Rheological Characteristics Research Articles

Effect of kefir grain concentration on rheological, microbiological, and physicochemical characteristics of bovine colostrum kefir

Bovine colostrum has high nutrition content such as protein, fat, peptide, micro-nutrients, antimicrobial components and bioactive compounds that benefit the body. Kefir is one way of diversifying food products as fermented beverage products to increase the utilization and functional properties of bovine colostrum, which has a unique taste. Production of colostrum kefir requires the right concentration of kefir grains to obtain high-quality characteristics. Evaluating the effect of kefir grain concentration on the rheological, microbiological, and physicochemical characteristics of bovine colostrum kefir was the purpose of this research. This study used one factorial design with the variation of kefir grain concentrations 10% (T1), 20% (T2), and 30% (T3) (w/v) with seven replications. Rheological analysis was conducted, followed by total lactic acid bacteria, yeast, microbes, protein, fat, ash, water content, carbohydrate, pH, total dissolved solids and alcohol content. Based on the result, different kefir grain concentrations significantly decreased total LAB, yeast, microbes, protein, ash, pH, and total dissolved solids but increased carbohydrate and water content with the addition of kefir grain concentration. Rheology behavior, fats, and alcohol content had no significant difference. Treatment of 10% of kefir grain concentration is the most suitable as it contains the highest total LAB and yeast.

Insight into Sequential Extrusion and Cysteine Treatment for Improving Rheological Characteristics and In Vitro Digestibility of Whey Protein Isolate.

The effects of sequential cold extrusion and cysteine (Cys) treatment on the rheological characteristics and in vitro digestibility of whey protein isolate (WPI) were researched in this work. Cold extrusion and Cys treatment increased the apparent viscosity, shear stress, Péclet number, and viscoelasticity of WPI. Furthermore, the emulsifying activity index enhanced in the order of WPI, Cys-treated WPI (Cys-WPI), cold-extruded WPI (CWPI), and extrusion-Cys treated WPI (Cys-CWPI). The emulsion stability index of Cys-CWPI was increased by 29.69% higher than that of WPI. Besides, the α-glucosidase inhibitory rate and xanthine oxidase inhibitory activity in the digests of Cys-CWPI were markedly increased compared with digests of WPI. The synergism of cold extrusion and Cys provides an effective approach for the application of whey protein-based thickeners and emulsifiers; meanwhile, its digestive products may assist in the development of hypoglycemic and uric acid-lowering foods.

Mechanism analysis on carbon-ash separation of coal gasification fine slag by high internal phase emulsion collector

ABSTRACT Coal gasification slag is a solid waste produced in modern coal chemical industry, its mixed characteristics of residual carbon and ash materials restrict its resource utilization. This study focused on improving the flotation effect of coal gasification slag and reducing the consumption of flotation reagents, a water in oil type high internal phase emulsion collector was prepared, and the microstructure, rheology, stability, particle size and other characteristics of the emulsion collector were analyzed. By comparing with the flotation effect of conventional kerosene collector, when the amount of organic liquid is basically equal, the ash content of the tailings increased by 4.02%, the yield of concentrate increased by 9.79% and the recovery of combustible matter increased by 11.11%. When the combustible matter recovery is similar, the emulsion collector can save 13.40% of kerosene. The flotation kinetics test shows that the emulsion collector can significantly improve the flotation speed. By analyzing the flocculating ability of emulsion collectors, emulsion collectors can significantly improve the flocculating ability of particles, thereby improving the flotation effect. The research results have certain guiding significance for improving the flotation efficiency of coal gasification slag.

Injectable Hydrogels for Programmable Nanoparticle Release

AbstractInjectable hydrogels represent a promising strategy for the extended release of biological molecules, thereby reducing the frequency of injections. This study introduces a novel system based on Michael addition of dextran and polyethylene glycol (PEG) polymers functionalized with oxanorbornadiene (OND) and thiol groups, respectively. Reliable control over gelation speed allows administration by injection using a simple syringe‐to‐syringe mixing protocol that entrains more than 95% of virus‐like particle (VLP) cargo. A combination of retro‐Diels‐Alder and hydrolytic ester bond cleavage gives rise to programmable release of the VLPs. Different release profiles, including burst, linear, and delayed release over a two‐week period, are engineered using different OND linkages, and rheological characterization shows the hydrogels to be well within the desired range of stiffness for subcutaneous use. The modular nature of this system offers a generalizable platform for developing degradable materials aimed at sustained release biomedical applications.

Development of a Novel Gluten-Free Cookie Premix Enriched with Natural Flours Using an Extreme Vertices Design: Physical, Sensory, Rheological, and Antioxidant Characteristics

This work aimed to develop novel alternative gluten-free premixes for use in the production of cookies by optimizing the formulation of three different starches (corn, potato, and tapioca starch) in a rice/corn formula and then enriching the optimized formula with various natural flours (acorn, soy, chestnut, chickpea, millet, and quinoa). An extreme vertices mixture design was used to optimize the mixing sub-part consisting of 30% (w/w) of starches. The enriched gluten-free cookies were characterized by physical, rheological, antioxidant, color, and sensory properties. An optimum was obtained by mixing 18.5084 g of corn starch, 6 g of potato starch, and 5.4916 g of tapioca starch. The enrichment results indicated that soy-enriched gluten-free cookies have a high specific volume (2.428 cm3/g) with the highest spread ratio (12.25) compared to other cookies. The rheological properties of enriched gluten-free doughs indicated a higher value of the consistency coefficient (K) of soy-enriched gluten-free cookies. The antioxidant characteristics were enhanced by replacing corn with several types of flours, with higher TPC for acorn (2.83 mg GAE/g dw) and soy-enriched cookies (2.49 mg GAE/g dw) with better antioxidant activities (DPPH, ABTS, and RED). The tasters gave all the cookies favorable ratings for overall acceptability. With an average rating of 7.09, cookies enhanced with chickpea flour have a high acceptability compared to the other cookies. Considering all the tested parameters, PCA analysis clustered millet, corn, quinoa, and chestnut gluten-free enriched cookies into the same group. However, acorn and soy cookies were placed in a separate group, and chickpea-enriched cookies were classified separately.

REDUCING THE VISCOSITY OF THE OIL MIXTURE BY A ROTARY PULSE APPARATUS IN UKHTA — YAROSLAVL OIL PIPELINE

Physical methods of exposure can be used to improve the rheological characteristics of viscous, resinous oils, the transportation of which through main pipelines requires additional operating costs. The authors of this article evaluated the effectiveness of the method for improving oil rheology due to multifactorial effects (shear loads, high–amplitude pressure pulses, developed turbulence) on a sample of a mixture of oils of the Ukhta - Yaroslavl oil pipeline in a rotary pulse apparatus (RIA). The specific power consumption for processing an oil sample was 2.84 kWh/m3. The initial rheological and physico-chemical parameters of the studied oil are described, according to which it is characterized as heavy, viscous, highly resinous oil. The analysis of the flow curves showed that, by the nature of the flow, the sample of a mixture of oils from the Ukhta — Yaroslavl main oil pipeline belongs to Newtonian liquids. The evaluation of the effectiveness of the multifactorial effect on the oil sample implemented in RIA was carried out using dimensionless coefficients showing the ratio of dynamic viscosity, the specific power required to maintain the flow of oil in a rotary viscometer before and after physical exposure to oil, as well as the ratio of the change in the energy of thixotropy of oil to the energy spent on the processing process. The samples were processed in an RIA-based installation, in which pressure pulsations, developed turbulence, and large shear loads are generated in the liquid flow. When comparing the viscosity values of untreated and treated mixed oil in a rotary pulse apparatus, the dynamic viscosity measured at 20 °C decreased by 8 %. The component composition of the oil after processing in RIA has practically not changed. Measuring the viscosity of oil before processing and immediately after processing in RIA shows a decrease in viscosity by more than two times, since the temperature of the oil flow increases after passing through RIA by more than 10 °C. The increase in oil temperature during processing is due to large shear stresses during its flow in slit channels and in the gap between the rotor and stator due to the large amplitude of pressure pulsations and flow velocity.The relaxation time of the rheological parameters of the treated oil was seven days.

Effects of wheat gluten-soy protein ratios and moisture levels on high-moisture extruded meat analogues for burger patties.

In response to the growing demand for plant-based meat alternatives, this study explores the impact of incorporating wheat gluten (WG) into soy protein isolate (SPI) on both the proximate and functional properties of protein blends. The research also examines the effects of high moisture extrusion processing, varying feed moisture levels (60%, 65%, and 70%), and WG-SPI blends on extruder response, as well as the textural, rheological, and solubility characteristics of the resulting extruded meat analogues. Moreover, the prime objective was to gain insights into the impact of using HMMA made at different ratios and feed moisture levels on plant-based burgers. As the WG incorporation level increased in SPI, the RVA viscosity, water absorption, and oil absorption capacities, and foaming stability exhibited a decrease while foaming capacity increased. As feed moisture and WG incorporation levels in SPI increased, the system parameters, rheological, and textural parameters of high moisture extruded meat analogs decreased. WG25-SPI75 showed the highest degree of texturization or sulfide bonds, and its extruded meat analogues at 60% feed moisture level burger patties resemble a similar textural to a chicken burger patty. This study is pivotal in understanding how wheat gluten in SPIs and feeding moisture level influence the textural and rheology properties of HMMA.

Effect of Mild Conditions on PVA-Based Theta Gel Preparation: Thermal and Rheological Characterization

Polyvinyl alcohol (PVA), possessing a strong ability to form hydrogels, has been widely used for various pharmaceutical and biomedical applications. In particular, the use of PVA-PEG in the form of theta gels for altered cartilage treatment has attracted an enormous amount of attention in the last 20 years. In this paper, we prepared 42 PVA-PEG in the form of theta gels at room temperature in an aqueous environment, testing the crystallization occurrence at basic pH (10 or 12). Using a statistical approach, the effect of PEG molecular weight, PVA molecular weight and alkaline pH values on water content and mechanical performance was evaluated. The used procedure permitted the theta gels to maintain swelling properties comparable to those of human cartilage, from 60% to 85%, with both polymers having the same influence. PEG MW mainly affected the hydrophilic properties, whereas the thermal properties were mostly influenced by the PVA. The shear and compression mechanical behavior of the produced materials were affected by both the polymers’ MWs. The sample obtained using PVA 125 kDa with PEG 20 kDa as a porogen appeared to be the most suitable one for cartilage disease treatment, as it had an equilibrium shear modulus in the range of 50–250 kPa, close to that of native articular cartilage, as well as optimal mechanical response under compression along the entire analyzed frequency range with a mean value of 0.12 MPa and a coefficient of friction (COF) which remained under 0.10 for all the tested sliding speeds (mm/s).

Evaluation of Hazelnut Cake Flour for Use as a Milk Powder Replacer in Ice Cream

Hazelnut oil cake, a by-product in the cold-pressing of hazelnut oil, is a rich in valuable nutrients, which makes it a promising option for supplementation or as a raw material in the development of functional products. The aim of this work was to study the influence of partial or complete replacing of skim milk powder (SMP) with hazelnut press cake flour (HPCF) in varying ratios (0%, 25%, 50%, 75%, and 100%) on the physicochemical properties and sensory attributes of milk ice cream. The replacement modified the chemical composition of the ice cream mixture, resulting in a reduction (p < 0.05) of milk solids non-fat (MSNF), protein, and carbohydrates content, while simultaneously elevating the hazelnut content, and total fat content. This modification influenced the rheological characteristics of the ice cream mixtures, leading to an increase in the consistency coefficient from 1.32 to 7.66 Pa sn. Furthermore, a decline in overrun values (from 26.99% to 15.85%), an increase in hardness (from 6881.71 to 23,829.30 g), retarded melting properties, and variations in colour attributes were observed with higher concentrations of HPCF. In the sensory evaluation test, it was found that consumer acceptance was enhanced for the samples with partial substitution of SMP when compared to standard milk ice cream. The findings suggest that a replacement of milk powder with hazelnut cake by up to 75% is achievable, in order to obtain functional ice cream with adequate physicochemical and sensorial qualities.

Monitoring the anticorrosion performance of developed epoxy-based paint formulations on metallic surfaces by electrochemical impedance spectroscopy

Purpose This study aims to investigate the impact of varying solid ratios in epoxy-based formulations on their corrosion resistance. The amounts of epoxy resin in the formulations were kept constant, and the behavior of paints with varying filler ratios was compared. It also examines the tensiometric and rheological properties of these formulations. Design/methodology/approach Three distinct epoxy-based formulations cured with amine compounds were prepared. The formulations underwent various testing protocols to evaluate their performance: coating tests: coated panels with cross lines were exposed to humidity and corrosive atmospheres. Tensiometric Measurements: Conducted using pendant and sessile drop methods. Rheological characterizations: ıncluded flow tests, oscillatory amplitude sweeps and three-interval thixotropy tests. Corrosion resistance assessment: after the panels were immersed in methanol for one week, measurements were taken using electrochemical impedance spectroscopy. Additional tests: neutral salt spray (NSS) and humidity testing. Findings The study observed that the coated panels, after exposure to NSS and humidity testing, demonstrated corrosion resistance within acceptable limits as defined by the ISO 12944-6 standard. Results indicate that the epoxy-based formulations show potential for improvements in paints and coatings, suggesting promising advancements in their anticorrosion performance. Originality/value This research provides insights into how the solid ratios in epoxy-based formulations influence their performance, particularly in terms of corrosion resistance, tensiometric and rheological properties. The findings contribute to the development of more effective epoxy resin-based coatings for industrial applications.

Rheological Characteristics of Concrete Mixtures Modified with Urease Additives

Statement of the problem. Rheological characteristics of concrete samples made with the use of various bioadditives are studied. Results. The results of experimental studies of the rheological properties of concrete, taking into account the effect of dietary supplements based on the following strains of bacteria B.subtilis, Ps.aeruginosa, with urease activity, are presented. Conclusions. The values of the cone sediment of concrete mixtures made using various grades of Portland cement were obtained, the values of conditional viscosity were also established, and the limiting shear stress and compressive strength of the obtained concrete cube samples made using urease bioadditives were determined. It was found that the use of dietary supplements leads to a decrease in the conditional viscosity of the mixture by 2 times, as well as to an increase in compressive strength by at least 15 %. Thus, it has been established that bioadditives improve the quality of the bond between the components of concrete, making it more durable and resistant to loads, as well as its rheological characteristics.

Self-Compacting Mixtures of Fair-Faced Concrete Based on GGBFS and a Multicomponent Chemical Admixture—Technological and Rheological Properties

The use of superplasticizers in a self-compacting concrete mix without the addition of a foaming agent in practice leads to a well-known problem associated with increased air entrainment and promotes the formation of harmful large bubbles, high-void content, and ununiform appearance. This paper presents research on the properties of cement paste consisting of Ordinary Portland Cement (OPC), powder based on ground granulated blast furnace slag (GBBS), and superplasticizer. The methodology of this study was the estimation of flow diameter and flow time, as well as the evaluation of the rheological characteristics. The influence of ground granulated blast furnace slag and polycarboxylate plasticizer on the flowability and viscosity of cement paste was studied. The effect of superplasticizer (SP) based on polycarboxylate esters (PCE) anti-foaming agent (AFA) based on a glycol ester and air-entraining admixture (AEA) based on an amphoteric surfactant on flowability, viscosity, rheological properties and the strength of the cement paste was evaluated. It was found that the increase of slag content in cement paste (25%) with the presence of superplasticizer (0.64%) significantly changes the flowability and viscosity. It was stated that the addition of 0.04% anti-foaming agents increases flowability (20%) and reduces viscosity (44%) of cement paste. It was stated that the addition of small dosages of glycol ester-based anti-foaming agent (0.02 and 0.04%) significantly changes the rheological properties, decreases the shear yield stress by 2.1–2.8 times, the plastic viscosity by 2.4–2.6 times and apparent viscosity 1.6–2.5 times, improves the compressive strength at the age of 1 and 7 days by 2.5 and 1.4 times, respectively. The addition of air-entraining admixture led to a decrease in the plastic viscosity by 1.2–1.4 times. It was stated that the presence of air-entraining admixture assists in increasing the apparent viscosity by 1.7–2.4 times. It was shown that the presence of complex admixtures of various origins, purposes, and mechanisms of action would assist in predicting the behavior of concrete mixtures under the conditions of the building site and reduce the consumption of polycarboxylate esters due to the enhancing plasticizing effect of anti-foaming agent and air-entraining admixture.

A numerical investigation on rheological turbulent flow through a 90° mixing elbow

Mixing elbows are widely used in various industrial processes to mix two different Newtonian or non-Newtonian fluids under turbulent flow conditions. This study numerically investigates the fluid flow and mixing characteristics in 90-degree elbows with different bend curvatures (curvature ratios of 3, 6, and 9) and Reynolds numbers ranging from 1 × 104 to 5 × 105 for both fluid types. The Reynolds-Averaged Navier–Stokes equations are solved using the turbulent k-epsilon model in ANSYS Fluent. Results show that the bend curvature creates an adverse pressure gradient that drives secondary flows, which become more pronounced with higher Reynolds numbers and lower curvature ratios. Higher Reynolds numbers improve mixing quality, as indicated by velocity and temperature variations quantified using standard deviations. For Reynolds numbers in the range of 104, velocity fluctuations initially increase, but at higher values (~ 105), they decrease, even by up to 64% as the Reynolds number rises from 1 × 105 to 5 × 105. Similarly, increasing the curvature ratio enhances mixing efficiency, with a 32% reduction in velocity fluctuations when the curvature ratio increases from 6 to 9. Furthermore, shear-thinning fluids (n=0.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 0.6$$\\end{document}) exhibit superior mixing performance, with a standard deviation of velocity fluctuations at the outlet of 0.32, compared to 0.54 for shear-thickening fluids (n=1.4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 1.4$$\\end{document}). In terms of temperature fluctuations also, a similar trend is observed. These findings are valuable for optimizing mixing and fluid transport in industries such as chemical processing and food production, where effective mixing of complex fluids is critical. This study provides insights for improving the design of mixing systems that handle fluids with various rheological characteristics.

Thermal and rheological behavior of aluminium-doped zinc oxide nanofluids: Experimental study and application of artificial neural network model

In this study, the influence of Al-doping concentration on the thermal and rheological characteristics of pristine zinc oxide (ZnO) nanofluids was investigated across a range of temperatures and nanoparticle concentrations. A multilayer perceptron (MLP) artificial neural network (ANN) with an optimized topology was employed to model the thermal conductivity and viscosity of nanofluids. The addition of 0.13 M of Al-doped zinc oxide nanoparticles at 1 % rate led to a remarkable 64 % increase in the thermal conductivity of the base fluid (50:50 ratio water + ethylene glycol mixture). Furthermore, incorporating 1 % of these Al-doped nanoparticles outperformed pure zinc oxide, resulting in a 44 % boost in thermal conductivity. The enhanced heat transfer capabilities of Al-doped zinc oxide were evident across different doping and nanoparticle concentrations. The viscosity of nanofluids increases with an increase in nanoparticle concentration and decreases with an increase in temperature. ZnO and Al-doped ZnO nanoparticles have been prepared and studied their structural, morphological and elemental properties using XRD, SEM and EDS respectively. The predicted thermal and rheological behaviours are in close agreement with the experimental values.

Features of the change in the thermal coefficient of electrical resistance upon heating electrically conductive composites of crystallizable polyolefins with carbon black

Objectives. To investigate electrically conductive polymer composite materials (EPCMs) based on crystallizable polyolefins and electrically conductive carbon black for the production of self-regulating heaters; to study the mechanism of the occurrence of positive and negative temperature coefficients (PTC and NTC) upon heating such composites.Methods. A comprehensive study of the structure and properties of crystallizable EPCMs with electrically conductive technical carbon was carried out. In order to measure the electrical characteristics of the composites, they were compacted into plates to model polymer heaters. Contact electrodes made of an ungreased brass mesh were embedded in their ends. The temperature dependencies of the electrical characteristics of the samples were investigated in a modified thermal chamber of an FWV 633.10 Vicat softening temperature meter. The change in the degree of crystallinity was analyzed by means of differential scanning calorimetry with a NETZSCH DSC 204 F1 Phoenix calorimeter. The dilatometric and rheological characteristics of the samples were studied using an IIRT-AM melt flow index tester.Results. It was determined that the self-regulation ability (an abnormally high positive thermal coefficient of electrical resistance) of selfregulating heaters made of composites of crystallizable polyolefins with electrically conductive technical carbon cannot be explained by the thermal expansion of EPCMs alone. It was shown that in crystallizable polyolefin-based EPCMs, the inversion of the thermal coefficients of electrical resistance (transition from PTC to NTC) is associated with a change in the aggregate state of EPCMs and the beginning of its transition to a viscous-flow state. A mechanism involving a sharp increase in the electrical resistance of self-regulating crystallizable polyolefin-based composite with electrically conductive technical carbon was proposed and substantiated. This mechanism takes into account the additional shear deformation effect produced on the crystalline phase of the EPCM by numerous expanding melt microvolumes formed at the early stages of the melting process with a minimum change in the degree of crystallinity.

Emulsifiers: Their Influence on the Rheological and Texture Properties in an Industrial Chocolate.

The complexity of the chocolate matrix leads to it having characteristic rheological properties that may pose difficulties for its industrial manufacture. Many factors influence the flow behaviour of chocolates, such as raw materials, the amount of fat, the moisture content, particle-size distribution, the concentration of emulsifiers, or manufacturing conditions, among others. This study focusses on the rheological properties of an industrially manufactured chocolate with a 48% cocoa content, and the effect caused by the addition of two emulsifiers (soya lecithin and polyglycerol polyricinoleate (PGPR)) on the rheological properties. In the case of lecithin, a clear effect has been observed on the plastic viscosity and the yield stress. Plastic viscosity decreases until a concentration of 0.6% lecithin is reached, and thereafter remains relatively constant, while yield stress increases over the studied range. This effect is not observed when PGPR is used as the emulsifying agent. In this case, a small concentration of PGPR decreases the yield stress. Thixotropy was determined using the Casson model, and its behaviour was found to be similar to that of plastic viscosity with respect to changes in the PGPR and lecithin concentrations. Textural determinations were also carried out, relating the rheology characteristics to the texturometry.

Insights into the Pickering emulsions stabilized by yeast dietary fiber: Interfacial adsorption kinetics, rheological characteristics, and stabilization mechanisms

This study developed Pickering emulsions based on yeast dietary fiber (YDF) and investigated the interfacial adsorption kinetics of YDF, rheological properties and stabilization mechanisms of emulsions. Results indicated that increasing YDF concentration enhanced its diffusion and rearrangement at the oil-water interface. At a concentration of 8 %, YDF exhibited the highest diffusion rate (0.1406 mN·m−1·s-0.5) and rearrangement rate (18.8 s−1). The emulsion stabilized at this concentration had the smallest droplet size (1.55 μm) and the slowest droplet migration rate (0.34 mm/h), effectively suppressing droplet aggregation due to collisions and thereby improving the overall emulsion stability. Confocal laser scanning microscopy results confirmed that emulsion stability relied on the co-adsorption of proteins and polysaccharides from YDF at the interface, with proteins primarily adsorbed at the oil-water interface and polysaccharides responsible for the continuous phase network formation. This study demonstrates YDF's potential as an emulsion stabilizer and elucidates the stabilization mechanism of YDF-induced emulsion.

Study on the fluid-solid transition mechanism of natural hydraulic lime pastes: Consider the water to binder ratio and polycarboxylate superplasticizer

Natural hydraulic lime (NHL) is used as a grouting material in the restoration of ancient buildings, the formation and evolution of its early workability are crucial for the reliability of the restoration effects. This paper conducts an in-depth study on the effects of water to binder (w/b) ratio and polycarboxylate superplasticizer (SP) dosage on the viscoelastic properties of fluid-solid transition process in NHL paste through tests on the fluidity, rheological characteristics, micro-rheology, hydration heat release, and early phase composition. The results show that the fluidity of NHL paste significantly increases with increasing w/b ratio and SP dosage, while its yield stress and plastic viscosity show downward trend, and it has shear thinning characteristics. In the initial stage, elevated w/b ratio leads to the significant reduction in both macroscopic viscosity index (MVI) and elastic index (EI) of NHL paste, along with delayed rapid increases, the effect is even more pronounced by adding SP. High w/b ratio or adding SP are able to enhance the dispersed state of solid particle in NHL pastes, the viscoelastic transition point of NHL paste is delayed and the viscoelastic transition time is prolonged. Increasing the w/b ratio and adding SP both inhibit the early dissolution and hydration of NHL paste, affecting the fluid-solid transition process. Overall, as the spatial network gradually develops by the solid particles dissolve and continue to hydrate, NHL paste undergoes a transition from a viscous fluid to an elastic semi-fluid state, exhibiting low strength and noticeable plasticity characteristics. With further hydration, NHL paste initiates consolidation and hardening processes, progressively transforming from a plastic semi-fluid into hardened paste.

Influence of micromorphology and water content on the rheological properties and performance evaluation model of loess mudflow

Evaluation of the rheological characteristics of loess mudflow is of great significance to ecological environment protection (by loess, we mean a wind-blown Quaternary silt deposit), and geological disaster assessment in the Loess Plateau of China. Rheological characteristics of rheology for loess mudflow are highly variable due to heterogeneity in particle micromorphology and water content, and current rheological models struggle to reconcile the structural dynamics with the equilibrium behavior of soil at different concentrations and microstructures. A rheological study of loess mudflow for five regions on the Loess Plateau was carried out in this investigation, and the results showed that loess transformed from a solid-like stage to a liquid-like stage under steady loads and exhibited significant shear thinning characteristics and shear rate dependence, in which the shear rate less than 2 s−1 was the main region of loess strength attenuation and the maximum yield stress is about 1411 Pa. A smaller water content and more complex particle micromorphology led to a higher yield stress, but there was no significant correlation between flow index and particle shape and water content. Additional structural dynamics and particle fractal theory were then introduced, providing an improved model that could reconcile the structural dynamics and particle micromorphology of loess with its equilibrium behavior at different water contents and shear stresses. All the test data were distributed around a dimensionless master curve. Considering the difficulty of obtaining rheological parameters, an evaluation criterion containing three levels (clay-rich, silt-rich, and sand-rich) for the evaluation of the rheological properties of loess mudflow was proposed, which can reconcile the test results and models under different working conditions. Such an evaluation criterion can also be applied to soils of other textures, providing a straightforward manner to determine the relevant rheological parameters. The research results provide a theoretical basis for ecological environmental protection and geological disaster assessment in the Loess Plateau region based on rheological characteristics.

Tailoring magnesium potassium phosphate cement-based adhesive for the improved bonding performance of CFRP/concrete interface

Magnesium potassium phosphate cement (MKPC) with rapid hardening and early high strength can be used as inorganic adhesive for externally bonded carbon fiber reinforced polymer (CFRP). This study aims to tailor MKPC as inorganic adhesive with good infiltration and bonding strength for CFRP-reinforced concrete. The influences of water-to-binder (w/b) ratios and particle sizes of potassium dihydrogen phosphate (PDP) on the fresh properties, hydration kinetics, pore structure, and strength development of MKPC were studied. The bonding strength of CFRP/concrete with MKPC-based adhesive was evaluated by double-shear tests. Results showed that a lower w/b ratio and a finer PDP enhanced the strength of MKPC due to a refined microstructure. The bonding strength of CFRP/concrete was dependent on the rheological characteristics and strength of MKPC. The use of a coarse PDP in MKPC was beneficial to enhance the bonding strength of CFRP/concrete. MKPC with coarse PDP and a w/b ratio of 0.2 resulted in the greatest bonding strength, corresponding to a 20% enhancement compared to epoxy resin. The superior bonding performance of MKPC was ascribed to its higher strength, a better infiltration for CFRP, and a larger MPC/concrete interfacial transition zone (ITZ).