Search

This study focuses on the rheological behavior of a cellulose nanocrystal gel. This system [5 wt. % cellulose nanocrystal (CNC) + 20 mM NaCl] is proved to be thixotropic, and the detected shear force tightly depends on the growth and break-up of the aggregates of CNC rods. From strain-controlled experiments, a nonmonotonic steady-state flow curve with a minimum stress value of ≈33 Pa is found, and the negative slope of stress versus shear rate suggests the existence of shear bands. From stress-controlled experiments (creep), the "static yield stress" is determined to be 67.5 ± 2.5 Pa. This difference proves that the local minimum stress of the flow curve does not coincide with the "static yield stress" determined by creep tests. However, this minimum stress can maintain flow provided that the material is already in a yielded state. At nominal shear rates below about 100 s−1, shearing is suggested to be localized in a shear band rather than over the whole material. The "dynamic yield stress" is found as "the minimum stress to maintain flow," or the onset of shear banding. Moreover, wall slip also occurs at low nominal shear rates which is related to the interaction between the dynamic microstructure of the CNC gel and the wall: it is hypothesized that the low shear rates allow the CNC aggregates to extensively grow and, thus, the oversized CNC aggregates detach from the asperities of the wall. Our finding of the robust connection between yielding, thixotropy, wall slip, and shear banding shall shed new light on the nature of the nonmonotonic flow curves of yield stress and thixotropic materials. [ABSTRACT FROM AUTHOR]

Hydrogels have emerged as promising candidates for biomedical applications, such as replacing natural articular cartilage, owing to their unique viscoelastic properties. However, sufficient mechanical properties, self‐healing ability, and adhesive nature are some issues limiting its application window. Here, a facile one‐pot synthesis of dual cross‐linked zinc‐coordinated copolymer hydrogels is presented. The network structure of the copolymer hydrogels is strategically developed via dynamic and reversible physical cross‐linking by Zn2+ ions and simultaneous covalent cross‐linking through a covalent cross‐linker viz methylene bisacrylamide. Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD) scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis have thoroughly characterized the structure of the synthesized hydrogels. The introduction of Zn2+ offers dynamic and reversible complexation, leading to excellent mechanical properties and self‐healing features. Moreover, the percentage of the equilibrium water content of zinc‐coordinated copolymer hydrogel samples is comparable with that of natural articular cartilage. The Shear sliding study shows the dominant adhesive behavior of HGel‐Zn(NO3)2 sample compared to the parent HGel sample. This facile dual cross‐linked hydrogel, HGel‐Zn(NO3)2, with a combination of good mechanical properties, efficient self‐recovery, adequate water content, and favorable adhesive nature, seems very promising to mimic the articular cartilage. [ABSTRACT FROM AUTHOR]

Engineered cementitious composites (ECCs) have garnered significant attention within the construction industry, owing to their exceptional mechanical properties and durability. This thorough review presents a meticulous analysis of the progress and prospects in ECC research. It begins by introducing the background and rationale for investigating ECCs, while outlining the objectives of the review. The review provides an encompassing overview of ECCs, encompassing their definition, characteristics, historical development, composition and constituent materials. Emphasis is placed on the examination of ECCs' mechanical properties, specifically their flexural behaviour, tensile behaviour, compressive strength and resistance to environmental factors. Furthermore, the rheological properties of ECCs, including workability, flowability, self-healing, crack mitigation, viscosity and thixotropy, are discussed in detail. The review delves into the influence of fibre reinforcement on ECCs, encompassing the types of fibres utilised and their impact on mechanical and structural properties, as well as fibre dispersion and orientation. Additionally, it explores the diverse applications of ECCs across various fields, such as structural applications and sustainable building practices. The challenges and limitations associated with ECCs, such as cost and availability, are addressed, alongside an exploration of future trends and research directions. [ABSTRACT FROM AUTHOR]

A comparative evaluation of the brand-name drug Mycospor and six generic drugs (IWAKI, Bifonol, F, YD, Sawai, and TEVA), all comprising a cream formulation containing the antifungal drug bifonazole, was performed based on physicochemical measurements. The pH of the various formulations was significantly higher for the generics Bifonol (pH 7.1), Sawai (pH 6.7), and TEVA (pH 7.3) and significantly lower for YD (pH 4.3) than for the brand-name drug Mycospor (pH 5.5). The viscosity of the various formulations was significantly higher for TEVA (25,011 mPa·s) versus Mycospor (22,376 mPa·s) and significantly lower for IWAKI, Bifonol, F, YD, and Sawai, with Bifonol (8,572 mPa·s) being particularly low. Considering the hysteresis loop area obtained for the shear rate vs. shear stress, which represents the thixotropic properties, and using the value of Mycospor as the reference for 100%, YD (179%), Sawai (557%), and TEVA (201%) showed significantly higher values. Furthermore, the membrane permeability of bifonazole at 24 hours was significantly higher for Bifonol (309 µg/mL) and F (182 µg/mL) and significantly lower for Sawai (124 µg/mL) and TEVA (92 µg/mL) than for Mycospor (153 µg/mL). Finally, optical micrographs showed that the dispersion of particles was similar in the various formulations, but the particles of F and TEVA were uniformly dispersed with a smaller particle size than the other formulations. Overall, significant differences were observed in the formulation characteristics between the brandname drug and generic drugs, which were attributed to differences in the manufacturing process and the types of additives. [ABSTRACT FROM AUTHOR]

To investigate the mechanism of polypropylene fiber (PPF) on the rheological and thixotropic properties of cemented paste backfill containing mineral admixtures, the concept of water film thickness (WFT) was introduced. The packing density of the tailings-binder-PPF (TBP) system was measured in dry and wet conditions and the WFT was calculated accordingly. Additionally, the rheological parameters (yield stress, thixotropy, etc.) of the fiber-reinforced cemented paste backfill (FRCPB) were quantified. The results demonstrate that the wet packing test is a more appropriate method for measuring the packing density of the TBP system. The PPF length has a slight adverse effect on the packing density, and the packing density initially increases and then decreases with the PPF content. The reasons can be attributed to the filling effect and wedge effect of the fibers, respectively. In addition to the packing density, the thixotropy of FRCPB is also affected by the interaction of fibers. WFT is a crucial factor affecting the yield stress of FRCPB, with which it exhibits a strong linear relationship. The study identified that the optimum PPF content for enhancing the rheological and thixotropic properties of CPB is 0.2%, with a fiber length of 9 mm, balancing flowability and stability for practical application in mining backfill operations. These insights can guide the optimization of CPB mixtures, enhancing their flowability and stability during placement in mined-out spaces. By improving the fill quality and reducing the risk of blockage during backfill operations, the results offer practical benefits in increasing the safety and efficiency of underground mining activities. [ABSTRACT FROM AUTHOR]

AbstractEmphasizing the viscoelasticity of ophthalmic gels is crucial for understanding the residence time, structure, and stability of hydrogels. This study primarily aimed to propose an innovative rheology analysis method for ophthalmic gels, considering complex eye movements. This method was applied to select ophthalmic gels with favorable rheological characteristics. Additionally, the physical characteristics and in vitro release of the selected Panax notoginseng total saponins (PNS) gel were demonstrated. The selected PNS gel significantly increased the activities of SOD and decreased intracellular levels of MDA, TNF-α, and IL-1β in H2O2-treated ARPE-19 cells. Finally, the optimal formulation was selected as a suitable platform for ophthalmic delivery and was shown to significantly rescue ARPE-19 cells from oxidative cellular damage. [ABSTRACT FROM AUTHOR]

The rheological behavior and printing characteristics of the screen-printing slurry for Nd-Fe-B grain boundary diffusion are key factors that determine the quality of printing and magnetic performance. However, few studies have focused on the organic medium, a crucial material for slurry. In this paper, the rheology, thixotropy, and thermal decomposition behavior of the organic vehicle in Nd-Fe-B screen printing slurry were studied. The results show that the organic vehicle formed by terpineol and polyvinyl butyral (PVB) exhibits typical non-Newtonian fluid characteristics, with excellent rheology and thixotropy, ensuring that the slurry prepared from it has excellent static stability and printing consistency. Additionally, the carbon residue of the organic vehicle formed by terpineol and PVB is less than 0.1% at 900 °C, avoiding excessive carbon entering the magnet during the diffusion process. Moreover, studying the rheology and thixotropy of the organic vehicle through a rheometer can quickly screen the slurry system. This work provides valuable guidance for designing an organic vehicle for screen-printing slurry for Nd-Fe-B grain boundary diffusion in future research. [ABSTRACT FROM AUTHOR]

In this paper, the rheological properties and viscosity reduction mechanism of waxy crude oil were reviewed. Firstly, the rheological behavior of waxy crude oil was introduced from the aspects of microscopic properties, viscosity, yield properties, thixotropy and viscoelasticity. Secondly, the effects of dissolved gas, light crude oil or alcohol on the rheological properties of crude oil were described respectively. Finally, the shortcomings and limitations of existing studies were further prospected. The future research will focus on exploring the mechanism of the effect of shear history on the microstructure of wax crystals, and establishing the constitutive model of crude oil considering the yield strain and yield stress based on the morphological and structural changes of wax crystals. Furthermore, to explore the mechanism and influence law of light component dissolution on crude oil rheology, and establish a reliable viscoelastic-thixotropic model of crude oil under the conditions of unsteady shear, wide range shear rate and ultra-low shear rate, will be the prerequisite and basis for the numerical calculation in restarting of gelled crude oil containing light component at low temperature. [ABSTRACT FROM AUTHOR]

Thixotropic yield-stress fluids (TYSFs) are a unique class of materials whose properties are affected by both shear rate and shear history. When sheared, these materials undergo a transition from an elastic solid to a viscoelastic fluid, which is accompanied by a structural transition that slowly recovers upon the cessation of shear. The strong interdependence between structure, dynamics, and rheological properties in TYSFs make it challenging to identify the fundamental physics controlling these phenomena. In this study, we vary the ionic strength of a suspension of cellulose nanocrystals (CNC) to generate model TYSFs with tunable moduli and thixotropic kinetics. We use a novel rheological protocol—serial creep divergence—to identify the physics underlying the yield transition and recovery of CNC gels. Our protocol identifies a critical transition that bifurcates the solid-like and fluid-like regimes of the gels to precisely determine the yield stress of these materials even in the presence of thixotropic effects. Additionally, the thixotropic kinetics collapse onto a single master curve, which we fit to a transient solution to a coupled diffusion–aggregation model. Our work thereby identifies the underlying physicochemical mechanisms driving yielding and thixotropic recovery in attractive colloidal gels. [ABSTRACT FROM AUTHOR]

In high‐temperature and high‐salt environments, emulsions stabilized by surfactants are susceptible to instability phenomena, such as droplet coalescence, thereby limiting their utility in tertiary oil recovery. The Pickering emulsions, which are stabilized by solid particles, have been proved to exhibit good stability. This study demonstrated that the nonionic surfactant C16E20 can adsorb onto SiO2 nanoparticles with an efficiency exceeding 99%, rendering C16E20 suitable for modulating the wettability of SiO2 nanoparticles. By adjusting the proper surfactant‐to‐nanoparticle ratio, such as 0.1%:1.0%, a hydrophilic–lipophilic equilibrium is obtained, which is beneficial for the preparation of Pickering emulsions. Laser confocal and cryo‐scanning electron microscopy results indicated that SiO2 nanoparticles in Pickering emulsions were dispersed at the oil–water interface, forming a network structure between the emulsion droplets. Further experiments illustrated that the Pickering emulsions showed excellent stability for at least 180 days at 80°C. Conventional emulsions behave as Newtonian fluids at lower oil‐phase ratios, while Pickering emulsions exhibit non‐Newtonian fluid properties, with their viscosity capable of increasing by over 100 times. Additionally, Pickering emulsions were found to exhibit thixotropy, attributed to the reversible formation and destruction of droplet bridging structures. Overall, Pickering emulsions are regarded as potential agents for Enhanced Oil Recovery in oilfield development. [ABSTRACT FROM AUTHOR]

As temperature and salt-resistant materials, hydrophobically associating polymers can form a reversible spatial network structure through the interaction between their hydrophobic groups, effectively improve the viscosity of the polymer solution through association, and enhance the temperature and salt resistance of the polymer. Hydrophobically associating monomers have different effects on the properties of polymer solutions. Herein, acrylic acid, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid were used as hydrophilic monomers. The three hydrophobic monomers with different carbon chain lengths were prepared by the bromination reaction. Hydrophobic associating polymers DQM1-PAM, DQM2-PAM, and DQM3-PAM were prepared by aqueous solution free-radical polymerization. The structure–activity relationship of the hydrophobic monomers with different carbon chain lengths on polymers was studied. It was confirmed by Fourier-transform infrared spectroscopy and 1H-NMR that the target product was successfully synthesized. Scanning electron microscopy revealed that with increasing hydrophobic carbon chain length, the hydrophobic microarea of molecular aggregation increased, forming a closer spatial network structure. Thermogravimetric and fluorescence tests revealed that with increasing hydrophobic carbon chain length of polymer molecules, the polymerization temperature resistance increased, intermolecular association degree increased, and critical association concentration decreased. Rheological property evaluation revealed that the viscosity of 0.5% polymer DQM1-PAM, DQM2-PAM, and DQM3-PAM was 71.32, 100.21, and 118.79 mPa·s after shearing at 120 °C and 170 s−1 for 1 h. With the increase in the carbon chain length, the retention rate of shear viscosity of polymer in a salt solution increased, showing good salt resistance. Concurrently, the molecular aggregation microarea of a solution with 0.5% polymer, degree of molecular chain action, viscoelasticity of the solution (G' > G''), and thixotropic area all increased. The performance of polymer solution can be improved by modifying hydrophobically associating polymers with long carbon chains, which has a broader application. [ABSTRACT FROM AUTHOR]

The transient rheological behaviour of semi-dilute kaolinite clay suspensions is investigated. Specifically, the flow curve hysteresis and step shear rate tests are used to investigate the shear behaviour of kaolinite suspensions. We found that there is a coupling effect between thixotropy and slip that dominates this transient rheological behaviour. It appears that the onset of solid-like slip in the system is a function of wall roughness and interfacial phenomena between the particles of the suspension and the wall. The coupled phenomena of slip and thixotropy are investigated using the application of sandpaper, varying the gap, and using different geometries. To illustrate the importance of slip in this system, we propose a Coupled Thixotropy and Slip (CTS) model that couples a thixotropic Structure Parameter Model (SPM) to an existing slip model. [ABSTRACT FROM AUTHOR]

We continue the systematic analytical study of the nonlinear Maxwell-type constitutive equation for shear flow of tixotropic viscoelastoplastic media formulated in the previous article. It accounts for interaction of deformation process and structure evolution, namely, the influence of the kinetics of formation and breakage of chain cross-links, agglomerations of molecules, and crystallites on viscosity and shear modulus and deformation influence on the kinetics. The constitutive equation is governed by an increasing material function and six positive parameters. Assuming that the stress is constant (in order to simulate creep conditions), we formulate the set of two nonlinear differential equations for two unknown functions (namely, strain and cross-links density) and obtain its exact general solution in explicit form. We examine the properties of creep curves generated by the model for arbitrary material function and material parameters and analyze dependence of creep curves and cross-links density on time, stress level, initial cross-links density, and material parameters governing the model. Thus, we prove that the model not only describes basic phenomena observed for simple shear flow of shear thinning fluids, but can simulate creep, relaxation, and other phenomena observed for solid bodies. [ABSTRACT FROM AUTHOR]

The challenge of insufficient proppant transportation capacity in slick water remains unresolved. To tackle this concern, a hydrophobically associating water-soluble polymer (HAWP), characterized by a low molecular weight (MW) of 8.11 × 105 g/mol, was successfully synthesized via a photo-initiation method. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The results show that in comparison to conventional drag reducers in slick water with an average MW of approximately 1 × 107 g/mol, HAWP demonstrates significantly reduced MW. The rheological test results indicate that upon addition of sodium dodecyl benzene sulfonate (SDS, 200 mg/L) to the HAWP solution (0.3 wt%), the storage modulus experienced a substantial increase from 0.14 Pa to 7.42 Pa, demonstrating enhanced mechanical properties. Meanwhile, drag reduction (DR) tests showed that the efficiency of drag reduction achieved by the polymer system (PS) drag reducer was comparable to that of conventional linear polymers. This research achievement effectively addresses the challenges of low molecular weight and resistance reduction encountered in previous endeavors. [ABSTRACT FROM AUTHOR]

In this paper, with the application of a MARS 60 high-pressure rheometer, experimental tests are conducted on Shengli crude oil to test its gel point, viscosity and thixotropy under different static pressures. Consequently, the effect of static pressure on the rheological parameters of waxy crude oil is revealed. It is proven that with the increase in the static pressure, the gel point of Shengli crude oil increases linearly, and the viscosity also gradually increases. The power law equation is employed to describe the relationship between the apparent viscosity and shear rate of Shengli crude oil under different static pressures. With the increase in the static pressure, the consistency coefficient (K) increases linearly, and the rheological index (n) decreases linearly. The relationship between the viscosity of Shengli crude oil and the static pressure and shear rate can be obtained. The Cross thixotropic model is used to describe the thixotropic curve of Shengli crude oil under different static pressures. With the increase in the static pressure, the thixotropic coefficient of consistency (ΔK) and the structure fracture constant (b) increase linearly. This is because a high pressure results in high structure strength and strong non-Newton rheological behavior in gelled crude oil and also causes remarkable structure fracture in crude oil. The results in this paper can provide an important theoretical basis for crude oil production and transportation. [ABSTRACT FROM AUTHOR]

Cement slurry is the medium of dispersion of coarse and fine aggregates when preparing concrete. The flow behavior of the cement slurries is governed by rheological parameters. The lower the value of these parameters is, the better the flowability and homogeneity of the cement slurry are. Static shear stress (τs), dynamic shear stress (τd), and the thixotropic index (β) are the basic rheological parameters. The effect of fly ash and silica fume on the rheology of Ordinary Portland Concrete (OPC) 43 and OPC 53 was studied by conducting tests on a coaxial rotating-type viscometer. Fly ash dosage was increased from 10% to 30% by the weight of cement in increment steps of 5% in binary and ternary mixes. Silica fume was kept constant at 5% in the ternary mixes. It was found that τs increases with fly ash in the OPC 43 but remains almost constant for the OPC 53 in both binary and ternary mixes. τd was almost constant for both the cement slurries in both binary and ternary mixes. β increases with an increase in fly ash for OPC 43 in binary and ternary slurries but decreases in OPC 53 slurries. The increment of fly ash increases the reversible built in the OPC 43 slurries, which can be broken on the application of shear. Thus, OPC 43 is a better cement from the rheological point of view in the development of various concrete mixes. [ABSTRACT FROM AUTHOR]

Here, we introduce an organic/inorganic composite hydrogel as a versatile gel electrode material. This composite hydrogel was formed by simply mixing an aqueous solution of flat microparticles of tungsten oxide, exhibiting superior water dispersibility, with a hydrogel composed of a water‐soluble polyaramide‐based polymer hydrogelator. The resulting composite hydrogel exhibited uniform dispersion of tungsten oxide flat particles throughout the hydrogel matrix, supplementing the structure formed by the polymer hydrogelator. It maintained the gel‐forming capability and thixotropic behavior inherent to the polymer hydrogelator while showcasing the electrochemical characteristics of tungsten oxide. With its spreadability and applicability to various electrode shapes, a composite hydrogel is presented as a potential spreadable gel electrode material. [ABSTRACT FROM AUTHOR]

The Rayleigh-Taylor instability (RTI) between a heavier Newtonian liquid and a lighter thixotropic liquid is studied in this paper by weakly compressible smoothed particles (WC-SPH). It is assumed that the thixotropic liquid obeys the Moore rheological model. First, the developed code is verified against available Newtonian RTI cases. Then, it is applied to thixotropic RTI cases to investigate the effects of the different non-dimensional parameters, including the thixotropic number (destruction-to-rebuild ratio), Reynolds number, Bond number, and Deborah number. It is shown that Bo is the most paramount non-dimensional parameter (i.e., it determines whether the two-phase boundary is stable or unstable), while Re , De , and thixotropic numbers have secondary influences on RTI. Based on the obtained results, the behavior of the thixotropic case is similar to the Newtonian high viscous counterpart at initial times; however, it is different at long times. It is demonstrated that the value of the thixotropic number determines when the transition between the short-time and long-time phenomena occurs. • The effects of thixotropy are investigated on single-mode and multi-mode RTIs by WC-SPH. • By increasing the thixotropic number, the spike position is more advanced. • The threshold for changing the behavior of the thixotropic RTI depends on the thixotropic number. • The impacts of thixotropic behavior appeared sooner for multi-mode RTI. [ABSTRACT FROM AUTHOR]

Effective thermal transport across solid-solid interfaces, essential in thermal interface materials (TIMs), necessitates both optimal thixotropy and high thermal conductivity. The role of filler surface modification, a fundamental aspect of TIM fabrication, in influencing these properties is not fully understood. This study employs the use of a silane coupling agent (SCA) to modify alumina, integrating experimental approaches with molecular dynamics simulations, to elucidate the interface effects on thixotropy and thermal conductivity in polydimethylsiloxane (PDMS)-based TIMs. Our findings reveal that varying SCAs modify both interface binding energy and transition layer thickness. The interface binding energy restricts macromolecular segmental relaxation near the interface, hindering desirable thixotropy and bond line thickness. Conversely, the transition layer thickness at the interface positively influences thermal conductivity, facilitating phonon transport between the polymer and filler. Consequently, selecting an optimal SCA enables a balance between traditionally conflicting goals of high thermal conductivity and minimal bond line thickness, achieving an impressively low interface thermal resistance of just 2.45–4.29 K·mm2·W−1 at 40 psi. [ABSTRACT FROM AUTHOR]

A systematic analytical study of the mathematical properties of the previously constructed nonlinear model for shear flow of thixotropic viscoelastic-plastic media, which takes into account the mutual influence of the deformation process and structure evolution, is continued. A set of two nonlinear differential equations describing the processes of shear at a constant rate and stress relaxation is obtained. Equation set describing creep is derived; a general solution of the Cauchy problem for the set is constructed in an explicit form (the equations of the families of creep, and structuredness curves are derived). For arbitrary six material parameters and (increasing) material function that govern the model, basic properties of the families stress-strain curves at constant strain rates, stress relaxation curves and creep curves generated by the model, and the features of structuredness evolution under these types of loading are analytically studied. The dependences of these curves on time, shear rate, stress level, initial strain, and initial structuredness of the material, as well as on the material parameters and function of the model, are studied. Several indicators of the applicability of the model are found which are convenient to check with experimental data. It was examined what effects typical for viscoelastic-plastic media can be described by the model and what unusual effects (unusual properties) are generated by a change in structuredness in comparison with typical stress-strain curves, relaxation curves, and creep curves of structurally stable materials. In particular, it is proved that creep curves always increase in time and have oblique asymptote, and structuredness under constant stress is always monotonous (unlike other loading modes), but can decrease or increase depending on the relation between the stress level and initial structuredness. The same condition controls creep curves to be convex up or down: at a certain (calculated) critical load creep curves change from convexity up (under smaller loads) to convexity down, and the structuredness becomes ascending instead of descending. The analysis proved the ability of the model to describe behavior of not only liquid-like viscoelastoplastic media, but also solid-like (thickening, hardening, hardened) media: creep, relaxation, recovery, a number of typical properties of experimental relaxation curves, creep and stress-strain curves, strain rate and strain hardening, flow under constant stress and so on. [ABSTRACT FROM AUTHOR]

Thixotropy is characterized by a time-dependent rise in viscosity under no or weak flow conditions and a decrease in viscosity over time when subjected to strong flow conditions. The characteristic timescale associated with the thixotropic phenomenon, particularly how the viscosity increases with time, has been termed the thixotropic timescale. Several approaches have been suggested in the literature for estimating the thixotropic timescale. The most prominent approach, however, infers it from a specific form of a kinetic expression for structure parameter evolution. In this paper, we study the various kinds of structural kinetic models. By carefully analyzing the same, we propose a parameter for the thixotropic timescale associated with the most generic form of kinetic expression for structure parameter evolution. We observe that increasing the thixotropic timescale weakens the thixotropic character of a system when the viscosity of the structural kinetic model continuously increases over time and eventually diverges under quiescent conditions. We also propose a new phenomenological measure of the thixotropic timescale: τ t h i x = (d ln η / d t) − 1 , where η is viscosity and t is time. The proposed definition allows a straightforward and unique way to determine the thixotropic timescale through experiments and agrees well with the conventional notion of thixotropy. [ABSTRACT FROM AUTHOR]

The thixotropic structural build-up is crucial in extrusion-based three-dimensional (3D) concrete printing. This paper uses a theoretical model to predict the evolution of static and dynamic yield stress for printed concrete. The model employs a structural kinetics framework to create a time-independent constitutive link between shear stress and shear rate. The model considers flocculation, deflocculation, and chemical hydration to anticipate structural buildability. The reversible and irreversible contributions that occur throughout the build-up, breakdown, and hydration are defined based on the proposed structural parameters. Additionally, detailed parametric studies are conducted to evaluate the impact of model parameters. It is revealed that the proposed model is in good agreement with the experimental results, and it effectively characterizes the structural build-up of 3D printable concrete. [ABSTRACT FROM AUTHOR]

This study proposes a constitutive model to simulate the clayey soil response to the external loads during soil-structure interaction, specifically in the context of pile installation and subsequent set-up. The model considers the alteration of soil structure during prolonged penetration and the gradual regaining of its thixotropic strength. The model is based on the disturbed state concept and critical state theory, with the Modified Cam-Clay model used to define the intact state response. The proposed model, referred to as the Critical State and Disturbed State Concept model, captures the elastoplastic behavior of both normally consolidated and over-consolidated soils. It was validated using triaxial test results and implemented in Abaqus software to simulate pile driving and the set-up phenomenon occurs after the end of pile driving. The model accurately predicts pile capacity and disturbance behavior in the soil, as demonstrated by field compression load tests. [ABSTRACT FROM AUTHOR]

Copyright of Materiały Budowlane is the property of Wydawnictwo SIGMA-NOT and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the functional and technological properties of proteins in the composition of dairy ice cream. The object of the research was the technology of ice cream with plant-based proteins. The problem to be solved was the improvement of physicalchemical and rheological characteristics of mixtures and ice cream with a low fat content by using moisture-binding structuring proteins of plant origin. It was established that pea protein concentrate has the highest foaming properties. Oat protein concentrate shows a moderate ability to form and stabilize foams, while soy protein isolate does not reveal this function at all. The presence of plant-based proteins in all ice cream mixtures increases their nominal viscosity, but the highest thixotropy is observed for the concentrate of pea (56.5–61.0 %) and oat (54.8–57.2 %) proteins. They form food systems with a pronounced coagulation structure, which are capable of self-repair of bonds during the maturation of mixtures for 8 hours. Soy protein isolate reduces the thixotropic ability of ice cream mixtures, which limits the expediency of its use. The defined physical-chemical indicators of ice cream make it possible to justify the rational content of proteins in the composition of ice cream, which is 1–2 % for pea protein concentrate and 1 % for oat protein concentrate. Data on the rheological behavior of ice cream mixtures do not always coincide with previously established patterns, which is due to the difference in chemical composition between the studied food systems, as well as methods of their preparation and use. The results of this work could be used in the technology of lowfat ice cream, as well as in compositions for new types of ice cream enriched with protein. [ABSTRACT FROM AUTHOR]

Chicken breast as the raw material was fully sheared and then the obtain minced meat was rested at 4 °C for different time (0~48 h). The thixotropy and rheological properties of the chicken minced meat was further analyzed, and the effect of resting time on the properties of the chicken minced meat gel was also investigated. The results showed that the chicken minced meat exhibited pseudoplasticity, thixotropy and weak gel properties (G'>G"), and the viscosity, thixotropy, elasticity (G') and viscosity (G") of the chicken minced meat gradually increased with the increase of resting time. The cooking loss rate of the chicken minced meat gel significantly increased (P<0.05) with the increase of resting time. The water-holding capacity, chewiness and viscosity of the chicken minced meat gel rested for 24 h, the strength and hardness of the chicken minced meat gel rested for 12 h, and the elasticity of the chicken minced meat gel rested for 36 h showed a significant increase (P<0.05). The above results show that the thixotropic properties of the chicken minced meat obviously affect the gelling properties, and the resting treatment has the potential to adjust the processing properties and the quality of meat products. [ABSTRACT FROM AUTHOR]

In this article, the particle concentration of finely dispersed copper(II) oxide nanosuspensions as precursors for reductive laser sintering (RLS) is optimized on the basis of rheological investigations. For this metallization process, a smooth, homogeneous and defect-free precursor layer is a prerequisite for adherent and reproducible copper structures. The knowledge of the rheological properties of an ink is crucial for the selection of a suitable coating technology as well as for the adjustment of the ink formulation. Different dilutions of the nanosuspension were examined for their rheological behavior by recording flow curves. A strong shear thinning behavior was found and the viscosity decreases exponentially with increasing dilution. The viscoelastic behavior was investigated by a simulated doctor blade coating process using three-interval thixotropy tests. An overshoot in viscosity is observed, which decreases with increasing thinning of the precursor. As a comparison to these results, doctor blade coating of planar glass and polymer substrates was performed to prepare precursor layers for reductive laser sintering. Surface morphology measurements of the resulting coatings using laser scanning microscopy and rheological tests show that homogeneous precursor layers with constant thickness can be produced at a particle–solvent ratio of 1.33. A too-high particle content results in an irregular coating layer with deep grooves and a peak-to-valley height S z of up to 7.8 μm. Precise dilution control allows the fabrication of smooth surfaces with a S z down to 1.5 μm. [ABSTRACT FROM AUTHOR]

Research has shown that reversible phenomena such as non-linearity, self-heating and thixotropy occur during laboratory fatigue testing on bituminous mixes. This work aims to develop a test protocol to separate and quantify the recovery of reversible phenomena and the restoration of damage. Besides proposing some adjustments to the protocol, in the present paper, its repeatability is evaluated by comparing the results obtained for several samples of the same bituminous mixture. The test procedure is composed of two parts: short complex modulus tests (200 cycles at 10 Hz) at temperatures ranging from 8°C to 14°C with strain amplitudes ranging from 50 to 110 µm/m are used and five partial fatigue tests (at 10°C) are carried out at 100,000 cycles, 100 µm/m and 10 Hz. Each fatigue lag is followed by a 48-h rest period which consists of short complex modulus tests. The test protocol appears to show reliability and provide repeatable results. [ABSTRACT FROM AUTHOR]

In many food applications, the mechanical properties of fats play a critical role in determining the processing performance of fat-rich products. In fact, fat crystal networks form a particular class of soft materials that exhibit viscoelastic properties. The uniqueness of the mechanical response is intricately linked to the hierarchical nature of the system, as fats possess a complex architecture encompassing features at different scale levels (i.e., length scales). Since the discovery of crystalline nanoplatelets (CNPs), it has been hypothesized that CNPs are the basic building blocks of lipid networks and that CNPs are the responsible units for the mechanical properties of fats. This hypothesis, however, has only been partially tested. In this article, we examine which units could be responsible (e.g., lamellae, CNP, CNP aggregates) for the mechanical breakdown of fat crystal networks, through Rheo-USAXS in beamline ID02 (ESRF, Grenoble, France). Time-resolved USAXS profiles were acquired during the three steps of a three-interval thixotropy test (3iTT), namely, pre-shear, shear and recovery. The results were then utilized to evidence which specific length scale is arranged (i.e., orientated) during rheological breakdown. The findings suggest that, at the tested shear rates, orientation is only visible from 250 nm onwards, suggesting that the rheological breakdown of triglycerides is primarily driven by the orientation, and possible disruption, of CNP aggregates. These results reveal the critical role of CNP aggregates in the mechanical properties of fats. In the longer term, we believe this study will steer future research toward a more focused understanding of CNP aggregation and disaggregation dynamics. [ABSTRACT FROM AUTHOR]

This is an article in the field of ceramics and composites. In order to study the early rheological properties of alkali-activated fly ash-slag cementitious system, the composite pastes with different mass ratios of fly ash (FA) to slag (GGBS) and alkaline activator content were prepared. The fluidity and rheological properties of the pastes were tested by mini-cone slump cone, Brookfield DV3T rheometer,respectively. Finally, the hydration exothermic rate of composite pastes with each ratio was tested by isothermal calorimeter. Results show that when FA/GGBS ratio is 3∶7, the fluidity of paste with 4% NaOH content is the lowest. With the increase of FA mass ratio and NaOH molar mass, the fluidity of alkali-activated FA-GGBS cementitious system increased, and the yield stress and plastic viscosity decreased. The growth of FA content decreases the early hydration rate significantly, while the increase of alkali activator content remarkably increases the peak rate of hydration heat release.

In order to study the yield stress and thixotropic behavior of the hydroxypropyl distarch phosphate (HPDSP) paste, HPDSP respectively derived from corn starch (CS) and waxy corn starch (WS) with different ratios of amylopectin were investigated. The critical mass fractions, yield stress, and thixotropic behavior of HPDSP pastes under various temperatures were studied. The results showed that, the critical mass fractions for the transition of the HPDSP solution at 5 ℃ from dilute to semi-dilute, and from semi-dilute to concentrated were 3wt% and 6wt%, respectively. The yield stress of 5wt% corn starch-hydroxypropyl distarch phosphate (CS-HPDSP) and waxy corn starch-hydroxypropyl distarch phosphate (WS-HPDSP) paste both showed weak correlations with temperature. However, at 6wt% concentration, the yield stress significantly decreased (P

Nonlinear rheology of Pickering emulsions is used to further investigate the nonlinear and unrecoverable transformation of inner structures, which is beyond the linear viscoelastic regime of tiny structural disturbances. Exploring various rheological methods plays a vital role in emulsion applications, such as simulating the macroscopic structural transformation between static and liquidlike flow states, strain overshoot, and regeneration for broken structures. According to our previous studies, cellulose nanofibers (CNFs) Pickering emulsions are a typical system for investigating polymer-based emulsions with the auxiliary surfactant [didodecyldimethylammonium bromide (DDAB)] for enhancing CNF absorption. To further study different rheological properties by varying CNF or DDAB contents, multiple interval thixotropic test, large amplitude oscillatory shear, and concentration-time-dependent superposition are employed to study the linear viscoelasticity and structural transformation of nonlinear range. This research was conducted based on the previous published works [Cui et al., Materials 15, 8285 (2022)] as a further characterization for the same sample series. [ABSTRACT FROM AUTHOR]

This paper assesses the suitability of geopolymers (GPs) for use as adhesives for ceramic tile fixing, including their compliance to the relevant EN 12004 specification. Two series prepared with different percentages of metakaolin (MK), blast-furnace slag (BFS), and limestone materials activated by an alkaline NaOH/Na2SiO3 solution are investigated. Tested properties included the thixotropy, setting, compressive strength, open time, and adhesion bond strength under different exposure conditions (that is, dry, wet, heat, or freezing-and-thawing cycles). Compared to cement-based mortars containing adjusted proportions of cellulose and redispersible polymers, the GPs exhibited higher thixotropy, reflecting additional energy for spreading the material over the substrate, yet better maintenance of the alternating patterns of ripples and grooves at rest. The bond strengths tested under different exposure conditions were remarkably high for the MK-based GP, given the fine MK particle sizes that foster geopolymerization and crosslinking of solid bonds in the hardened structure. The BFS-based GP exhibited relatively lower bond strengths (compared to MK) due to coarser particles. Such results can be of interest to civil engineers and manufacturers of ready-to-use building materials that aim at reducing the portland cement footprint while assuring performance and sustainability of tiling applications. [ABSTRACT FROM AUTHOR]

Linear amplitude sweep tests have been demonstrated to have good potential in being used for the evaluation of self-healing properties of neat and polymer-modified bituminous binders. Past research works, however, have neglected the effects of material non-linearity and thixotropy. This implies that the whole material integrity loss is attributed to damage and all restoration to self-healing, thus resulting in the possible overestimate of both damage and self-healing when evaluating the fatigue performance of materials. In the study described in this paper, specific experimental and analytical methods were adopted with the purpose of separating non-linearity and thixotropy in LAS healing tests. Non-linearity was assessed by means of multiple strain sweep tests carried out to determine the material non-linear viscoelastic moduli at specific testing temperatures. Thixotropy was considered by coupling self-healing LAS testing with a purposely defined test in which loading was applied to the undamaged material after a rest period equal to that applied in self-healing tests. Obtained results were processed by means of an analytical approach based on the simplified viscoelastic continuum damage model. Quantification of self-healing included the determination of material integrity and damage parameters recovered after the rest period. Such parameters, calculated by excluding time-dependent and non-linear biasing effects, can be used as straightforward indicators of the self-healing potential of neat and polymer-modified bituminous binders. Moreover, obtained results substantiate the concept that time–temperature superposition is still applicable when non-linearity is incorporated into the simplified viscoelastic continuum damage model. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is normally characterized with high pressures exerted on the formwork during casting. The pressures can easily exceed bearing capacity of a regular formwork when casting a high structural member in one step. The contribution shows new ways of reducing the pressures using mineral additives based on calcinated clay minerals and clay nanoparticles whose addition together with interrupted casting process leads to a substantial reduction of the formwork pressures. Short interruptions in the casting lead to microstructural changes and flocculation, thixotropy and early strength evolution. The positive effects are studied systematically in microstructural studies performed on modified cement pastes using microscopy and viscosimetry. Rheological behavior of standard SCCs is improved towards thixotropy of the mixture by using the mineral additives. The newly developed recipes are tested on SCCs used on real construction sites. Examples of their practical utilization and on-site measurements show on up to 50% pressure reductions in enriched SCCs compared to ordinary SCCs. [ABSTRACT FROM AUTHOR]

In the realm of cementitious materials, integrating nanoclay shows promise in enhancing properties relevant to additive manufacturing. This paper presents a novel mathematical model that combines simple empirical dissolution/nucleation Avrami-like kinetics with a thixotropic kinetics equation. To analyze the initial exothermic peak, two sets of the calculation parameter function are built to describe the exothermic rate as a function of time, following an exponential pattern. This allows for the prediction of the changes in cumulative heat and heat rate during hydration, considering different concentrations of nanoclay. In the rheological aspect, the relationship between shear stress, shear rate, and time is modeled as a combination of exponential dependencies. This enables the prediction of the variations in shear stress with one variable while holding the other constant (either time or shear rate). By integrating these aspects, this model effectively describes both the first exothermal peak and the rheological behavior during cement hydration with the inclusion of nanoclay. Validated against experimental results, these models demonstrate good accuracy (overall below 3% error), reliability, and applicability. The findings offer valuable insights into the thermal and rheological aspects of concrete printing, enabling informed design decisions for both scientific and industrial applications. [ABSTRACT FROM AUTHOR]

In rheological testing, different test regimes can result in large differences in the rheological curves, and the pre-shear procedure is one of the most important parts of the test. In order to investigate the effect of the pre-shear regime on the rheological properties of cement pastes, an Anton Paar 102 rotary rheometer was used for the test. Two different pre-shear regimes (RF and CP pre-shear), three different pre-shear duration times (50 s, 100 s, 150 s), and four different pre-shear rates (25 s-1, 50 s-1, 100 s-1) are carried out for the test. The results showed that with the increase of pre-shear duration or rate, the four rheological parameters (plastic viscosity, yield stress, rheological index, and thixotropy) of the pastes decrease in different degrees. RF pre-shear was more influenced by shear time, while CP pre-shear was influenced by shear time and rate. The pre-shear regimes led to different changes in the flocculation structure of the cement paste, which had a great influence on rheological parameters ultimately. Based on the improved Krieger-Dougherty model, the effective solid volume fraction of cement paste was calculated. Analysis shows that the phenomenon of "deflocculation" and "re-flocculation" occurs when the cement paste is subjected to shear action, thus, the pre-shear regimes destroy the structure of the pastes. With the increase of pre-shear duration or rate, the effective volume fraction decreased, which indicated that the initial flocculation structurewas broken. The greater the damage degree of pre-shear, the slower the establishment rate of the internal structure of the pastes in dynamic shear, resulting in lower rheological parameters. [ABSTRACT FROM AUTHOR]

This study numerically explores the influence of thixotropy on flow and mixing in a staggered-herringbone micromixer (SHM), employing a structure-kinetics model to simulate the microstructure formation and breakup in thixotropic fluids. This study represents the first of its kind to incorporate a thixotropic fluid model into microfluidic mixing in channels with patterned grooves. Specifically, we examine the effects of the destruction factor ( k d ) and the thixotropy number (Th) on microstructure, flow, and mixing in the SHM, covering extensive ranges (0.01 ≤ k d ≤ 10 and 0.01 ≤ Th ≤ 100). Higher values of k d and Th , particularly for k d > 1 and Th > 1 , lead to larger spatial variations of the structure parameter (λ) and viscosity (η), with a notable decrease in λ near the groove tops, leading to the lowest viscosity in these areas. Conversely, at the groove bottoms, where shear deformation is minimal, there is less reduction in λ , leading to increased viscosity and higher flow resistance. The viscosity variations inside the grooves impede lateral flows, adversely affecting mixing in the higher k d and Th regimes. Therefore, an in-depth understanding of the complex thixotropic behaviors, as influenced by k d and Th near the grooves, is essential for achieving effective mixing in the SHM when using thixotropic fluids. Our results suggest that lowering the channel height, for a given groove depth, slightly improves the mixing of thixotropic fluids. Further enhanced mixing is achieved by combining a reduced channel height with double-sided groove patterns. [ABSTRACT FROM AUTHOR]

In order to study the yield stress and thixotropic behavior of the hydroxypropyl distarch phosphate (HPDSP) paste, HPDSP respectively derived from corn starch (CS) and waxy corn starch (WS) with different ratios of amylopectin were investigated. The critical mass fractions, yield stress, and thixotropic behavior of HPDSP pastes under various temperatures were studied. The results showed that, the critical mass fractions for the transition of the HPDSP solution at 5 °C from dilute to semi-dilute, and from semi-dilute to concentrated were 3wt% and 6wt%, respectively. The yield stress of 5wt% corn starch-hydroxypropyl distarch phosphate (CS-HPDSP) and waxy corn starch-hydroxypropyl distarch phosphate (WS-HPDSP) paste both showed weak correlations with temperature. However, at 6wt% concentration, the yield stress significantly decreased (P<0.05) by 69.52% and 77.95% respectively at 85 °C. Additionally, the thixotropic behavior of HPDSP was influenced by both mass fraction and temperature. At 5 °C, 5wt% CS-HPDSP and WS-HPDSP showed limited thixotropy, while at 6wt% of mass fraction, the areas of thixotropic loops of CS-HPDSP and WS-HPDSP were 163.49 and 85.00 Pa/s, respectively, and decreased by 86.38% and 92.18% at 85 °C, respectively. WS-HPDSP exhibited less thixotropic behavior than CS-HPDSP, and showed better stability in three interval thixotropy test (3iTT). In conclusion, WS-HPDSP showed less yield stress and thixotropy compared with CS-HPDSP. This study provides theoretical supports for practical application of HPDSP as thickening agents in food products. [ABSTRACT FROM AUTHOR]

A systematic analytical study of the mathematical properties of the previously constructed nonlinear model of the shear flow of thixotropic viscoelastic-plastic media, which takes into account the mutual influence of the deformation process and structure evolution, is carried out. A set of two nonlinear differential equations describing shear at a constant rate and stress relaxation was obtained. Assuming six material parameters and an (increasing) material function that control the model are arbitrary, the basic properties of the families of stress-strain curves at constant strain rates, stress relaxation curves (Part 2) and creep curves (Part 3) generated by the model, and the features of the evolution of the structuredness under these types of loading were analytically studied. The dependences of these curves on time, shear rate, stress level, initial strain and initial structuredness of material (for example, degree of physical crosslinking), as well as on material parameters and function governing the model, were studied. Several indicators of the model applicability are found, which are convenient to check with experimental data. It was examined what effects typical for viscoelastic-plastic media can be described by the model and what unusual effects (properties) are generated by structuredness changes in comparison to typical stress-strain, relaxation and creep curves of structurally stable materials. The analysis proved the ability of the model to describe behavior of not only liquid-like viscoelastoplastic media, but also solid-like (thickening, hardening, hardened) media: the effects of creep, relaxation, recovery, a number of typical properties of experimental relaxation curves, creep and stress-strain curves at a constant rate, strain rate and strain hardening, flow under constant stress, etc. The first part of the article is devoted to formulation of the model and preparation of basis for the second part: the proof of the uniqueness and stability of the equilibrium point of the nonlinear equations set, analytical study of the equilibrium point dependence on all material parameters, possible types of phase portraits and the properties of integral and phase curves of the model. [ABSTRACT FROM AUTHOR]

The formulation of biphasic gels as potential semi-solid carriers for hydrophilic and lipophilic active substances is promising for the development of pharmaceutical preparations. The aim of this study was to design a stable bigel composition and to determine the influence of the organogel/hydrogel ratio on the gel's physical-chemical and structural-mechanical properties. The investigated compositions of organogel/hydrogel remained stable at ratios ranging from 5/95 to 40/60. After texture and microstructure analysis, bigels with 20/80 and 25/75 ratios were selected as carriers for the active ingredients, sodium diclofenac and camphor, for use as topical preparations for the treatment of muscle-joint inflammation and pain. Although other researchers have published data on the preparation and evaluation of bigels, there are no scientific results on the development of a two-phase gel with our proposed combination of APIs. Sodium diclofenac release was found to be higher when combined with camphor, which revealed the advantages of the biphasic formulation. The pseudoplastic behavior, thixotropy, and thermal stability of flow of the studied bigel samples was investigated by rheological analysis. Ongoing stability studies confirmed the minimal 6-month period. [ABSTRACT FROM AUTHOR]

The rheological characteristics of high-pour-point (high-PPT) oil are crucial for its economical and safe production and transportation. However, current research on the viscosity–temperature prediction and viscoelastic-yielding transition of high-PPT oil is insufficient. The Arrhenius formula faces challenges in accurately depicting the viscosity–temperature relationship, and there is a lack of a quantitative description of the viscoelastic-yielding transition behavior in gelled high-PPT oil. This study addresses these gaps through a series of rheological experiments. The results reveal that the viscosity–temperature relationship of high-PPT oil can be classified into three regions, each associated with a sequentially increasing activation energy E a . Introducing two characteristic parameters, T 0 and n , yields a modified Arrhenius formula with an extended range of applicability. Thixotropy and gelation process experiments demonstrate an exponential increase in thixotropic strength with a decreasing temperature below the wax appearance temperature, while an optimum cooling rate maximizes the gelation degree of high-PPT oil. A brittleness index B I was defined to quantitatively describe the fracture mode of gelled crude. Critical characteristic strains and B I exhibit a decrease with an increase in the reciprocal of the average free degree 1 / w free , where the diminishing trend of B I follows a robust power-law form. This comprehensive investigation contributes valuable insights into the rheological behavior of high-PPT oil, offering a foundation for more accurate modeling and control strategies in its production and transportation. [ABSTRACT FROM AUTHOR]

Hexakis(2-alkoxy-1,5-phenyleneimine) macrocycles were synthesized using a simple one-pot procedure through precipitation-driven cyclization. The acetal-protected AB–type monomers, 2-alkoxy-5-aminobenzaldehyde diethyl acetals, underwent polycondensation in water or acid-containing tetrahydrofuran. The precipitation–driven cyclization, based on imine dynamic covalent chemistry and π–stacked columnar aggregation, played a decisive role in the one–pot synthesis. The progress of the reaction was analyzed using MALDI–TOF mass spectrometry. The macrocycles with alkoxy chains were soluble in specific organic solvents, such as chloroform, allowing their structures to be analyzed using NMR. The shape-anisotropic, nearly planar, and shape-persistent macrocycles aggregated into columnar assemblies in polymerization solvents, driven by aromatic π-stacking. The octyloxylated macrocycle OcO–Cm6 exhibited an enantiotropic columnar liquid crystal-like mesophase between 165 °C and 197 °C. In the SEM image of (S)-(–)-3,7-dimethyloctyloxylated macrocycle (–)BCO–Cm6, columnar substances with a diameter of 200–300 nm were observed. The polymerization solution for the 2-(2-methoxyethoxy)ethoxy)ethoxylated macrocycle (TEGO–Cm6) gelled, and showed thixotropic properties by forming a hydrogen bond network. [ABSTRACT FROM AUTHOR]

The objective of this work was to analyse the effect of partial sucrose replacement by isomalt on the thermal, rheological, and moisture sorption behaviour of cocoa-flavoured confectionery coatings. Formulations were elaborated using sucrose, isomalt, cocoa powder, vegetable oil, lecithin, glycerol, and water. Full-sugar sample (0%) was used as control and reduced-sugar formulations were obtained by replacing 25% and 50% of the sucrose by isomalt. Flow behaviour and thixotropy of liquid formulations were evaluated. Thermal properties (by differential scanning calorimetry) and moisture adsorption and desorption isotherms at 25 °C of films (dried by casting at 40 °C and 26% relative humidity for 24 h) were obtained in the water activity range of 0.225–0.927. Rheological behaviour was described by the Cross model and a first-order structural kinetic model. Sorption isotherms were analysed applying the Generalised D'Arcy and Watt (GDW) and Chi models. The presence of isomalt affected the rheology of liquid formulations, especially in the 50% sample. Similar thixotropic behaviour was found between 0% and 25% samples, with a ~ 100% recovery, indicating a better coating performance. The range of the mean onset (36–41 °C) and melting (95–155 °C) temperatures obtained was high, suggesting that the solid structure of films will be preserved at room storage conditions. The sorption isotherms showed a type-III shape, evidencing two characteristic surfaces with different sorption energies, and hysteresis between adsorption and desorption. The GDW and Chi models accurately described the isotherms. These results are useful to control the elaboration and conservation of reduced-sugar confectionery coatings. [ABSTRACT FROM AUTHOR]

Copyright of Multipurpose Utilization of Mineral Resources / Kuangchan Zonghe Liyong is the property of Multipurpose Utilization of Mineral Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thin bonded ultra-high-performance concrete (UHPC) overlay is an advanced technology for bridge deck rehabilitation. UHPC should be tailored to secure adequate flowablility and high thixotropy to facilitate mixing and placement with a low risk of sagging of the material on sloped bridge deck surfaces. The synergetic effect between nanoclay (NC) and polycarboxylate ether (PCE) superplasticizer or cellulose-based viscosity modifying admixture (VMA) and PCE on the rheological properties (yield stress, plastic viscosity, and thixotropy), cement hydration, autogenous shrinkage, compressive strength, and porosity was systematically investigated. The bond strength between conventional concrete (CC) representing existing bridge deck concrete and thixotropic UHPC and the flexural performance of UHPC-CC composite beams were determined. Test results indicate that the incorporation of 1% cellulose-based VMA combined with 0.4% PCE can increase thixotropy from 12 to 60 Pa/min when the initial fluidity of the mortar phase of the UHPC was maintained at 200 mm. Such increase was limited to 19 Pa/min in mixtures prepared with 1% NC and 1.55% PCE. The thixotropic UHPC containing NC and cellulose-based VMA provided tensile bond strength higher than 3 MPa. The combination of NC and PCE improved the flexural toughness and strength by up to 45% and 30%, respectively, for composite beam specimens. It also led to slightly higher compressive strength associated with greater cement hydration and decreased porosity. The combined use of cellulose-based VMA and PCE led to 15% and 40% greater flexural strength and toughness, respectively, despite the 10% lower compressive strength due to a 30% increase in the volume of pores with diameters larger than 5 µm.