Thaw Cycles Research Articles

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.

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

Wetting–Drying–Freezing–Thawing Cycle Effect on the Swelling Pressure of Yanji Mudstone Using Various Determination Methods

Wetting–Drying–Freezing–Thawing Cycle Effect on the Swelling Pressure of Yanji Mudstone Using Various Determination Methods

Idiosyncratic invasion trajectories of human bacterial pathogens facing temperature disturbances in soil microbial communities

Current knowledge about effects of disturbance on the fate of invaders in complex microbial ecosystems is still in its infancy. In order to investigate this issue, we compared the fate of Klebsiella pneumoniae (Kp) and Listeria monocytogenes (Lm) in soil microcosms. We then used environmental disturbances (freeze–thaw or heat cycles) to compare the fate of both invaders and manipulate soil microbial diversity. Population dynamics of the two pathogens was assessed over 50 days of invasion while microbial diversity was measured at times 0, 20 and 40 days. The outcome of invasion was strain-dependent and the response of the two invaders to disturbance differed. Resistance to Kp invasion was higher under the conditions where resident microbial diversity was the highest while a significant drop of diversity was linked to a higher persistence. In contrast, Lm faced stronger resistance to invasion in heat-treated microcosms where diversity was the lowest. Our results show that diversity is not a universal proxy of resistance to microbial invasion, indicating the need to properly assess other intrinsic properties of the invader, such as its metabolic repertoire, or the array of interactions between the invader and resident communities.

Response of sand added with various biopolymer contents under repetitive loading and freeze–thaw cycles

Biopolymers have recently been used as ecofriendly materials for soil improvement in terms of stabilization, compressibility, and engineering parameters. The objective of this study is to assess the effect of biopolymer content in sand mixtures during freeze–thaw repetitive loading cycles. The biopolymers were mixed at weight ratios of 0.0, 0.5, 1.0, 2.0, 5.0, and 10 % (BPC 0.0—BPC 10), and the relative density and degree of saturation were fixed at 60 % and 20 %, respectively. The measurement system was located in an ice chamber for freeze–thaw, and 100 cycles of repetitive loads were applied. The test results showed that the deformation decreased from BPC 0.0, to BPC 1.0 owing to the cementation effect produced by the biopolymer chain and coating. However, the deformation increased from BPC 1.0 to BPC 5.0 because high-viscosity solutions might separate the sand particles, causing a density reduction and generating more deformation by compaction. The relative permittivity varied with respect to BPC and freeze–thaw repetitive loading stages that were affected by unfrozen water content, volume contraction, and water consumption during dehydration. The shear wave velocity gradually increased from BPC 2.0 to BPC 10 because the effect of fines in coarse–fine mixtures, rather than the cementation effect. Therefore, the module containing the sensors used in this study can be used to understand the role of biopolymers as reinforcing materials in railway subgrades.

Constitutive Characteristics of Rock Damage under Freeze–Thaw Cycles

Freeze–thaw effect is one of the most important environmental conditions that rocks may be subjected to. Through laboratory model tests, the damage characteristics of rocks under the FTC were studied. Based on assuming that the strength of rocks subject to the FTC follows the Weibull distribution, the cumulative damage variable of the number of FTCs was introduced. A cumulative damage constitutive model of shear strength attenuation of rock that meets the Mohr–Coulomb criterion is established. The rationality and applicability of the proposed damage constitutive model are verified by comparing the results of rock shear strength parameters under cyclic freeze–thaw loads.

Analytical validation of the Mindray CL1200i analyzer high sensitivity cardiac troponin I assay: MERITnI study.

This study performed an analytical validation study of the Mindray high-sensitivity cardiac troponin I (hs-cTnI) assay addressing limit of blank (LoB), limit of detection (LoD), precision, linearity, analytical specificity and sex-specific 99th percentile upper reference limits. LoB, LoD, precision, linearity and analytical specificity were studied according to Clinical and Laboratory Standards Institute. We used one reagent lot and one CL1200i analyzer. Skeletal troponin I and T, cardiac troponin T, troponin C, actin, tropomyosin, myosin light chain, myoglobin and creatine kinase (CK-MB) were studied for cross-reactivity. Interference with biotin was examined. Lithium heparin samples (one freeze thaw cycle) from healthy males and females were measured to determine the 99th percentiles by using the non-parametric method. Analyses were performed before and after excluding subjects with clinical conditions and/or increased surrogate biomarkers. The Mindray hs-cTnI assay met criteria to be considered as a hs-cTn assay. LoB and LoD was <0.1 ng/L and 0.1 ng/L, respectively. Repeatability had a coefficient of variation 1.2-3.8 %, and within-laboratory imprecision 1.7-5.0 %. The measuring interval ranged from 1.1 to 28,180 ng/L. The analytical specificity was clinically acceptable for the interferents studied. After exclusions, the 99th percentile URLs obtained were 10 ng/L overall, 5 ng/L for females and 12 ng/L for males. Analytical observations of the Mindray hs-cTnI assay demonstrated excellent LoB, LoD, precision, linearity and analytical specificity, that were in alignment with the manufacturer's claims and regulatory guidelines for hs-cTnI. The assay is suitable for clinical investigation for patient-oriented studies.

Effect of silicon impregnant on freeze–thaw durability of silane-treated recycled aggregate concrete

To enhance the freeze–thaw durability of saline-treated recycled aggregate concrete, the impact of three types of silicon impregnants (organosilicon, methyl sodium silicate, potassium methyl silicate) applied on the recycled aggregate concrete surface and the interior was studied. By conducting salt freeze–thaw test and observing recycled aggregate concrete surface microstructure after freeze–thaw cycles, the performance of impregnants in enhancing the salt freeze–thaw durability of silane-treated recycled aggregate concrete can be ranked as follows: organosilicon (internal) ≈ methyl sodium silicate (internal) > organosilicon (external) > potassium methyl silicate (external). Microstructure images confirm impregnants’ ability to reduce surface cracks, correlating with freeze–thaw resistance. The optimal strategy involves a 50 % combination of organosilicon internally and silane externally, with economic and practical implications for construction in cold areas.

Volume changes and consolidation of expansive subgrades under short- and long-term effects of freeze–thaw cycles

ABSTRACT Pavements and light structures constructed on expansive subgrade layers have experienced severe damage due to volume changes. These layers have been exposed to climatic changes such as freeze–thaw (FT) cycles. Accurate estimation of design parameters regarding heave/settlement is essential for sustainable performance. This work study the instantaneous and long-term effects of successive FT-cycles on the volume stability, swelling, and compressibility characteristics of natural and lime-treated expansive subgrades. Volume changes were traced during successive 15FT cycles. Swelling and consolidation characteristics were studied immediately after FT-cycles. The long-term effect of FT was tested at different recovery periods around year. FT-cycles significantly affects volume changes and compressibility, this effect is proportional to soil type and limited up to a certain number of FT-cycles. During the long-term recovery, a considerable part of underwent deformation is a permanent and not recovered, even after year the soil still memorizes this effect. Due to the propagated cracks, the plastic deformation increased with increase in FT-cycles.

Durability of alkali-activated fly ash-slag concrete- state of art

India ranks among the foremost global producers and consumers of cement, and the cement industry contributes significantly to carbon emissions. Alkali-activated materials have gained significant attention as a sustainable alternative to Portland cement, offering the potential to mitigate carbon dioxide emissions and promote effective recycling of waste materials. Fly ash (FA) and Ground granulated blast furnace slag (GGBS) are preferred raw materials for Alkali-activated concrete (AAC) owing to their effective repurposing of waste, widespread accessibility, advantageous chemical composition, and performance attributes. This review provides a comprehensive analysis of the current state-of-the-art on the durability aspects of fly ash/slag-based AAC. The paper explores the unique characteristics of FA/GGBS-based AAC, emphasizing their potential to enhance the durability of concrete structures. Insights into the material behaviour under various environmental exposures, including aggressive chemical environments and freeze–thaw cycles, are presented. Furthermore, the article addresses both the obstacles and prospects associated with implementing fly ash/slag-based AAC as a potential construction material suitable for large-scale infrastructure projects. This overview is designed to direct future research efforts and provide practitioners with insights into the potential of FA/GGBS-based AAC for ensuring the prolonged durability of concrete structures.

Enhancing Osteogenic Potential in Bone Tissue Engineering: Optimizing Pore Size in Alginate–Gelatin Composite Hydrogels

Bone tissue engineering relies on crucial scaffolds for tissue formation and stem cell differentiation. A composite scaffold of alginate‐gelatin effectively supports these processes. This study aims to design a porous alginate‐gelatin hydrogel and assess pore size effects on cell behavior, focusing on morphology, adhesion, and proliferation in distinct osteogenic environments. Hydrogels are prepared using various alginate‐gelatin concentrations: 4% alginate and 6% gelatin (4A6G) or 3% alginate and 5% gelatin (3A5G), cross‐linked with 2% CaCl2. Pore size optimization employs simple freezing and thawing cycles. Scanning electron microscopy reveals varying pore sizes: 340 µm ± 30 µm for 4A6G and 635 µm ± 25 µm for 3A5G. Stiffness measurements indicate significant differences: ≈26.3 kPa ± 0.6 KPa for 4A6G and 21.6 kPa ± 0.2 KPa for 3A5G. Cell interaction studies demonstrate higher adhesion and proliferation rates in larger‐pored hydrogels. Evaluation of bone tissue formation, including RT‐PCR, ALP activity, and ARS staining, reveal superior osteogenic potential in the 3A5G hydrogel compared to 4A6G. In conclusion, the 3A5G hydrogel (3% alginate and 5% gelatin) holds promise for bone tissue regeneration due to its biodegradability and favorable bone‐forming properties.

Mechanical performance degradation investigation on FRP reinforced concrete based on neural network design method

To predict the effect of chemical-freezing coupling erosion on the properties of four kinds of FRP-reinforced concrete. Rapid freeze–thaw tests were conducted. The mass loss rate, relative dynamic elastic modulus, compressive strength, and flexural capacity were tested to investigate the Mechanical Performance of specimens. The compression specimens are cylindrical specimens wrapped with FRP, and the flexural specimens are pasted with FRP prismatic specimens on the pre-cracked side. A database was built based on 45 groups of experimental test results, and the prediction effect of the BP neural network and CNN model on compressive strength and flexural capacity was compared, respectively. The results showed that CNN did a better job. Finally, the maximum number of freeze–thaw cycles of different FRP-reinforced specimens was predicted based on the CNN model with mass loss rate and relative dynamic modulus as the evaluation criteria. This method can provide a new perspective for predicting the durability of FRP-reinforced concrete.

Histological evaluation of decellularization of freeze dried and chemically treated indigenously prepared bovine pericardium membrane.

Decellularization is regarded as a xenogenic antigen-reduction technique because it effectively eliminates all cellular and nuclear components while mitigating any negative impact on the composition, biological functionality, and structural integrity of the remaining extracellular matrix. This study aimed to histologically evaluate native, freeze dried and chemically decellularized bovine pericardium membrane. Also, this study focused on preservation of extracellular matrix after decellularization. Bovine pericardium membrane was decellularized by freeze thaw cycle followed by freeze drying and 1% sodium dodecyl sulphate. Unprocessed pericardium was used as control. The effectiveness of Decellularization was assessed based on the reduction of histologically visible nuclei. Decellularization by freeze thaw cycle followed by freeze drying resulted in 17.84% reduction in nuclei content and decellularization by sodium dodecyl sulphate results in 92% reduction in nuclei content compare to control group. Picrosirius red staining for freeze dried group displayed loosely organised, thin collagen bundles that exhibit reddish-yellow birefringence and sodium dodecyl sulfate group revealed dense collagen bundles that are parallelly organised and compact, exhibiting reddish-yellow birefringence and showed good structural integrity. These results suggested that the sodium do decyl sulfate showed optimal decellularization results with better extracellular matrix preservation. It may be a suitable protocol for producing a suitable scaffold for periodontal tissue regeneration.

Experimental Study of Shear Strength of Loess under Freeze-thaw Cycles

In order to study the shear strength characteristics of loess under the action of freeze-thaw cycle, through the freeze-thaw test, straight shear test, to analyze the change rule of water content and freeze-thaw cycle on loess cohesion, internal friction angle and shear strength. The test results show that: loess cohesion gradually decreases with the increase of water content and the number of freeze-thaw cycles, when the freeze-thaw 7 times, the change of cohesion gradually tends to stabilize; the angle of internal friction decreases gradually with the increase of water content and the number of freeze-thaw cycles, but the rate of decrease is smaller than the rate of cohesion; the change of shear strength is affected by the cohesion more than the angle of internal friction, and the shear strength at different times of freezing and thawing increased linearly with the vertical stress, and the relationship equations between the shear strength and the water content and the number of freezing and thawing cycles were established.

Phytic acid extracted cellulose nanocrystals for designing self-healing and anti-freezing hydrogels’ flexible sensor

Phytic acid (PA), a naturally occurring organic acid, has been extensively researched in various fields such as flame retardants, electroactive materials, metal coatings and flexible sensors. This study proposes a method for extracting cellulose nanocrystals (CNCs) utilizing PA and ingeniously applies them to hydrogels, endowing the hydrogels with exceptional mechanical properties, anti-freezing capabilities and high electrical conductivity. First of all, the CNCs@PA and PA were integrated into a multi-component network consisting of hyperbranched polyethyleneimine (HPEI), polyvinyl alcohol (PVA), and zinc chloride (ZnCl2), and their complex interactions resulted in the formation of a robust three-dimensional structure. Consequently, the hydrogels formed after just a single freeze–thaw cycle exhibited exceptional mechanical properties (2.6 MPa) and a significant self-healing ability (92.3 %). Moreover, the strategic addition of PA to the hydrogels effectively immobilizes H2O, providing anti-freeze properties and enabling the hydrogels to maintain their structure and performance even at −20.0 °C. Notably, following hydrolysis, PA generates a substantial number of hydrogen ions, markedly enhancing the conductivity (2.3 S/m) and a sensitivity gauge factor (GF = 2.5) of the hydrogels. This work offers a cost-effective, eco-friendly, and scalable method for the manufacturing of nanomaterials, and opens new avenues for creating anti-freeze wearable flexible sensors.

Microbially-mediated reductive dissolution of Fe-bearing minerals during freeze-thaw cycles

Constraining the role of microbes in the structural iron (Fe) reduction of iron-bearing minerals improves our understanding of sediments and ice sheets as a source of dissolved Fe (dFe) to the oceans. However, bio-mediated structural Fe-reduction has yet to be studied in cryospheric environments. Here, we show that the Fe reducing psychrophile bacterium Shewanella vesiculosa, isolated from sea ice in Antarctica, reduced structural Fe in nontronite (NAu-2) and maghemite (γ-Fe2O3), common mineral phases in glacial ice, and marine sediments in Antarctica, during two freeze–thaw cycles (−10 °C to +15 °C), resulting in the release of dFe. The modification of turbostratically disordered nontronite (ferric iron dominant phase) to discrete ordered illite-like structure (ferrous iron dominant phase), and the aggregation of altered small maghemite particles with neoformation of vivianite (Fe3(PO4)2·nH2O) indicated the microbially induced reductive dissolution of nontronite and maghemite, respectively. The biotic Fe-reduction gradually decreased and ceased as the temperature approached freezing (−8 °C), however the rection reactivated in the thawing cycle (−7 to +15 °C). No discernable biotic Fe-reduction was measured for either mineral under freezing conditions, suggesting that temperature limits the activity of the microbes. Further, and regardless of temperatures during two freeze–thaw cycles, Fe-reduction was not observed in abiotic control. Overall, these results highlight the importance of microbially induced Fe reduction during seasonal freeze–thaw cycles of ice and sediments in continuous supplying bioavailable dFe to cryospheric environments and the often Fe-limited polar oceans.

Freeze–thaw damage analysis and life prediction of modified pervious concrete based on Weibull distribution

An assessment of the freeze–thaw durability of pervious concrete was conducted using a rapid freezing method to investigate the durability of modified pervious concrete within a freeze–thaw environment. The optimal proportion of the modified material was determined by evaluating the mass-loss rate and the relative dynamic elastic modulus as indicators of freeze–thaw performance. Scanning electron microscopy (SEM) was employed to observe microcrack propagation and reaction products. A freeze–thaw damage model, based on the Weibull probability distribution, was formulated. Freeze–thaw damage analysis and life prediction assessment were carried out using curves such as freeze–thaw damage velocity curves, freeze–thaw damage acceleration curves, failure rate curves, and reliability life curves. The outcomes revealed that the inclusion of polyacrylonitrile (PAN) and silica ash had a favourable impact on improving the frost resistance of pervious concrete at later stages. The optimal proportions for PAN fibre and silica ash were determined as 0.6 % and 8 %, respectively. As the number of freeze–thaw cycles approached approximately 52.03 times, the freeze–thaw cycle velocity peaked. Subsequently, the freeze–thaw damage velocity was categorised into three stages based on the freeze–thaw damage acceleration curve. The degradation of pervious concrete due to freeze–thaw cycles followed a typical loss-type failure pattern. Notably, a 50 % increase in PAN fibre content resulted in a 62.92 % reduction in failure rate. Furthermore, a predictive analysis was conducted to estimate the lifespan of pervious concrete in a representative freeze–thaw region in China was performed.

Mechanical Analysis of Concrete Piers of Cross Sea Bridges under Freezing and Thawing Cycle Conditions and Wave Effects

Mechanical Analysis of Concrete Piers of Cross Sea Bridges under Freezing and Thawing Cycle Conditions and Wave Effects

Analysis of damage evolution and study on mesoscopic damage constitutive model of granite under freeze–thaw cycling

Analysis of damage evolution and study on mesoscopic damage constitutive model of granite under freeze–thaw cycling