content from 17.36% to 11.75% after treatment. Data obtained from performance tests carried out under sub-freezing weather conditions indicated that the treatment was effective in limiting the infiltration and migration of water into the soil matrix when compared with the untreated soil. As such, engineered water repellency may be a viable solution for airports and Departments of Transportation seeking methods to mitigate frost action.

The presence of frost susceptible soils makes the design, construction, and maintenance of geostructural systems such as pavement difficult. This pronounced in areas that experience seasonally cold weather characterized by freezing sub-zero temperatures. An innovative approach in mitigation is to render frost susceptible soils hydrophobic. This is achieved by treating soils with cost-effective and environmentally compatible polymers in a process that makes them water repellent (Engineered Water Repellency). This paper investigates the treatment of selected frost susceptible soils using commercially available chemicals (ATS-100, Terrasil, DOWSIL IE6683) at varying concentration dosages. The degree of hydrophobicity imparted, and performance was determined using contact angle measurements and Water Drop Penetration Tests. Treatment using ATS-100 and Terrasil were found to be effective even at small concentrations with values ranging from 73 degrees to 144 degrees for ATS-100 and from 103 degrees to 145 degrees for Terrasil. Effective values for DOWSIL IE6683 were obtained at a ratio of 1:10.

Organo-silane (OS) modification has been shown experimentally to render soil water repellent. Engineered water repellency has the potential for widespread use in geotechnical and geoenvironmental applications. One such application is mitigating the effects of frost action in susceptible subgrade soils, particularly for unbound, unsurfaced roads. As part of a larger project to evaluate the feasibility of post-construction treatment of such roads, testing was performed with two commercially available OS products at varying dosages. This paper summarizes experimentally observed relationships between treatment, apparent contact angle, and water entry head for four samples of frost-susceptible soil collected from different regions across Iowa. Soil water characteristic curves were used to estimate the prevailing pore size and to relate that to water entry head for a given sample. Modification with two different OS chemicals yielded apparent contact angles between 119 degrees and 143 degrees. The water entry head was determined to range from 15 to 63 cm of water. Inverse relationships were observed between average pore radius and water entry head. These results are expected to be useful to agencies interested in evaluating engineered water repellency for use in new construction as well as rehabilitation of existing infrastructure underlain by frost susceptible soils.

Engineered water repellency has the potential to mitigate frost heave in geotechnical systems such as roads and foundations. Models can be used to inform design approaches and predict performance; the literature is replete with general models of frost action. There are comparatively fewer reports on how to practically incorporate the effect of mineral surfaces, pore fluid composition, and engineered water repellency into thermo-hydro-mechanical-chemical (THMC) models. An aspect of such models involves describing the state of pore fluid in the frozen fringe and unfrozen soil beneath an impinging freezing front and growing ice lens. Capillary and osmotic gradients are created as ice formation reduces moisture content while increasing the concentration of ions in the remaining unfrozen pore fluid. The work reported here is part of a larger effort to quantify the relative role of osmotic and matric potential on frost heaving, while exploring the use of organosilanes to mitigate ice lens formation and growth. As a precursor to incorporating the broader array of physicochemical processes in frost action, this paper reviews the sensitivity of unsaturated flow to changes in contact angle. Unsaturated flow gradients are created in response to simulated matric, osmotic, and cryogenic suction within a two-dimensional model. Results indicate that an increased contact angle results in a reduction in unsaturated flow, regardless of induced gradient.