Freeze-thaw Research Articles

Freeze–Thaw Response of Permeability and Absorption Channel Structure and Moisture Distribution in Different Coal Ranks

Freeze–Thaw Response of Permeability and Absorption Channel Structure and Moisture Distribution in Different Coal Ranks

A Comprehensive State of the Art on the Impact of Freeze–Thaw Cycles on the Engineering and Index Properties of Soils

A Comprehensive State of the Art on the Impact of Freeze–Thaw Cycles on the Engineering and Index Properties of Soils

Aging of Limestones and Silane–Siloxane-Based Protective Hydrophobics: The Impact of Heating–Cooling and Freeze–Thaw Cycles

Stones are traditionally used in construction and architectural applications as building elements due to their aesthetic and technical/structural performance. Like other environmental factors (rain, humidity, moisture, salt presence, biological activity, etc.), heating–cooling and freeze–thaw cycles significantly threaten the longevity of stone materials. Hence, considering the socio-economic and cultural value of stones, preventive measurements such as hydrophobic coatings are applied to prevent or mitigate damage. The scope of this study is the performance assessment of limestones with different characteristics and the efficiency of various commercial silane/siloxane-based hydrophobic coatings when exposed to thermal variation and freeze–thaw. For that purpose, the standards EN 14066:2013 (determination of resistance to aging by thermal shock) and EN 12371:2010 (determination of frost resistance) were followed. Open porosity and static contact angles were estimated to assess the stone durability and water protection capabilities of the hydrophobics. Additionally, sound speed propagation velocity, quality of building material index, elastic modulus and flexural strength were measured to evaluate the variation of mechanical properties. Static contact angle revealed that the coatings maintained an efficient level of hydrophobicity even after thermal-shock and freeze–thaw weathering tests. The study also revealed a critical interaction between freeze–thaw cycles, hydrophobic coatings and structural integrity of the stones, mostly on more porous ones. When they are subjected to harsh environmental conditions, untreated porous limestones keep structural cohesion, allowing for the natural absorption and release of water during freezing and thawing. On the contrary, when limestones are treated, the hydrophobic coatings can moderately obstruct the water release due to the partial saturation of the porous framework by the products. It also probably resulted from the different mechanical behavior between the inner matrix and layer of stone coated, resulting in a premature breakout and mechanical damage of the stone.

Freeze–Thaw Events Change Soil Greenhouse Gas Fluxes Through Modifying Soil Carbon and Nitrogen Cycling Processes in a Temperate Forest in Northeastern China

Freeze–thaw events are predicted to be more frequent in temperate forest ecosystems. Whether and how freeze–thaw cycles change soil greenhouse gas fluxes remains elusive. Here, we compared the fluxes of three soil greenhouse gases (CO2, CH4, and N2O) across the spring freeze–thaw (SFT) period, the growing season (GS), and the annual (ALL) period in a temperate broad-leaved Korean pine mixed forest in the Changbai Mountains in Jilin Province, Northeastern China from 2019 to 2020. To assess the mechanisms driving the temporal variation of soil fluxes, we measured eleven soil physicochemical factors, including temperature, volumetric water content, electrical conductivity, gravimetric water content, pH, total carbon, total nitrogen, total-carbon-to-total-nitrogen ratio, nitrate (NO3−), ammonium (NH4+), and dissolved organic carbon, all of which play crucial roles in soil carbon (C) and nitrogen (N) cycling. Our findings indicate that the soil in this forest functioned as a source of CO2 and N2O and as a sink for CH4, with significant differences in greenhouse gas (GHG) fluxes among the SFT, GS, and ALL periods. Our results suggest freeze–thaw events significantly but distinctly impact soil C and N cycling processes compared to normal growing seasons in temperate forests. The soil N2O flux during the SFT (0.65 nmol m−2 s−1) was 4.6 times greater than during the GS (0.14 nmol m−2 s−1), likely due to the decreased NO3− concentrations that affect nitrification and denitrification processes throughout the ALL period, especially at a 5 cm depth. In contrast, soil CO2 and CH4 fluxes during the SFT (0.69 μmol m−2 s−1; −0.61 nmol m−2 s−1) were significantly lower than those during the GS (5.06 μmol m−2 s−1; −2.34 nmol m−2 s−1), which were positively influenced by soil temperature at both 5 cm and 10 cm depths. Soil CO2 fluxes increased with substrate availability, suggesting that the total nitrogen content at 10 cm depth and NH4+ concentration at both depths were significant positive factors. NO3− and NH4+ at both depths exhibited opposing effects on soil CH4 fluxes. Furthermore, the soil volumetric water content suppressed N2O emissions and CH4 oxidation, while the soil gravimetric water content, mainly at a 5 cm depth, was identified as a negative predictor of CO2 fluxes. The soil pH influenced CO2 and N2O emissions by regulating nutrient availability, particularly during the SFT period. These findings collectively contribute to a more comprehensive understanding of the factors driving GHG fluxes in temperate forest ecosystems and provide valuable insights for developing strategies to mitigate climate change impacts.

Damage Evolution and NOx Photocatalytic Degradation Performance of Nano-TiO2 Concrete Under Freeze–Thaw Cycles

The internal pore structure of nano-TiO2 concrete deteriorates gradually during freeze–thaw (F–T) cycles. The deterioration process can reveal the F–T damage mechanism and the deterioration law of photocatalytic performance. The evolution law of the pore structure of nano-TiO2 concrete during F–T damage was investigated. Moreover, this paper defined the microscopic F–T damage factor based on porosity and fractal dimension. The results showed that a 2% dosage of nano–TiO2 concrete had better frost resistance and lower porosity in this experiment. Its porosity only increased by 13.3% after 200 F–T cycles, which was much smaller than that of ordinary concrete. Furthermore, the presence of nano-TiO2 enhanced the volume fractal dimension of concrete pores larger than 100 nm, increasing the complexity of the pore structure and contributing to improved frost resistance. F–T damage led to a decrease in the photocatalytic performance of nano–TiO2 concrete. Still, it helped the nitrate on the surface of the concrete to dissolve and disappear more quickly under rainwater washout. Finally, a thermodynamic theory-based concrete F–T damage correction model was constructed, and the model was used to predict F–T damage values for some scholars. The results showed that the correlation between the model values and the experimental values was more than 0.95, which could accurately reflect the degree of F–T damage of concrete. In addition, a prediction model of photocatalytic NO reduction by nano-TiO2 concrete based on microscopic damage factor was established. It provides a theoretical basis for the application of nano-TiO2 concrete in the field of gas pollutant treatment.

Evaluating concrete quality under freeze–thaw damage using the drilling powder method

Evaluating the safety of in situ concrete structures under freeze–thaw (F–T) damage presents significant challenges. Existing methods require large coring samples, which are unsuitable for ongoing monitoring. This study investigates a minimally invasive drilling powder technique to assess the F–T resistance of concrete with varying properties. We evaluated the durability factor and powder porosity before and after F–T exposure. The results indicate that the drilling powder method effectively assesses the safety of concrete under F–T damage using threshold powder porosity. In conclusion, this technique offers a promising approach for the F–T damage assessment with minimal structural impact.

Experimental assessment of freeze-thaw deterioration in compression-cast fiber-reinforced concrete

An increasing number of critical infrastructures are built in cold and perma-frost regions, resulting in higher susceptibility to damage due to freeze-thaw (F-T) cycles. This paper assesses the mechanical properties and F-T damage evolution of compression-cast fiber-reinforced concrete (CCFRC) through rapid F-T cycling tests. Nine types of fiber-reinforced concrete (FRC) are experimentally investigated through 144 cubic and 39 prismatic specimens. The main parameters considered in the tests include the casting pressure applied during the compression casting procedure (between 0 and 15 MPa), type of the internal added fibers (polypropylene, end-hooked steel, or their combination), fiber content, and number of F-T cycles. The effects of these parameters on the failure modes, strength degradation rates, deterioration evolution, frost resistance durability, microscopic behavior, and F-T resistance of FRC specimens, are examined in detail. The microscopic performance of different specimens is further investigated using the X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and backscattered scanning electron (BSE) tests. Based on the test results, it is shown that: (i) compared with the mass loss rate, the relative dynamic elastic modulus can be a more suitable index to assess the F-T resistance of FRC; (ii) compression casting and addition of fibers can effectively enhance the F-T denudation resistance of CCFRC; (iii) compression casting reduces the compressive and flexural strength degradation rates of CCFRC, but at the expense of more brittle behavior; and (iv) compression casting and use of the mixed polypropylene and end-hooked steel fibers can effectively delay the F-T cycling induced damage, reduce porosity and internal defects, and enhance the micro-structural behavior and F-T resistance of CCFRC. F-T deterioration prediction models are also proposed and shown to provide accurate and effective representation of the behavior of CCFRC materials.

High-strength poly(vinyl alcohol) physical eutectogels: Effects of polymer molecular weight, DES composition, and heat treatment

A one-step manufacturing process is employed to fabricate stretchable physical eutectogels. It involves directly mixing polyvinyl alcohol (PVA) with choline chloride as a hydrogen bond acceptor and either ethylene glycol or glycerol (Gly) as a hydrogen bond donor. This process results in the formation of numerous crystallite domains of PVA within the deep eutectic solvent (DES), which act as physical crosslinking points in the eutectogel. The study systematically investigates the effects of PVA molecular weight, DES composition, and various heat treatments on the mechanical properties of eutectogels. The stress–strain curves demonstrate that a higher PVA molecular weight, the addition of Gly to the DES, and repeated freeze–thaw cycles can enhance the mechanical properties of the PVA physical eutectogel. Finally, scanning electron microscopy and X-ray diffraction are used to examine and analyze the polymer networks and crystallite domains in terms of pore size, crystallinity, and crystallite domain size.

Effect of freezing–thawing cycles and high temperatures on concretes containing partial replacement of fine grain blast and Electric Arc Furnace slags

This study examines the effects of local industrial by-products, such as iron slag and steel slag, as partial replacements of fine grain at 10%, 15%, and 25%, individually and combined. The research evaluates the impact on mechanical resistance under freeze–thaw cycles and high temperatures. Additionally, the study explores the effects of incorporating 0.3% polypropylene fibers by volume and 10% microsilica by cement weight (500 kg/m3). The durability of concrete samples exposed to freezing–thawing at the age of 28 days with 100 cycles and at temperatures of 400 °C and 800 °C at the age of 90 days in the gas furnace were investigated in terms of compressive strength. Samples subjected to 100 freeze–thaw cycles showed increased porosity and expansion of microcracks, leading to a loosened macrostructure and a 0.8% decrease in weight. Findings indicate that the partial replacement of slag in the fine grain and combining these materials with polypropylene and microsilica fibers improved mechanical properties like compressive strength. Additionally, the freeze–thaw cycle caused a 32.46% decrease in sample resistance compared to the control state. Moreover, incorporating 10% slag enhanced the mechanical properties of samples at 400 °C and 800 °C, with a lower resistance loss when compared to designs without additives. The inclusion of 10% microsilica and 0.3% polypropylene fibers, however, reduced sample resistance at 800 °C compared to 400 °C. Microstructural analysis of GGBS in concrete using Scanning Electron Microscopy (SEM) revealed that the addition of GGBS produces a denser matrix populated with more angular particles, resulting in improved bonding properties compared to plain concrete.

Groundwater Response to Snowmelt Infiltration in Seasonal Frozen Soil Areas: Site Monitoring and Numerical Simulation

Spring snowmelt has a significant impact on the hydrological cycle in seasonally frozen soil areas. However, scholars hold differing, and even opposing, views on the role of snowmelt during the thawing period in groundwater recharge. To explore the potential recharge effects of spring snowmelt on groundwater in seasonal frozen soil areas, this study investigated the vadose zone dynamics controlled by soil freeze–thaw processes and snowmelt infiltration in the Northeast of China for 194 days from 31 October 2020 to 12 May 2021. Responses of groundwater level and soil moisture to snowmelt infiltration show that most snowmelt was infiltrated under the site despite the ground being frozen. During the unstable thawing period, surface snow had already melted, and preferential flow in frozen soil enabled the recharge groundwater by snowmelt (rainfall), resulting in a significant rise in groundwater levels within a short time. The calculated and simulated snowmelt (rainfall) infiltration coefficient revealed that during the spring snowmelt period, the recharge capacity of snowmelt or rainfall to groundwater at the site is 3.2 times during the stable thawing period and 4.5 times during the non-freezing period.

Optimal Utilization of Biochar, Polyacrylamide, and Straw Fiber for Subgrade Stabilization of Forest Roads

Subgrade stabilization is crucial for forest road construction, especially in Northeast China and the Russian Far East, with great economic growth potential. This study explored a novel and green solution of integrating biochar (BC), polyacrylamide (PAM), and straw fiber (SF) in the form of a ternary composite for stabilizing forest subgrade soil in cold regions. Using central composite design-based response surface methodology, the optimal mix ratio design was obtained, and the composite stabilizer was designated as BPS. Afterward, the stabilizing performance of BPS was studied by conducting an unconfined compression strength (UCS) test. The results showed that the optimum composition of BC:PAM:SF stood at 81:9:10. The UCS and deformation modulus with 3% BPS at 28 days reached 565.42 kPa and 17.24 MPa, respectively, which were 3.36 and 6.05 times higher than those of the untreated samples. The BPS-treated soil also possessed better resistance to freeze–thaw cycles. The freezing–thawing-induced loss ratio of strength was 49.3% lower than that of natural soil. Moreover, empirical models for the UCS of BPS-stabilized soil, as well as its relationships with the modulus, were established and validated by data in the literature. Finally, the “filling, cementing, and reinforcing” stabilization mechanism of BPS was elucidated by scanning electron microscopy analysis.

Centrifugal Test Study on the Vertical Uplift Capacity of Single-Cylinder Foundation in High-Sensitivity Marine Soil

Offshore wind power is a new type of clean energy with broad development prospects. Accurate analysis of the uplift capacity of offshore wind turbine foundations is a crucial prerequisite for ensuring the safe operation of wind turbines under complex hydrodynamic conditions. However, current research on the uplift capacity of suction caissons often neglects the high-sensitivity characteristics of marine soils. Therefore, this paper first employs the freeze–thaw cycling procedure to prepare high-sensitivity saturated clay. Subsequently, a single−tube foundation for wind turbines is constructed within a centrifuge through a penetration approach. Ten sets of centrifuge model tests with vertical cyclic pullout are conducted. Through comparative analysis, this study explores the pullout capacity and its variation patterns of suction caisson foundations in clay with different sensitivities under cyclic loading. This research indicates the following: (1) The preparation of high-sensitivity soil through the freeze−thaw procedure is reliable; (2) the uplift capacity of suction caissons in high−sensitivity soil rapidly decreases with increasing numbers of cyclic loads and then tends to stabilize. The cumulative displacement rate of suction caissons in high-sensitivity soil is fast, and the total number of pressure–pullout cycles required to reach non-cumulative displacement is significantly smaller than that in low-sensitivity soil; (3) the vertical cyclic loading times and stiffness evolution patterns of single-tube foundations, considering the influence of sensitivity, have been analyzed. It was found that the secant stiffness exhibits a logarithmic function relationship with both the number of cycles and sensitivity. The findings of this study provide assistance and support for the design of suction caissons in high-sensitivity soils.

Experimental Study on Reloading Creep Characteristics of Marble After Unloading–Freezing–Thawing Damage

ABSTRACTThe reloading characteristics of slope projects such as water conservancy and hydropower in cold regions after excavation and unloading are the key to the long‐term stability problem of bank slopes in reservoirs. After pre‐peak unloading and freeze–thaw, uniaxial gradient loading creep test was carried out with marble, and the unloading creep mechanical behavior of marble under different temperature ranges and different numbers of freeze–thaw cycles was studied. The results show that the temperature range of freeze–thaw and the number of cycles control the reduction of creep damage stress and long‐term strength as well as the increasing trend of creep strain of marble, and the time‐mechanical response of unloaded marble under the action of freeze–thaw with large temperature difference is more obvious. Based on the traditional Burgers model, a non‐constant Burgers model considering freeze–thaw damage was proposed, and the applicability and rationality of the model were verified.

Recovered graphene-hydrogel nanocomposites for multi-modal human motion recognition via optimized triboelectrification and machine learning

Hydrogels have extensive applications in portable, flexible, wearable, and self-powered electronic devices based on triboelectric nanogenerators (TENGs). An important issue with hydrogels is their tendency to dehydrate over time, which leads to a decline in both ionic conductivity and mechanical flexibility. Furthermore, the current techniques used to produce these hydrogels mostly rely on the freeze–thaw process, which has limited ability to modify the polymer conformation. Herein, a novel water-assisted recovered hydrogel is proposed using a simple strategy to prepare high-performance hydrogel-based TENGs by optimizing the cross-linking and crystalline domains. Synthesis of the electrostatic electrode in the TENG involved the incorporation of polyethylene oxide (PEO) into a polyvinyl alcohol (PVA) hydrogel network via cross-linking. Graphene nanoplatelets (GNP) were added to precisely tune the electrical conductivity. GNP constructs the backbone structures in the hydrogel and enhances the charge transport capacity. Electrical conductivity is changed by the GNP concentration and thus, electrical output of the hydrogel can be facilely controlled. The water reabsorption increased density and crystallinity of the cross-linking and allowed the hydrogel to show superior performance compared to the original one. The 7th recovery hydrogel produced around 594 V, 40 μA, and 32 nC. The 7th recovery hydrogel had exceptional endurance, with the capacity to withstand over 16,000 cycles of contact separation. Moreover, it could be stretched up to 541 % of its original length and improved by almost twice as much as that without the recovery process. By combining multi-modal graphene-based TENG sensors with machine learning, a state-of-the-art behavioral monitoring system was created that could reliably detect tapping fingers with an average accuracy rate of 95 %. The findings of this research will pave the way for new approaches to the development of autonomous motion sensors and flexible renewable energy sources.

Full-scale testing and monitoring of geosynthetics-stabilized flexible pavement in Alberta, Canada

Freeze-thaw (F-T) cycles are a primary contributor of pavement damages in seasonal frost regions. Geosynthetics stabilization has been a promising solution for enhancing the roadways performance in cold regions. However, in comparison with the practical applications, research on the geosynthetics stabilization in cold-region roads is scarce and its efficacy is yet to be quantified. This study presents the full-scale test on geosynthetics-stabilized sections in a flexible pavement in Sturgeon County, Alberta. It focused on the investigation of three separate test sections with bases stabilized by two types of geocells and one geogrid composite, each fully instrumented with earth pressure cells, thermocouples, and moisture sensors. This experimental program consisted of plate loading tests and trafficking tests on each test section before and after the first F-T season, and monitoring of soil temperatures, moisture contents, and loads transferred to subbases while the sections were open to general traffic. The results showed seasonal F-T cycles resulted in increased pavement settlement, decreased load transfer ratio, and increased stress distribution angle under the plate loading. The traffic-induced stress on the subbases increased during the spring thaw but decreased afterwards.

Seasonal freeze–thaw front dynamics and effects on hydrothermal processes in diverse alpine grasslands on the northeastern Qinghai–Tibet Plateau

The dynamics of the freeze–thaw front strongly affect the transfer and exchange of water and energy in seasonally frozen zones. This study aimed to characterize the variations in the seasonal freeze–thaw fronts of diverse alpine grasslands and their effects on hydrothermal processes in the Qinghai Lake Basin (QLB). Field experiments were carried out on alpine meadow and steppe transition (AMS), alpine steppe (ASP) and Achnatherum splendens steppe (AST) ecosystems in the QLB, with 2 years of continuous high-frequency year-round observations. The results revealed that the seasonal freeze–thaw front was characterized by three distinct stages, in which the durations of slow freezing period (SF) and thawing period (T) were much shorter than that of rapid freezing period (RF). The maximum seasonal freezing depth in 2018–2020 were ranged from AMS (322.65 cm), AST (271.98 cm) and ASP (200.00 cm). The liquid soil volumetric water content (SVWC) decreased in all three ecosystems during the RF period, but increased during the SF and T periods. During the RF period, the SVWC of the AMS, ASP and AST decreased the most by −13.28 %, −9.52 % and −15.29 %, respectively. In the SF period, the SVWC of the AMS, ASP and AST increased the most, by 3.97 %, 9.52 % and 6.33 %, respectively, and by 13.37 %, 12.73 % and 12.44 % in the T period. During the freeze–thaw process, the SVWC and soil temperature mainly exhibit logarithmic and quadratic functions. The changes in the freeze–thaw front and SVWC in AMS were largely consistent, while those in ASP and AST experienced time lags. The freeze–thaw depth and net radiation of the RF, SF and T periods were fitted via the quadratic polynomial method. The freeze–thaw depth and soil heat flux were linearly fitted in the RF and SF periods, and the quadratic polynomial method was used in the T period. The effect of net radiation and soil heat flux accumulation on thawing front were more obvious in AMS than in ASP and AST. These findings are important for improving our understanding of water and heat transfer processes during the freeze–thaw period.

Effect of freezing and freezing-thawing pretreatment on wood properties and drying characteristics of Eucalyptus urophylla × E. grandis

ABSTRACT Eucalyptus wood has uneven density and poor permeability, which can lead to defects such as wrinkling and cracking during the drying process, limiting applications. Freezing and freeze–thaw treatments can improve wood permeability by disrupting its microstructure, thus enhancing drying quality. In this experiment, Eucalyptus urophylla × E. grandis was subjected to cold trap freezing (CF), refrigerator freezing (RF), cold trap freeze–thaw (CFT), and refrigerator freeze–thaw (RFT) pretreatments. The pretreated materials were then dried and tested to investigate properties such as permeability, moisture absorption, shrinkage, and drying characteristics. The results indicated that the moisture content (MC) during pre-freezing, with lower freezing temperatures leading to greater reductions in MC. The water absorption rates for the CF, RF, CFT, and RFT pretreated wood increased by 16%, 7%, 16%, and 14%, respectively, showing significant improvement in permeability, which in turn resulted in increased drying rates of 24%, 11%, 26%, and 13%, respectively, when the MC exceeded the fiber saturation point (FSP). The shrinkage ratios were reduced by 8%, 2%, 4%, and 8%, respectively, but increased the equilibrium moisture content (EMC) by 5% for all groups. Overall, the improvement in drying rate from freeze–thaw treatment was greater than that from freezing treatment.

Effect of nano‐silica on the mechanical performance and porosity evolution of concrete under freezing and thawing cycles

AbstractThe enhancement of freeze–thaw resistance in concrete is crucial for improving the durability and longevity of infrastructure in cold regions. Although the benefits of nano‐silica (NS) on concrete's freeze–thaw resistance have been demonstrated, there is still controversy surrounding the optimal concentration of admixture and underlying mechanisms. In this study, the mechanical performance (mass weight, elastic modulus, compressive and splitting strength) and porosity evolution (total porosity, porosity distribution and micro‐surface morphologies) of control concrete and concrete modified with five different NS admixture concentration (1%–5%) were tested under freezing and thawing (F–T) cycles, and damage models were established to assess the correlations between macroscopic and microscopic damages. The results indicate that F–T cycles lead to both damage in mechanic properties and porosity in concrete specimens. The effects of NS particles on macroscopic and microscopic damage under F–T conditions depend on their admixture concentration. A 2% concentration mitigates while a 5% dosage promotes both macroscopic and microscopic damages during F–T cycles. These differences can primarily be attributed to different dispersion status of NS particles in concrete, leading to variations in porosity evolution during F–T cycles. The macroscopic damage exhibit stronger correlation with microscopic damage factor modified by proportion of large pores compared to that only based on total porosity, suggest that the microscopic damage, especially large pores' proportion, contribute to macroscopic damage of concrete specimens under F–T cycles. These findings provide valuable references for field concrete engineering applications in cold areas.

Quantification of chloride saline soil freezing–thawing temperature threshold based on thermodynamic theory

Quantification of chloride saline soil freezing–thawing temperature threshold based on thermodynamic theory

Enhancement of Mechanical Properties and Freeze–Thaw Durability of Recycled Aggregate Concrete using Aggregate Pretreatment

Enhancement of Mechanical Properties and Freeze–Thaw Durability of Recycled Aggregate Concrete using Aggregate Pretreatment