Freeze-thaw Cycles Research Articles

Atomistic origin of montmorillonite clay subjected to freeze-thaw hysteresis

The freeze-thaw cycles of frozen soil could significantly affect its thermo-hydro-mechanical-chemical (THMC) properties, causing the frost heaving and thawing settlement. The microscale essence is the water-ice phase transition, but the microscale details are still poorly understood, especially at ultra-low temperatures. Nuclear magnetic resonance (NMR) technology and molecular dynamics (MD) simulation methods were performed to explore the freeze-thaw behaviors of montmorillonite clay under temperature of 210 - 293 K. Then, the water-ice phase transition, freeze-thaw hysteresis, ice nucleation mechanism, and surface effect of clay at an atomistic level were discussed. A classification method of different types of unfrozen water through NMR experiment was proposed, including bulk, capillary, and bound water. Here, it is found that: (1) the freeze-thaw process of frozen soil at the macroscale was essentially the occurrence of ice-water phase transition at the microscale. (2) The freeze-thaw hysteresis was caused by different growth and melting rates of ice crystals, where the ice growth/nucleation on clay surface was more difficult to develop. (3) The surface effect of clay was essential for the ice nucleation and the existence of bound water. For example, little unfrozen water still existed in unfrozen soil even at 213 K. (4) For unsaturated frozen soil, the quasi-liquid water was an essential component of unfrozen water that cannot be ignored. This work could provide an atomistic insight to unravel the atomistic origin of the freeze-thaw mechanism of montmorillonite clay and complement relevant experimental evidence.

Tailoring structural and mechanical properties of konjac glucomannan/curdlan composite hydrogels by freeze-thaw treatment

To improve the gelling properties of konjac glucomannan/curdlan (KGM/CUD) composite hydrogels, KGM/CUD composite hydrogels were treated by freeze-thawing. Herein, we focus on the effects of freeze-thaw cycles, freezing temperature, and freezing time on the structural and mechanical properties of KGM/CUD composite hydrogels. SEM and SAXS results showed that ice crystals generated by freezing extruded the molecular chains and increased the cross-linking density between molecular chains, which resulted in a denser gel microstructure. Among them, the freeze-thaw treatment at −20 °C for 12 h can effectively reduce the correlation length (ξ). According to mechanical testing, freeze-thawed gels for 48 h reached 408-, 826-, and 840-fold of the hardness, gumminess and chewiness of unfrozen, respectively. After freeze-thaw treatment, the energy storage modulus (G') of the gel increased to 9872 Pa, the residual mass after heating was up to 27.9 %, the water holding capacity (WHC) was reduced to 80.85 %. In addition, low-field nuclear magnetic resonance results confirmed that the freeze-thaw treatment promoted the formation of ice crystals from water molecules, which realized the transition of the water state, thus reducing the water mobility of the gel. This study provides a facile and efficient strategy for designing hydrogels products with exceptional texture and sensory characteristics.

Strength analysis and microstructural characterization of calcined red mud based-geopolymer concrete modified with slag and phosphogypsum

This research aims to comprehensively investigate the combined use of calcined red mud (RM), calcium sulfate dihydrate (CSD), and ground granulated blast furnace slag (GGBFS) in geopolymer concrete (GC), demonstrating how their optimized proportions improve GC's fresh, mechanical, durability, and microstructural properties. This study investigated the influence of partially replacing calcined red mud (RM) with GGBFS and Phosphogypsum or CSD in GC. The test program included tests on the fresh, mechanical, and durability properties of these blends, including slump value, compressive strength, ultrasonic pulse velocity, water absorption and porosity, rapid chloride penetration, electrical resistivity, mass loss due to freeze-thaw cycles, and resistance to sulfate attack. Material characterization of the GC blends was conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermogravimetric analysis (DTG). One-way ANOVA analysis was also used to examine the significance of variation between the results due to the replacement of calcined RM with GGBFS and CSD. The results showed that the mix R40-G45-C15, with 40% calcined red mud, 45% GGBFS, and 15% CSD, demonstrated the highest density at 2401 kg/m³, 15.93% greater than the R70-G15-C15 mix, and achieved a compressive strength 73.40% higher at 28 days. Additionally, R40-G45-C15 showed superior durability, with water absorption and porosity reductions of 87.42% and 83.86%, an 85.78% reduction in charge passed at 7 days, and a 40.94% lower mass loss from freeze-thaw cycles compared to R70-G15-C15. SEM analysis confirmed the formation of N–A–S–H and C–A–S–H gels in the blends, contributing to improved density and strength. XRD tests indicated the nominated peaks of calcite, quartz, and portlandite in the blends, with increased portlandite intensity due to higher RM content. These results indicate that partially substituting the calcined RM with CSD and GGBFS in GC could be a viable alternative option, offering potential contributions to sustainable construction with improved structural performances.

Formulation of Cushion Preparations from Duck Egg Shells and SPF Value Testing Using the UV-Vis Spectrophotometry Method

The effectiveness of a sunscreen can be indicated by the value of Sun Protection Factor (SPF), which is defined as the amount of UV energy needed. Cream is a semi-solid dosage from containing one or more medicinal ingredients dissolved or dispersed in a suitable base material. One of the compounds contained in eggshells is CaCO3. Calcium carbonate is necessary for cell regeneration and as a barrier to ultaviolet (UV) rays. This study aims to determine the potential SPF in duck eggshell, the SPF value contained in the cushion and the physical properties of the cushion preparation. Here, three variations of duck egg shell flour concentrations (4%, 8% and 16%) were made, tested in vitro using UV-Vis spectrophotometry from a wavelength of 290-320 nm every 5 nm and the absorbance was measured and the properties were tested. and physical stability (organoleptic, pH, spreadability, stickiness, viscosity, centrifugation, and Freeze-Thaw Cycling for 6 days (3 cycles) at temperatures of 40°C and 4°C). Our research results show that the duck egg shell formulation cannot be used as an SPF product. Formula 1 has an SPF value of 2.6, formula 2 has an SPF value of 3.3 and formula 3 has an SPF value of 3. The test results for the properties and stability of formula 2 with a concentration of 8% duck egg shell flour show the most stable results compared to the other 2 formulas

Evidence for stability of cardiac troponin T concentrations measured with a high sensitivity TnT test in serum and lithium heparin plasma after six-year storage at-80 °C and multiple freeze-thaw cycles.

As high-sensitivity cardiac troponin T (hs-cTnT) is making the transition from diagnostic to prognostic use, a long-term stability study of 5th generation hs-cTnT according to EFLM CRESS recommendations was set up for investigation of frozen clinical specimens (two matrices). Study samples collected in serum tubes and lithium heparin tubes with gel from patients admitted for suspected minor myocardial damage were measured directly after completion of the study (0 years), and after 3-year and 6-year storage at-80 °C, and recovery of hs-cTnT concentrations after long-term storage (%hs-cTnT concentration compared to 0-year) was calculated. Hs-cTnT changes were also compared to decisive delta changes, such as the ones proposed in the ESC NSTEMI 0 h/1 h algorithm (<3 or >5 ng/L for ruling out and ruling in suspected NSTEMI patients). Eighty-six patients were included in the study, whereof 28 both lithium heparin plasma and serum samples were collected simultaneously, in others only serum (n=30) or plasma (n=28). Multiple aliquots per patient were made, so that 479 serum and 473 plasma samples were available for analysis. Across the overall hs-cTnT measuring range, median recovery after 6 years was 105.4 % and 106.2 % for serum and plasma, respectively. Based on these decisive delta changes, serum showed consistent results upon long term storage (max 0.8 % of samples above delta threshold of >5 ng/L) as compared to heparin plasma (up to 19.2 % of samples above threshold). Over 6 years of storage at-80 °C, recovery of hs-cTnT in serum and heparin plasma was similar and within common lot-to-lot variation. Yet, when evaluating absolute delta increments around hs-cTnT clinical decision points, long-term stored sera displayed better clinical performance compared to heparin plasma samples.

Study on Performance Deterioration of Asphalt and Asphalt Mixtures Containing Mafilon under Internal Salt Freeze-Thaw Cycles

The purpose of this work is to determine the implications of internal salt freeze-thaw cycles on performance deterioration to asphalt and asphalt mixtures containing Mafilon (MFL). The deterioration to different numbers of F-TCs and different MFL contents on asphalt properties and mechanism were investigated by physical properties tests and microcosmic tests. Then the damages of road performance indexes of asphalt mixtures containing different MFL contents were studied by road performance tests. The experimental results show that asphalt containing MFL after F-TCs has a remarkable decline in ductility and penetration, while growth in softening point. Internal salt F-TCs are most damaging to the cryogenic properties of asphalt. Chemical reactions and salt aging effects occur in salt F-TCs, raising the glass transition temperature of asphalt. Road performance tests indicate the deterioration of internal salt F-TCs to high temperature stability and water stability is the most pronounced, with 29.18% and 21.78% reduction, respectively.

Investigation on mesostructural characteristics of different pore types within asphalt mixtures under freeze–thaw cycles using CT scanning technology

The distribution of water within asphalt pavement contributes to water-induced damage, with pores serving as the primary conduit for water infiltration. However, understanding the microstructural changes in various pore types amid extreme water conditions remains limited. This study focuses on three type asphalt mixtures which common used in the surface-layer of asphalt pavement and utilises Computed Tomography (CT) technology to categorise internal pores in asphalt mixtures into isolated, semi-connected, connected, and open pores. Examining the impact of freeze–thaw cycles, the research quantifies the connectivity and evolution of each pore type in asphalt concrete. The findings reveal that after freeze–thaw cycles, small isolated pores emerge while some larger isolated pores amalgamate with open pores, leading to a reduction in isolated pores. Volumetric alterations predominantly occur in open pores, where semi-connected pores either expand autonomously or merge with existing connected pores. Overall, the pore network enlarges, yet its complexity remains relatively stable. Notably, microstructural parameters of isolated and semi-connected pores exhibit a weaker correlation compared to total and open pores, with the most robust correlation found between average coordination number, volume, and other microstructural characteristics. Among the pore types, open pores demonstrate the highest sensitivity to freeze–thaw cycles. Substantial variations in correlation coefficients and freeze–thaw sensitivity are observed across different pore types and within the same pore type with distinct microstructural parameters. Thus, a comprehensive analysis encompassing multiple microstructural parameters across diverse pore types is imperative for a thorough evaluation of pore micro characteristics.

Shear behavior of cold region clay-concrete interface under temperature-controlled direct shear tests

The shear properties of the permafrost-structure interface play a crucial role in analyzing the performance of engineering structures in cold regions. Direct shear tests were carried out on the permafrost-concrete structural interface by means of self-improved and optimized temperature-controlled direct shear apparatus to investigate the effects of temperature, moisture content and freeze-thaw cycles. Test results were used to establish a shear characteristic model under coupled influence of temperature and humidity. Preparation of specimens consisting of precast C30 concrete blocks and soil samples taken from borehole cores of the pile foundation of the Middle Bridge No. 3 on the road from Sai Township to Qiuluo Village, Sakya County, Tibet, China, and were treated to different effective confining pressure (σn = 300 kPa, 400 kPa, 500 kPa and 600 kPa), different temperatures (T = −20 °C, −15 °C, −5 °C, 0 °C, 5 °C, 15 °C, and 20 °C), different moisture contents (ω = 5 %, 10 %, 15 %, and 20 %), and different numbers of freeze-thaw cycles (N = 0, 1, 3, 5, 7and11) from −15 °C to 15 °C, test results are given and analyzed. The peak shear stress (τp) is significantly higher than the residual stress (τr) at negative temperature, τp is greater than 1.5 times to 3.2 times of τr. τp is greatly affected by temperature changes, τp under negative temperature is 17 % higher than that under positive temperature, because the water in the soil freezes at negative temperatures, forming a concrete-ice-soil bond interface, which increases the peak strength of the interface. While τr is insensitive to temperature changes. At negative temperatures, the cohesion (c') changes less with increasing water content (ω), and the effect of ω on the external friction angle (φ′) is more significant. At positive temperature, the cohesion decreases with increasing ω, and the effect of ω on the external friction angle is not significant. When N < 5, the cohesion increases with the increase of N; when N = 5, c' reaches the maximum value; when N > 5, c' decreases with the increase of N. Moreover, regardless of the type of shear behavior, the first five freeze-thaw cycles have the greatest impact on the external friction angle. Compared with the sample that has not experienced freeze-thaw cycles, when N = 5, the total decrease in the external friction angle of the sample is 25.6 %.

Damage characteristics and mechanisms of shear strength at the interface between fiber-reinforced concrete and rock under freeze-thaw cycles

In concrete reinforcement projects conducted in cold regions, freeze-thaw cycles contribute to the deterioration of the 'concrete-rock' interface strength. To examine the characteristics of shear stress and the evolution of damage at the interface of PVA fiber-reinforced concrete and rock under freeze-thaw conditions, a series of freeze-thaw shear tests were performed utilizing a self-developed fully saturated shear apparatus. This experimental approach was complemented by CT and scanning SEM analyses to investigate the structural changes at the interface under varying degrees of freeze-thaw damage. The findings revealed that the ECC-S specimens with PVA fibers exhibited an approximate 17.64 % increase in porosity and a 46.5 % reduction in rock strength after 45 freeze-thaw cycles. In contrast, OC-S specimens without PVA fibers experienced an approximate 10.51 % increase in porosity and a strength reduction of about 22.9 % under identical conditions. Furthermore, the study indicated that as the number of freeze-thaw cycles increased, the strength did not consistently rise with the angle of shear. A threshold was identified at an angle of 45°, beyond which the strength did not exhibit significant increases. This research holds considerable theoretical significance and practical implications for enhancing concrete reinforcement methodologies in cold regions, thereby ensuring the safe and efficient operation of rock engineering projects in such environments.

Experimental Study on Mechanical Properties and Stability of Marine Dredged Mud with Improvement by Waste Steel Slag

As marine-dredged mud and waste steel slag in coastal port cities continue to soar, the traditional treatment method of land stockpiling has caused ecological problems. Thus, it is necessary to find a large-scale resource-comprehensive utilization method for dredged mud and waste steel slag. This study uses waste steel slag and composite solidifying agents (cement, lime, fly ash) to physically and chemically improve marine-dredged mud. The physical improvement effect of the particle size and dosage of waste steel slag was studied by the shear strength test under the effect of freeze–thaw cycle. Then, based on the Box–Behnken design of the response surface method, the interaction effects of the solidifying agent components on the unconfined compressive strength were studied. Then, the water stability under dry–wet cycles and a microscopic mechanism were analyzed by XRD and SEM tests. The results show that the waste steel slag with a dosage of 30% and a particle size of 1.18~2.36 mm has the best improvement. The interaction between cement and lime and lime and fly ash has a significant effect on the linear effect and surface effect of 7d unconfined compressive strength, and the strength increases first and then decreases with the increase in its dosage. For the 14d unconfined compressive strength, only the interaction between cement and lime is still significant. The unconfined compressive strength prediction model is established to optimize the mix ratio of the composite solidifying agent. In the water stability, the water stability coefficients of the 7d and 14d tests are 0.68 and 0.95, respectively, and the volume and mass loss rates are all below 1.5%, showing a good performance in dry–wet resistance and durability. Microscopic mechanism analysis shows that waste steel slag provides an ‘anchoring surface’ as a skeleton, which improves the pore structure of dredged mud, and the hydration products generated by the solidifying agent play a role in filling and cementation. The results of the study can provide an experimental and technical basis for the resource engineering of marine-dredged mud and waste steel slag, helping the construction of green low-carbon and resource-saving ports.

Biogenesis and Regulation of the Freeze–Thaw Responsive microRNA Fingerprint in Hepatic Tissue of Rana sylvatica

Background: Freeze-tolerant animals undergo significant physiological and biochemical changes to overcome challenges associated with prolonged whole-body freezing. In wood frog Rana sylvatica (now Lithobates sylvaticus), up to 65% of total body water freezes in extracellular ice masses and, during this state of suspended animation, it is completely immobile and displays no detectable brain, heart, or respirometry activity. To survive such extensive freezing, frogs integrate various regulatory mechanisms to ensure quick and smooth transitions into or out of this hypometabolic state. One such rapid and reversible regulatory molecule capable of coordinating many aspects of biological functions is microRNA. Herein, we present a large-scale analysis of the biogenesis and regulation of microRNAs in wood frog liver over the course of a freeze–thaw cycle (control, 24 h frozen, and 8 h thawed). Methods/Results: Immunoblotting of key microRNA biogenesis factors showed an upregulation and enhancement of microRNA processing capacity during freezing and thawing. This was followed with RT-qPCR analysis of 109 microRNA species, of which 20 were significantly differentially expressed during freezing and thawing, with the majority being upregulated. Downstream bioinformatics analysis of miRNA/mRNA targeting coupled with in silico protein–protein interactions and functional clustering of biological processes suggested that these microRNAs were suppressing pro-growth functions, including DNA replication, mRNA processing and splicing, protein translation and turnover, and carbohydrate metabolism. Conclusions: Our findings suggest that this enhanced miRNA maturation capacity might be one key factor in the vital hepatic miRNA-mediated suppression of energy-expensive processes needed for long-term survival in a frozen state.

Frost resistance and improvement techniques of recycled concrete: a comprehensive review

In the pursuit of sustainable construction practices, the utilization of recycled concrete has emerged as a pivotal strategy, distinguished by its commitment to resource conservation and environmental stewardship. Nevertheless, the inherent micro-porosity and micro-cracking within the old mortar of recycled concrete may lead to weak bonding performance at the interfacial transition zone, culminating in diminished strength, reduced density, and elevated water absorption rates compared to conventional concrete, which critically impairs its performance in cold climates subjected to freeze-thaw cycles. Consequently, this paper provides a structured examination of the frost resistance properties of recycled concrete subjected to freeze-thaw cycling. Initially, the study delineates the mechanisms of frost-induced damage in recycled concrete by synthesizing the degradation pathways observed in both conventional and recycled concrete during freeze-thaw exposure. Subsequently, a detailed analysis is conducted to identify the pivotal factors affecting frost resistance, encompassing the proportion and moisture affinity of recycled aggregates, the addition of silica fume and fly ash, the water-to-cement ratio, and the degree of water saturation. In the final segment, the study compiles and reviews the strategies for bolstering the frost resistance of recycled concrete, including the incorporation of air-entraining admixtures, fiber reinforcement, and aggregate modification approaches. The objective of this research is to offer a thorough comprehension of recycled concrete, with a concentration on the mechanisms of frost damage, the critical determinants of frost resistance, and interventions to augment its resilience against freezing conditions. On this basis, the present paper, in conjunction with the characteristics and current research status of recycled concrete, proposes recommendations for the application of recycled concrete in cold regions. This review is anticipated to facilitate researchers in gaining a comprehensive understanding of the freeze-thaw characteristics of recycled concrete and the measures to enhance its frost resistance. Furthermore, it aims to assist engineering and technical personnel in selecting appropriate treatment methods to improve the frost resistance of recycled concrete in cold regions, thereby promoting the practical engineering application of recycled concrete in such areas.

Rapid Generation of Microplastics and Plastic-Derived Dissolved Organic Matter from Food Packaging Films under Simulated Aging Conditions.

In this study, we show that low-density polyethylene films, a prevalent choice for food packaging in everyday life, generated high numbers of microplastics (MPs) and hundreds to thousands of plastic-derived dissolved organic matter (DOM) substances under simulated food preparation and storage conditions. Specifically, the plastic film generated 66-2034 MPs/cm2 (size range 10-5000 μm) under simulated aging conditions involving microwave irradiation, heating, steaming, UV irradiation, refrigeration, freezing, and freeze-thaw cycling alongside contact with water, which were 15-453 times that of the control (plastic film immersed in water without aging). We also noticed a substantial release of plastic-derived DOM. Using ultrahigh-resolution mass spectrometry, we identified 321-1414 analytes with molecular weights ranging from 200 to 800 Da, representing plastic-derived DOM containing C, H, and O. The DOM substances included both degradation products of polyethylene (including oxidized forms of oligomers) and toxic plastic additives. Interestingly, although no apparent oxidation was observed for the plastic film under aging conditions, plastic-derived DOM was more oxidized (average O/C increased by 27-46%) following aging with a higher state of carbon saturation and higher polarity. These findings highlight the future need to assess risks associated with MP and DOM release from plastic wraps.

Study on the Effect of Basalt Fiber Content and Length on Mechanical Properties and Durability of Coal Gangue Concrete

The massive accumulation of coal gangue not only causes a waste of resources but also brings serious environmental pollution problems. To promote the utilization of coal gangue resources, mitigate environmental pollution from coal gangue, and address the shortage of natural aggregates, this study investigates the use of coal gangue to replace coarse aggregate at a 40% replacement rate to prepare coal gangue concrete (CGC). The current research on the modification of gangue concrete by BF has been less often compared with the research on the effect of basalt fiber (BF) on the properties of ordinary concrete, so in this study, BF with different admixtures and lengths were added into CGC. Additionally, basalt fibers (BFs) of varying amounts and lengths were incorporated into CGC. The study explored the effects of BF on the tensile strength, splitting tensile strength, and flexural strength of CGC. It was found that the mechanical properties of CGC improved significantly when the BF dosage was 0.10–0.15% and the length was 18 mm. This is evidenced by an increase in the compressive strength of 3.94–5.11%, split tensile strength of 11.20–16.18%, and flexural strength of 8.23–12.97%. BF was able to refine pore space, prevent crack development, and bridge cracks in CGC. To further investigate the effect of BF on the long-term service performance of CGC, the effects of BF on the appearance, quality, and compressive strength of CGC in sulfate and freeze–thaw environments were examined. The results indicated that a BF dosage of 0.10–0.15% significantly enhanced the sulfate erosion resistance and freeze–thaw resistance of CGC. This is shown by a 36.76–46.90% reduction in the rate of loss of compressive strength of CGC under the freeze–thaw cycling and a 6.21–8.50% increase in the corrosion resistance factor of CGC under a sulfate attack. BF improved the pore structure and reduced seepage channels, thereby enhancing the durability of CGC.

Evaluation of moisture migration and microstructure of quick-frozen wet rice flour after freeze-thaw cycles and changes in texture, cooking, and sensory properties.

This study investigated the quality changes of quick-frozen wet rice flour before and after freeze-thaw cycles. As the freeze-thaw cycle was prolonged, the water mobility of quick-frozen wet rice flour decreased and the pore size and porosity of the microstructure increased. As a result, the hardness, cooking loss, water absorption, and water precipitation of the rice flour increased, while the sensory score and viscosity decreased. Correlation analysis showed that porosity was positively correlated with the hardness and water absorption of rice flour, and negatively correlated with structural properties such as shearing work and resilience. Water absorption and water precipitation rate were positively related to cooking loss. Thus, moisture migration in rice flour induced microstructural changes to cause alterations in texture, cooking, and sensory properties. Interestingly, quick-frozen wet rice flour still possessed good texture, cooking, and sensory qualities after two freeze-thaw cycles. This study laid the foundation for the development of high-quality quick-frozen wet rice flour.

Experimental Study on Mechanical Characteristics of Stabilized Soil with Rice Husk Carbon and Calcium Lignosulfonate.

In cold regions, the extensive distribution of silt exhibits limited applicability in engineering under freeze-thaw cycles. To address this issue, this study employed rice husk carbon and calcium lignosulfonate to stabilize silt from cold areas. The mechanical properties of the stabilized silt under freeze-thaw conditions were evaluated through unconfined compressive strength tests and triaxial shear tests. Additionally, scanning electron microscopy was utilized to analyze the mechanisms behind the stabilization. Ultimately, a damage model for rice husk carbon-calcium lignosulfonate stabilized silt was constructed based on the Weibull distribution function and Lemaitre's principle of equivalent strain. The findings indicate that as the content of rice husk carbon and calcium lignosulfonate increases, the rate of improvement in the compressive strength of the stabilized silt progressively accelerates. With an increase in the number of freeze-thaw cycles, the deviatoric stress of the stabilized soil gradually diminishes; the decline in peak deviatoric stress becomes more gradual, while the reduction in cohesion intensifies. The decrease in the angle of internal friction is relatively minor. Microscopic examinations reveal that as the number of freeze-thaw cycles increases, the soil pores tend to enlarge and multiply. The established damage model for stabilized silt under freeze-thaw cycles and applied loads demonstrates a similar pattern between the experimental and theoretical curves under four different confining pressures, reflecting an initial rapid increase followed by a steady trend. Thus, it is evident that the damage model for stabilized silt under freeze-thaw conditions outperforms traditional constitutive models, offering a more accurate depiction of the experimental variations observed.

Failure of the SRC under freeze- thaw cycles by the push-out tests

This paper explores the impact of freeze-thaw cycles, the thickness of the protective layer, embedment length, and volumetric hoop ratio on the bond performance at the SRC interface, assessed through freeze-thaw and push-out tests. Results from SEM indicated significant cracking in concrete exposed to freeze-thaw cycles, with an increase in both the number and diameter of pores. Despite significant damage to the concrete exterior, the interface exhibited considerably less deterioration. Following 200 freeze-thaw cycles, the specimens displayed a maximum crack depth of 2.3 mm and a porosity rate of 35.1 %. As the cycles progressed, the failure mode of specimens under push-out loading transitioned from splitting to interfacial shear failure. Notably, the length of cracks on the end surfaces was markedly reduced, and the majority of specimens exhibited minimal cracking on the side surfaces. Additionally, interfacial bond stress decreased progressively with the increasing number of cycles. The ultimate bond stress declined more rapidly than residual bond stress, with the rate of decrease stabilizing after surpassing 100 cycles. Enhancements in protective layer thickness, embedment length, and volumetric hoop ratio effectively mitigated the reductions in bond stress. Among these, the protective layer had the most significant impact, followed by the volumetric hoop ratio, while embedment length had the least influence. The study concludes with proposed formulas for calculating bond stress and slip eigenvalues after freeze-thaw cycles, integrating experimental results and theoretical analysis.

Axial compression performance of slurry‐wrapping recycled aggregate concrete‐filled steel tube short columns under freeze–thaw cycles

<scp>Axial</scp> compression performance of slurry‐wrapping recycled aggregate concrete‐filled steel tube short columns under freeze–thaw cycles

Experimental and numerical evaluation of soil water and salt dynamics in a corn field with shallow saline groundwater and crop-season drip and autumn post-harvest irrigations

In areas with shallow saline groundwater, soil salts inevitably accumulate in the root zone during the growth period due to irrigation and upward movement of salts from the groundwater. In Northern China, autumn irrigation (AIR) with large amounts of water is commonly employed post-harvest to mitigate soil salt stress on crop growth in the subsequent year. Optimizing the total irrigation depth during both crop-growth and non-growth periods is challenging because of the movement of soil salts, which is influenced by their two-dimensional distribution around drippers and the impact of the winter freeze-thaw cycles, significantly affecting water flow and solute transport during winter. In this study, the HYDRUS-1D and HYDRUS-2D models were integrated and calibrated using experimental data collected from 2021 to 2023 in China's Ordos south bank irrigation area. This model integration was conducted to assess soil water and salt dynamics during the non-growth and corn-growth periods under different irrigation strategies: a) AIR with high (AH) and low (AL) irrigation depths, and b) drip irrigation (DIR) with high (DH), medium (DM), and low (DL) irrigation depths. The results indicated that HYDRUS effectively modeled the electrical conductivity of the saturation paste extract (ECe) across different irrigation strategies, yielding an average coefficient of determination (R2) and the root mean square errors (RMSE) of 0.87 and 0.53 dS m−1, respectively. Generally, ECe increased during the growth period with DIR and decreased during the non-growth period with AIR. For the 0–40 cm soil layer, ECe decreased by 5.7 % and 12 % for every 100 mm increase in the AIR and DIR depths, respectively. Compared with the AHDM and AHDL treatments, reducing an AIR depth and increasing a DIR depth resulted in lower ECe in the 0–40 cm layer during the growth period and higher crop yield (CY) and irrigation water productivity (WPI). Specifically, the average ECe in the 0–40 cm layer decreased by 4.8 % during the growth period in the ALDH treatment compared to the AHDM treatment, and CY and WPI increased by 7.2 % and 10.3 %, respectively. Additionally, the irrigation strategy was the most effective in reducing ECe when AIR accounted for 35 % of the total irrigation. This study suggested that combining low AIR and high DIR could enhance water and field productivity.

Low and intermediate temperature fracture performance of hot mix asphalt (HMA) reinforced with nano-reduced graphene oxide (NRGO) under freeze-thaw cycles and aging conditions

ABSTRACT This study evaluates the effect of nano-reduced graphene oxide (NRGO) and conditions of short- and long-term (three freeze-thaw cycles (3 FTC)) failure and six days of ageing (6 AM) on bituminous mixtures from the viewpoint of fracture toughness (KIIC and KIIIC) and fracture energy (FEII and FEIII) at ±15 °C. The results showed the fracture stiffness was improved at ±15 °C (under three conditioning states). However, the fracture flexibility was decreased and increased at low and medium temperatures, respectively. At low temperatures, the results indicated that FEIII and KIIC had the lowest resistance under unconditioned and AM conditions, while FEII and KIIC had the lowest resistance under FTC. At intermediate temperatures, FEIII and KIIC under non-conditioned and FTC conditions and FEII and KIIC under AM conditions obtained the lowest resistance. Therefore, it was recommended to check both loading states in determining the shear performance (in-plane and out-of-plane) of asphalt mixtures. Finally, by providing the minimum short- and long-term properties required to control shear and tear cracks, reinforced mixtures lead to increased service life, reduced maintenance costs and improved road safety in cold and tropical regions.