Freeze-thaw Research Articles

Comprehensive analysis of the relationship between yield stress and dewatering performance in sludge conditioning: Insights from various treatment methods

Understanding the relationship between sludge yield stress (σy) and dewatering performance is essential for optimizing sludge conditioning processes. This study systematically investigates the effects of various conditioning methods—including thermal hydrolysis (TH), freezing/thawing (FT), anaerobic digestion (AD), polyaluminum chloride (PAC), polyacrylamide (PAM), and Fenton treatment (Fenton)—on sludge yield stress and its correlation with dewatering efficiency. Using linear regression, partial least squares regression (PLSR), and correlation heatmap analyses, we reveal significant variations in the correlation between σy and dewatering indexes, including moisture content (Mc), capillary suction time (CST), and bound water proportion (Wb/Wt), depending on the conditioning method and intensity. Under FT and PAM conditioning, σy shows a strong negative linear correlation with dewatering performance, with Pearson's r values exceeding −0.880, indicating that a decrease in σy corresponds to improved dewatering efficiency. Conversely, AD conditioning exhibits a positive linear correlation, with r values up to 0.993, suggesting that an increase in σy correlates with reduced dewatering efficiency. For TH, PAC, and Fenton treatments, the correlation between σy and dewatering metrics is highly sensitive to changes in treatment intensity. In the PLSR analysis, the VIP values, which quantify the importance of each predictor variable, indicate that Wb/Wt in TH conditioning (VIP = 1.649) and CST in PAC (VIP = 1.309) and Fenton (VIP = 1.299) conditioning strongly influence σy. This study highlights the significant impact of conditioning methods and intensities on the correlation between σy and dewatering performance. While σy provides valuable insights as a predictive indicator, its predictive power is limited in more complex conditioning scenarios. Therefore, optimizing conditioning intensity and incorporating multiple rheological parameters are essential for achieving superior sludge dewatering outcomes.

Mechanical properties and acoustic emission characteristics of basalt fiber reinforced cemented silty sand subjected to freeze–thaw cycles

Freeze–thaw (F–T) cycling poses a significant challenge in seasonally frozen zones, notably affecting the mechanical properties of soil, which is a critical consideration in subgrade engineering. Consequently, a series of unconfined compressive strength tests were conducted to evaluate the influence of various factors, including fiber content, fiber length, curing time, and F–T cycles on the unconfined compression strength (UCS) of fiber-reinforced cemented silty sand. In parallel, acoustic emission (AE) testing was conducted to assess the AE characteristic parameters (e.g., cumulative ring count, cumulative energy, energy, amplitude, RA, and AF) of the same material under F–T cycles, elucidating the progression of F–T-induced damage. The findings indicated that UCS initially increased and then declined as fiber content increased, with the optimal fiber content identified at 0.2%. UCS increased with prolonged curing time, while increases in fiber length and F–T cycles led to a reduction in UCS, which then stabilized after 6 to 10 cycles. Stable F–T cycles resulted in a strength loss of approximately 30% in fiber-reinforced cemented silty sand. Furthermore, AE characteristic parameters strongly correlated with the stages of damage. F–T damage was segmented into three stages using cumulative ring count and cumulative energy. An increase in cumulative ring count to 0.02 × 104 times and cumulative energy to 0.03 × 104 mv·μs marked the emergence of critical failure points. A sudden shift in AE amplitude indicated a transition in the damage stage, with an amplitude of 67 dB after 6 F–T cycles serving as an early warning of impending failure.

Experimental Study on the Frost Resistance of Basalt Fiber Reinforced Concrete.

In this paper, the effect of basalt fiber (BF) on the frost resistance of concrete under different curing conditions was investigated, and its frost resistance mechanism was analyzed. Three different curing conditions (normal curing, short-term curing, and seawater curing) were adopted, and concrete with different BF volume contents was designed. Freeze-thaw (FT) tests were carried out using the rapid freezing method to test the frost resistance of basalt fiber reinforced concrete (BFRC). Additionally, the mass loss rate (MLR), relative dynamic modulus of elasticity (RDME) change, and compressive strength reduction of specimens during the freeze-thaw cycles (FTCs) were evaluated. The results show that when the BF content is 0.15%, under normal curing, short-term curing, and seawater curing conditions, the residual compressive strength of BFRC after FTCs was increased by 5.4%, 28.1%, and 30.9%, respectively, compared to plain concrete. By incorporating BF into concrete, the development of microcracks can be effectively retarded, and damage generation during FTCs can be reduced. In addition, the microscopic morphological characteristics and pore structure characteristics of concrete further elucidate the frost resistance mechanism of BFRC from a microscopic perspective.

Rapid and sensitive liquid chromatographic–tandem mass spectrometric methods for the quantitation of dolutegravir in human plasma and breast milk

BackgroundDolutegravir (DTG) is part of a first-line antiretroviral therapy (ART) for HIV management in drug-naïve individuals and is recommended for the treatment of HIV during pregnancy. Robust analytical tools to quantify DTG are necessary to support clinical trials that characterize its multi-compartment drug distribution. MethodsPotassium EDTA (K2EDTA) plasma or whole breast milk was spiked with DTG and an isotopically labeled internal standard. Samples were prepared via protein precipitation prior to LC–MS/MS analysis. The assays were validated in accordance with regulatory recommendations. ResultsAnalytical measuring ranges for DTG quantitation in plasma and breast milk were 100–10,000 ng/mL and 0.500 to 1000 ng/mL, respectively. Inter-assay precision and accuracy were 2.73 % to 3.41 % and −10.6 % to −5.37 % for plasma, and 4.24 % to 12.4 % and −5.63 % to 7.49 % for breast milk, respectively. DTG was stable for three freeze–thaw cycles and for at least 72 h at room temperature in matrix (plasma or breast milk). Additionally, whole blood was stable for 24 h at room temperature and 2 h under conditions of extended heat and humidity. Matrix effects for DTG in plasma and breast milk ranged from 101 % to 108 % and 78.2 % to 99.3 %, respectively. Quantitation in remnant plasma samples yielded measurable concentrations within the primary linearity of the assay. ConclusionsMethods to quantify DTG in human plasma and breast milk have been developed and validated. These assays were designed to satisfy all criteria for implementation in clinical and clinical trial settings.

Employing automated electrical resistivity tomography for detecting short- and long-term changes in permafrost and active-layer dynamics in the maritime Antarctic

Abstract. Repeated electrical resistivity tomography (ERT) surveys can substantially advance the understanding of spatial and temporal freeze–thaw dynamics in remote regions, such as Antarctica, where the evolution of permafrost has been poorly investigated. To enable time-lapse ERT surveys in Antarctica, an automated ERT (A-ERT) system is required, as regular site visits are not feasible. In this context, we developed a robust A-ERT prototype and installed it at the Crater Lake CALM-S site on Deception Island, Antarctica, to collect quasi-continuous ERT measurements. We developed an automated data processing workflow to efficiently filter and invert the A-ERT datasets and extract the key information required for a detailed investigation of permafrost and active-layer dynamics. In this paper, we report on the results of two complete year-round A-ERT datasets collected in 2010 and 2019 at the Crater Lake CALM-S site and compare them with available climate and borehole data. The A-ERT profile has a length of 9.5 m with an electrode spacing of 0.5 m, enabling a maximum investigation depth of approximately 2 m. Our detailed investigation of the A-ERT data and inverted results shows that the A-ERT system can detect the active-layer freezing and thawing events with high temporal resolution. The resistivity of the permafrost zone in 2019 is very similar to the values found in 2010, suggesting the stability of the permafrost over almost 1 decade at this site. The evolution of thaw depth exhibits a similar pattern in both years, with the active-layer thickness fluctuating between 0.20–0.35 m. However, a slight thinning of the active layer is evident in early 2019, compared to the equivalent period in 2010. These findings show that A-ERT datasets, combined with the new processing workflow that we developed, are an effective tool for studying permafrost and active-layer dynamics with very high resolution and minimal environmental disturbance. The ability of the A-ERT setup to monitor the spatiotemporal progression of thaw depth in two dimensions, and potentially in three dimensions, and to detect brief surficial refreezing and thawing of the active layer reveals the significance of the automatic ERT monitoring system to record continuous resistivity changes. An A-ERT monitoring setup with a longer profile length can investigate greater depths, offering effective monitoring at sites where boreholes are costly and invasive techniques are unsuitable. This shows that the A-ERT setup described in this paper can be a significant addition to the Global Terrestrial Network for Permafrost (GTN-P) and the Circumpolar Active Layer Monitoring (CALM) networks to further investigate the impact of fast-changing climate and extreme meteorological events on the upper soil horizons and to work towards establishing an early warning system for the consequences of climate change.

Differences in physicochemical properties and structure of red sorghum starch: Effect of germination treatments

AbstractBackground and ObjectivesGermination has been extensively studied, but the changes in different starch components have not yet been entirely elucidated. The aim of this study was to assess the effects of germination on the starch composition, physicochemical properties, and structure of red sorghum seeds.FindingsGermination of red sorghum starch led to decreased amylose, water absorption, and syneresis, but increased oil absorption, solubility, and swelling power. The freeze–thaw stability of germinated sorghum starch improved. However, the starch paste exhibited thinning under shear, suggesting its gel structure was susceptible to damage. The starch's peak viscosity and breakdown value increased significantly with the increase in germination time, whereas the setback value decreased. Germination treatment did not alter the chemical structure of the starch, but it increased the porosity and the number of dents on the surface of starch granules. Notably, the in vitro digestibility of the starch increased significantly after germination.ConclusionsThe germination treatment of red sorghum affected the structure and physicochemical properties of the isolated starch to some extent.

Effects of Preanalytical Sample Collection and Handling on Comprehensive Metabolite Measurements in Human Urine Biospecimens.

Epidemiology studies evaluate associations between the metabolome and disease risk. Urine is a common biospecimen used for such studies due to its wide availability and non-invasive collection. Evaluating the robustness of urinary metabolomic profiles under varying preanalytical conditions is thus of interest. Here we evaluate the impact of sample handling conditions on urine metabolome profiles relative to the gold standard condition (no preservative, no refrigeration storage, single freeze thaw). Conditions tested included the use of borate or chlorhexidine preservatives, various storage and freeze/thaw cycles. We demonstrate that sample handling conditions impact metabolite levels, with borate showing the largest impact with 125 of 1048 altered metabolites (adjusted P<0.05). When simulating a case-control study with expected inconsistencies in sample handling, we predicted the occurrence of false positive altered metabolites to be low (< 11). Predicted false positives increased substantially (≥63) when cases were simulated to undergo alternate handling. Finally, we demonstrate that sample handling impacts on the urinary metabolome were markedly smaller than those in serum. While changes in urine metabolites incurred by sample handling are generally small, we recommend implementing consistent handling conditions and evaluating robustness of metabolite measurements for those showing significant associations with disease outcomes.

How water, temperature, and seismicity control the preconditioning of massive rock slope failure (Hochvogel)

Abstract. The anticipation of massive rock slope failures is a key mitigation strategy in a changing climate and environment requiring a precise understanding of pre-failure process dynamics. Here we exploit &gt;4 years of multi-method high-resolution monitoring data from a large rock slope instability close to failure. To quantify and understand the effect of possible drivers (water from rain and snowmelt, internal rock fracturing, and earthquakes), we correlate slope displacements with environmental data, local seismic recordings, and earthquake catalogues. During the snowmelt phase, displacements are controlled by meltwater infiltration with high correlation and a time lag of 4–9 d. During the snow-free summer, rainfall induces accelerations with a time lag of 1–16 h for up to several days without a minimum activation rain sum threshold. Rock fracturing, linked to temperature and freeze–thaw cycles, is predominantly near the surface and unrelated to displacement rates. A classic Newmark analysis of recent and historic earthquakes indicates a low potential for immediate triggering of a major failure at the case site, unless it is already very close to failure. Seismic topographic amplification of the peak ground velocity (PGV) at the summit ranges from a factor of 2–11 and is spatially heterogeneous, indicating a high criticality of the slope. The presented in-depth monitoring data analysis enables a comprehensive rockfall driver evaluation and indicates where future climatic changes, e.g. in precipitation intensity and frequency, may alter the preconditioning of major rock slope failures.

Enhancement of intracellular extraction from Oscillatoria okine and the potential use of the extract as a supplement to fetal bovine serum in animal cell culture

A robust cell wall and well-organized thylakoid cyanobacteria can be candidates as a promising resource for C-phycocyanin (C-PC) and intracellular applications in various biotechnological areas. However, the development of extraction techniques with minimal chemical contamination to obtain the components remains an ongoing challenge. This study aimed to assess the efficacy of C-PC and intracellular extraction from Ocillatoria okeni TISTR8549 utilizing freezing-thaw (FT), pulsed electric field (PEF), and high-pressure homogenization (HPH) techniques. Additionally, the potential of O. okeni extract as a supplement and substitute for fetal bovine serum (FBS) in HaCaT cell culture was investigated. FT appeared to be the most proper method for C-PC extraction, yielding the highest purity and yield, although requiring 18 cycles for product accomplishment. PEF seemed unsuitable for intracellular component extraction from cyanobacteria with thick cell walls. The need for increased pulses resulted in thermal elevation and prolonged incubation times led to protein degradation. HPH proves to be an effective method for intracellular extraction, yielding high protein content suitable for the potential substitution of FBS in mammalian cell culture. Particularly, increasing pressure during HPH extraction leads to a decrease in protein yield. Resazurin and SRB assays revealed that adding algal extract in culture medium at concentrations of 1 % (w/v) improved HaCaT cell viability without disrupting cell morphology and metabolic processes. However, substituting algal extract in FBS resulted in cell proliferation decrease. Therefore, supplementing O. okeni extract during cell culture improved HaCaT cell proliferation, but it was unsuitable substitute for FBS in the culture medium. However, the feasibility of employing algal extracts as FBS replacements in cell culture is interesting and warrants further detailed investigation into the specific intracellular components that could serve as substitutes for FBS. Such an approach could offer an alternative source, mitigating ethical concerns and reducing costs associated with FBS usage.

Chestnut soil organic carbon is regulated through pore morphology and micropores during the seasonal freeze–thaw process

Soil aggregates are basic structural units in soil organic carbon (SOC) protection. In alpine ecosystems, the seasonal freeze–thaw (FT) process characterizes soil formation and nutrient cycling. However, previous studies were mostly based on simulated FT experiments, which amplified the effects of natural FT processes. And, the regulations of pore structure on SOC protection/loss of aggregates during the FT processes were still not well understood. To investigate the effect of the seasonal FT process on SOC and pore structure of aggregates, as well as the interactions among them, soil samples were selected during a whole seasonal FT cycle, which can be divided into four periods: unstable freezing (UFP), stable frozen (SFP), unstable thawing (UTP), and stable thawed periods (STP). The results demonstrated that freezing increased SOC concentration as the total organic carbon (TOC) content of all aggregate fractions peaked in the SFP (17.46 g/kg on average). The TOC content of aggregates in the UFP dropped to 7.91 g/kg on average, which revealed a dramatic SOC loss after thawing began. Thawing also decreased the proportions of particulate organic carbon (POC) compared with mineral-associated organic carbon (MAOC). The highest microbial abundance was also found in the SFP. Freezing promoted the formation of pores > 80 μm while thawing increased the regularity of pore morphology. Pore structure explained 48.77 % of the SOC variance in the thawing period, but only 19.29 % of that in the freezing period. Overall, in the freezing process, soil pore structure impacted the SOC input by mediating pore morphology. In the thawing process, soil pore structure inhibited SOC loss by enhancing the formation of pores < 15 μm. These results demonstrate new perspectives on the soil aggregate microstructure–microbe–SOC interactions.

Freeze-thaw impacts on geocell-stabilized bases considering effects of water supply and compaction

Although Novel Polymeric Alloy (NPA) geocells have been applied to stabilize road bases against the freeze-thaw (F-T) damage in practice, the relevant research lags the application. A scarcity of research has been reported to comprehensively evaluate the benefits of geocell stabilization in enhancing the F-T performance of bases. This study aims to investigate quantitatively the F-T performance of geocell-stabilized bases, focusing on two influencing factors-i.e., water supply and degree of compaction in the bases. A series of model-scale experimental tests (19 tests) was conducted using an upgraded customized apparatus. The results showed that the inclusion of geocells was beneficial for reducing frost heave and thaw settlement as well as mechanical properties (i.e., stiffness and ultimate bearing capacity) of road bases. The benefit of geocells was more remarkable for the well compacted bases than for the poorly compacted bases. The benefit was more pronounced in the open system than in the closed system.

Experimental Investigation on the Performance of SBS-Modified Asphalt Waterproofing Membrane by Thermo-Oxidative Aging and Freeze-Thaw Cycle.

With global warming in recent years, extreme weather conditions have increased in frequency and intensity, exacerbating the challenges for waterproofing materials. The current stages of SBS asphalt waterproofing membrane aging research mainly focus on the raw materials and modifiers in a single factor; multifactor-coupled aging research is less studied. This study focused on the coupled aging characteristics of SBS-modified asphalt waterproofing membranes, aiming to reveal the mechanism of its influence on the material's performance under the environmental effects of high temperature and freeze-thaw. Through the accelerated aging test, we simulated the environmental conditions of high temperature in summer and freeze-thaw in winter to observe the mechanical properties of waterproofing membranes, low-temperature flexibility, and apparent phenomena. Then, Fourier transform infrared spectroscopy (FTIR) evaluated the performance and chemical structure of SBS-modified asphalt waterproofing membranes after aging by the coupled aging of the thermo-oxidative freeze-thaw cycle. The results showed that the low-temperature flexibility of the waterproofing membranes was significantly reduced after the coupled aging effect, and, at the same time, their tensile strength was also reduced. However, despite the tensile properties being impaired, the membrane maintained good ductility, and its elongation at break did not fall below 47%.

Study on mechanical properties of a roadbed rehabilitation polyurethane grouting material after freeze–thaw cycles

Study on mechanical properties of a roadbed rehabilitation polyurethane grouting material after freeze–thaw cycles

Effect of alkali dosage and silicate modulus on the deterioration of alkali-activated concrete properties subjected to sodium chloride attack and freeze thaw cycles

The deterioration mechanism of alkali-activated slag-fly ash-steel slag concrete (AAC) under sodium chloride attack and freeze-thaw (SF-T) cycles was investigated through a multi-scale methodology. Results showed that appropriate water glass modulus and higher Na2O dosage increased the compressive strength and salt-frost resistance of AAC. The mass loss in AAC was concentrated in the first 100 SF-T cycles, but PCC increases linearly with the SF-T cycles. The salt-frost resistance of PCC was similar to that of AAC samples Na2O dosage of 5 %. Higher Na2O dosage reduces the amount of unreacted precursor, thus reducing the porosity and improving the pore structure of concrete. However, increasing Na2O dosage has not limited the crack development, and the crack width in AAC was greater than in PCC after SF-T cycles. The porosity and average pore size of the concrete increased after SF-T cycles. Friedel's salt was only present in PCC, and NaCl crystals were observed in AAC.

An Investigation of the Effects of Thermo-Oxidative Aging and the Freeze–Thaw Cycle on the Performance of Polyester-Based, Self-Adhesive Asphalt Waterproofing Membranes

An Investigation of the Effects of Thermo-Oxidative Aging and the Freeze–Thaw Cycle on the Performance of Polyester-Based, Self-Adhesive Asphalt Waterproofing Membranes

Evaluation of Dynamic Mechanical Properties of Steel-Fiber-Reinforced Concrete Subjected to Freeze–Thaw Cycles

This study investigates the structural characteristics of SFRC with different amounts of steel fibers following exposure to freeze–thaw cycles, while taking into account various levels of confinement pressure and rates of deformation. The focus of the research is to examine the dynamic mechanical properties of SFRC exposed to freeze–thaw cycles. The inclusion of steel fibers improves the strength of concrete during freeze–thaw cycles, with 1% steel fiber content being the most effective. Strain rate and confining pressure significantly impact the strength and failure mode of SFRC. The strength of concrete increases linearly with the strain rate. With no confining pressure, the cracks in the concrete specimen align with the direction of the applied stress. And with confining pressure, concrete exhibits diagonal shear failure. Microstructural analysis results from scanning electron microscopy are consistent with the macroscopic properties.

A self-adaption robust superhydrophobic cement mortar for resistance of cold environment

Superhydrophobic coatings have wide range of engineering applications due to its excellent wettability. However, the durability of superhydrophobic coatings is still challenging under complex environments, especially in cold regions. In this study, we prepared a new self-adaption superhydrophobic cement mortar (SSCM) by wettability modified aggregates with polydimethylsiloxane adhesive and silica nanoparticles decorated by 1H,1H,2H,2H-perfluorodecyltriethoxysilane. Subsequently, a series of multi-scale characteristics of the SSCM sample were systematically investigated, including the micro morphology, the chemical compositions, the self-adaption robustness, the anti−/de-icing properties, and the freeze-thaw (F-T) resistance. The results indicate that surface and inside of the SSCM samples exhibit a self-adaption superhydrophobicity with the 150.0° contact angle due to the low surface energy micro/nano structure of wettability modified aggregates. Meanwhile, the SSCM sample shows excellent anti−/de-icing abilities due to the stable rough micro/nano structure under negative-temperature ambient, which can delay the droplet freezing time by 4.3 times than that of the contrast sample. Additionally, the newly exposed section of SSCM sample can still have the self-adaption superhydrophobicity and endow significant F-T resistance even if the surface of SSCM was damaged. Meanwhile, the SSCM sample can improve the F-T resistance by 45 % compared to the contrast sample. This work provides a new strategy to solve the durability limitation of superhydrophobic coating in engineering practice.

Experimental investigation of freeze–thaw effects on the micropore properties of expansive soil using NMR–SEM techniques

Experimental investigation of freeze–thaw effects on the micropore properties of expansive soil using NMR–SEM techniques

Research on performance variations of different asphalt binders results from microwave heating during freeze-thaw cycles

Microwave heating (MH) as a sustainable pavement maintenance method can effectively repair the cracks caused by freeze-thaw (FT) damage. However, binders' properties may be weakened during this process then reduces the pavement life. For this purpose, this work aims to investigate the performance changes of neat binders (Nb) and high-viscous binders (Hb) during FT and MH. The physicochemical, rheological, and deformation properties are investigated after FT and MH. Results indicate that asphalt binders become harder and lead to an increase in carbonyl index (CI) and sulfoxide index (SI) after FT. MH has a limited damage level for binders especially for Hb, causing a slight increase in CI and SI, compared to binders after FT. Polymers play an important role in the viscoelastic responses of asphalt binders. Changes in viscoelastic properties of Nb mainly result from the binder damage of FT and MH, while viscoelastic changes of Hb are mainly due to the damage of polymers. This different damage mechanism causes Hb to show better resistance compared to Nb, which is reflected in modulus and phase angle. BBR tests indicate that MH can further deteriorate the damage of both binders, but Hb shows a lower performance decline compared to Nb, and it is recommended to conduct MH at the region with a minimum temperature above −12 °C. MSCR results reveal that FT and MH can improve the rutting resistance of Nb due to the hardening phenomenon after damage, and reduce the elastic stability of Hb due to the damage to polymers. In summary, Nb is sensitive to MH, its performance can be further damaged after MH. Hb has better resistance to MH, its properties do not further deteriorate, so Hb is more applicable to MH.

Impact of Preanalytical Procedures on Complement Biomarkers in Cerebrospinal Fluid and Plasma from Controls and Alzheimer's Disease Patients.

Studies comparing cerebrospinal fluid (CSF) and plasma complement proteins in Alzheimer's disease (AD) patients versus healthy controls (HC) have yielded inconsistent results. Discrepancies in the preanalytical sample handling could contribute to the heterogeneity in the reported findings. Using qualified immunoassays, we aimed at assessing the impact of preanalytical procedures on complement proteins in blood and CSF from AD patients and HCs. We supplemented HC and AD CSF/plasma with complement stabilizers and measured the complement proteins C4a, C4, C3a, C3, Factor Bb and Factor B by immunoassay. We tested the impact of freeze-thaw (FT) cycles on fluid complement proteins. Most complement proteins were mildly impacted by FT cycles in plasma but not CSF, except for C3a which displayed greater sensitivity to FTs in CSF than in plasma. In CSF, the effect of FTs on C3a was reduced but not prevented by the supplementation with EDTA (±Futhan). Our findings provide recommendations for CSF/plasma sample handling to ensure robust and reproducible complement biomarker analyses in AD.