Freezing Tests Research Articles

Characterization and impact analysis of freezing and expansion disease of roadbed in seasonal freezing zone: A case of heavy railroads

The freezing and expansion diseases of railroad roadbeds are prevalent in areas that experience seasonal freezing. This study aims to investigate the features of the freezing and expansion mechanism of seasonal frozen railroad roadbeds and the effects of the freezing and expansion diseases on the roadbeds. This article presents a study of the Shuo-Huang Heavy Duty Railway. Initially, on-site monitoring tests were conducted to analyze the roadbed temperature, water content and deformations due to freezing. Through these tests, the pattern of development of the roadbed freezing and swelling was understood, and the effect of this on the vibration response of the roadbed was investigated. Subsequently, load-free freezing tests were performed to investigate the freezing and expansion features of the roadbed. Through on-site monitoring, it has been determined that the seasonal freezing layer is approximately 0.5 ​m deep. The depth of the frozen expansion on both sides of the road shows clear differences. The frozen and expansion disease significantly amplifies the vibration acceleration of the roadbed, with a tendency towards low-frequency and high-amplitude vibrations. Through indoor testing, we compared the deformation of frozen specimens and their final freeze and expansion rates at different cold-end temperatures and various initial moisture content levels. We find that the initial moisture content has a greater impact on specimen freezing and expansion. The findings in this paper can be used as a reference for researching and addressing roadbed freezing and expansion problems.

Durability of antireflective SiO2 coatings with closed pore structure

The use of antireflective coatings to increase the transmittance of the cover glass is a central aspect of achieving high efficiencies for solar collectors and photovoltaics alike. Considering an expected lifetime of 20–30 years for solar energy installations, the durability of the antireflective surfaces is essential. Here, a novel antireflective SiO2 coating with a hexagonally ordered closed pore structure, produced with an aerosol-based sol-gel method is benchmarked against two commercial coatings; produced with acid etching and sol-gel roll coating. The optical and mechanical properties together with contact angle characteristics were evaluated before and after various durability tests, including climate chamber tests, outdoor exposure, and abrasion. Compared to the commercial antireflective coatings with open pore structures, the novel coating performed in parity, or better, in all tests. Based on the results of humidity freeze and industrial climate chamber tests, it appears that the coating with closed pore structure has a better ability to prevent water adsorption. Additionally, the closed pore structure of the coating seems to minimize the accumulation of dirt and deposits. The abrasion and cleanability test further confirm the advantages of a closed pore structure, showcasing the coating's mechanical durability. While the coatings exhibit similar hardness and reduced elastic modulus, the closed pore coating proves to be even harder after undergoing the industrial climate chamber test, but also slightly more brittle, as indicated by the probability of crack initiation. In summary the closed pore structure is well suited for tempered and arid climates, making it a truly competitive alternative to existing antireflective coatings.

Effects of Microencapsulated Phase Change Material on the Behavior of Silty Soil Subjected to Freeze–Thaw Cycles

Freeze–thaw (F-T) cycles are one of the most important factors affecting the performance of silty soils with high kaolin content in seasonally freezing regions. This study investigates the improvement of a high-plasticity clayey silt soil (MH) with microencapsulated phase change material (mPCM) to prevent changes in mechanical properties when subjected to freeze–thaw cycles. Unconfined compression, one-dimensional compression, and freeze and thaw tests were performed to evaluate the behavior of treated soil under different freeze/thaw cycles and with different mPCM ratios. It has been observed that the mPCM additive decreased the unconfined compression strength (UCS); however, the strength of the soil held constant during the increasing F-T cycles, and the increase in the mPCM additive content increased the strength of the soil. The inclusion of mPCM affected the compression of the soil and increased settlement (∆H), although the settlement remained constant with increasing freeze–thaw cycles. It has been noted that the compression behavior, which is least affected by the unconfined compressive strength and freeze/thaw cycles, is achieved with the addition of 10% mPCM. As a result of the tests, it was determined that the most suitable additive mPCM ratio is 10% for the compression and strength behaviors.

Understanding unsaturated sulfate saline soil in cold regions: A comprehensive hydraulic–thermal–air–salt–mechanical model with experimental research

The destruction of infrastructure built on saline soil in cold regions is closely related to water and salt migration, and soil deformation in foundations. Consequently, it is imperative to understand the mechanisms of heat and mass transfer, along with deformation in saline soil. Based on the unsaturated soil mechanics and porous media theory, a hydraulic–thermal–air–salt–mechanical (HTASM) coupled mathematical model for frozen unsaturated sulfate saline soil is proposed. The model incorporates the impact of ice-water phase change, sodium sulfate crystallization, and vapor flow on heat and mass transfer during the freezing process. Two parameters—salt crystallization pressure, and ice pressure—are introduced into the mechanical control equation to capture the effects of phase change on deformation. In addition, the relationship between the density of soil particles, water, ice and gas, and temperature and pressure is considered to reflect the dynamic change of density during freezing. Finally, the numerical simulation using the HTASM model is conducted and its efficacy is validated by comparing the numerical results with those obtained from indoor unidirectional freezing tests. The coupling effect of the HTASM model is revealed by analyzing the dynamic changes of temperature, water content, salt content, vapor flux and crystallization pressure in the soil column during freezing. The results show that the proposed HTASM model can well simulate the heat and mass transfer behavior in freezing unsaturated sulfate saline soil.

Investigation on the frost heave-induced pressure and hydro-thermal processes in freezing soil under rigid constraint and hydraulic pressure

Frost damage in engineering is closely related to hydraulic pressure in artificial freezing ground areas and cold regions; however, limited studies have focused on this relationship. To clarify the evolution of frost heave-induced pressure (FHIP) and its effect on engineering stability, unidirectional freezing tests are performed under rigid constraint and various hydraulic pressures. The results indicate that the development of the FHIP is induced by ice growth. Meanwhile, the FHIP increases with hydraulic pressure, which consequently increases the pore water pressure (PWP) at the base of the warmest ice lens. When the PWP on both sides of the frozen fringe reaches equilibrium, the water stops migrating, ice stops growing, and FHIP stops increasing. The frozen fringe is captured via X-ray computed tomography, and a model for calculating the maximum FHIP is developed based on the frozen fringe theory. The model is validated and compared with the experimental results. The increased FHIP prevents water migration in freezing soil by increasing the soil density and decreasing the segregation temperature of the frozen fringe. Additionally, the factors contributing to the increase in FHIP are discussed, and an application of this study to engineering design and maintenance in cold regions is proposed.

Water and salt migration characterization in NaHCO3 saline soils during unidirectional freezing conditions

In cold regions, the eutectic action of the NaHCO3-H2O binary system during the freezing process affects the migration of water and salt in NaHCO3 saline soils. This study aims to investigate the migration of water and salt in open and closed systems, utilizing unidirectional freezing tests with different salt contents. By considering the phase diagram of pore solution and phase transition theory, two phase-change paths can be observed in NaHCO3 saline soils during freezing. These paths result in different migration patterns for water and salt, depending on the salt and water content conditions of the samples. The theoretical and experimental results both validate that water migrates from the unfrozen zone towards the eutectic action and ice crystallization zone during the freezing process. Under low-salinity conditions, salt migrates from the ice crystallization zone towards the eutectic action and unfrozen zone. Conversely, under high-salinity conditions, salt migrates from the unfrozen zone towards the eutectic action. Moreover, it is observed that a high salt content hinders water migration.

Freezing front evolution in chloride soils under unidirectional freezing conditions and the characterization via electrical conductivity

Frozen wall thickness (FWT) is an essential index to determine the freezing process in artificial ground freezing (AGF) project. Empirical equations based on soil temperature are typically used to estimate FWT. However, the error resulting from estimation can be excessively large, partly due to a lack of consideration of soluble salt content effects. In this paper, open-system unidirectional freezing tests were conducted on silty clay with various chloride salt contents (0%, 0.5%, 1%, and 2%) to measure the freezing front propagation and the variation of bulk electrical conductivity (σb) simultaneously. The results indicate that the freezing front develops fast in high salt content specimens and stabilizes within a short time, because the thermal conductivity of silty clay with higher salt content is larger at the initial freezing temperature. The freezing front evolution was modeled considering the effect of salt content. The results predicted via the proposed model fit well with the measured ones, and the estimation of the freezing front locations at the steady state is at the safe side for specimens with various salt contents. Moreover, σb measured by 5TE sensors exhibits staged variations during freezing as the dominant ion conductivity pathway changes. The σb reaches a steady state once the freezing front arrives at the location of the 5TE sensor. Based on the experimental results, a novel method was proposed to improve the accuracy of estimating the frozen wall evolution via the in-situ σb measurement, and two critical locations with different depths are recommended to place the sensors.

Frost hardiness of almond flower buds during dormancy

Frost hardiness of flower buds of twenty almond genotypes was investigated in five dormancy periods by determining LT50 values after artificial freezing tests. The main aim of our work was modelling the changing of frost hardiness of the observed accessions during dormancy and assessing the potential best frost tolerance of them. The effect of genotype and year had significant impact on frost hardiness of flower buds. The potential frost hardiness of accessions has been characterised by LT50 values of flower buds averaged of the bests of the four years. ‘Sóskút 96/5’ was the most sensitive with -17.16 °C, and ‘Tétényi keményhéjú’ was the most frost hardy with -21.08 °C in averaged of years, but both showed lower and higher frost tolerance as well in different years. Flower buds were most frost-tolerant in December and January but did not achieve the same frost resistance every year. From this, we conclude that temperature plays an important role in the hardening process of them. From the aspect of safe yield, frost hardiness of flower buds is an important trait of cultivars, because Hungary is situated at the northern part of economical almond growing area. Our work contributes to facilitating practical considerations in orchard planning.

Utilizing waste latex paint toward improving the performance of concrete

In this paper, incorporating the waste latex paint (WLP) into the conventional concrete as a partial replacement of sand to improve its durability was investigated. The fresh and hardened characterizations, in addition to the durability of concrete, were examined. The slump test was used to evaluate the fresh properties, while the hardened properties were evaluated through the volume of voids and absorption rate, in addition to the compressive, splitting tensile, and flexural strengths tests. The durability performance was evaluated by the surface resistivity, bulk electrical resistivity, as well as freeze and thaw resistance tests. The results showed a reduction in the workability with the addition of WLP, which required high dosages of superplasticizer to maintain the same slump in all the mixtures. Although there was a reduction in the compressive, splitting tensile, and flexural strengths, incorporating the WLP into the OPC concrete improved the durability significantly. Specimens had 5% and 10% of WLP passed the 300 freeze and thaw cycles without deterioration in the relative dynamic modulus of elasticity, compared with the reference mixtures that failed after only 144 cycles. Simultaneously, the surface and bulk electrical resistivity increased by approximately 125% and 138%, respectively, as result of reducing the volume of air voids that was decreased by 9%. The SE images and EDS spectrums showed denser cementitious matrixes with a film of polymeric layer covered the hydration products with adding waste latex paint.

Formulation of a gambier catechin-loaded nanophytosome and the MTT assay on HeLa cell lines

Background: Catechins are good free radical scavengers but exhibit low stability and permeability. Nanophytosomes are currently being developed as the delivery system for phytoconstituents to protect them from decomposition by oxidants or enzymes and increase their permeability. Objectives: To formulate gambier catechin-loaded nanophytosomes and perform the MTT assay on HeLa cell lines. Method:Five formulations were prepared using soya lecithin at various molar ratios of cholesterol by thin-layer hydration and sonication. The nanophytosomes were characterised by the determination of vesicle size, zeta potential, polydispersity index, morphology with Transmission Electron Microscope, Fourier Transform Infrared Spectroscopy (FT-IR) analysis, freeze and thaw test, entrapment efficiency, and the in vitro cytotoxicity test. Result: The optimal formula (F4) with a molar ratio of 1:1:0.8 (catechin:lecithin:cholesterol) resulted in spherical vesicles with an average size (106 ± 0.218) nm, zeta potential -68 mV, polydispersity index 0.412, 93.5% entrapment efficiency and that were stable to temperature changes. FT-IR showed the formation of catechins and lecithin complexes. The activity of catechin-loaded nanophytosomes against HeLa cells showed an IC50 of 36.307 g/ml. There was a significant difference in the average percentage of cells undergoing apoptosis in all treatment groups (p < 0.05). Conclusion: Catechin-loaded nanophytosomes with a molar ratio of 1:1:0.8 (catechin:lecithin:cholesterol) showed moderate cytotoxic activity against HeLa cell lines.

Discussion on the frost susceptibility of sandy soil under hydraulic pressure

A non-frost susceptibility soil is generally not considered to generate significant frost heave. However, recent researches indicate that significant frost heave occurs in coarse fill in engineering, which implies that the frost susceptibility classification based on fine content and particle size may be not reliable. To investigate the frost susceptibility of sandy soil under hydraulic pressure, nine groups of 1-D freezing tests based on the orthogonal array are conducted considering the combination of hydraulic pressure, cooling temperature, fine content and dry density. The results indicate that considerable frost heave occurs in freezing sandy soil. A multivariate regression model is developed to predict the frost heave ratio and to assess the frost susceptibility of sandy soil. From the regression equation, the hydraulic pressure has the largest influence on frost heave ratio of sandy soil, followed by fine content, and the effect of cooling temperature and dry density on sandy soil frost heave can be ignored. In addition, it is found that the reliability of the current standards is poor when assessing the frost susceptibility of sandy soil. The invalidation for frost susceptibility classification is owing to the increased saturation and the increased driving force for water migration. It is proposed that the PWP at the base of freezing front can be used as an indicator for assessing the frost susceptibility of soil.

Hydrological–Thermal Coupling Simulation of Silty Clay during Unidirectional Freezing Based on the Discrete Element Method

A hydrological–thermal coupling discrete element model depicting the unidirectional freezing process of unsaturated silty clay was developed in order to investigate the migration law of unfrozen water in unsaturated silty clay under unidirectional freezing circumstances. The model uses the contact heat transfer equation to calculate the heat transfer process while taking into account the latent heat of phase transition. To obtain the silty clay’s freezing characteristic curve, the model combines the unfrozen water content curve with the Clausius–Clapeyron equation. The water migration from the unfrozen zone to the frozen zone was calculated using Harlan’s model and the frozen fringe hypothesis. The discrete element application MatDEM 3.0 was used to incorporate the mathematical model for computation, and the output was compared to the result of indoor unidirectional freezing tests. The soil closest to the stable freezing front had the largest water content, according to the findings of numerical modeling and laboratory testing, and unfrozen water in the soil would move from the unfrozen zone to the frozen zone under the action of water potential difference. The results of laboratory tests and numerical simulations can accurately describe the temperature variation and water migration of soil during freezing, demonstrating the accuracy of the established discrete element model and proving the viability of the discrete element method in the study of frozen soil.

A multifield coupled thermo‐chemo‐mechanical theory for the reaction‐diffusion modeling in photovoltaics

AbstractA comprehensive coupled thermo‐chemo‐mechanical modeling framework is proposed in this work to study the reaction‐diffusion phenomena taking place inside photovoltaics (PV). When exposed to hygrothermal conditions, the encapsulant ethylene‐co‐vinyl acetate (EVA) layers undergo chemical degradation that significantly influences the overall PV performance. Aiming at efficient thermo‐mechanical modeling, the coupled displacement‐temperature governing equations for the EVA layers are formulated, and its 3D finite element (FE) implementation is derived in detail. Subsequently, the chemical reaction‐diffusion processes occurring in the EVA layers are described, and the corresponding numerical implementation is formulated with the consideration of spatial and temporal variation of diffusivity and chemical kinetic rates. Specifically, the thermo‐mechanical solution accounting for the heat generation from chemical reactions is projected to the FE model of the reaction‐diffusion system in order to determine the kinetic rates and diffusion coefficients for its subsequent analysis. The proposed modeling method is applied to simulate the evolution of reaction‐diffusion species at different damp heat tests, and predictions show a very satisfactory agreement with the analytical solution and experimental electroluminescence images taken from the literature. Its capabilities to predict the spatio‐temporal variation are demonstrated through the simulation of the humidity freeze test, where the cyclic temperature boundary condition is imposed. With this modeling framework, it is possible to evaluate the degradation of PV modules under varying environmental boundary conditions, thus providing a guideline to design new products tailored for specific climatic zones.

Integrated Science Teaching in Atmospheric Ice Nucleation Research: Immersion Freezing Experiments.

This paper introduces hands-on curricular modules integrated with research in atmospheric ice nucleation, which is an important phenomenon potentially influencing global climate change. The primary goal of this work is to promote meaningful laboratory exercises to enhance the competence of students in the fields of science, technology, engineering, and math (STEM) by applying an appropriate methodology to laboratory ice nucleation measurements. To achieve this goal, three laboratory modules were developed with 18 STEM interns and tested by 28 students in a classroom setting. Students were trained to experimentally simulate atmospheric ice nucleation and cloud droplet freezing. For practical training, this work utilized a simple freezing assay device called the West Texas Cryogenic Refrigerator Applied to Freezing Test (WT-CRAFT) system. More specifically, students were provided with hands-on lessons to calibrate WT-CRAFT with deionized water and apply analytical techniques to understand the physicochemical properties of bulk water and droplet freezing. All procedures to implement the developed modules were typewritten during this process, and shareable read-ahead exploration materials were developed and compiled as a curricular product. Additionally, students conducted complementary analyses to identify possible catalysts of heterogeneous freezing in the water. The water analyses included: pH, conductivity, surface tension, and electron microscopy-energy-dispersive X-ray spectroscopy. During the data and image analysis process, students learned how to analyze droplet freezing spectra as a function of temperature, screen and interpret the data, perform uncertainty analyses, and estimate ice nucleation efficiency using computer programs. Based on the formal program assessment of learning outcomes and direct (yet deidentified) student feedback, we broadly achieved our goals to (1) improve their problem-solving skills by combining multidisciplinary science and math skills and (2) disseminate data and results with variability and uncertainty. The developed modules can be applied at any institute to advance undergraduate and graduate curricula in environmental science.

Use of screw pile foundations to reduce temperature of warming permafrost: Lab tests and numerical modeling

Steel screw piles may be a viable pile foundation type in the permafrost region of the Canadian Arctic but the effects of climate change may accelerate the creep settlement rate of the pile. Reducing the temperature around a pile is an effective way of enhancing the long-term performance of a pile. This study proposes a technique that combines the steel screw pile with the artificial ground freezing method, where liquid coolant is circulated through the hollow screw pile shaft to lower the temperature of surrounding permafrost. A series of laboratory experiments of freezing tests was conducted to verify the feasibility of the proposed technique. A finite element model was then developed to evaluate the cooling effect of this technique by analysing the duration of the permafrost freezing and the power of removing the heat from the soil. The numerical model was calibrated against laboratory freezing tests. A series of numerical analyses were performed to investigate the effects of soil properties and screw pile shaft configuration on the ground freezing process in field application. The duration required for freezing the soil at a radial distance of 450 mm to −2 °C was estimated and compared. The results showed that the proposed method was applicable in the field. Numerical results showed that the power of removing the heat from the soil was larger when using the screw segment than the smooth segment. The results are expected to guide the field application of artificial ground freezing around screw piles installed in permafrost.

Experimental Study on the Influence of Snow-Melting Agents on Fiber-Reinforced Cemented Soil under Freezing-Thawing Cycles

To explore the effect of snow-melting agents on the glass fiber-reinforced cemented soil under freezing-thawing cycles, three widely used snow-melting agents, including potassium acetate, magnesium chloride, and sodium sulfate, were used in this article. The effects of snow-melting agent types on the apparent damage, mass loss, and mechanical properties of fiber-reinforced cemented soil under freezing-thawing cycles were analyzed through salt freezing and unconfined compressive strength tests. The results show that the snow-melting effect of potassium acetate is the best, the snow-melting effect of magnesium chloride is the second, and the snow-melting effect of sodium sulfate is the worst. Notably, as the number of freezing-thawing cycles increases, the strength of the test block decreases to varying degrees. After the fifth freezing-thawing cycle, the strength of the block without fiber decreased by 61.30%, 70.22%, and 81.58% in clear water, potassium acetate, and magnesium chloride solution, respectively, while the test block in sodium sulfate solution lost its bearing capacity. A series of studies proved that the snow-melting agent with sodium sulfate as the main component has the most apparent erosion effect on the cemented soil, followed by magnesium chloride, and the erosion effect of potassium acetate is the weakest. The incorporation of glass fiber can effectively improve the resistance of the cemented soil under the action of various salt solution erosion and freezing-thawing coupling and has a significant effect on slowing the development of surface cracks, improving peak strength, and reducing the mass loss rate. This research will provide theoretical support for the design of subgrade and the selection of snow-melting agents in cold areas.

Optimization of the Equine-Sperm Freeze Test in Purebred Spanish Horses by Incorporating Colloidal Centrifugation.

The Purebred Spanish Horse, according to our clinical experience, is characterized by having a high number of stallions that do not meet the international commercial recommendations for equine-sperm cryopreservation. This means that artificial insemination with frozen semen from these stallions is less widespread than in other breeds. In this study, we investigated if the incorporation of single-layer colloidal centrifugation prior to cryopreservation in clinical conditions could increase the number of ejaculates of Purebred Spanish stallions suitable for this processing, observing the influence of centrifugation and freezing extender protocol on post-thawed sperm motility. Using colloidal centrifugation, the percentage of ejaculates available to be frozen was increased from 35% (6/17) to 71% (12/17), doubling the number of samples that could have been subjected to cryopreservation. We only found significant differences in linearity (LIN) and lateral head displacement (ALH) after 5 min of incubation at 37 °C between colloidal and simple centrifugation processing techniques. No significant differences were found between the two different colloidal protocols in any of the variables considered. Colloidal centrifugation allowed us to obtain, from worse fresh-quality ejaculates, thawed sperm doses with similar quality to that of good-quality ejaculates. BotuCrio® produced, in general, higher motility parameters and its characteristics than the other extenders analyzed, with significant differences found in comparison to Inra-Freeze® and Lac-Edta in both total (MOT) and progressive motility (PMOT) when using colloidal centrifugation and only in PMOT when applying simple centrifugation. Colloidal centrifugation optimized the efficiency of cryopreservation, as it allowed us to increase the number of ejaculates of Purebred Spanish Horses suitable to be frozen. Including these semen processing techniques in the freeze test could help to optimize equine-sperm cryopreservation protocols, especially when dealing with individuals or breeds for which initially low sperm quality prevents or limits their inclusion in sperm cryopreservation programs.

Influence of the Coupling Action of Flexural Load and Freezing–Thawing on the Chloride Diffusion of Marine High-Performance Concrete

The chloride diffusion of marine high-performance concrete under a couple of actions, flexural load and freezing–thawing, was investigated by a fast freezing and thawing test in NaCl solution. Concrete specimens of 100 × 100 × 515 mm were tested under bending load and 300 freeze–thaw cycles under the stress levels of 15%, 30%, and 50% of the ultimate fracture modulus. The change in the microstructure of the concrete was analyzed by SEM and MIP. The results indicated that the chloride diffusion coefficient of concrete under the coupling effect of flexural load and freezing–thawing or simple flexural load increased with the increasing in the flexural stress level, and the chloride diffusion coefficient was approximately exponential to the flexural stress level, as D = 0.8777e1.668σ for a couple of actions of flexural load and freezing–thawing, and D = 0.8336e1.3231σ for a simple flexural load. The resistance ability of concrete to chloride diffusion was reduced by the freezing–thawing procedures, the resisted ability dropped more severely under a couple of actions of flexural load and freezing–thawing than simple flexural load at the same stress level. Micro-cracks at the interfacial transition zone between the aggregate and the paste matrix in concrete was induced under a couple of actions of flexural load and freezing–thawing, which increased the average pore size and total pore volume, resulting in the modification of the pore size distribution in the concrete. The influence of a couple of actions of flexural load and freezing–thawing on the concrete was greater than that of simple flexural load.

Mitigating embankment frost heave with nano-ZnO in the Arctic

Non-frost susceptible soils (e.g., gravel) are typically used as embankment fill to minimize the frost heave problem on the highways in the Arctic. However, accesses to the non-frost susceptible soils are limited in the remote regions, and the transportation costs for it are very high, thereby resulting that frost susceptible soils have to be used to fill the embankments. In this study, nano-ZnO was added to two types of frost susceptible soils, namely silty clay and clay, to reduce the frost susceptibility of soils and to mitigate the frost heave. Firstly, the unconfined compressive strengths of the soil samples whose the mass ratios of the nano-ZnO to the silty clays were 1.5 wt%, 3.0 wt%, 4.5 wt% and 6.0 wt% were tested. A series of isotropic freezing tests were then conducted to study the temperatures and frost heave deformations of the soil samples with the nano-ZnO of 0.0 wt%, 1.5 wt%, 3.0 wt% and 4.5 wt%, thereby verifying the effectiveness of the nano-ZnO in reducing the frost susceptibility of the soils. The optimal mass percentage of the nano-ZnO was determined by the mechanical and freezing tests. Finally, a clay embankment model with the nano-ZnO of the optimal mass percentage (defined as the nano-ZnO embankment model) during freezing-thawing cycles under various artificial rainfall conditions in the Arctic environment was tested. A clay embankment model without nano-ZnO was the control case, and defined as the control embankment model. Experimental results revealed that 1) with the increased nano-ZnO, the unconfined compressive strengths of the soil samples initially increased and subsequently decreased, and the maximum value corresponded to the mass percentage of 4.5 wt%; 2) the usage of the nano-ZnO can considerably reduce the freezing point and the frost heave deformations of the soil samples; 3) the optimal mass percentage of the nano-ZnO was 4.5 wt%. Compared with the soil sample without the nano-ZnO, the frost heave deformation of the soil sample with the nano-ZnO of 4.5 wt% was reduced by 71.98% and 78.44% using the rapidly cooling and step by step cooling method, respectively; 4) the usage of 4.5 wt% nano-ZnO was reduced the frost heave deformation of the clay embankment model by a maximum value of 74.06% under artificial rainfall, whereas the frost heave deformation of the embankment model reduced by a maximum value of 31.94% without artificial rainfall. Moreover, the mechanisms of the increase in the compressive strength and the decrease in the frost heave were analyzed. This study can provide considerable insights for mitigating the frost heave problems in highways in the Arctic when frost susceptible soil is used as embankment fill.

Mechanical Properties on Various FRP-Reinforced Concrete in Cold Regions

The evaluation of frost resistance varies with different reinforcement methods, but it is a hot research topic for concrete reinforced with Fiber-Reinforced plastic (FRP). Freezing and thawing tests of FRP-reinforced concrete prisms and cylinders are presented to simulate beams and piers of buildings in cold climates. To evaluate the specimens’ frost resistance, tests with various reinforcement techniques, morphological analysis, weight tests, and relative dynamic modulus of elasticity tests were used. Examined also were the variations in stress–strain curves for axial compression tests and load–displacement curves for bending tests following various freeze–thaw cycles. The findings indicated that after 100 freeze–thaw cycles, the weight of unreinforced concrete cylinders decreased by 9.7%, and its compressive strength decreased by 27.6%. On the other hand, CFRP-reinforced concrete cylinders (Carbon-Fiber-Reinforced Plastics) and GFRP (Glass-Fiber-Reinforced Plastics) gained 1.1% and 1.58% in weight, respectively, while the compressive strength decreased by 7.4% and 8%. After 100 freeze–thaw cycles, the weights of concrete prisms with reinforcement, without reinforcement, and with CFRP reinforcement decreased by 12.13%, 8.7%, and 9.6%, respectively, and their bending strength was reduced by 20%, 42%, and 53%, respectively. The frost resistance of the two FRP-reinforced concrete types had significant differences under freeze–thaw cycles because the prismatic specimens were not fully wrapped with FRP materials. Finally, finite element software ABAQUS was used to simulate the freeze–thaw cycle test of the two specimens. Calculated values were compared to experimental results for the load–displacement curve and the axial stress–strain curve under bending load. The comparison of peak displacement produced a maximum error of 8.6%, and the FRP-reinforced concrete model validity was verified.