Freeze-thaw Cycles Research Articles

The influence of volcanic ash (VA) on the mechanical properties and freeze-thaw durability of lime kiln dust (LKD)-stabilized kaolin clayey soil

Improving soft clay soil's mechanical properties and durability has been the subject of intense research. In this context, traditional stabilizers such as cement and lime have been introduced as the most widely used materials. However, the utilization of these conventional additives poses several challenges due to recent global concerns regarding the reduction of greenhouse gas emissions. Therefore, international research is shifting toward using environmentally friendly soil-stabilizing waste materials. This study, for the first time, evaluates the stabilization of kaolin clay soil using lime kiln dust (LKD) as a high CaO content waste pozzolan and volcanic ash (VA) as a natural pozzolan with considerable SiO2 and Al2O3 contents. In general, the research aims to demonstrate the effective performance of these two inexpensive and environmentally friendly additives in improving the mechanical characteristics and durability of kaolin clay soil, thereby providing the essential groundwork for the practical application of this method in stabilizing soft clay soil. This study included preparing samples with LKD at 3%, 5%, 7%, and 10% of the dry weight of clay and replacing LKD with VA at 0%, 25%, 75%, and 100%. The specimens were cured for 3, 7, and 28 days. Following the curing process, the optimal sample was subjected to varying numbers of freeze-thaw (F-T) cycles. The samples were examined by conducting a series of standard compaction, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) tests at different stages of adding stabilizers, as well as before and after exposure of F-T cycles. The findings revealed that adding LKD and VA increased the UCS by accelerating and improving the pozzolanic and hydration reactions. Also, the combination of LKD and VA in kaolin soil enhanced F-T durability, resulting in less strength deterioration even after 10 cycles, when compared to the untreated control sample. In particular, the optimal mixture containing 5% LKD and 25% VA replacement improved 11 times in UCS compared to untreated kaolin clay and showed a slight reduction of only 7% after 10 F-T cycles. Overall, the incorporation of LKD and VA enhanced the mechanical properties and F-T durability of kaolin clay soil, making it a low-cost, sustainable, and eco-friendly option for soil improvement.

FeAl-LDH-modified biochar (FeAl-LDH@BC): A high-efficiency passivator for hexavalent chromium (Cr(VI)) reduction and immobilization in contaminated soil

A composite FeAl-LDH@BC obtained by successfully loading FeAl-LDH onto biochar (BC) is used to the Cr(VI)-contaminated soil remediation. The efforts of loading, initial pH, concentration and dosage are investigated. The results indicate that the immobilization process of Cr(VI) in soil could be well described by the pseudo-second-order kinetic model and maximum adsorption capacity of FeAl-LDH@BC is 42.78 mg/g at a temperature of 298 K. Additionally, The physicochemical properties of FeAl-LDH@BC are characterized by SEM, EDS, XRD, FTIR and XPS. The characterization results suggest that the immobilization mechanism involved adsorption and reduction. Cr(VI) is immobilized by adsorption to the layers of FeAl-LDH, the reduction of Cr(VI) to Cr(III) is then accomplished using Fe(II) as a reducing agent. In order to demonstrated the stability of composites for environmental restoration, the TCLP tests, dry-wet, freeze-thaw aging cycles, soil phytotoxicity tests, and microbial community are analyzed. The study shows that we provided a material for soil immobilization with high performance for the remediation of Cr(VI)-contaminated soil.

Mechanical properties of CFRP and shrinkage compensating concrete actively confined and strengthened short columns under freeze–thaw cycles

AbstractThis paper investigates the use of CFRP precast tubes filled with shrinkage‐compensating self‐consolidating concrete (SSCC) for strengthening columns. Compared to ordinary self‐consolidating concrete (OSCC), SSCC can address the stress hysteresis issue caused by the poor cooperation between CFRP and concrete structures, while also enhancing the mechanical properties of columns. Experimental and theoretical studies were conducted to examine the tensile mechanical properties of CFRP materials and the axial compressive mechanical properties of CFRP precast tubes strengthened with OSCC or SSCC under freeze–thaw cycles. Various variables were considered, such as freeze–thaw cycles, types of strengthening concrete, and the number of CFRP layers. The results indicate that freeze–thaw cycles do not affect the ultimate tensile strength of CFRP but significantly reduce its ultimate tensile strain. SSCC‐strengthened specimens exhibit higher load‐carrying capacity and better ductility compared to OSCC‐strengthened specimens. In addition, compared to the strengthening of two‐layer CFRP and SSCC, the strengthening of one‐layer CFRP and SSCC more effectively demonstrates the advantage of the post‐tensioning effect. However, the ductility coefficient of the columns decreases with an increase in the number of freeze–thaw cycles, regardless of the number of CFRP layers or type of strengthened concrete. Modified theoretical model accurately predicts the normalized peak stress and strain of the strengthened specimens.

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Diagnostic Value of Anti-HTLV-1-Antibody Quantification in Cerebrospinal Fluid for HTLV-1-Associated Myelopathy.

The diagnostic accuracy of cerebrospinal fluid (CSF) anti-human T-cell leukemia virus type I (HTLV-1) antibody testing for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM) remains unclear. Therefore, we measured the anti-HTLV-1 antibody levels in CSF using various test kits, evaluated the stability of CSF antibodies, and performed a correlation analysis using the particle agglutination (PA) method, as well as a receiver operating characteristic (ROC) analysis between patients with HAM and carriers. The CSF anti-HTLV-1 antibody levels were influenced by freeze-thaw cycles but remained stable when the CSF was refrigerated at 4 °C for up to 48 h. Measurements from 92 patients (69 patients with HAM and 23 carriers) demonstrated a strong correlation (r > 0.9) with the PA method across all six quantifiable test kits. All six test kits, along with CSF neopterin and CXCL10, exhibited areas under the ROC curve greater than 0.9, indicating a high diagnostic performance for HAM. Among these, five test kits, Lumipulse and Lumipulse Presto HTLV-I/II, HISCL-UD (a kit under development), HTLV-Abbott, and Elecsys HTLV-I/II, established a cutoff with 100% sensitivity and maximum specificity, achieving a sensitivity of 100% and a specificity ranging from 43.5% to 56.5%. This cutoff value, in combination with clinical findings, will aid in the accurate diagnosis of HAM.

An Antiferroelectric‐Coated Metal Foam Infiltrated with Liquid Metal as a Dielectric Capacitor

Nickel metal foams serve as both a substrate and bottom electrode for a dielectric capacitor using atomic‐layer deposition (ALD) and a eutectic gallium–indium (EGaIn) liquid metal (LQM) counter electrode. The conformal dielectric has a composition of 6.25% Al–HfO2 in the antiferroelectric phase, confirmed with polarization versus electric field measurements. Liquid EGaIn is pressure‐infiltrated within the coated foams to form the dielectric capacitor. Capacitances up to 4 μF are realized. Calorimetry of the infiltrated capacitor shows a 60 J g−1 latent heat upon melting a frozen EGaIn electrode, suggesting that the phase change can alleviate thermal deviations from pulsed power capacitor operation. Infiltrated capacitors are also shown to survive bending and freeze–thaw cycles. The metal foam–ALD dielectric–LQM capacitor shows a combined set of thermal and electrical properties not available in other classes of capacitors.

Development of an intelligent geographic information system for mountain roads monitoring: Ground data collection and analysis

This study examines the development of an intelligent geographic information system for mountain road monitoring. To make well-informed and timely management decisions in the planning, construction, and maintenance of mountain roads, and to anticipate potential critical situations and their effects on road conditions, it is imperative to employ modern methodologies. This study involves data collection from a specific section of a mountain road situated near Almaty, Kazakhstan. We gathered data on the road section through visual assessment, measurements of the coefficient of adhesion, and the acquisition of material samples from the structural layers of the roadbed. Based on the visual assessment and surface adhesion measurements, it became evident that the deformation of the studied road section, which includes a network of cracks and "non-standard" transverse cracks, is attributed to mountain mass shifts and water flows from slopes. Laboratory analysis of the collected samples revealed that excessive water saturation could result in cracks during freeze-thaw cycles, while a low resistance coefficient would lead to softening during humid conditions. An Intelligent Geographic Information System (IGIS) will incorporate the collected data alongside open remote sensing and weather data. The objective is to utilize this integrated system in the future for forecasting road conditions and maintenance requirements for similar roads in mountainous regions of the area. The measurements are carried out according to the state standards. That makes the system useful for government management purposes.

Experimental Study on Water and Salt Migration and the Aggregate Insulating Effect in Coarse-Grained Saline Soil Subgrade under Freeze–Thaw Cycles

Understanding multiphase transformations and the migration of heat, water, vapor, and salt in coarse-grained saline soil under groundwater recharge and environmental freeze—thaw cycles is crucial for ensuring the stability of highway infrastructures. To clarify the water, heat, vapor, and salt migration patterns in coarse-grained saline soil, as well as the salt-insulating effect of the aggregate insulating layer, an experimental study was conducted in a soil column model under pressureless water replenishment with fluorescein-labeled liquid water under freeze—thaw cycles. The results showed that the temperature in the saline soil columns periodically changed and that hysteresis effects occurred during temperature transfer. External water replenishment and the content of liquid water inside the soil exhibited nonlinear changes with environmental temperatures. After multiple freeze—thaw cycles, two water and salt accumulation zones formed within the coarse-grained saline soil subgrade. The migration of liquid water resulted in a water and salt accumulation zone in the nonfrozen zone, whereas the migration of water vapor yielded a water and salt accumulation zone in the frozen zone. To prevent water and salt migration, a 20 cm thick gravel insulating layer could be laid at a distance of 10 cm from the bottom of the roadbed, which could provide a satisfactory salt-insulating effect. The research results provide a theoretical basis and guidance for regulating the stability of subgrades in saline soil areas.

Hydration mechanism of alkali-activated cementitious materials entirely prepared by solid wastes

This study explores the hydration mechanisms and mechanical performance of alkali-activated cementitious materials made entirely from industrial solid waste, specifically fly ash and blast furnace slag. With increasing demand for sustainable construction solutions, these materials are alternatives to traditional cement. However, despite recent advancements, challenges remain in optimizing their hydration processes and enhancing material performance. Using 6.45 %NaOH as the base activator, the Si−O and Al−O bond vibrations were significantly stronger at 28 and 90 days of hydration compared to 5.13 %Na2CO3 and 20 % CCS, with the Si−O vibration peaks shifting from 459 cm−1 to 451 cm−1, suggesting that the solvation and aggregation of silicates and aluminates were enhanced, producing more C−S−H and N(C)−S−H gels. The compressive strength of NaOH reached 29.76 MPa at 28 days and 52.30 MPa at 90 days as compared to the compressive strengths of 29.12 MPa and 11.6two MPa for Na2CO3 and CCS, respectively. Scanning electron microscope scans showed that the microstructure of NaOH was denser, which allowed for a rapid stimulation of the raw material activity. After 25 freeze-thaw cycles, the loss of strength was less than 1.46 %, and the mass loss was less than 0.41 %, showing excellent durability. Corrosion resistance is also high, with coefficients of 143.54 % and 119.96 % in NaOH and Na2SO4 environments, respectively. This study optimized the alkali activator ratio in alkali-activated cementitious materials made from solid waste, enhancing freeze-thaw stability, corrosion resistance, and mechanical properties by promoting the formation of C−S−H and N(C)−S−H gels. Using sodium carbonate, sodium hydroxide, and calcium carbide slag as activators accelerated hydration and reduced hardening time, offering a theoretical and technological foundation for green, sustainable construction materials.

Dynamic Behavior of Rubber Fiber-Reinforced Expansive Soil under Repeated Freeze–Thaw Cycles

Large volumes of waste tires are generated due to the rapid growth of the transportation industry. An effective method of recycling waste tires is needed. Using rubber from tires to improve problematic soils has become a research topic. In this paper, the dynamic response of rubber fiber-reinforced expansive soil under freeze–thaw cycles is investigated. Dynamic triaxial tests were carried out on rubber fiber-reinforced expansive soil subjected to freeze–thaw cycles. The results showed that with the increase in the number of freeze–thaw cycles, the dynamic stress amplitude and dynamic elastic modulus of rubber fiber-reinforced expansive soils first decrease and then increase, and the damping ratio first increases and then decreases, all of which reach the turning point at the 6th freeze–thaw cycle. The dynamic stress amplitude and dynamic elastic modulus decreased by 59.4% and 52.2%, respectively, while the damping ratio increased by 99.8% at the 6th freeze–thaw cycle. The linear visco-elastic model was employed to describe the hysteretic curve of rubber fiber-reinforced expansive soil. The elastic modulus of the linear elastic element and the viscosity coefficient of the linear viscous element first decrease and then increase with the increase in the number of freeze–thaw cycles; all reach the minimum value at the 6th freeze–thaw cycle. The dynamic stress–dynamic strain curve calculation method is established based on the hyperbolic model and linear visco-elastic model, and the verification shows that the effect is better. The research findings provide guidance for the improvement of expansive soil in seasonally frozen regions.

Cold Temperatures and Weather Processes on Human Bone

Amongst research on forensic skeletal material found in a variety of environmental conditions, cold climate contexts and the effects of various associated weather processes are very under-researched. This paper will examine existing sources on the effects of cold and freezing weather conditions on forensic anthropology analyses. It will review the various taphonomic processes that occur from sub-zero temperatures, like snow, ice, and freeze-thaw cycles on bone, as well as the associated challenges that could arise in identifying important features and analyzing skeletal remains when found in these conditions. Finally, this paper will discuss the research gap of the effects of cold weather climates on bone and will explore some much-needed new and expanding avenues of research on this topic, which could aid forensic identifications and analyses on human remains in cold climates.

B-051 Clinical Validation of Vectra® DA: A Multi-Biomarker Based Test for the Objective Measurement of Disease Activity in Patients with Rheumatoid Arthritis

Abstract Background The Vectra® DA test measures serum levels of 12 protein biomarkers associated with rheumatoid arthritis (RA) and uses these levels in an algorithmic calculation to generate a numeric score that represents RA disease activity where established categories are low for scores 1 to 29, moderate for 30 to 44, and high for 45 to 100. LabCorp Specialty Lab in Calabasas, CA completed the quantitative analytical validations of 12 Vectra biomarkers (SAA, CRP, VCAM-1, IL-6, TNF-RI, EGF, VEGF-A, Leptin, Resistin, MMP-1, MMP-3, and YKL-40) and the clinical verification of the Vectra score algorithm. Methods The Vectra test consists of the quantitative measurements of EGF, Leptin, MMP-1, TNF-R1, VEGF, MMP-3, Resistin, VCAM, YKL-40, CRP, SAA and IL-6 using multiplex immunoassay platforms. The data acquired from each biomarker assay is processed through an algorithm where a composite Vectra score adjusted based on age, gender, and adiposity of the patient is computed. Analytical parameters validated for each biomarkers include sensitivity, precision, accuracy, specificity and stability. Precision was validated using pooled human serum controls at low, moderate, and high Vectra score levels. Method comparison was performed using 584 clinically defined serum samples. Quantitatively measured analyte values and computed Vectra scores by the Labcorp Vectra assay were compared with Vectra data produced by Myriad laboratory. Results Intra- and inter-assay sample precision of the final Vectra score was <13% and <18%, respectively. Sample stability using freshly collected serum subject to ambient and refrigerated temperature up to 14 days and frozen up to 364 days and up to 6 freeze-thaw cycles were acceptable. Of 584 clinical Vectra data compared, Labcorp vs Myriad, 96% of data were comparable within the acceptable criteria. Correlation of Vectra score from Labcorp and Myriad was excellent. A linear least square model resulted in a correlation coefficient (R) of 0.981 and a Deming slope of 1.009. Qualitative method comparison of Vectra scores resulted in excellent agreement of risk of radiographic progression and rheumatoid arthritis disease activity. A 91% agreement of risk category match between Labcorp and Myriad and 100% agreement of Vectra scores within 1 risk category was achieved. Conclusions We validated the Vectra® DA multiplex assay for measuring serum levels of 12 protein biomarkers associated with RA. Vectra combines biomarker levels into a personalized disease score that represents a patient’s RA inflammation and predict their risk of radiographic progression. High Vectra® DA scores (> 44) have been associated with a 20% 1-year risk of radiographic progression while low scores (< 30) carry only a 1% risk. Thus, the Vectra score provides an objective measurement of RA disease activity that can be used in combination with existing assessment tools to aid physicians to manage patients with RA.

B-021 Impact of Assay Conditions on FT4 Measurement Accuracy of Equilibrium Dialysis LC/MS/MS Clinical Assay

Abstract Background Reliable FT4 measurements are vital for accurate diagnosis and effective management of thyroid disorders. However, currently used FT4 immunoassays (IAs) lack standardization, leading to significant variations between platforms. Equilibrium dialysis (ED) coupled with LC-MS/MS analysis, considered the gold standard for FT4 measurement, has been adopted as a reference measurement procedure (RMP) for IA standardization. This study aimed to establish a high-throughput version of the routine clinical FT4 assay based on ED-LC/MS/MS technology and assess the impact of altered assay conditions on measurement accuracy. Methods A commercially available micro-ED plate was employed for ED-LC/MS/MS analysis. FT4 extraction from the dialysate was performed by utilizing a 96-well C18 SPE plate, followed by FT4 quantitation via LC-MS/MS in positive ion mode. Certified primary reference material was used to calibrate the assay. To evaluate assay robustness, the effects of minor method modifications were studied, including incubation time of ED, serum/buffer ratios in ED inserts, ED incubation temperature, shaker speed during ED, serum sample dilution ratio, and dialysate sample dilution ratio. Additionally, short-term and long-term stability of serum FT4 were assessed. Results The developed ED-LC/MS/MS assay successfully resolved T4, T3, reverse triiodothyronine (rT3), and other interferences within 4 minutes using C18 chromatography. The assay's linear range (0.5-100 pg/mL) encompassed clinically relevant FT4 concentrations across hypo- and hyperthyroid patient samples. Excellent agreement was observed between the routine assay based on ED-LC/MS/MS and CDC RMP with a Deming regression slope near 1 (95%CI: 0.87-1.06). Furthermore, serum/buffer ratios from 1:1 to 1:2.5 in ED inserts, shaker speeds from 75 to 150 rpm, and ED incubation times from 16 to 20 hours did not significantly affect FT4 measurement. However, elevated ED temperature (38°C) led to a more than 10% increase in FT4 values. Serum FT4 remained stable when exposed to room temperature for 12 hours, five freeze-thaw cycles, and -70°C storage for 1.5 years. Additionally, dilution of sera by up to 3-fold before ED did not alter FT4 measurement results. Diluting dialysate samples at least 3 times prior to SPE extraction proved accurate for samples exceeding the calibration curve range. Conclusions In conclusion, we successfully developed a routine clinical FT4 assay based on ED-LC/MS/MS that generates data comparable to the RMP. The assay exhibits robustness, with several altered conditions not significantly impacting measurement accuracy. This high-throughput and accurate assay demonstrates suitability for both clinical laboratories and large-scale epidemiological studies. Disclaimer: The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention/the Agency for Toxic Substances and Disease Registry. Use of trade names is for identification only and does not imply endorsement by the Centers for Disease Control and Prevention, the Public Health Service, and the US Department of Health and Human Services.

A-277 Viability of multi-drug resistant organisms in a fecal collection and transport system stored at ultra-low temperature

Abstract Background Epidemiological studies are constantly investigating new, easier ways to collect and store patient specimens that allow for flexible testing windows and long-term storage as well as accurate quantification of organisms of interest. The FecalSwabTM system (Copan, Brescia, Italy) is intended for the collection and preservation of rectal and fecal specimens. This system includes a preservation medium which serves to maintain the viability of enteric pathogens during transport to a clinical laboratory for up to 72 hours at 4oC. The objective of this study was to assess the continued viability of multi-drug resistant organisms (MDROs) suspended in the FecalSwab sample format when frozen at -80°C and the impact of freeze-thaw cycles. Methods A total of 40 organisms were chosen spanning methicillin-resistant Staphylococcus aureus (MRSA, n=10), carbapenem-resistant Pseudomonas aeruginosa (CRPA, n=5), carbapenem-resistant Enterobacterales (CRE, n=5), vancomycin-resistant Enterobacterales (VRE, n=10) and extended-spectrum beta-lactamase containing Enterobacterales (ESBL, n=10). Each organism was spiked into FecalSwab at standardized concentrations. At each time point, FecalSwab media was plated onto blood agar and colonies were quantified. Each of the 40 organisms were assessed one-week post-freeze and over the course of freeze-thaw cycles at days 3 and 5. The survival of each MDRO was evaluated by calculating a difference between the concentration of organisms recovered (CFU per 10uL media) at each time point and the concentration of organisms confirmed present at the time of inoculation. Percent recovery was calculated from this difference. Results One week after freezing, the percent recovery for MRSA, VRE, ESBL, CRE, and CRPA averaged to 102%, 201%, 17.8%, 7.6%, and 0.8%, respectively (Kruskal Wallis p < 0.001), with significant differences noted between gram positive and gram negative organisms (Kruskal Wallis p <0.001). Conclusions Epidemiological studies interested in MDRO surveillance rely on methodologies that allow for accurate quantification of viable organisms. In this study, we’ve evaluated the viability of several multi-drug resistant organisms when frozen at -80°C in the FecalSwab. The FecalSwab system is intended for the collection of rectal swab and fecal specimens and to preserve the viability of enteric pathogenic bacteria for testing in the clinical laboratory. Although it was not specifically designed to preserve MDROs, it performed well with MRSA and VRE, but less well with CRE, CRPA and ESBL organisms. When using the FecalSwab system, the observed gram-specific differences may inform the suitability of this system depending on the organism(s) of interest.

Experimental investigation on the frost resistance of RCC layers with various interface treatments

This research investigates the influence of various interface treatment methods on the frost resistance performance of Roller Compacted Concrete (RCC) layers. Freeze-thaw cycle tests were conducted on RCC with interfaces treated using cement mortar, expansion agent mortar, and nano-SiO2 mortar. The study evaluated shear failure modes, shear strength, crack expansion, pore structure, and liquid uptake of the RCC interface after freeze-thaw cycles under different treatment methods. Results reveal that expansion agent mortar and nano-SiO2 mortar improve the shear strength of RCC after freeze-thaw cycles more effectively than cement mortar. The freeze-thaw cycles increase the width and expansion rate of cracks at the RCC interface during the shear process, while mortar treatments help delay crack development. Additionally, the pore volume at the RCC interface gradually increases, and the uniformity of pore distribution decreases under freeze-thaw cycles. During liquid uptake, mortar treatments slow down the upward migration of liquids by improving the pore structure at the interface. The liquid uptake of RCC exhibits a distinct linear relationship with its shear strength and pore structure. As liquid uptake time increases, water first fills larger pores before gradually entering smaller ones. Freeze-thaw cycles cause an increase in pore volume and enlargement, which leads to greater liquid uptake. Based on the damage mechanism of the RCC interface under freeze-thaw conditions, a model of shear strength degradation due to freeze-thaw cycles was established, aligning well with experimental results. Mechanism analysis indicates that nano-SiO2 and expansion agents enhance frost resistance by filling interface pores and cracks through reactions with certain compounds, thereby improving the microstructure.

Study on resistance of basalt fiber reinforced concrete to sulfate erosion after cryogenic freeze-thaw cycles

This study aims to investigate the mechanical properties of concrete structures, such as liquefied natural gas (LNG) storage tanks, subjected to the effects of cryogenic freeze-thaw cycles and erosive environmental conditions. Mechanical properties of basalt fiber reinforced concrete (BFRC) with normal temperature (25 °C) and different temperature gradients (25 °C ∼ -80 °C, 25 °C ∼ -160 °C), fiber content (0 %, 0.1 %, 0.2 %), and sulfate erosion days (0, 60, 120) were determined. The morphology of the eroded specimens was examined, and the microstructural characteristics were investigated by scanning electron microscope (SEM). The findings revealed that the introduction of basalt fiber (BF) in the concrete significantly changes the failure mode following sulfate erosion, causing specimens to fail by ductile failure rather than brittle failure. Moreover, the mechanical properties of concrete specimens decreased significantly with increasing temperature gradients of freeze-thaw cycles. Under non-erosive conditions, the compressive strength of plain concrete after undergoing freeze-thaw cycles from 25 °C to -160 °C decreased by 22.4 % compared to plain concrete that did not undergo freeze-thaw cycles, and the tensile strength decreased by 32.5 %. Adding fibers increased the mechanical properties of specimens. Specially, after undergoing freeze-thaw cycles from 25 °C to -160 °C and being subjected to 120 days of sulfate erosion, compared with plain concrete, the compressive strength of specimens with 0.2 % fiber content increased by 20.6 %, the tensile strength increased by 37.8 %, while also increasing flexural toughness. In addition, the sulfate erosion days also had a considerable impact on the deterioration of the mechanical properties of specimens. Specially, after undergoing freeze-thaw cycles from 25 °C to -80 °C and being subjected to 120 days of erosion, the eroded specimen with 0.1 % fiber content, the compressive strength decreased by 10.9 %, the tensile strength decreased by 11.6 % compared to specimens that were not eroded, while also decreasing flexural toughness. Combined with the experimental results, the strength deterioration models of BFRC related to the sulfate erosion days and BF content were proposed at 25 °C, after freeze-thaw cycles from 25 °C to -80 °C, and after freeze-thaw cycles from 25 °C to -160 °C. The aim is to provide some data reference for the development and application of BFRC in cryogenic environments.

Sustainable stabilization/solidification of Cu-contaminated seasonal frozen soil by epoxy resin: environmental risk assessment and engineering applicability

There are significantly toxic Cu contaminants in seasonal frozen soil areas under industrial production and mineral exploitation. However, the hydration reactions of mainstream alkaline curing agents such as cement are disturbed by the solidification and thawing of moisture, and their solidification/stabilization is ineffective to heavy metals. Therefore, there is an urgent requirement to optimize the use of current curing agents to improve the solidification/stabilization (S/S) effect of Cu contaminants in seasonal frozen soil areas. In this study, the Epoxy resin (EP) with excellent waterproofing and frost resistance was incorporated into artificially prepared Cu-contaminated soil to maintain a steady engineering application strength and inhibit the outward diffusion of toxic Cu contaminants under freeze-thaw cycles. The freeze-thaw resistance of EP-cured Cu-contaminated soil and the feasibility of EP remediation technology have been investigated, including mechanical properties, environmental effects and microstructure. The decline in mechanical strength and the increment in Cu leaching during freeze-thaw cycles are effectively suppressed by the remediation of EP. Even after 8 freeze-thaw cycles, there is merely a mechanical strength decline of 5%, solely a secondary Cu leaching of 4.74mg/L, and astonishingly a leachable index of 11.70 in the specimens with 12% EP dosage. The expansion phenomenon of pores and clay fractures under freeze-thaw cycles were gradually alleviated after incorporation of EP. The above results demonstrate the Cu-contaminated seasonal frozen soil remedied by EP are high-strength, basically non-toxic, and environmentally friendly material which are suitable for in-situ stabilization/solidification in seasonal frozen soil areas.

Investigation on the evolution of concrete pore structure under freeze-thaw and fatigue loads

Hydraulic concrete structures in seasonal frozen regions serve under freeze-thaw cycles and cyclic loading conditions which cause notable alterations in the concrete pore structure and a significant reduction in the mechanical properties and durability of concrete. To understand the macroscopic and mesoscopic damage processes and mechanism of concrete subjected to freeze-thaw cycles and cyclic loading lead, the compressive experiment and computed tomography test of concrete after freeze-thaw and fatigue loading tests were conducted. And the influences of freeze-thaw cycle damage and cyclic loading damage on the pore structure of concrete were analyzed. The relationships between concrete pore fractal dimension, compressive strength, and elastic modulus were revealed. The concrete average pore size can be regarded to grows linearly under freeze-thaw and cyclic loading. The porosity, pore volume, and pore surface area increase with the increase in freeze-thaw cycles, and their relationship can be represented by a quadratic function. However, they first decrease and then increase with the increase of loading cycles after a specific freeze-thaw cycles number. Under the combined action of freeze-thaw cycles and cyclic loading, the non-uniformity degree of concrete pore distribution decreases, and the overall structure is more regular. The distribution of single pore morphology tends to be spherical and banded, respectively. The cyclic loading promotes the extension of the internal pores and cracks of freeze-thaw-damaged concrete which aggravates damage of concrete. Under freeze-thaw cyclic loading, the concrete compressive strength and elasticity modulus is linearly and positively correlated with fractal dimension. With the increase of loading cycles number after freezing and thawing, the fractal dimension and compressive strength decrease, and the elasticity modulus has a larger dispersion. The relationship model between concrete compressive strength and fractal dimension can well describe the macroscopic and mesoscopic evolution of concrete under freeze-thaw and cyclic loading. The results can provide a scientific basis for improving the design and maintenance of concrete and benefit extending the long-term service life of hydraulic concrete structures in cold climates.

Heat transfer-deformation characteristics and fracture damage analysis during LN2 freeze-thaw process in different rank coals

Exploring the heat transfer and deformation characteristics of coal bodies of different coal ranks during the freeze-thaw process is of significant importance for analyzing the fracture mechanism under the effect of liquid nitrogen (LN2). This experiment targets lignite, bituminite, and anthracite under both saturated and dry conditions. A real-time temperature-strain monitoring system was employed to observe the heat transfer and deformation characteristics of coal samples with different ranks throughout the freeze-thaw cycle. Additionally, a nuclear magnetic resonance system was utilized to examine the characteristics of pore damage before and after fracturing. The findings reveal: (1) During the freeze-thaw process, the absolute value of the temperature evolution rate for dry coal samples shows a negative correlation with coal rank, indicating a close link between temperature diffusion and intrinsic coal properties like oxygen content and porosity. (2) For saturated coal samples, the absolute value of the temperature change rate during freezing decreases as the coal rank increases, with the opposite trend observed during thawing. The phase change effect of water in fractures during freezing can enhance internal temperature diffusion in the coal body, while it acts as an inhibitor during thawing. (3) Based on the trend of strain fluctuations, the coal body deformation process during the freeze-thaw cycle can be segmented into seven stages, summarizing the general mechanisms of deformation failure. (4) Under saturated conditions, the amplitude of elastic deformation for each sample is negatively correlated with coal rank, with the sequence for dry coal samples being bituminite > anthracite > lignite. (5) The formation of a sealed space at the beginning of freezing is identified as a necessary condition for deformation during the freeze-thaw process, with the formation and strength of the sealed space depending on the temperature diffusion rate, moisture content, and inherent properties of the coal sample.

Effect of gelled phases on the relevance of double emulsion gels for probiotics encapsulation, rheological properties, and stability

This study aimed to develop a stable double emulsion gel (DEG) based on whey protein cold-set gelation of the external water phase and carnauba wax-based solidification of the oil phase as a potential delivery system for probiotics in high-protein food products. The effect of the gelation of different phases on the microstructure, gel properties, and stability of DEGs under storage and freezing–thawing conditions and the viability of L. plantarum loaded in the inner water phase of DEGs were evaluated. The oil phase crystallization allowed the formation of stable DEGs during storage, showing negligible changes in consistency index, G′, and particle size after 56 d of storage and under four freeze–thaw cycles. The gelation of both the oil and external water phases allowed a stronger gel network formation, with a six times lower creaming index than non-gelled double emulsions. All samples demonstrated that the encapsulation of L. plantarum into the inner water phase of the DEG is beneficial for the storage stability of probiotics.