Free Water Content Research Articles

Fine Tuning Water States in Hydrogels for High Voltage Aqueous Batteries.

Hydrogels are widely used as quasi-solid-state electrolytes in aqueous batteries. However, they are not applicable in high-voltage batteries because the hydrogen evolution reaction cannot be effectively suppressed even when water is incorporated into the polymer network. Herein, by profoundly investigating the states of water molecules in hydrogels, we designed supramolecular hydrogel electrolytes featuring much more nonfreezable bound water and much less free water than that found in conventional hydrogels. Specifically, two strategies are developed to achieve this goal. One strategy is adopting monomers with a variety of hydrophilic groups to enhance the hydrophilicity of polymer chains. The other strategy is incorporating zwitterionic polymers or polymers with counterions as superhydrophilic units. In particular, the nonfreezable bound water content increased from 0.129 in the conventional hydrogel to >0.4 mg mg-1 in the fabricated hydrogels, while the free water content decreased from 1.232 to ∼0.15 mg mg-1. As a result, a wide electrochemical stability window of up to 3.25 V was obtained with the fabricated hydrogels with low concentrations of incorporated salts and enhanced hydrophilic groups or superhydrophilic groups. The ionic conductivities achieved with our developed hydrogel electrolytes were much higher than those in the conventional highly concentrated salt electrolytes, and their cost is also much lower. The designed supramolecular hydrogel electrolytes endowed an aqueous K-ion battery (AKIB) system with a high voltage plateau of 1.9 V and contributed to steady cycling of the AKIB for over 3000 cycles. The developed supramolecular hydrogel electrolytes are also applicable to other batteries, such as aqueous lithium-ion batteries, hybrid sodium-ion batteries, and multivalent-ion aqueous batteries, and can achieve high voltage output.

Development of soy protein isolate gels added with Tremella polysaccharides and psyllium husk powder as 3D printing inks for people with dysphagia.

The aim of this study was to investigate the feasibility of soy protein isolate (SPI) gels added with Tremella polysaccharides (TPs) and psyllium husk powder (PHP) as 3D printing inks for developing dysphagia-friendly food and elucidate the potential mechanism of TPs and PHP in enhancing the printing and swallowing performance of SPI gels. The results indicated that the SPI gels with a TP : PHP ratio of 3 : 7 could be effectively used as printing inks to manufacture dysphagia-friendly food. The addition of TPs increased the free water content, resulting in a decrease in the viscosity of the SPI gels, which, in turn, reduced the line width of the 3D-printed product and structural strength of the gel system. The addition of PHP increased disulfide bond interactions and excluded volume interactions, which determined the mechanical strength of SPI gels and increased the line width of the printed product. The synergistic effects between TPs and PHP improved the printing precision and structural stability. This study presents meaningful insights for the utilization of 3D printing in the creation of dysphagia-friendly food using protein-polysaccharide complexes.

Key factors for the survival of Lactiplantibacillus plantarum IDCC 3501 in manufacturing and storage.

Functional microbiome development has steadily increased; with this, the viability of microbial strains must be maintained not only after the manufacturing process but also at the time of consumption. Survival is threatened by various unavoidable factors during freeze-drying and shelf storage. Here, the aim was to optimize the manufacturing process of the functional strain Lactiplantibacillus plantarum IDCC 3501 after freeze-drying and storage. Explosive growth was achieved using a medium composition with two nitrogen sources and a mineral, and growth was drastically improved by neutralizing the medium pH during the culture of L. plantarum IDCC 3501. Culture optimization involved a smaller cell size, leading to less intracellular free water. Moreover, when maltodextrin (MD) powder was directly added to the harvested cells, some intracellular free water was extracted from the bacterial cells, resulting in a dramatic increase in the viability of L. plantarum IDCC 3501 after freeze-drying and subsequent storage. Furthermore, MD enhanced survival in a dose-dependent manner. Bacterial survival was correlated with lysozyme tolerance; therefore, the positive result might have been caused by the osmotic dehydration of intracellular free water, which would potentially damage the bacterial cells via ice crystallization and/or a phase transition during freeze-drying. These critical factors of L. plantarum IDCC 3501 processing provide perspectives on survival issues for manufacturing microbiome strains. KEY POINTS: • Culture conditions for probiotic bacteria were optimized for high growth yield. • Osmotic dehydration improved bacterial survival after manufacturing and shelf storage. • Reduction in intracellular free water content is crucial for intact survival.

Influence of Salt Concentration on Electrochemical Stability Window in Aqueous Electrolytes

The thermodynamic limit of water electrolysis restricts the output voltage of aqueous metal ion batteries (MIBs) due to the low electrochemical stability window of water (1.23 V) in dilute electrolytes. It occurs due to the electrolysis of free water molecules into O2 or H2. Such value is unfortunately too low for many applications. For effective utilization of this technology, the ESW needs to be expanded to at least 2 V to achieve high energy density in metal batteries. Interestingly, water electrolysis can be suppressed by binding free water content with high concentrations of salts in highly concentrated water-in-salt electrolytes.In this work, low-cost non-flammable aqueous Zn(ClO4)2 electrolytes have been studied for their electrochemical behaviour at different concentrations. The electrolytes have been evaluated via Raman spectroscopic analysis to examine the modification in local water structures associated with increasing salt concentration. We also used linear sweep voltammetry on a glassy carbon electrode to determine the electrochemical stability window of the electrolytes. Electrochemical results indicate the existence of two distinct regions in the concentration behavior of the onset potential for oxygen evolution reaction (OER) at a cut-off current density of 0.1 mA cm-2. In dilute electrolytes, the overpotential in OER increases with a low slope with increasing concentration, while there is a sharper overpotential increase at higher salt concentrations in the water-in-salt electrolytes. Raman spectroscopic analysis provides evidence of this electrochemical stability expansion as being a result of the disruption of the hydrogen bonding network present in pure water. A more compact and strongly coordinated ion hydration structure occurs in the water-in-salt electrolytes. In this way, a significant increase in oxidative stability and a decline in the Zn oxidation overpotential has been achieved in the highly concentrated water-in-salt electrolytes. Our results indicate that the Zn(ClO4)2 water-in-salt electrolytes offer more efficient Zn redox reactions and a higher electrochemical stability window than the diluted aqueous electrolytes, which is particularly beneficial for the development of high-voltage aqueous Zn ion batteries [1].

Recombinant microgels utilized to formulate green Pickering emulsions

The fabrication of a stable food-grade Pickering emulsion (PEs) system has been challenging because of difficulties in ensuring the safety of auxiliary reagents and the compatibility of the materials. In this study, inspired by our previous experiments, we devised recombinant microgels (RMs) with a compact structure by freeze–thaw cycles (FTCs) method, which was used to fabricate a green food-grade PE system. The application of FTCs demonstrated an enhancement of RMs in the crystallinity, surface wettability, and textural properties. Specifically, RMs subjected to 3 FTCs had a compact cube structure (0.6–1.1 μm), near neutral surface wettability (89.95°), and an amorphous crystallinity (55.93%), which may be attributed to the decrease of free water content and the formation of hydrogen bonds. A concentration of 0.5% RMs was used to stabilize PEs, which showed a uniform microscopic distribution and a particle size of 13.87 μm. It was found that when the concentration of the external phase exceeded 0.5% stable oil-in-water emulsions formed. Otherwise, multiple emulsions formed. This study underscores the viability of using RMs to construct green food-grade PE systems.

Effect of Rice Bran and Retrograded Time on the Qualities of Brown Rice Noodles: Edible Quality, Microstructure, and Moisture Migration.

Brown rice, as a kind of whole-grain food, has attracted significant attention due to its health benefits. This paper aimed to investigate the effect of rice bran content and retrograded time on the physicochemical properties and culinary qualities of brown rice noodles (BRNs). The results indicated that the addition of rice bran altered the pasting properties, gel properties, and texture of the brown rice flours (BRFs). The optimal cooking time and water absorption of BRNs were reduced after the incorporation of rice bran to 14.9% and 41.9%, respectively, while the breaking rate increased from 2.2% to 23.3%. The color of BRNs became darker and yellower, and the overall acceptability by the consumer decreased. The addition of rice bran also led to a decrease in hardness, chewiness and crystallinity. The binding water inside the BRNs decreased, while the free water increased, resulting in a looser structure. This study revealed that the retrograded time of the BRNs also affected its quality. When the retrograded time was 7 h, the cooked BRNs had a lower breaking rate, good hardness, cohesiveness, chewiness, and better overall acceptability by consumers. The structure was compact, the internal binding water content of BRN was higher, and the free water content was lower. This study provides insights into developing nutritionally healthy, high-quality novel rice flour products, and offers a theoretical basis for the industrial production of BRNs.

Pemurnian Minyak Goreng Bekas Dengan Adsorben Ampas Tebu Untuk Pembuatan Biodisel

Biodiesel, which is generally defined as monoalkyl esters from plant and animal fats, is an alternative fuel that has the potential to be used as a substitute for diesel fuel because of its characteristics. Used cooking oil or used cooking oil haD the potential to be processed into biodiesel and this study aims was to produce waste cooking oil into biodiesel from the results of the pre-treatment process of used cooking oil with bagasse waste, to find out the optimum result of the oil pretreatment proces and the raw material used was used cooking oil from the Rocket Chicken Food Court restaurant. Waste from sugarcane bagasse was useful as an adsorption process for the purification of used cooking oil which was able to reduce free fatty acid levels, water content, and impurities levels for the biodiesel process. The optimum particle size of bagasse waste for used cooking oil pretreatment was 30 mesh, with the analytical data was 1.93% of free fatty acid, 0,0018 % for water content and 0,03% of firt level. The results of the Biodiesel analysis from the pre-treatment process were the viscosity was 5.7 Cst, the density was 860 kg/m3 and the acid number was 0.8 mg KOH/g oil. This result was accordance to the indonesian national standard No. 04-7182-2006.

Self-sensing characteristics of smart high-performance cementitious composites containing multiwall carbon nanotubes, steel fibers, and steel slag aggregates under compression

Smart high-performance cementitious composite (SHPCC) with sensing abilities, high mechanical, and high durability is a potential smart material instead of current sensors applied for structural health monitoring systems of infrastructures. This study deeply investigated the sensing properties of SHPCCs containing multiwall carbon nanotubes (MWCNTs), steel fibers, and steel slag aggregates (SSAs) under compression. SHPCCs containing different contents of MWCNTs (0.1% and 0.5% of cement weight), steel fibers (2 and 4 vol%), SSAs (10% and 50% instead of sand), and free water (fully dried and moisture specimens) were prepared and evaluated. The results indicated that the SSA content was a key factor controlling the electrically conductive network response and the stress-sensing ability of SHPCCs. MWCNTs significantly enhanced the stress-sensing ability of fully dried SHPCCs under compression. Besides, the free water content in pore systems significantly influenced the stress-sensing ability of SHPCCs. A conductive network of SHPCCs with MWCNTs, fibers, SSAs, and free water at micro and nano levels was proposed and analyzed to explain the electrical resistivity response under compression.

Montmorillonite-based edible coating enhances the postharvest quality of sweetpotato by regulating ROS and membrane lipid metabolism

The quality deterioration of sweetpotatoes easily during postharvest storage owing to their high respiration rate and accumulation of reactive oxygen species (ROS). In this study, an edible coating (MCW) assembled using montmorillonite, chitosan, and whey protein isolate was fabricated to improve the postharvest quality of sweetpotatoes, and the regulatory mechanism of the edible coating treatment on sweetpotato quality has investigated. The results confirmed that edible coating treatment had a positive effect on maintaining the appearance, firmness, colour, and sensory quality of sweetpotatoes, especially in maintaining free water, starch and soluble protein content, inhibiting respiration rate and delaying weight loss of sweetpotatoes stored at 25 °C for 30 d. Meanwhile, this study illuminated the MCW coating regulates ROS metabolism by upregulating superoxide dismutase, ascorbate peroxidase, and glutathione reductase gene expression, resulting in lower O2−. content in postharvest sweetpotato. Furthermore, the relative expression of the genes encoding lipoxygenase, phospholipase C, and phospholipase D was downregulated by the edible coating treatment and contributed to lower enzyme activity, electrolyte leakage and malondialdehyde content, which further reduced the degree of membrane lipid peroxidation and effectively maintained the structure of plasma membrane and then protected the cell integrity of sweetpotato. Collectively, this study provides useful information at the transcriptional level that MCW coating can enhance the post-harvest quality of sweetpotatoes by regulating ROS and membrane lipid metabolism.

Preference of Silicon Accumulation on the Shade Foliage of Tree Crown and its Implication in Juniperus chinensis L.

PurposeThe passive accumulation of silicon (Si) generally depends on the regulation of plant transpiration rates after its uptake. It is challenging to comprehend how plants use Si to adapt to shady habitats where they have low transpiration rates and photothermal energy. Therefore, we speculated that Si accumulation is not entirely dependent on the transpiration rate.MethodsTo test this speculation, the concentrations of Si and total minerals and water status at various positions of shady shoots (stems and their foliage) and stems within the crown of Juniperus chinensis L. were examined to determine whether shady shoots or stems had a preferred allocation to resist shade.ResultsThe concentrations of total minerals and Si in the shoots were consistently higher in shady areas than in areas within the same crown, regardless of the position within the crown or shoot age. However, shoot Si accumulation displayed a greater dependence on available light or photothermal supply, which is linked to crown orientation. Additionally, stem Si accumulation displayed a weak dependence on available light. Compared with the bound water content, the water potential and free water content of shady shoots were higher than those of sunny shoots. In light of the fact that water prefers to move readily towards regions with low water potential, these results demonstrate that the movement of minerals and water is not fully coupled in the same crowns.ConclusionTherefore, the accumulation of Si and minerals in shady foliage is partially independent of water flow, which helps to offset the low-carbon supply due to the photothermal decrease in the shady crown area.

РОЛЬ МСКТ И МРТ В ДИФФЕРЕНЦИАЛЬНОЙ ДИАГНОСТИКЕ ОСЛОЖНЕНИЙ СРЕДНЕЙ ЗОНЫ ЛИЦА У ПАЦИЕНТОВ С ПАТОЛОГИЕЙ ГРИБКОВОЙ ЭТИОЛОГИИ

Abstract. Introduction. Fungi are one of the constituents of an ecosystem. There are about 250 known human- pathogenic fungi species: From the widely spread Candida to the pathogene of aspergillosis that may lead to fatal consequences in certain conditions. Studies performed by Russian and foreign authors show the increase in the frequency of chronic sinusitis determined by the presence of fungi or fungal-microbial associations. Aim of this study is to perform the differential diagnosis of midface complications in patients with fungal pathology according to multispiral computed tomogrsphy and magnetic resonance tomography. Materials and Methods. A retrospective study was conducted based on the findings of multispiral computed and/or magnetic resonance tomographies of 68 patients. Presence of a fungal process was confirmed by histopathologic, mucroscopic, and cultural investigations. Results and Discussion. Histological investigations of surgical specimen detected the presence of fungal bodies formed by mycelium, i.e., a cluster of densely, compactly located fungal flocci in 28 of 48 (58.3 %): In 28 patients with maxilla sinus lesions, in 14 patients with sohenoidal sinus lesions, and in 5 patients with ethmoidal sinus lesions. In case of acute invasive fungal rhinosinusitis, the computed tomography of paranasal sinuses detected mucosal thickening and the bone density decrease associated with an erosive process. Unilateral lesions, erosions, and thinning of the sinus bone walls. According to magnetic resonance tomography, there was low signal in T2 mode, which is determined by the high concentrations of various metal elements in fungi, as well as by a high protein level and low free water contents in mucine. Conclusions. Visualization is essential to staging the disease and assessing the involvement of deeper structures, which may be clinically unmanifest. Although both computed tomography and magnetic resonance tomography are useful, the contrast-enhanced magnetic resonance tomography is the method of choice and helps assess the spread of the disease, especially regarding the deep extension into maxilla-facial area and brain.

Influence of plasma-activated γ-aminobutyric acid on tissue browning and water migration in fresh-cut potato during storage

Plasma-activated water (PAW) accelerated tissue browning in fresh-cut fruit. In this study, plasma-activated γ-aminobutyric acid (PG) was applied in potato slices. We aimed to contrast the impacts of PAW, γ-aminobutyric acid (GABA), and PG on changes in phenol metabolism and water distribution in potato slices. The results highlighted that PG proved to be the most effective treatment in terms of sterilization, inhibition of browning, and prevention of water. PG facilitated the activation of antioxidant enzymes, thereby eliminating reactive oxygen species and maintaining the integrity of cell membranes. Furthermore, PG exhibited the capacity to inhibit enzymatic browning caused by polyphenols, which was achieved through enhancing the activities of enzymes associated with phenylpropane metabolism and suppressing polyphenol oxidase activity. PG also protected the surface integrity of the potato slices as evident from SEM analysis. Additionally, NMR result indicated that PG played a role in maintaining free water content and inhibiting moisture migration.

Influence of lipid fraction of Black Soldier fly larvae on productivity, resistance and metabolic processes in milk-fed period calves

Relevance. There is evidence of increased immunity in animals when they are fed components from insect larvae. The research objectives are to study some aspects of the composition and bactericidal properties of the lipid fraction obtained from the biomass of Black Lion larvae (LCL-lf); to establish the effectiveness of using LCL-lf as an additive to the diet of calves of the dairy growing period.Methodology. Scientific and economic experience in studying the effect of various levels of use of the lipid fraction obtained from the biomass of Black Lion larvae in the diets of dairy calves (from the 59th to the 123rd day) of the growing period was carried out in JSC «Molodi» of the Moscow region. The animals of the control group were fed a balanced diet in terms of energy and nutrients, the 1st experimental in addition to the main diet daily (individually) in the morning feeding was fed 5 g of LCHL-lf, the 2nd experimental – 10 g of LCHL-lf.Results. Fatty acid composition of LCHL-lf: the sum of saturated LC – 85.9%, lauric acid – 55.6%. The antimicrobial properties of the extract from LCL-lf are largely noted in relation to gram-positive bacteria. It was noted that feeding larvae in the diets of young animals improved the bactericidal properties of the blood serum of experimental animals – from 31.4 to 42.9–48.6% (p < 0.05). The content of erythrocytes (11.6% vs. 10.3 × 1012/l in the control, p = 0.08) and hematocrit (40.9 vs. 37.1% in the control, p = 0.02) was higher in the blood of group 2 animals, which indicates an increase in the redox capacity of the blood of experimental animals. In the blood of animals of the experimental groups, the content of free water–soluble antioxidants increased – from 14.8 mg/l in the control to 17.8 mg/l (p = 0.08) and to 15.7 mg/l (p = 0.39) in the blood of animals of the experimental groups, 1st and 2nd, respectively. In general, over the two-month period of the experiment, the increase in SSP was: in group 1 – 8.4%, in group 2 – 18.7% compared with the control (703.1–769.5 g vs. 648.4 g, p < 0.05).

A new approach for characterizing internal stress of fresh concrete during thermal treatment period

Addressing the scarcity of research on the residual expansion deformation of steam-cured concrete and its underlying factors, this study introduces a testing apparatus to characterize the internal stress in fresh concrete during the thermal treatment. It explores the impact of water-to-cement ratio (w/c) and paste-to-aggregate ratio (p/a) on internal stress and elucidates the developmental patterns of internal stress in concrete throughout the thermal treatment phase. The key findings are as follows: (i) During the thermal treatment, the internal stress in concrete under constraint is predominantly compressive, exhibiting a rapid increase in the heating stage, followed by a gradual decline in the constant temperature treatment stage, and a continued decrease with a decelerating trend during the cooling stage. (ii) Both w/c and p/c significantly influence internal stress in concrete, and this stress can be enhanced by reducing the initial free water content and augmenting the initial structural strength of the concrete. This paper serves as a valuable foundation and reference for further investigations into the residual expansion deformation of steam-cured concrete.

Antimicrobial Activity of Natural Solid Soap with a Combination of Liquid Cheese Waste, Turmeric (Curcuma longa), and Dragon Fruit (Hylocereus polyrhizus) Peel

Yoghurt whey is a product from fermented cheese liquid waste. Yoghurt cheese liquid waste has been known to contain lactoferrin. Lactoferrin functions as an antimicrobial. yoghurt made from whey has not been widely utilized as a solid soap ingredient. This research focuses on producing solid natural soap made of yoghurt whey with added natural dye turmeric and dragon fruit peel, soap quality testing, and analysis of the soap's antibacterial activity toward Staphylococcus aureus. The solid soap was processed through the saponification reaction between palm oil, coconut oil, zaitun oil, and canola oil with sodium hydroxide. Variations of yogurt whey used in this study yoghurt 25%,75%,100% whey) was added natural dye (turmeric and dragon fruit peel). The quality test was done by determining free alkali, water content, pH, and foam height. Antibacterial activity test using the well diffusion method. The result shows that the quality test yoghurt soap meets with INS (Indonesia National Standard) 2016, for all the criteria. Performs inhibition against bacteria Staphylococcus aureus. Yoghurt whey is potently used as an antibacterial agent in the manufacture of natural solid soap.

Effects of Tremella polysaccharide on frost resistance of frozen dough considering water state, physical property and gluten structure

To explore the effects of Tremella polysaccharide (TP) on frost resistance in dough, different concentrations of TP (0, 0.2, 0.4, 0.6, 0.8, and 1.0 %) were added to frozen dough, and the effects on the water state, physical property, and gluten structure of the dough were studied. The results showed that 0.6 % TP concentration caused a reduction in the freezable water content and growth rate of free water, and inhibited the recrystallization of ice in dough during frozen storage. The tensile test and rheological analysis results showed that 0.6 % TP concentration could significantly protect the tendons of dough and thus maintain its dominant elasticity. Free sulfhydryl group content determination and infrared spectrum scanning confirmed that 0.6 % TP concentration yielded the lowest transition of the ordered structure to a disordered structure in the dough and maintained the integrity of the dough gluten structure with minimal porosity. These findings indicate that TP can be used as a potent food cryoprotectant to mitigate the deterioration of frozen dough quality and has promising application prospects in the food industry.

Survivability of probiotics in Pickering emulsion gels stabilized by salmon by-product protein / sodium alginate soluble complexes at neutral pH

Adequate amounts of live probiotics reaching the gut are necessary to maintain host health. However, the harsh environment during processing, the low pH of human gastric acid, and the high concentration of bile salts in the gut can significantly reduce survivability of probiotics. In this work, we propose a simple Pickering emulsion gels strategy to encapsulate Lactobacillus plantarum Lp90 into oil droplets filled in calcium alginate gels to improve its viability under pasteurization and gastrointestinal conditions. The emulsion gels were stabilized by the soluble complexes of salmon by-product protein (SP) and sodium alginate (ALG), and the aqueous phase was solidified by the addition of calcium. The interaction between SP and ALG and the effect of ALG concentration on emulsifying ability and emulsion stability were studied. The results from optical imaging, nuclear magnetic resonance, and rheological properties showed that the stability and viscosity of the emulsions gradually increased with the increased ALG concentration, while the droplet size of the emulsions and the content of free water in the system decreased significantly. Especially when the concentration of ALG was 1 %, the emulsion system was stable under the environment of high temperature and high ionic strength, and the water holding capacity was the highest. Through pasteurization and gastrointestinal digestion experiments, it was found that the survival rate of probiotics encapsulated in emulsion gels was significantly higher than that encapsulated in emulsions or hydrogels, which benefited from the dual action of oil droplets and calcium alginate gels network. These results provide a new strategy for the processing of probiotics and the high-value utilization of marine fish by-products.

Establishing Ultralow Self-Discharge Zn-I2 Battery by Optimizing ZnSO4 Electrolyte Concentration.

As one of promising candidates for large-scale energy-storage systems, Zn-I2 aqueous battery exhibits multifaceted advantages including low cost, high energy/powder density, and intrinsic operational safety, but also suffers from fast self-discharge and short cycle/shelf lifespan associating with I3 - shuttle, Zn dendrite growth, and corrosion. In this paper, the battery's self-discharge rate is successfully suppressed down to an unprecedent level of 17.1% after an ultralong shelf-time of 1000h (i.e., 82.9% capacity retention after 41 days open-circuit storage), by means of manipulating solvation structures of traditional ZnSO4 electrolyte via simply adjusting electrolyte concentration. Better yet, the optimized 2.7 mZnSO4 electrolyte further prolongs the cycle lifespan of the battery up to >10000 and 43000 cycles at current density of 1 and 5Ag-1, respectively, thanks to the synthetic benefits from reduced free water content, modified solvation structure and lowered I2 dissolution in the electrolyte. With both long lifespan and ultralow self-discharge, this reliable and affordable Zn-I2 battery may provide a feasible alternative to the centuries-old lead-acid battery.

Frost-Heaving Behavior and Enhancement Approaches of Cement-Based Grout Materials under Freeze–Thaw Conditions

In the seasonally frozen regions, during the grouting of prestressed bridge ducts in low-temperature environments, incompletely cured grout materials undergo volumetric changes due to freeze–thaw cycling, resulting in structural cracks along the prestressing ducts of the bridge, thereby diminishing the bridge’s operational lifespan. In order to investigate the freeze–thaw characteristics of grouting materials under the influence of freeze–thaw cycles and propose improvement measures, the influence of various additives on the freeze–thaw stress characteristics of mortar under freeze–thaw cycle conditions was elucidated through freeze–thaw stress tests. The mechanisms for improving the freeze–thaw characteristics of grouting materials were explored through analyses of free water content, setting time, compressive strength, XRD, and SEM. In light of the requirements for comprehensive performance of grouting materials, composite additives are employed to enhance the freeze–thaw performance of the grout. The results indicate that reducing the water-cement ratio, incorporating calcium formate, sulfoaluminate cement, air-entraining agents, and carbamide all have a positive impact on mitigating frost-heaving stress in grout materials. However, the improvement mechanisms differ, and employing a single measure alone is insufficient to effectively reduce frost-heaving stress while meeting performance criteria such as compressive strength, setting time, and flowability. Free water content emerges as a crucial indicator determining the magnitude of frost-heaving stress in grout materials, with 11.5% of free water content representing the critical threshold for frost heaving in grout materials. Utilizing composite admixtures can simultaneously decrease free water content, lower the freezing point of free water, and alleviate frost-heaving deformation, resulting in a more efficient reduction of frost-heaving stress. When the admixture content reaches 9.9%, frost-heaving stress is eliminated, and the comprehensive performance parameters, including compressive strength, setting time, and flowability, meet the specified requirements. Overall, the conclusions of this research will offer a scientific foundation for the choice of cold-resistant grouting materials, the mitigation of grout material freeze–thaw risk, and the improvement of quality assurance levels in bridge construction within seasonally frozen areas.

Hydration characteristics and mechanism analysis of β-calcium sulfate hemihydrate based on low-field NMR

Free water plays a crucial role in the hydration process of β-calcium sulfate hemihydrate (β-HH) based plaster. To further understand the hydration mechanism of β-HH, this study monitored water consumption and pore structure evolution of plaster prepared by different water/β-HH (W/H) ratios using low-field NMR. The hydration characteristics were jointly analyzed using X-ray diffraction (XRD), thermogravimetric (TG), and isothermal calorimetry. In addition, the pore structure of the plaster was characterized by BET and MIP. Results indicated that during early hydration (0–10 min), free water migrated from macropores to micropores in β-HH samples. The specific surface area and free water content of β-HH based plaster decreased during rapid hydration period. It is also found that increasing the W/H ratio accelerated free water consumption but resulted in larger pore diameter. Furthermore, signal intensity and transverse relaxation time were found to be exponentially related (y = Ae(-x/B) + y0) to the CaSO4∙2H2O crystal content, hydration degree, and heat release. These correlations suggest that low-field NMR correlated well with other measurements and could be viable method to characterize the plaster hydration process.