Freeze-thaw Research Articles

Repeated freezing to very low temperatures does not impact the amount ejected from EpiPen® and Jext® adrenaline autoinjectors

ABSTRACT It has previously been shown that EpiPen® autoinjectors are likely to activate normally following up to five excursions to −25°C but data about the post-freezing performance of other brands of adrenaline autoinjectors has not previously been published. Additionally, conditions experienced by polar medics may be substantially colder than this and the performance of adrenaline autoinjectors following more extreme freeze–thaw cycles remains uncharacterised. Investigators in Antarctica and the United Kingdom performed laboratory testing on two brands of adrenaline autoinjector, EpiPen® and Jext® (12 devices of each type). A single freeze–thaw cycle involved freezing the device to −80°C then allowing it to come to room temperature. Devices were exposed to 0, 1, 5 or 15 freeze–thaw cycles. The mass of liquid ejected from each device, when activated, was then measured. No significant differences in the mass of the liquid ejected was found between the test groups. Multiple freeze–thaw cycles to −80°C are unlikely to significantly impact the amount of adrenaline solution expelled from EpiPen® and EpiPen® autoinjectors. This preliminary finding encourages further work investigating the safety and effectiveness of adrenaline autoinjectors after exposure to very low temperatures. This information would be valuable for future polar medics planning and delivering medical provision in extreme environments.

Development of an efficient process to extract C‐phycocyanin from marine cyanobacterial strains and evaluation of its bioactive potential

AbstractBACKGROUNDPhycocyanin (PC), a natural blue photosynthetic pigment found in cyanobacteria, rhodophyta and cryptophyta has numerous applications in biotechnology and the food industry. The phycocyanin extraction method has a significant impact on its bioactivities, purity index, cost and potential applications; thus, the development of an efficient extraction strategy continues to be a primary research goal.RESULTSThis study evaluated the efficacy of different methods for the extraction of cyanobacterial phycocyanin (C‐PC) from three marine cyanobacterial isolates, namely Arthrospira platensis, Phormidium sp. and Pseudoscillatoria sp. wet biomass. The pretreatment step of soaking biomass in extraction buffer for 60 min, followed by a combination of freeze–thaw (one cycle; 2 h) and sonication (2 min) treatment was found to be the most effective extraction strategy, producing the highest C‐PC yield (16.19 ± 0.34%, 15.89 ± 0.61% and 15.56 ± 0.69% dry cell weight for strains A. platensis, Phormidium sp. and Pseudoscillatoria sp., respectively). Furthermore, a biomass‐to‐solvent ratio of 0.02 g mL−1 was optimal to attain food‐grade purity ((A620/A280) ≥ 0.7). Bioactivity evaluation of crude and purified C‐PC exhibited its potential as antioxidant compounds and as an antimicrobial agent with significant inhibitory effects against various pathogenic microorganisms.CONCLUSIONThe study proposed an efficient and cost‐effective C‐PC extraction process for cyanobacteria and highlighted the potential of C‐PC as a valuable bioactive compound with various applications. © 2024 Society of Chemical Industry (SCI).

Numerical investigation of artificial ground freezing–thawing processes in tunnel construction

Artificial ground freezing is a frequently used method for temporary support of the soil in geotechnical interventions, such as tunneling. Besides the time required to form a supporting frozen soil structure during freezing, the prediction of temperature evolution during the thawing process and the final thawing time are also relevant, since settlements induced by thawing of the frozen soil can pose a risk to sensitive structures in urban tunneling. The freezing and thawing process of soils depends strongly on the unfrozen liquid content. The unfrozen liquid content during the freezing and thawing cycles is known to have a pronounced hysteresis response, whose effect on the temperature distribution and groundwater flow, especially at the structural level has not been extensively studied. In this work, we present a thermo-hydraulic finite element model for freezing soils and incorporate the hysteresis behavior of soil. We aim to investigate the suitability of the presented numerical model for tunnel construction on the one hand, and quantify the extent of the influence of the hysteresis response of the unfrozen liquid content at the structural level on the other. To this end, the model is first validated with the help of experimental data from a soil test subjected to a freezing–thawing cycle and subsequently used to analyze three problems of artificial ground freezing in tunnel construction during the freezing phase or freezing–thawing phases. The results show a good agreement with the experimental measurements. We show that the computational model is capable of providing accurate prognosis of the temperature profile as well as broader metrics such as the thickness and shape of the frozen body for tunneling applications under hydrostatic and seepage flow conditions. The hysteresis response is shown to have a significant influence on the coupled thermo-hydraulic process, with thawing times differing depending on whether hysteresis is considered. It is concluded, that the inclusion of the hysteresis response is crucial for obtaining an accurate representation of the freezing process.

Effect of Surface Reinforcer on Compressive Strength and Microscopic Mechanism of Freeze–Thaw-Deteriorated Concrete

Due to the deterioration caused by repeated freeze–thaw cycles, concrete materials in cold regions often develop cracks, which have serious effects and challenge the durability of concrete-based structures. Therefore, it is worthwhile to repair and strengthen freeze–thaw-damaged concrete to extend the service duration of the structure. In the present study, to investigate the restorative effect of surface reinforcer on freeze–thaw-deteriorated concrete specimens, the effects of the surface reinforcer type, its action duration, and the number of applications on the strength and deformation parameters of repaired specimens were systematically studied. Moreover, pore size distribution, pore structure at different depths, and the micromorphology characteristics were investigated by nuclear magnetic resonance (NMR), pore structure, and scanning electron microscope (SEM) tests to reveal the repair mechanism of different surface reinforcer types. The results indicated that the compressive strength of freeze–thaw-deteriorated concrete could be increased by up to 15.67% after the application of the surface reinforcer. Both the values of compressive strength and deformation modulus E50 increased with the increase in the action duration. In addition, the surface reinforcer could efficiently penetrate the interior of the deteriorated specimen and was able to decrease the total proportion of multi-harmful pores and harmful pores. Furthermore, the pore structure parameters could be significantly improved at a depth of 10 mm; however, the reparative effect of the surface reinforcer gradually decreased with the increase in the action depth. The surface reinforcer could efficiently promote the second hydration of cement and generate more cementitious materials to fill the microvoids, thereby improving the compactness and mechanical properties of the repaired specimens.

Durability Assessment of Eco-Friendly Bricks Containing Lime Kiln Dust and Tire Rubber Waste Using Mercury Intrusion Porosimetry

The global challenge faced due to the impact of the construction industry on climate change, along with the issues surrounding sustainable waste disposal, has necessitated various research on using waste products as eco-friendly alternatives in construction. In this study, the avoidance of waste disposal through landfills in Australia was encouraged by incorporating lime kiln dust (LKD) and tire rubber waste (TRW) into masonry mixes to manufacture green bricks. Furthermore, the investigations in this article highlight the use of mercury intrusion porosimetry (MIP) to determine the durability of the LKD-TRW bricks when exposed to freeze–thaw (F-T) cycles by examining the pore size distribution within the bricks. The LKD waste was blended with ground granulated blast furnace slag (GGBFS) at a 70:30 blending ratio and combined with the TRW in stepped increments of 5% from 0 to 20% to produce these eco-friendly bricks. The compressive strength (CS), flexural strength (FS), frost resistance (FR), pore size distribution according to mercury intrusion porosimetry (MIP), and the water absorption (WA) properties of the bricks were assessed. The CS and FS values at 28 days of curing were recorded as 6.17, 5.25, and 3.09 MPa and 2.52, 2, and 1.55 MPa for 0, 5, and 10% TRW contents, respectively. Durability assessments using the F-T test showed that the bricks produced with 0% TRW passed as frost-resistant bricks. Furthermore, the results from the MIP test showed a total pore volume of 0.033 mL/g at 3 µm pore size for the 0% TRW content, further confirming its durability. Hence, the 0% LKD-TRW bricks can be utilized in cold regions where temperatures can be as low as −43 °C without deteriorating. Lastly, WA values of 7.25, 11.76, and 14.96% were recorded for the bricks with 0, 5, and 10% TRW, respectively, after the 28-day curing period. From all of the results obtained from the laboratory investigations, the LKD-TRW bricks produced with up to 10% TRW were within the satisfactory engineering requirements for masonry units.

Understanding climate risks to world cultural heritage: a systematic analysis and assessment framework for the case of Spain

Understanding the spatial distribution of world cultural heritage in its present-day geographical context is the foundation for the identification of and subsequent protection from key threats and vulnerabilities, particularly those arising from anthropogenic climate change. To address this challenge, we classified 45 Spanish world cultural heritage sites (WCHS) listed in the UNESCO register (as of 2023) according to type, entry date, and creation date. To establish a basis for a detailed analysis of the specific impact of climate change on the Spanish WCHS, a spatial cartographic database was developed showing the relationships between the WCHS and key geographical and climatic variables. We then used historical climate data, combined with a review of the impact mechanism of climate conditions on cultural heritage, to quantitatively evaluate the extent to which the WCHS in Spain are affected by local climate conditions from five aspects: freeze thaw cycle, thermal stress (thermoclastism), hydrodynamic scoring, corrosion, and biodegradation. Based on the above climate condition risks, we identified the five Spanish WCHS with the greatest potential climate condition risks, including Santiago de Compostela (Old Town), Pyrénées—Mont Perdu, the Roman Walls of Lugo, the Routes of Santiago de Compostela: Camino Francés and Routes of Northern Spain, and the Tower of Hercules. Additionally, based on different shared socioeconomic pathways (SSPs), we conducted a qualitative assessment of climate risk changes for WCHS in Spain under climate change. We found that the SSP1-2.6 scenario had the lowest climate risk, emphasizing the importance of achieving carbon neutrality for the protection of the WCHS. Our work translates historical climate conditions into specific climate risk levels for cultural heritage, providing data and theoretical support for effectively assessing the climate risks to Spanish WCHS.

Deterioration mechanisms of tuff with surface fractures under freeze–thaw cycles

In practical engineering, the development of surface cracks is one of the most important reasons for the destruction of the rock mass, and the development of complex morphology fractures on the rock mass surface significantly influences rock mass mechanics. This paper addresses the freeze–thaw damage issue in rock mass containing surface fractures in cold regions. Tuffs and a control group are selected as research samples, with the control group being prefabricated surface jointed specimens with an inclination angle of 70° and a fracture depth ratio d (crack depth) /t (sample width) of 0.26. The study analyzes the mass, wave velocity loss, macro-microcosmic fracture damage morphology, and mechanical properties of the two specimen groups through laboratory freeze–thaw cycle tests, uniaxial compression tests, and scanning electron microscopy examinations. The results show an overall decrease in mass, wave velocity, and uniaxial compressive strength as the cycle number increases, with the prefabricated jointed group samples showing more significant changes. However, the two specimen groups exhibit different macroscopic failure fracture states. In addition, scanning electron microscopy images illustrate that after freeze–thaw cycles, the large rock mass particles break into smaller fragments, resulting in looser particle arrangements and a transition from initial surface cementation to point contact., which weakens the compressive strength of the rock mass. The paper also explains the mechanism of the diminishing impact of freeze–thaw cycles on the strength of the rock mass after a certain number of cycles. The research outcomes hold significant reference value for engineering construction in cold regions.

Weather ageing effects on the long-term thermal conductivity and biological colonisation of thermal insulating mortars with EPS, cork and aerogel

The use of thermal insulation materials in the opaque walls is one of the best strategies toward the improvement of the thermal performance of the building envelope, thereby contributing to increase the energy efficiency of the built environment. In this context, an increasing number of studies are focusing on the development of mortars with enhanced thermal performance, i.e., thermal insulating mortars. However, considering the innovative character of these materials, reliable data on their long-term performance is still lacking, particularly concerning the thermal performance and suitability to refurbishment works. The aim of this paper is to evaluate the long-term thermal conductivity and biological colonisation of industrially produced and experimentally designed thermal mortars with EPS, cork and silica aerogel aggregates. The long-term performance of the mortars was assessed prior, during and after exposure to three accelerated ageing tests including elevated temperature, freeze–thaw cycles and high humidity levels. For each test, an empirical model (i.e., Arrhenius law, Peck model, and Coffin-Manson equation) was used to compute the acceleration factor, thus allowing to correlate the accelerated and natural ageing results and to estimate the degradation levels that would be obtained after 10 years of exposure to natural weather conditions. The results of the thermal conductivity show that a maximum increase of 10 % and 30 % can be obtained after ageing for the industrially produced and experimentally designed mortars, respectively. Moreover, all mortars were susceptible to mould growth, with the greatest biological colonisation levels obtained after the high moisture content ageing for the experimentally designed mortars.

Evolution of Freeze–Thaw Damage Characteristics and Corresponding Models of Intact and Fractured Rocks Under Uniaxial Compression

Evolution of Freeze–Thaw Damage Characteristics and Corresponding Models of Intact and Fractured Rocks Under Uniaxial Compression

Advancing Field Aging Simulation Methods for Cantabro Abrasion Loss Testing

Over the past several years, the asphalt industry has progressively increased efforts to evaluate mixtures after laboratory conditioning for the purpose of simulating field aging, and has also increased reliance on mixture testing. AASHTO T 401-22 describes Cantabro Mass Loss testing and has an appendix of field aging simulation protocols that can be used to estimate field aging by making use of compacted specimens. T 401-22 is one of the few methods to contain both a field aging simulation protocol and a mixture property index test. This paper uses roughly 1,000 tested specimens from forty-nine mixes (mostly dense-graded asphalt with minor amounts of stone-matrix asphalt) evaluated for up to four years of field aging in a hot and non-freeze climate alongside twenty-five different laboratory conditioning protocols. This paper’s objective is to provide information to improve T 401-22 by way of recommendations to update the appendix of conditioning protocols with more comprehensive assessments of their effectiveness in simulating field aging in a hot, non-freeze climate. The overarching recommendation of this work culminates with four protocols. Two of these protocols use only oven conditioning, whereas the remaining two protocols use a combination of stages exposing specimens to oxidation in ovens, moisture effects in hot water baths, and freeze–thaw cycling. The time required to administer the recommended protocols varies from approximately 6 to 28 days and they simulate between 1 and 5 years of field aging depending on the protocol selected.

A frost heave pressure model for fractured rocks subjected to repeated freeze-thaw deterioration

Rock engineering in the Tibetan Plateau is usually suffered severe freeze-thaw (F-T) deterioration, triggering numerous geotechnical engineering disasters. As the essential triggering factor of F-T damage, the frost heave pressure (FHP) in rocks should be quantitatively described and predicted. In this study, a novel theoretical model is established and validated to estimate the critical entire evolution process of FHP in fractured rocks subjected to repeated F-T deterioration, in which the influence of fracture geometric configuration, rock mechanical properties and F-T conditions are comprehensively considered. Besides, given the obvious five-stage manner of FHP evolution, the combination effect of different dominant mechanisms in different stages is theoretically addressed. During freezing, after a silence stage induced by temperature above freezing point of water, volumetric expansion and frost-heave cracking separately controls the generation and reduction stages of FHP, and the solutions are obtained based on elastic mechanics and Griffith energy balance theory, respectively. During thawing, ice segregation dominates the second-arising stage of FHP that is quantitatively described via segregation potential and water migration velocity, and then the FHP enters the dissipation stage owing to complete melting of fracture ice. In addition, a decay coefficient is introduced to estimate the influence of F-T cycle number on FHP, and a piecewise FHP model is finally constructed for fractured rocks subjected to repeated F-T deterioration. To validate our new model, a total of 12 F-T cycle tests with real-time FHP monitoring are conducted on granite and sandstone specimens considering three typical influencing factors, i.e., fracture width, rock types and freezing temperatures. A rational consistency is identified between the theoretical and testing results in terms of the FHP evolution curves and the peak FHPs in rock fracture, demonstrating the generalizability and robustness of our proposed model.

Research Progress of Superhydrophobic Coatings in the Protection of Earthen Sites

As an important part of human cultural heritage, earthen sites are subject to damage caused by a variety of environmental factors, such as cracking, weathering, and flooding. Due to the low mechanical strength of earthen site materials, especially in humid environments, they are susceptible to hazards like moisture penetration, freeze–thaw cycles, and biological invasion. Superhydrophobic coatings show promising potential in the protection of earthen sites, with key properties that include waterproof performance, breathability, robustness, and transparency. By exploring various material systems and preparation methods, the current state of research on the protection of building materials with superhydrophobic materials has been demonstrated, highlighting advantages in the corrosion resistance, self-cleaning, frost prevention, anti-scaling, and other aspects. At the same time, it also points out the challenges faced in the practical application of earthen site protection and the prospects for future research. These include enhancing the bonding strength between the coating and soil particles, improving durability and breathability, and developing large-scale, low-cost, and efficient coating construction techniques.

Compression and Splitting Tensile Strength Model of Recycled Seawater and Sea Sand Concrete after Seawater Freeze–Thaw Cycles

Using seawater, sea sand, and recycled bricks to make concrete for nearshore and marine engineering can save resources and protect the environment. Therefore, this article studies the mechanical degradation law and failure mechanism of recycled seawater and sea sand concrete (SSC) after seawater freeze–thaw (SFT) cycles. Using the replacement rate of recycled brick coarse aggregate as a variable, the mass loss rate, relative dynamic elastic modulus, compression and splitting tensile strength, and microstructure changes of specimens under different SFT cycles were tested, and a mechanical performance degradation model was established. The results indicate that the SFT failure of recycled brick coarse aggregate SSC results from the action of physical SFT and chemical crystallization. Friedel’s salts without cementitious properties and ettringite with expansive properties are generated inside the concrete due to the chloride and sulfate ions in the internal concrete and external seawater reacting with cement hydration products. The formation of harmful crystals leads to the loosening of the concrete, especially in the interface area between brick aggregates and cement. The calculated results of the mechanical model established in this article agree with the test results. The compression and splitting tensile strength decrease linearly with the increase in SFT cycles.

The Risk of Alkali–Carbonate Reaction and the Freeze–Thaw Resistance of Waste Dolomite Slag-Based Concrete

The alkali–carbonate reaction (ACR) is a type of alkali–aggregate reaction (AAR) that may lead to serious damage in concrete construction. There is sufficient research on the effect of the ACR on dolomite limestone; however, research on the effect of the ACR on pure dolomite is absent, and there are a large number of dolomite resources that cannot be effectively utilized in civil engineering. This study aims to investigate whether the ACR occurs in pure dolomite spoil and to determine the freeze–thaw resistance of pure waste dolomite slag-based concrete (PWDSC). In this study, X-ray diffraction (XRD) and the lithofacies method (LM) confirmed that the tested samples were pure dolomite. The rock cylinder method (RCM) and rapid preliminary screening testing for carbonate aggregates (AAR-5) were employed to determine the alkali activity of pure dolomite: the RCM indicated a variation of −0.09% in length during the 84-day test period, the AAR-5 exhibited a length expansion rate of 0.03% within 28 days, and the expansion rates were less than 0.1%. These findings suggest that pure waste dolomite slag (PWDS) does not possess alkali activity. The freeze–thaw cycle test showed no significant spalling on the concrete surface, the inside of the cement produced few micro-cracks according to scanning electron microscopy (SEM), and the uniaxial compressive strength (UCS) test showed a decrease of approximately 20% after 200 freeze–thaw cycles. The results verified that ACR does not occur in PWDS and that it can withstand freeze–thaw damage, to a certain extent, when used as concrete coarse aggregate.

Freeze-Thaw Cycle Durability and Mechanism Analysis of Zeolite Powder-Modified Recycled Concrete.

The inferior mechanical performance and freeze-thaw (FT) resistance of recycled concrete are mostly due to the significant water absorption and porosity of recycled coarse particles. In this study, different dosages of zeolite powder were used in recycled concrete. A series of macroscopic tests were used to evaluate the workability and FT durability of zeolite powder-modified recycled concrete (ZPRC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to reveal the micro-mechanisms of FT resistance in ZPRC. The results show that the increase in zeolite powder content leads to a decrease in the slump and water absorption of ZPRC. Additionally, ZPRC with 10% zeolite powder has superior mechanical characteristics and tolerance to FT conditions. The higher strength and FT resistance of the ZPRC can be attributed to the particle-filling effect, water storage function, and pozzolanic reaction of zeolite powder, which results in a denser microstructure. The particle-filling effect of zeolite powder promotes the reduction of surface pores in recycled coarse aggregates (RCAs). The water storage function of zeolite powder can provide water for the secondary hydration of cement particles while reducing the free water content in ZPRC. The pozzolanic reaction of zeolite powder can also promote the generation of hydrated calcium silicate and anorthite, thereby making the microstructure of ZPRC more compact. These results provide theoretical guidance for the engineering application of recycled concrete in cold regions.

Experimental study on mechanical properties of alkali activated concrete after freeze–thaw cycles

In order to study the frost resistance of alkali activated concrete (AAC), 15 AAC cube specimens and 15 cylindrical specimens were designed and manufactured. The frost thawing cycle test and mechanical performance test were used to study the frost resistance of AAC. The results showed that after freeze–thaw cycles, small pores appeared on the surface of the specimen, and the surface roughness increased, resulting in a darker appearance. As the number of freeze–thaw cycles increases, the highest mass loss rate of AAC reaches 1.88%. The cube compressive strength and axial compressive strength of AAC first increase and then decrease, while the elastic modulus gradually decreases. After 50 freeze–thaw cycles, the compressive strength of the specimen was greater than that of the normal temperature specimen. When the freeze–thaw cycles reached 200, the elastic modulus of the specimen degraded by 9.7%, the compressive strength decreased by 18.6%, and the axial compressive strength decreased by 31.2%. Based on the experimental results, a method for calculating the residual strength of AAC after freeze–thaw cycles and key parameters of the freeze–thaw damage constitutive equation were proposed.

Development of Self-Heating Concrete Using Low-Temperature Phase Change Materials: Multiscale and In Situ Real-Time Evaluation of Snow-Melting and Freeze–Thaw Performance

Development of Self-Heating Concrete Using Low-Temperature Phase Change Materials: Multiscale and In Situ Real-Time Evaluation of Snow-Melting and Freeze–Thaw Performance

Investigating the Strength and Microstructure of Cemented Sand–Gravel Mixtures Subjected to Freeze–Thaw Cycles

Investigating the Strength and Microstructure of Cemented Sand–Gravel Mixtures Subjected to Freeze–Thaw Cycles

Estimation of Uniaxial Compressive Strengths of Cappadocia Pyroclastic Rocks after Freeze–Thaw Cycles Using Point Load Strength Index

Estimation of Uniaxial Compressive Strengths of Cappadocia Pyroclastic Rocks after Freeze–Thaw Cycles Using Point Load Strength Index

Effect of different endometrial preparation methods on pregnancy outcome of FET in women with a normal menstrual cycle

ABSTRACT Objective: This study aims to explore the relationship between different endometrial preparations and pregnancy outcomes among patients with regular ovulatory cycles in order to find the best endometrial preparation methods in the freeze–thaw embryo transfer (FET) cycle. Materials and Methods: This is a retrospective study to investigate FET pregnancy outcomes in women who had a regular menstrual cycle, were younger than 35 years old, and underwent a modified natural cycle (mNC), ovulation induction (OI), or a hormone replacement treatment (HRT) cycle. A total of 1071 frozen cycles were included for analysis. Results: The implantation rate and live birth rate (LBR) in the OI group show a significant difference when compared to the mNC and HRT groups (P < 0.01). After adjusting for confounding factors, the logistic regression analysis revealed that the number of embryos transferred, the embryo stage, and quality were significantly associated with clinical pregnancy rate and LBR. The LBR was additionally affected by the mode of the endometrial preparation; the OI cycle could increase LBR. Conclusions: Endometrial preparation methods affect the LBR in women with a regular menstrual cycle. The OI cycle had an advantage in the LBR of FET.