Rheological Index Research Articles

Using the Rheological Index to Quantitatively Evaluate the Mechanical Performance of High‐Elasticity Modified Asphalt

High‐elasticity modified asphalt is widely used in OGFC and bridge deck paving due to its high viscosity and strong displacement recovery capacity. It can improve the high‐temperature deformation resistance and elastic recovery ability of the pavement. Especially in bridge deck pavement, high‐elastic modified asphalt can inhibit the formation of reflective cracks and extend the service life. In order to quantitatively evaluate properties of the high‐elasticity modified asphalt, rheological properties are studied by using a dynamic shear rheometer (DSR) test. The parameters were fitted with the Burgers model, and the constitutive equation was established. The 3 s elastic recovery rate Er was proposed to quantitatively evaluate the elastic recovery of high‐elasticity modified asphalt. The experimental results show that the instantaneous modulus of elasticity G0 and the delayed modulus of elasticity G1 can be used to evaluate the elastic capacity. Er can quantitatively evaluate the elastic resilience of high‐elasticity modified asphalt. The correlation coefficient between the test results of high‐elasticity modified asphalt and those of impact toughness evaluation reached 0.9966, and the 3 s elastic recovery rate Er could be used to evaluate the elastic recovery ability of high‐elasticity modified asphalt.

Effects of Astragalus Polysaccharides Nanoparticles on Cerebral Thrombosis in SD Rats.

ObjectiveTo investigate the efficacy and improvement of Astragalus polysaccharides (APS) and APS-nano on cerebral thrombosis in rats.MethodsA total of 72 SD rats were randomly divided into NC group, Model group, APS-Nano group, and APS group. The cerebral thrombosis Model of SD rats was established by injecting compound thrombus inducer into the internal carotid artery. After 14 days of different intervention treatments, the TTC staining of brain tissue were performed, and A/left brain wet weight ratio, left brain/right brain wet weight ratio, blood rheology indexes, and coagulation function indexes of cerebral thrombosis were measured. ELISA was used to measure the contents of thromboxane 2 (TXB2), 6-keto-prostaglandin F1α (6-Keto-PGF1α), tissue factor (TF), neuron-specific enolase (NSE), S-100β, catenin (CAT), superoxide dismutase (SOD), as well as malondialdehyde (MDA). The binding specificity between miR-885-3p and TF was verified by the double-luciferin reporting experiment, and western blot was used to measure the expression level of TF protein.ResultsCompared with the Model group, after treatment with APS-nano or APS, the ratio of left brain/right brain wet weight decreased significantly. Whole blood low shear viscosity (WBLSV), whole blood high shear viscosity (WBHSV), plasma viscosity (PV), and erythrocyte aggregation index (Arbc) was all reduced. In addition, prothrombin time (PT) and activated partial thromboplastin time (APTT) were increased, and fibrinogen (FIB) content was decreased. The expression of TXB2, 6-Keto-PGF1α, and TF showed a downward trend. Similarly, the expression of TF protein was decreased. Furthermore, the contents of NSE and S-100β proteins were all decreased, whereas the contents of CAT and SOD were increased, and the contents of MDA was decreased. At the same dose, compared with APS treatment, APS-nano treatment had a significant inhibitory effect on cerebral thrombosis in rats. Finally, we found that TF is a target gene of miR-885-3p and specifically binds to miR-885-3p.ConclusionAPS has a significant inhibitory effect on the formation of cerebral thrombosis induced by compound thrombus inducers. Moreover, APS-nano has a more significant inhibitory effect on cerebral thrombosis. Meanwhile, the regulation of miR-885-3p regulating TF expression may be related to the occurrence of cerebral thrombosis.

Evaluation of cracking susceptibility of Alaskan polymer modified asphalt binders using chemical and rheological indices

Asphalt pavement cracking (especially thermal cracking) is one of the most prevalent pavement distresses in Alaska and other northern states in the United States. Rheological indices such as the Glover-Rowe (G-R) parameter and ΔTc have been reported to have potential in evaluating cracking susceptibility (durability) of asphalt binders, though not been applied to Alaskan asphalt binders yet. The objectives of this study are to evaluate the cracking susceptibility of Alaskan asphalt binders by using these indices and other chemical parameters, and to assess the applicability of these indices. A total of 13 plant-produced asphalt binders (neat and polymer-modified) were collected from Alaskan paving projects. Fourier transform infrared spectroscopy tests were conducted to obtain the chemical index (i.e., Carbonyl Index), and dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were performed to determine rheological indices such as the G-R parameter, the crossover frequency, the rheological index (R-value), and ΔTc. The Carbonyl Index results during asphalt oxidative aging indicated that the modified asphalt binders were less prone to oxidative aging than the neat asphalt binder. However, the ΔTc results reached the opposite conclusion. The modified asphalt binders showed more negative ΔTc values than the neat asphalt binder at long-term aging states (e.g. 40 h pressure aging vessel (PAV)). The G-R parameter results indicated the studied Alaskan asphalt binders were not susceptible to cracking at long-term aging state (e.g. 20 h PAV). In addition, it was found that Asphalt binders from different suppliers could have different cracking susceptibilities (durability) even though they had the same performance grade. The ranking correlation analysis results between Carbonyl Index and G-R parameter (and ΔTc) indicated that both G-R parameter and ΔTc had potential to assess the cracking susceptibility of Alaskan asphalt binders. However, more data is needed to further validate the conclusion. It was not recommended to use crossover frequency and R-value to assess the cracking susceptibility of Alaskan asphalt binders studied since it’s the crossover frequency and R-value were difficult to be obtained precisely due to the low phase angle value (sometimes lower than 45° along the whole frequency range). Within the scope of this study, the applicable of the current standard linear amplitude sweep (LAS) testing and analysis protocols to the Alaskan highly modified asphalt binders is questionable.

Influence of the composition of composite mixtures with a reduced gluten content on the rheological properties of the dough based on their basis

The article presents experimental data on the assessment of the rheological properties of dough from new types of flour, formed on the basis of cumulative curves using the Mixolab device. The data of mixolabograms and radial diagrams (Mixolab profiler) made it possible to reveal the existing differences in the parameters of the rheological profile and Mixolab indices. The object of the study is composite mixtures of gluten-free flours: No. 1 is 50% of pumpkin and 50% of corn flour, No. 2 is 50% of linseed and 50% of corn flour, No. 3 – 50% of rice and 50% of corn flour, No. 4 – 75% of linseed and 25% of corn flour, No. 5 is 30% of linseed and 70% of rice flour. The use of composite mixtures is promising due to high oven rise and low starch thickening because of its high water absorption capacity (WAC). In addition, there is certain economic efficiency, since it is possible to produce more dough at a lower cost.

Horizontal flow reactor optimization for biogas recovery during high solid organics fermentation: Rheological characteristic analyses

Continuous improvements in human living standards, water supply quality, and poor solid waste collection systems in China has led to increased production of municipal sewage sludge and organic solid waste (MOSW), which incurs a potential risk for human health and the environment. Solid anaerobic fermentation, which has exhibited advantageous energy recovery and biosolid stabilization, has been considered for urban organic solid waste treatment. The primary objective of this study was to optimize horizontal flow reactor operations for the efficient fermentation of high solid organics and subsequent biogas production via rheological characteristic analyses. The effects of operational parameters, such as paddle type, paddle diameter, pitch diameter ratio, stirring efficiency, torque, and power consumption, on the reactor performance were simulated using computational fluid dynamics (CFD). The solid content greatly influenced the rheological characteristics of the MOSW; increasing the solid content (5 %–30 %) of the MOSW led to a significant decline in the rheological index (0.532 to 0.224). The optimized parameters simulated by CFD included a screw-type stirring paddle with a pitch of 0.6 D, pitch of the screw with the value of 0.75 D, stirring shaft (set vertically and eccentrically downward) with the value of 0.15 D, and stirring speed less than 10 rpm. Moreover, the higher the consistency coefficient, the lower the rheological index and required power consumption. The reactor energy consumption analysis indicated that the average energy consumption can reach 48.20 kJ/m3 with an efficient operation.

Correlation between geometric parameters of coarse aggregates and mixing rheological indices of asphalt mixture

The workability of asphalt mixtures significantly influences the construction of the asphalt pavement. In this study, a mixing rheometer was developed to characterize the workability of asphalt mixtures during mixing and further to investigate the effect of coarse aggregates. In addition, the corresponding rheological indices for evaluating the mixing rheological properties were proposed, including the b value related to the initial mixing resistance and the k value related to the steady-state mixing resistance. Moreover, the correlation between the geometric properties of the coarse aggregate and the mixing rheological indices was established. Results show that the sieving diameter/shape index of single-size aggregates (SA) and single-size aggregate mixtures (SAM) exhibits a strong linear correlation with the rheological indice k value. The fluctuation of SAM’s mixing rheological indices was reduced by about 1 time compared with SA’s. Therefore, asphalt plays a lubricating role in the mixture to reduce mixing resistance and reduce the sensitivity of aggregate geometric characteristics to mixing rheological indices. As the aggregate size increases, the mixing rheological properties of the mixture deteriorate. During the initial mixing, the b values of SA, SAM and GAM are most sensitive to the aggregate shape index, angularity and sieving diameter, respectively. During the steady-state mixing, the aggregate sieving diameter is most sensitive to the mixing rheological indice k value, followed by the shape index, while the angularity is less sensitive to the k value.

Variations and model of the rheological parameters of low damage BCG − CO2 fracturing fluid

AbstractA BCG − CO2 fracturing fluid composed of a new thickener and CO2 causes low amounts of formation damage, and it can be used to stimulate low‐permeability gas reservoirs with water sensitivity. However, at present the rheological properties of this foam fracturing fluid are unclear, which has limited its field application to some degree. The main purpose of this study was to ascertain the rheological parameters and a model of the BCG − CO2 fracturing fluid. The rheological properties of the BCG − CO2 fracturing fluid were evaluated by using a foam rheological test system. The unfoamed condition test results showed that when the shear rate was lower than 1000 s−1, the effective viscosity exhibited a rapid decreasing trend. The effective viscosity of the BCG − CO2 fracturing fluid was 4 to 26 mPa · s under foamed conditions. The comparison results showed that the viscosity of the BCG − CO2 foam was suitable as a low damage fracturing fluid. The measured data were fitted using the H‐B and power law models in this study. The power law model, by contrast, was fit for describing the relationship between shear rate and shear stress. The foamed condition rheological index n′ first decreased and then increased with increasing foam quality, and the rheological coefficient k′ first increased and then decreased with increasing foam quality. For the different foam qualities, the rheological index n′ first increased and then decreased with increasing temperature. The rheological coefficient k′ showed a decreasing trend with increasing temperature. When an exponential function, in which the foam quality and temperature were independent, was used for fitting, it was not accurate in predicting the rheological properties. The fitting results based on a quadratic polynomial surface model were better. The average calculation errors of the rheological parameters were all less than 3.32%. The findings of this study can help develop a better understanding of the heat transfer and flow coupling process in wellbore and fracture in fracturing treatment.

Development of new performance indices to evaluate the fatigue properties of asphalt binders with ageing

This work presents the development of new fatigue performance indices for asphalt binders based on viscoelastic continuum damage (VECD) theory and failure energy. Five plant-produced asphalt mixtures were subjected to three different conditioning levels (short-term ageing during production and loose mix ageing for 5 and 12 days at 95°C in the laboratory) and the corresponding binders were extracted and recovered. Direct Tension Cyclic Fatigue (DTCF) tests were performed on the mixtures to characterise the mixture fatigue properties using the simplified viscoelastic continuum damage (S-VECD) analysis approach. Frequency and temperature sweep tests and the Linear Amplitude Sweep (LAS) test using a Dynamic Shear Rheometer (DSR) were conducted on the recovered binders to evaluate the binder rheological and fatigue properties. Three new performance indices are explored from the LAS test: Strain Tolerance (εT ), Strain Energy Tolerance (Εf ), and Average Reduction in Integrity to Failure (IR ). These indices were used to track the evolution of binder fatigue properties with ageing. A unique aspect of these indices is that they capture the failure point of the binder during the LAS test and combine the stress and strain histories of the material. Compared with the traditional A and B parameters from the LAS test, the new indices show a consistent decrease in the fatigue properties of the binders with ageing. The newly proposed parameters show improved correlations with mixture fatigue performance index (DR ) from the DTCF test, indicating their potential for evaluation of asphalt mixture fatigue properties. In addition, the new indices developed from this study have been shown to effectively capture the ageing gradient within the pavement structure and can also be used together with the binder rheological indices (e.g. G-R parameter and ΔTc) to evaluate both environmental and fatigue cracking of asphalt pavements at the same time.

New Insights into the Formation Mechanism of Solid-Liquid Segregation in the Semi-Solid Processing: Macro-Micro Linkage Theory

Solid-liquid segregation is a typical problem in multiphase flow, especially in the die casting of metallic alloys. The avoidance of phase segregation in High Pressure Die Casting (HPDC), and Semi-solid Processing (SSP) for suspended flow is a benefit for improving product performance. At present, there is not a unified statement on the cause of the solid-liquid segregation defect. The formation mechanism of phase segregation is investigated by theoretical analysis from the perspective of hydrodynamic and rheology. The relationship between hydrodynamic parameters and characteristic rheological index is established. Maps of critical velocity, power-law index n, and consistency coefficient k are depicted for the semi-solid slurries. Then experiments and corresponding multiphase simulations were conducted to verify this theory. The macroscopic and microscopic linkage mechanism was proposed based on the theoretical discussion. This investigation not only provides important insights into the flow map of the semi-solid slurry, but also offers a key criterion of filling velocity for the avoiding of phase segregation for shear-thinning non-Newtonian fluids.

Phase-field simulation of slurry displacement efficiency in borehole with a sudden contraction or expansion

Due to the influence of geological and engineering factors, the irregular wellbore is commonly found in the field operation, resulting in a low slurry displacement efficiency. Compared with experimental and analytical methods, numerical simulation is an effective method to investigate the slurry displacement in a wellbore system with complex geometry. However, the present numerical simulation methods are usually unsuitable for the irregular wellbore because of the numerical dissipation triggered by the sharp curvature or difficulty in interfacing tracking. In this work, based on the fluid mass conservation equation, Navier-Stokes equation and Cahn-Hiliard equation, the phase-field mathematical models for slurry displacement is established. Through this method, the flow field and the evolution of the displacement interface in the irregular wellbore are analyzed in detail. The results show that, the disturbance of the irregular part can (1) generate the vortex within the expansion region or the downstream corner of the contraction, (2) cause unstable fluid-fluid interface, both of which result in poor displacement efficiency and subsequent poor cementation quality. Higher slurry's consistency coefficient, slurry's rheological index, the displacement rate or displacement time facilitate the improvement of the displacement efficiency in the irregular wellbore. The proposed phase-field method could avoid the numerical dissipation and track the fluid-fluid interface, and this method can also be applied for the displacement process in a channel with small size, such as slim hole or eccentric annulus due to the incorporation of surface force.

Effect of rheokinetics on convective heat transfer of microalgae slurry in tube during hydrothermal conversion

Hydrothermal pretreatment is a suitable technique to release microalgae biomass into liquid phase, which prepared for further biofuel production. During the hydrothermal treatment process, the dynamic rheological behavior leads to the complex convective heat transfer performance of microalgae slurries in tube, which increased the difficulty in designing the heat exchanger. Herein, we experimentally investigated the temperature-dependent rheokinetics in a rheometer and convective heat transfer characteristics of the microalgae slurry in tube flow. The results revealed that the rheological index varied with the reaction time in hydrothermal pretreatment processing, and the variation tendency was affected by temperature. Besides, the variation of Nusselt number (Nu) with temperature appears a peak Nu at 363 K, which was affected by the rheological index of microalgae slurry in stable state. Considering the effects of the rheological index, volume fraction, and Peclet number, an empirical equation was proposed to describe the Nu of the microalgae slurry in tube flow from 293 to 423 K. It is a guidance to design the large scaled tubular heat exchanger for microalgae hydrothermal conversion.

Evaluation of rheological master curves of asphalt mastics and asphalt-filler interaction indices

Understanding the rheological behavior of the asphalt mastic is an important step towards improving the shear-stress response of the mixture. The objective of this study is to observe the rheological master curves and the asphalt-filler interaction of the asphalt mastics in the linear viscoelastic (LVE) range by using various rheological indices. The frequency sweep (FS) test was utilized to investigate the influence factors of the rheological indexes and the applicability of the asphalt-filler interaction indexes. Simultaneously, the correlation of various asphalt-filler interaction indices was established. The results showed that the influence of filler volume fraction and the aging effect exhibited a stonger significant effect on the rheological indices were significantly stronger than that of the binder type and filler type. The aging effect could reduce the difference in the rheological indices between various mastics. The analysis of the asphalt-filler interaction indices showed that the addition of the modifier had a negtive effect on the critical filler volume fraction (Φm) of the mastic. Moreover, the indices of the complex modulus coefficient (△G*), K.D.Ziegel-B-G* (K-B-G*) and complex viscosity coefficient (△η*) presented the consistency in evaluating the asphalt-filler interaction ability. The value of K-B-G* increased with the aging degree, that is, the filler-asphalt interaction increased with aging degree

Correlation analysis between aging behavior and rheological indices of asphalt binder

The aging of the asphalt binder seriously affects the performance of the asphalt pavement, so it is expected to obtain indices that can not only evaluate the aging resistance of the asphalt binder but also indicate the performance of the asphalt mixture. In this study, the changing of the rheological indices before and after asphalt aging were observed. The sensitivities to aging characterized by different rheological indices were also compared with each other. Moreover, the relationships among rheological indices were discussed. The results show that the aging has a significant impact on the rheological properties of asphalt. The addition of modifier obviously reduced the low-temperature relaxation modulus of asphalt and increased the absolute value of relaxation rate, thereby improving the low-temperature performance of asphalt road. The sensitivity analysis results of rheological indices to aging behavior show that rheological indice [R3.2kPa] obtained by multiple stress creep recovery test was most sensitive to short-term aging, while rheological indice [R]3.2kPa obtained by repeated creep recovery test was most sensitive to long-term aging, which helps to provide technical support for the quantitative characterization of the aging behavior of asphalt binder. Correlation analysis of rheological indices show that the indice mr(60 s) in frequency sweep test at low temperatures show a linear correlation with the indices Jnr3.2kPa in MSCR test and Nf in linear amplitude sweep test, indicating that the low-temperature relaxation rate of asphalt is closely related to its high temperature performance and fatigue performance.

PREPARATION OF CASTOR-BASED POLYURETHANE COMPOSITES FILLED WITH WASTE CARBON TYRES (WCT) AS GROUTING MATERIAL

This research focused on the fabrication of castor-based polyurethane composite (CPUC) filled with waste carbon tyres (WCT) with particle size of 200 µm that acts as reinforcing filler. WCT was first sieved using a sieving machine to obtain uniform particle size. WCT loading was varied at 0wt%, 2wt%, 4wt% and 6wt%. The effect of WCT loading in CPUC was evaluated based on their foam reaction time, apparent density, rheology, compression strength, morphology and thermal properties. The foam reaction time of CPUC achieved was in the range of industrial PU grout’s properties. The rheology index and compression strength of CPUC decreased with increasing WCT loading. CPUC with 2wt% of WCT loading achieved the optimum compression strength where it increased from 2.58 MPa to 3.39 MPa with the improvement of 31.40% compared to neat PU. FESEM micrograph showed that CPUC consists of closed foam cell indicating the rigidity of the CPUC. The addition of 2wt% of WCT resulted in achieving the optimum thermal stability of CPUC where CPUC2 had the highest char residue content. The high residue content indicated that CPUC2 had the lowest decomposition of elements as WCT acted as heat barrier in CPUC matrix thus increasing the thermal stability of CPUC2.

Development of the Composition and Technology of a New Dental Gel with Anti-Inflammatory and Antimicrobial Action

The development of a dental gel that meets modern requirements for the effectiveness and safety of a medicinal product is a serious scientific study related to the selection of active and auxiliary substances, providing the necessary biopharmaceutical and rheological properties of the gel composition, standardizing the quality of the dosage form. The article presents the results of a study on the development of the composition and technology of the soft dosage form of the new dental gel «Matripin- Dent» using pharmacologically active ingredients of the sum of flavonoids from Populus balsamifera L. buds (pinostrobin, pinocembrin, chrysin, techtochrysin) and the sum of terpenoids from Matricaria chamomilla L. (bisabolol oxides A and B, chamazulene). Three bases are selected: fat, gel, and multicomponent. According to the results of pharmacological studies, the optimal composition is a gel base containing polyethylene oxide 1500 and 400. The rheological index of the gel base confirms its thixotropic properties, good spreadability, the ability of the obtained gel to extrude from the tube, and stability. The indicators of control and critical points of the technological process are determined and a technological scheme for the production of dental gel is developed.

Diffusion mechanism and sensitivity analysis of slurry while grouting in fractured aquifer with horizontal injection hole

Investigating the diffusion law of slurry while grouting in fractured aquifer is of great significance to the safety in coal mining. In this paper, we comprehensively studied the slurry diffusion in the fractured aquifer, which was grouted through horizontal injection holes. A theoretical model of slurry diffusion in the inclined tubular fractures, as well as the relationship between the distance of slurry diffusion and the grouting time, was established. Then the influence of different factors on the distance of slurry diffusion was analyzed, including rheological coefficient, the fracture width, grouting pressure, the fracture dip angle, and the velocity of flowing water. Finally, sensitivity analysis on the distance of slurry diffusion for pseudoplastic fluid and expansive fluid along the flowing water direction was made and the results show that the sensitivity of each factor to the diffusion distance of the two fluids along the flowing water is different, rheological index is the very significant factor to the diffusion distance of pseudoplastic fluid. However, for the expansive slurry, the fracture width is the very significant factor to the diffusion distance of it.

Improvement of the method of rheological assessment of grain quality in the spring wheat breeding

It was established that the question of the grain quality of spring durum wheat is the main one when developing new varieties. First of all, it is important for manufacturers of food products (pasta, cereals) and the grain market as a whole. To create popular varieties, the breeders need methods for evaluating grain material at the early stages of selecting experimental material. One of such express-methods is the method of assessment of the rheological properties of dough made from durum wheat flour (semolina) according to the rating scale of the mixographic curve. It has been found out that the stronger and more elastic gluten is, the more resistant to be overboiled pasta is, and therefore better their nutritional and culinary properties are. This is especially important for the production of thin spaghetti. It has been determined that the rheological indices of the new spring durum wheat variety “Pamyati Vasilchuka” during dough kneading do not correspond to any of the nine points on the rating scale of mixographic curves. There has been considered the possibility to increase the mixogram rating scale to 10 points.

Pulsating Flow of an Ostwald—De Waele Fluid between Parallel Plates

The flow between two parallel plates driven by a pulsatile pressure gradient was studied analytically with a second-order velocity expansion. The resulting velocity distribution was compared with a numerical solution of the momentum equation to validate the analytical solution, with excellent agreement between the two approaches. From the velocity distribution, the analytical computation of the discharge, wall shear stress, discharge, and dispersion enhancements were also computed. The influence on the solution of the dimensionless governing parameters and of the value of the rheological index was discussed.

Linking chemical to rheological properties of asphalt binder with oxidative aging effect

ABSTRACT This study aimed to establish the chemical-rheological property relationships of asphalt binders subjected to oxidative aging. Five asphalt binders were aged in the oven at several different temperatures for various durations. The chemical characteristic in terms of carbonyl index and rheological characteristic in terms of complex shear modulus and phase angle. The aged asphalt binders were measured using the Fourier Transform infrared spectroscopy (FTIR) and Dynamic Shear Rheometer (DSR) techniques, respectively. During oxidative aging process, the carbonyl index was predicted using the Glover’s aging kinetic model. Crossover frequency and rheological index generated from the aging mastercurves, correlates well with the carbonyl index of asphalt binders, and the correlations are independent of aging temperature and time. Christensen-Anderson model is used in combination with crossover frequency-carbonyl index and rheological index-carbonyl index relationships to predict complex shear modulus and phase angle master curves of the binder with respect to aging.

Metal-containing nanocomposites based on isotactic polypropylene

The effect of additives of metal-containing nanofillers, including zinc oxide nanoparticles, on the properties of nanocomposites based upon isotactic polypropylene (PP), using X-ray phase analysis (XPA) and thermogravitometric (TGA) analysis was studied.The improvement of the strength and rheological indexes, as well as the thermooxidative stability of the nanocomposites obtained was revealed.