Evolution Of Rheological Properties Research Articles

Pressure-based analysis of rheological equilibrium distances of pumped self-consolidating concrete (SCC)

The influence of pumping on the rheological properties of self-consolidating concrete (SCC) is widely recognized, but there is still limited understanding of its behavior within the pipeline. In this study, we propose a novel approach using equilibrium distances to investigate the evolution of rheological properties along the pipeline. Full-scale horizontal pumping circuits spanning 328 m were established to assess the axial development of SCC's rheological properties. Thirteen mixtures, with water-to-cement (w/c) ratios ranging from 0.22 to 0.27, were pumped at discharge rates varying from 5.77 to 12.69 L/s. Our findings show that for pumping setups and material studied, both the w/c ratio of SCC and the discharge rate significantly affected the influence of rheological equilibrium distances on pressure loss gradient changes. In all tested samples, viscosity values required the entire length of the pipeline to reach post-pumping levels, while yield stress values rapidly achieved their fully developed state upon entering the pipeline. Importantly, the predicted pressure loss displayed a strong correlation with experimental measurements, with an accuracy of 89.42% across all tested mixtures. Our predictive model showed an average improvement of 4.6% in accuracy compared to the linear approach, with the most significant enhancement observed in samples with higher w/c ratios. This research sheds new light on the behavior of SCC during pumping and provides valuable insights for optimizing the pumping process.

Influence of clay impurities on the performance of calcined clay‐limestone cements

AbstractThe use of blended cements including novel supplementary cementitious materials is the most powerful lever to cut down the carbon footprint of cementitious materials. This has led to an increased interest in research on calcined clay limestone cement (CCLC) over the last years. In this study, we investigate the fresh and early hydration properties of CCLC using kaolinitic clays with a wide range of chemical and mineralogical compositions, which are all of industrial origin. Results show that early performance of calcined clays is not only dependent on kaolinite content but that the total specific surface area of the raw and calcined clays plays a key role in the onset and evolution of rheological properties as well as early hydration and reactivity. Further analysis indicated that among secondary mineral impurities, iron phases affect the physiochemical properties of calcined clays. This is shown by the high specific surface area of these clays. It appears possible that by causing higher kaolinite structure disorder, iron phases also impact hydration.

Early-age rheology and hydration control of ternary binders for 3D printing applications

Achieving and controlling the desired strength build-up is important for 3D concrete printing. In this paper, we investigate the possibility of using calcium aluminate cement (CAC) as an accelerator for Ordinary Portland Cement (OPC) for 3D extrusion printing. Both ternary and binary cement systems were studied whereby for the former, the third component was a calcium sulfate source (C$).Experiments are conducted on mixes both in presence and absence of retarders. They focus on hydration progress, evolution of rheological properties and microstructural development. It is concluded that CAC-C$ can be effectively used as an accelerator to achieve the desired rates of strength build-up. Additionally, it is shown that strength build-up has is directly related to CAC dosage, irrespective of the presence of retarders. Based on microstructure characterization results, AFt and AH3 are found to be formed in the first hour after acceleration and responsible for the observed strength build-up.

Influence of the flocculation effect on the rheological properties of cement slurry

The rheological properties have an important impact on the migration and diffusion of cement slurry in grouting reinforcement applications. The microscopic interaction between particles affects the macroscopic rheological behaviors of cement slurry. However, the detailed influence mechanisms still remain unclear. In this work, five different fineness cements were selected to investigate the rheological properties. The focused beam reflectance measurement (FBRM) system was used to detect the in-situ flocculation characteristics under different water-to-cement ratios, cement fineness, and shear rates. In addition, the initial and time-dependent rheological properties under various conditions were measured by a rotary viscometer. The results reveal that these three factors influence the number and particle size distribution of flocculent particles, and the degree of flocculation increases linearly with time. Cement slurry with a water-to-cement ratio ranging from 0.6:1 to 1.6:1 follows the Bingham model. The yield strength and plastic viscosity decrease with increasing water-to-cement ratio, and increase with increasing cement fineness. The apparent viscosity is reversible with the change of shear rate. The influence of water-to-cement ratio, cement fineness, and shear rate on the flocculation effect is consistent with the influence on rheological parameters. Three factors and time affect the rheological properties by influencing the formation and destruction of the flocculation structure, and then changing the content of free water and intergranular force in cement slurry. Our study has revealed the evolution of rheological properties from a microscopic point of view, which can provide theoretical guidance for the design and application of cement slurry.

Comparative analysis on rheological characteristics of different modified asphalt based on DSR and BBR evaluation

PurposeIn order to evaluate the rheological properties of asphalt more comprehensively and effectively, and to explore and discuss the practicability of relevant models in the evaluation of the rheological properties of asphalt.Design/methodology/approachBased on the rheological and viscoelastic theories, temperature scanning, frequency scanning and multiple stress creep recovery (MSCR) tests of different modified asphalt were carried out by dynamic shear rheometer (DSR) to obtain relevant viscoelastic parameters and evaluate the high temperature properties of different modified asphalt. Based on the time-temperature equivalence principle, the main curve was constructed to study the viscoelastic properties of asphalt in a wider frequency domain. The main curve was fitted with the CAM model, and the rheological properties of different modified asphalt were evaluated through the analysis of model parameters. The creep stiffness and creep velocity of different modified asphalt were obtained through the rheological test of bending beam (BBR), and the low-temperature performance of different modified asphalt was analyzed by using Burgers model to fit the creep compliance.FindingsThe results show that the high temperature rheological properties of several modified asphalt studied in the test are ranked from best to worst as follows: PE modified asphalt > SBS modified asphalt > SBR modified asphalt. Short-term aging can improve the high temperature performance of asphalt, and different types of modifiers can promote or inhibit this improvement effect. Based on BBR test and Burgers model fitting analysis, SBR modified asphalt has the best low temperature performance, followed by SBS modified asphalt, while PE modified asphalt has poor low temperature performance, so it is not suitable to be used as road material in low temperature area.Originality/valueCombined with effective evaluation methods, the rheological properties of asphalt at different temperatures and angles were systematically evaluated, and the evolution of rheological properties of asphalt characterized by model parameters was further analyzed by advanced model simulation.

Effect of sedimentation on the rheological properties of cement pastes

Rheology has been widely used to describe the flow properties of fresh cement-based suspensions. Nevertheless, the characterization and understanding of the rheological behavior of cement-based materials have become essential with the recent introduction of novel applications like digital construction in the field of civil engineering, among others. It has been well documented that concrete and mortar may suffer stability problems (i.e. the ability of the mixture to maintain homogeneous). At the scale of cement paste, this phenomenon can still arise and affect the rheological properties of the measured paste. Therefore, inaccuracies during the measurements and incorrect interpretation may occur, resulting in erroneous conclusions. This study explores the impact of sedimentation of cement particles when characterizing the rheological properties of cement paste. The w/c employed in the pastes were 0.45 and 0.35 with the addition of superplasticizer to obtain a dispersed system. The rheological properties were measured using a coaxial cylinder configuration and followed up to 180 min after the contact between cement and water. Repeated measurements were executed with and without a homogenization procedure after each application of a measuring procedure. Comparing the results shows a clear influence of sedimentation on the evolution of rheological properties with time, and the effect is more pronounced for the mixtures with high w/c and for the procedure with the larger shear rate. Therefore, it is strongly recommended to keep a measuring procedure sufficiently short in duration.

Rheological behavior and compressive strength of concrete made with recycled fine aggregate of different size range

This study aims to examine the rheological properties and compressive strength of concrete containing recycled fine aggregate (RFA) with different particle size ranges. A developed polycarboxylatesuperplasticizer (SP2) was firstly applied in this study to optimize the rheological properties of concrete with RFA. The evolution of rheological properties of concrete containing RFA with the similar initial slump were investigated. Experimental results showed that the developed SP2 was more compatibility with RFA than ordinary polycarboxylatesuperplasticizer because of the lower static and dynamic yield stress when the slump was in the similar range and the lower time loss of slump in the range of 5.00%-11.63% in 30 min. The finer particles of RFA, smaller than 0.15 mm, led to the slow evolution of static yield stress and higher plastic viscosity in 30 min. Rheological properties of corresponding mortar were closely related with concrete. Different particles size range of RFA had clear impact on the compressive strength of concrete. The RFA with finer particles, smaller than 0.15 mm, had relative lower strength. But RAC-3 had the highest compressive strength, which may be attributed to the continuous gradation and denser packing structure of RFA in the particle size of G3.

Agglomeration properties of gluten-free flours under water addition and shearing conditions

Agglomeration properties of gluten-free cereals such as corn, manioc, amaranth, buckwheat, and quinoa flours were investigated. The different states of agglomeration were identified by the evolution of rheological properties under water addition and shearing conditions using a Caleva® mixer torque rheometer. The Mi-Pro® high-shear granulator has been used to produce wet agglomerates, which were characterized by fraction distribution, water content, density, and agglomeration yield. Results show that all samples present the same rheological characteristics: four agglomeration states are identified. The most highly developed cohesion was obtained with the amaranth flour with a mean torque of 2.4 N.m. Wet agglomeration with Mi-Pro® granulator showed that all selected flours can be granulated except for manioc flour, which did not give agglomerates. Using corn flour leads to a better uniformity on the size distributions but less for amaranth, buckwheat and quinoa flours. This study shows that it is possible to agglomerate these gluten-free flours for the preparation of couscous, which may diversify the choice of couscous types for people suffering from celiac disease.

Characterization of physical aging by time-resolved rheometry: fundamentals and application to bituminous binders

Physical aging is a ubiquitous phenomenon in glassy materials and it is reflected, for example, in the time evolution of rheological properties under isothermal conditions. In this paper, time-resolved rheometry (TRR) is used to characterize this time-dependent rheological behavior. The fundamentals of TRR are briefly reviewed, and its advantages over the traditional Struik’s physical aging test protocol are discussed. In the experimental section, the TRR technique is applied to study physical aging in bituminous binders. Small-diameter parallel plate (SDPP) rheometry is employed to perform cyclic frequency sweep (CFS) experiments over extended periods of time (from one to 8.6 days). The results verify that the mutation of rheological properties is relatively slow during physical aging (mutation number N′mu << 1), thus allowing rheological measurements on a quasi-stable sample. The effects of temperature, crystallinity, and styrene-butadiene-styrene (SBS) polymer modification on the physical aging of bitumen are evaluated. The time-aging time superposition is found to be valid both for unmodified and for polymer-modified bitumen. Vertical shifts are necessary, in addition to horizontal time-aging time shifts, to generate smooth master curves for highly SBS-modified bitumen.

Influences of shear-mixing rate and fly ash on rheological behavior of cement pastes under continuous mixing

The shear rate experienced by the cement pastes inside fresh concrete depends on the placing operations and the nature of concrete, and it plays an important role in the evolution of rheological properties and stability of fresh concrete over time. In this study, the effects of continuous shear mixing and fly ash on thixotropy, apparent viscosity, and shear-thickening behavior of cement pastes were experimentally investigated. Various shear rates of 1 s−1, 15 s−1 and 30 s−1 were selected to continuously shear the cement pastes. Results showed that the action of high-rate shear mixing slowed down the evolution of thixotropy, but the efficiency of reduction was gradually limited. Under the state of continuous shear mixing, the apparent viscosity of reference paste was significantly increased and the shear-thickening intensity at higher shear rate range was decreased. However, for the cement pastes containing fly ash, only slight increase in apparent viscosity was observed and the shear-thickening intensity also exhibited a slight increase behavior. It would be an effective way to hinder the evolution of flocculation structure by exerting a continuous shear mixing at an appropriate shearing rate and adding fly ash.

Linking Rheology and Printability for Dense and Strong Ceramics by Direct Ink Writing

Direct ink writing of dense and strong ceramic objects remains an important open challenge. We develop a universal dimensionless criterion for printing such objects. Boehmite, an Al2O3 precursor, was used to assess the rheological properties leading to dense structures in ceramics manufactured by direct ink writing. Boehmite suspensions undergo time dependent gelation, thus providing a rheological laboratory of flow behaviours that can be correlated with printability requirements. We measured the evolution of rheological properties over several days and quantified the deformation of simple printed shapes at different aging times. We then identified the relevant physical parameters leading to printable suspensions. We defined a dimensionless number, Ξ, based on measured rheological properties, that predicts deformation of the printed object and determines the printability criterion. An important difference with this criterion is that Ξ necessarily accounts for capillary forces and gravitational slumping. We show that boehmite inks reach a printed shape fidelity > 90% when Ξ > 1, and that Al2O3 bars printed under these conditions can be sintered to 97% density, without printing defects, and have flexural strengths (500–600 MPa) competitive with commercial aluminas. Using Ξ, researchers can rationally design inks for printing dense materials by tailoring their rheological properties such that Ξ ≈ 1.

Early age evolution of rheological properties of over-stabilized bitumen emulsion-cement pastes

This paper focuses on the early age evolution of consistency and rheological properties of fresh bitumen emulsion-cement (BEC) pastes. The tested BEC pastes were fabricated using a Portland limestone cement and an over-stabilized bitumen emulsion and were characterized by water to cement ratio ranging between 0.33 and 1 and by bitumen to cement ratio ranging between 0 and 1. The testing plan included the measurement of sedimentation tendency, setting time and evolution of viscosity with increasing storage time. Rheological measurements were also carried out on bitumen emulsion-filler mastics prepared with a reference filler. Results showed that, regardless of water content, the initial and final setting time of BEC pastes increased when the proportion of bitumen with respect to cement was increased. When the total concentration of the dispersed phases was low, the increase in bitumen concentration with respect to cement led to a reduction in the rate of viscosity increase with storage time; on the other hand, when the total concentration of the dispersed phases was high the increase of storage time led to a change in the physical state of the pastes (from fluid to plastic) due to coalescence of bitumen droplets.

The viscoelastic characterisation of thermally-treated waste activated sludge

Compositional change in sewage sludge due to thermal treatment drives rheological changes in the sludge. In this study, the viscoelastic characteristics of waste activated sludge (WAS) was investigated by measuring viscoelastic properties of sludge, the storage (G′) and loss (G″) moduli over 1h thermal treatment at different temperatures ranging from 20 to 80°C as well as after treatment when sludge cooled down to 20°C (thermal history effect). The soluble chemical oxygen demands (COD) was also measured at the same thermal treatment conditions.The results showed a distinctive difference between thermally-treated sludge and raw sludge in transitions from solid-like to liquid-like behaviour. It was observed that thermally induced compositional change in sludge impacted on both viscoelastic properties (G′ and G″) and viscous properties of sludge. Modified Cox-Merz rule (or Rutgers-Delaware) was successfully used to determine the sludge flow curve from the linear viscoelastic measurements of sludge.It was also found that the effect of short-time thermal treatment at high temperature on viscoelastic properties of sludge is similar to the effect of long-time thermal treatment at low temperature. This indicates that the amount of supplied thermal energy was the key controlling parameter of the evolution of rheological properties and the degree of organic matter solubilisation. A linear proportionality was also established between a dimensionless form of the released soluble COD and a dimensionless form of both G′ and G″. This suggests a possibility of controlling thermal treatment processes via rheological measurements.

Oxidation of bitumen: molecular characterization and influence on rheological properties

Rheological properties such as stiffness, elasticity, and viscosity are crucial parameters for the use of bitumen as a construction material. In bitumen oxidation studies, the increased viscosity has often been related to an increase in polar interactions from oxygen-containing compounds, like carbonyl groups. In this study, bitumen was subjected to two oxidation processes, aging and air blowing. Aging was performed using the rolling thin film oven test (RTFOT) and the pressure aging vessel (PAV), whereas air blowing was conducted in a laboratory unit. This investigation gives more insights in the changes observed during oxidation and highlights the differences between aging and air blowing. Moreover, the oxidation tests provide bitumen samples of increasing viscosity, which are used to evaluate relations between molecular and viscoelastic characteristics. As a comparison, the changes observed in harder bitumen samples prepared by a continued distillation are also included. As expected, the evolution of rheological properties with oxidation time is very similar in the PAV and in the air-blowing unit, although the timescales are very different. Fourier transform infrared spectroscopy (FT-IR) and acidity measurements reveal clear differences in the formation of oxygen-containing functional groups depending on the oxidation process. UV–visible spectroscopy shows that during aging as well as during air blowing, larger conjugated aromatic compounds are formed. These findings suggest that the formation of polyaromatic compounds may be the main contributor to the increase in elasticity and viscosity during oxidation.

Long-term viscoelasticity monitoring of enzymatic degradation of chitosan scaffolds

Event Abstract Back to Event Long-term viscoelasticity monitoring of enzymatic degradation of chitosan scaffolds Caroline Ceccaldi1, 2, Satu Strandman3, Eve Hui1, 2, Emmanuel Montagnon3, Cedric Schmitt3, Anis Hadj Henni3 and Sophie Lerouge1, 2 1 École de technologie supérieure, Department of Mechnical Engineering, Canada 2 CHUM research centre, Laboratory of Endovascular Biomaterials, Canada 3 Rheolution Inc., Canada Introduction: Hydrogels are extensively used for tissue engineering and regenerative medicine. Their mechanical properties determine not only their function but also cell response (i.e. proliferation and differentiation of stem cells) and their degradation kinetics is particularly important to predict scaffold resorption, new tissue formation and integration after implantation. Non-destructive methods are needed to screen and follow long-term evolution of rheological properties. In this work, we demonstrate the potential of a new non-destructive instrument, ElastoSensTM Bio2 (Rheolution Inc., Montréal, QC), that measures in real-time and without contact the evolution of rheological properties of chitosan hydrogels during network formation and degradation during exposure to human lysozyme. Materials and Methods: Validated[1] and patented[2] ElastoSensTM Bio2 technology is based on acoustic vibration. Response is measured using a laser and converted into elasticity. 1) Measuring viscoelastic properties of hydrogels: several chitosan thermogels (2% w/v; Mw 250kDa; DDA 94%) were prepared by mixing chitosan solution with a combination of phosphate buffer (PB) or beta-glycerophosphate (BGP) and sodium hydrogen carbonate (SHC) as gelling agents. Viscoelastic properties were measured after 1 and 24 hours of gelation at 37°C and compared with conventional rheometry (Physica MCR301) and compression tests (Bose Electroforce). 2) Following degradation: Chitosan thermogels with high (HDDA) or low degree of deacetylation (LDDA) were prepared. After 24h of gelation, a solution of lysozyme (1mg/mL) was added in the sample holder and kinetics of lysozyme-induced degradation was monitored once a day. Results and Discussion: ElastoSensTM Bio2 data confirmed that viscoelastic properties of chitosan thermogels are highly dependent on formulation. The results correlated with Young’s secant modulus obtained by compression tests (Figure 1), while conventional rheometry showed higher shear modulus for two formulations. Lysozyme is known to cleave the linkages between acetylated groups and lower DDA is expected to increase the degradation rate. Preliminary results showed that changing DDA of chitosan can impact the kinetics of degradation (Figure 2). In contrast to conventional in vitro degradation studies which follow the evolution of polymer mass with time, these results give rapid and direct insight on the degradation of mechanical properties and their possible adjustment by varying hydrogel composition. Conclusions: This study presents a new non-destructive approach to characterize viscoelastic properties of biomaterials in real-time during long periods. This new tool would allow fine-tuning the biomaterial formulations in terms of mechanical properties and degradation kinetics for targeted applications. It could also be used in presence of encapsulated cells for tissue engineering applications. Funding by Natural Sciences and Engineering Research Council of Canada (Engage grant). Caroline Ceccaldi acknowledges FRQ-S scholarship.

Rheology evolution and CFD modeling of lignocellulose biomass during extremely high solids content pretreatment

Design of industrial scale pretreatment reactors requires the accurate physical and rheological parameters of lignocellulose biomass. Rheological properties of raw and pretreated lignocellulose materials had been characterized in previous studies. A large gap of rheological properties between the raw and pretreated lignocellulose raised a difficulty for designing proper pretreatment reactors with maximum efficiency and minimum power consumption. In this study, the dilute acid pretreatment was operated in a 20-L reactor equipped with helical ribbon impeller agitation at high solids content up to 70% (w/w) dry solids. The operation was stopped at different time points, and then the completely or incompletely pretreated lignocellulose materials were released and sent for rheological property measurement. The changing rheological properties of lignocellulose materials were recorded into an evolution profile. The apparent viscosity change was found to be closely related to pretreatment temperature, and then affected the consequent enzymatic hydrolysis yield. The dynamic rheological parameters were fitted into power law model and the CFD model was established for high solids content pretreatment and used for industrial reactor design. Furthermore, the apparent viscosity of the raw and pretreated corn stover and wheat straw increased, instead of decreased, raising an instinct difference with the system of rigid solid particles and water. The study provided the first insight into the evolution of rheological properties during the high solids content pretreatment and the basis for industrial scale pretreatment reactor design.

Revealing New Structural Insights from Surfactant Micelles through DLS, Microrheology and Raman Spectroscopy

The correlation between molecular changes and microstructural evolution of rheological properties has been demonstrated for the first time in a mixed anionic/zwitterionic surfactant-based wormlike micellar system. Utilizing a novel combination of DLS-microrheology and Raman Spectroscopy, the effect of electrostatic screening on these properties of anionic (SLES) and zwitterionic (CapB) surfactant mixtures was studied by modulating the NaCl concentration. As Raman Spectroscopy delivers information about the molecular structure and DLS-microrheology characterizes viscoelastic properties, the combination of data delivered allows for a deeper understanding of the molecular changes underlying the viscoelastic ones. The high frequency viscoelastic response obtained through DLS-microrheology has shown the persistence of the Maxwell fluid response for low viscosity solutions at high NaCl concentrations. The intensity of the Raman band at 170 cm−1 exhibits very strong correlation with the viscosity variation. As this Raman band is assigned to hydrogen bonding, its variation with NaCl concentration additionally indicates differences in water structuring due to potential microstructural differences at low and high NaCl concentrations. The microstructural differences at low and high NaCl concentrations are further corroborated by persistence of a slow mode at the higher NaCl concentrations as seen through DLS measurements. The study illustrates the utility of the combined DLS, DLS-optical microrheology and Raman Spectroscopy in providing new molecular structural insights into the self-assembly process in complex fluids.

Coupled effect of cement hydration and temperature on rheological properties of fresh cemented tailings backfill slurry

The fluidity of fresh cemented tailings backfill (CTB) slurry depends on its rheological properties. Hence, it is crucial to understand the rheology of fresh CTB slurry, which is related to the cement hydration progress and temperature evolution within CTB mixtures. For this reason, a numerical model was developed to predict the evolution of the rheological properties of fresh CTB slurry under the coupled effect of cement hydration and temperature. Experiments were conducted to investigate the rheological behaviours of the fresh CTB slurry. By comparing the simulated results with the experimental ones, the availability of this developed model was validated. Thereafter, the model was used to demonstrate the coupled effect of cement hydration and temperature on the evolution of fresh CTB slurry's rheological properties, under various conditions (initial CTB temperature, cement to tailings ratio, and water to cement ratio). The obtained results are helpful to better understanding the rheology of CTB slurry.

Study on the rheological properties of Portland cement pastes with polycarboxylate superplasticizers

The coupling effects of temperature and time on the fluidity of fresh cement mixtures were investigated. Mini-cone tests on cement mortars and rheological tests on cement pastes under different temperatures (0 to 60 °C) were conducted to characterize the development of the fluidity of fresh cement mixtures over time. In addition, total organic carbon tests were performed to quantify the adsorption amount of superplasticizers on the cement surface. The amount of free water in cement pastes was determined via centrifugation. Isothermal calorimetry was employed to characterize the hydration kinetics of cement under different temperatures. Results show that the spread diameter of mortars decreases in a roughly linear fashion over elapsed time. Higher temperature facilitates a sharper decrease in fluidity with time, although the initial fluidity of fresh mortars is not significantly affected by temperature. Higher temperature results in a greater amount of adsorbed polycarboxylate ester/ether on the cement surface and a lower amount of free water in fresh cement pastes, which is believed to result from the higher hydration rate of cement. The evolution of rheological properties over time can be attributed to the development of hydration degree. Relative hydration degree is introduced to indicate the development of rheological properties with time. Two models to describe the evolution of yield stress and plastic viscosity for fresh cement pastes were developed.

와이오밍 벤토나이트의 유변학적 특성: 염분농도의 역할

팽윤성 점토의 전단강도 및 유변학적 특성은 점토입자의 크기, 양이온 교환능력, 점토광물학적 조성과 형상 등에 영향을 받는다. 본 연구는 고운 분말가루의 와이오밍(Wyoming) 벤토나이트에 대해 염화나트륨 0g/L 와 30g/L 농도로 24시간 수화시킨 후 염분농도에 따른 물성-강도특성 및 유변학적 특성변화를 살펴봄으로써, 유변학적 특성, 유변화적 모델들의 적용성 및 흙 입자의 구조변화에 따른 항복응력-점도와의 상관관계를 설명하고자 한다. 실험결과에 따르면, 팽윤성 점토는 전단담화(shear thinning)와 항복응력과 소성점도로 표현가능한 Bingham 유체 거동을 보이는 것으로 조사되었다. 염분농도가 낮고 함수비가 높아질수록 벤토나이트는 완전소성거동에 가깝게 나타나며, 전단변형률속도에 따른 변화의 폭이 미미한 것으로 조사되었다. 반면, 염분농도가 높아질수록 전형적인 전단담화거동을 보이며, 전단변형률속도를 증가시킬수록 염분농도에 따른 벤토나이트의 전단강도의 차이는 커진다. S=0g/L에 대해 Carreau, Herschel-Bulkley 및 멱수법칙 모델이, S=30g/L에 대해서는 이중선형, Herschel-Bulkley 및 멱수법칙 모델 등이 흐름특성을 가장 잘 표현한다. 이것은 염분농도에 따른 흙 입자간 구조적 배열과 형상이 입자간 발생하는 인력인 능-능(EE), 능-면(EF), 및 면-면(FF) 구조를 변화시키고 역학적 특성에 영향을 미치기 때문이다. The rheological properties of Wyoming bentonites are strongly influenced by the size of particles, cation exchangeable capacity, arrangement and morphology of clay mineral. This paper presents the results of rheological investigations on the Wyoming bentonites aqueous dispersions: two types of particle flocculation were considered. For the Wyoming bentonite, 0g/L and 30g/L NaCl equivalent salinity were added in fresh and salt water to examine the rheological behavior. This paper examined the general rheological characteristics, compatibility of rheological models and correlation between soil structure and change in rheological properties of Wyoming bentonite caused by increasing salinity. From flow curves of bentonites hydrated with fresh water and salt water, the observed general flow behavior is very close to shear thinning with yield stress (or ideal Bingham fluid with yield stress and plastic viscosity). However, the change of shear stress at the same shear rate is clear, particularly for lower shear rate. Well-known rheological models are used to fit the data. There is a good agreement between rheological model and data: Carreau, Herschel-Bulkley and power-law for S=0g/L and bilinear, Herschel-Bulkley and power-law for S=30g/L. It may be due to the fact that the internal structural bonding (strong modification of particle-particle interactions from edge-to-edge and/or edge-to-face to face-to-face) in soil matrix is affected from the evolution of rheological properties with different salinities.