Changes In Rheological Parameters Research Articles

Cost-effective enhancement of high viscosity modified bitumen anti-aging properties using organic layered double hydroxide/fume silica nanoparticles composite nanomaterials

High-viscosity modified bitumen (HVMB) is prone to thermal-oxidative and photooxidative aging, resulting in pavement diseases. The use of conventional Nano-modifiers to enhance the aging resistance of bitumen is often hindered by high costs, limiting their adoption in widespread applications. This study aims to evaluate the impact of a cost-effective Multi-Dimensional Nano-Composite (MDNC) modifier on the durability of HVMB, which includes organically modified Layered Double Hydroxides (OLDHs) and Fumed Silica Nanoparticles (FSNPs). Additionally, Zero-Dimensional Nanomaterials (ZDNs) such as FSNPs, Nano-SiO2, or Nano-TiO2, in combination with various MDNC modifiers consisting of OLDHs and ZDNs, were also utilized as comparative anti-aging modifiers for HVMB binders. FTIR, XRD, and contact angle tests indicate that LDHs modified with KH560 (OLDHs) exhibit improved hydrophobicity and increased interlayer distance. The temperature sweep test of the unaged binders and the FESEM test of the Nano-modifier indicate that the branched network structure of the FSNPs significantly enhances the high-temperature elasticity of the HVMB binders. Rheological test results have shown that both ZDNs and MDNC modifiers can delay the changes in rheological parameters after aging. Combining FTIR and SARA (Saturates, Aromatics, Resins, Asphaltenes) results, it was found that the combination of OLDHs/FSNPs synergistically inhibited the increase in the content of heavy components in bitumen during thermal oxygen and ultraviolet aging. The enhancement of the HVMB's thermal oxidation aging resistance by OLDHs/FSNPs composite modifiers is primarily due to the multidimensional structure of the composite nanomaterial, which effectively prevents the penetration of oxygen molecules. Meanwhile, the improvement in resistance to ultraviolet aging is mainly due to the absorption and scattering characteristics of FSNPs. Therefore, OLDHs/FSNPs are demonstrated to be a cost-effective multidimensional nano-modifier.

Study on multiscale structures and digestibility of cassava starch and medium-chain fatty acids complexes using molecular simulation techniques

Effect of complexation of three medium-chain fatty acids (octanoic, decylic and lauric acid, OA, DA and LA, respectively) on structural characteristics, physicochemical properties and digestion behaviors of cassava starch (CS) was investigated. Current study indicated that LA was more easily to combine with CS (complex index 88.9%), followed by DA (80.9%), which was also consistent with their corresponding complexed lipids content. Following the investigation of morphology, short-range ordered structure, helical structure, crystalline/amorphous region and fractal dimension of the various complexes, all cassava starch-fatty acids complexes (CS-FAs) were characterized with a flaked morphology rather than a round morphology in native starch (control CS). X-ray diffraction demonstrated that all CS-FAs had a V-type crystalline structure, and nuclear magnetic resonance spectroscopy confirmed that the complexes made from different fatty acids displayed similar V6 or V7 type polymorphs. Interestingly, small-angle X-ray scattering analysis revealed that α value became greater following increased carbon chain length of fatty acids, indicating the formation of a more ordered fractal structure in the aggregates. Changes in rheological parameters G′ and G′′ indicated that starch complexed with fatty acids was more likely to form a gel network, but difference among three CS-FAs complexes was significant, which might be contributed to their corresponding hydrophobicity and hydrophilicity raised from individual fatty acids. Importantly, digestion indicated that CS-LA complexes had the lowest hydrolysis degree, followed by the greatest RS content, indicating the importance of chain length of fatty acids for manipulating the fine structure and functionality of the complexes.

Changes in rheological parameters of blood, microcirculation, and accumulation of antibiotic in the focus of acute inflammation of patients with maxillofacial phlegmon

BACKGROUND: Despite the modern development of dentistry, the frequency of purulent inflammatory diseases of complicated caries tends to increase. Up to 60%–70% of patients had odontogenic phlegmon in maxillofacial hospitals. With the spread of the process to the neck and mediastinum, mortality reaches 60%, and with the generalization of infection leading to septic shock, it increases to 90%. This study aimed to examine the state of rheological parameters and blood microcirculation in cases of acute purulent inflammation in patients with maxillofacial phlegmon based on blood viscosity, analysis of the microcirculatory bed according to laser Doppler flowmetry, and concentration of the antibiotics in the blood. This study will allow us to analyze pathophysiological changes and coordinate adequate drug therapy.
 AIM: To examine the state and rheological properties of blood in the microcirculation and antibiotic concentration in cases acute purulent inflammation in patients with maxillofacial phlegmon to improve the effectiveness of treatment.
 MATERIALS AND METHODS: The study enrolled 20 patients. Their age ranged from 28 to 62 years, and there were 13 (65%) men and 7 (35%) women. The average body weight of the patients in the study group was 79–95 kg. All patients under endotracheal anesthesia underwent phlegmon dissection. During the operation and treatment, microcirculation, blood viscosity, and laser Doppler flowmetry were evaluated, and the antibiotic concentration in the inflammation area was assessed.
 RESULTS: The results of the study of 20 patients were analyzed. As a result of studying the rheological parameters of blood obtained from the peripheral vein in patients with phlegmon of the maxillofacial region of various localization, changes in blood viscosity towards thickening compared with normal values were revealed.
 CONCLUSION: With acute purulent inflammation of the maxillofacial region, pathophysiological changes occur in the microcirculatory bed, which must be considered when prescribing adequate antibacterial therapy.

Postmastectomy phlebothrombosis and methods of physical therapy

The leading complication of radical breast cancer treatment is upper limb edema. In its pathogenesis, intravasal disorders, i.e. phlebothrombosis, are also possible. 98 breast cancer patients (53.8 years old) were observed. The patients were diagnosed with phlebolymphedema stage II caused by subacute occlusive thrombosis (non-embolic) of the axillary vein on the side of the operation. After diagnosis, the hemorheological properties in patients were studied, and basic pharmacotherapy with enoxaparin was prescribed. The patients were randomized into 3 groups: group 1 (n=40) additionally received local magnetic therapy with an alternating magnetic field, group 2 (n=37) — continuous infrared laser radiation for 10–12 days, and group 3 (n=21) received only basic pharmacotherapy. The initial rheological parameters: structural and dynamic viscosity of blood exceeded the reference values by 2.8 and 1.6 times, respectively, aggregation of erythrocytes — by 1.5 times, and aggregation of platelets — by 1.4 times. On day 7 from the start of the procedures, pharmacotherapy did not cause statistically significant changes in rheological parameters, while in groups 1 and 2, there was a decrease in structural and dynamic viscosity of blood by an average of 15.5 % and 16.5 %, respectively, in aggregation of erythrocytes — by 14.5 %, and in aggregation of platelets — by 14.5 % (P<0.05). A comparative analysis of the degree of change in these parameters in patients of groups 1 and 2 did not reveal statistically significant differences, which indicates the unidirectional effect of the magnetic field and laser radiation on blood rheology. After the course of treatment, edema decrease accounted for 16.5±1.2 % in group 1, 13.8±1.8 % in group 2, and 7.5±1.4 % in group 3. Recanalization of the axillary vein lumen in group 1 was up to 80 %, in group 2 — up to 70 %, and in group 3–30 %. The rheological status of patients can be a potential marker of the effectiveness of their rehabilitation.

The Effects of the Deacetylation of Chitin Nanowhiskers on the Performance of PCL/PLA Bio-Nanocomposites.

The multiple roles of organic nanofillers in biodegradable nanocomposites (NC) with a blend-based matrix is not yet fully understood. This work highlights combination of reinforcing and structure-directing effects of chitin nanowhiskers (CNW) with different degrees of deacetylation (DA), i.e., content of primary or secondary amines on their surface, in the nanocomposite with the PCL/PLA 1:1 matrix. Of importance is the fact that aminolysis with CNW leading to chain scission of both polyesters, especially of PLA, is practically independent of DA. DA also does not influence thermal stability. At the same time, the more marked chain scission/CNW grafting for PLA in comparison to PCL, causing changes in rheological parameters of components and related structural alterations, has crucial effects on mechanical properties in systems with a bicontinuous structure. Favourable combinations of multiple effects of CNW leads to enhanced mechanical performance at low 1% content only, whereas negative effects of structural changes, particularly of changed continuity, may eliminate the reinforcing effects of CNW at higher contents. The explanation of both synergistic and antagonistic effects of structures formed is based on the correspondence of experimental results with respective basic model calculations.

Study on rheological behaviors and rheokinetics of urushiol/MDI resin system during curing process

The gelation and curing process of urushiol and MDI system were studied by dynamic rheology. Rheometer was used to monitor the changes of rheological parameters (storage modulus G', loss modulus G", complex viscosity η* and loss tangent tanδ) during continuous heating, isothermal aging and high-frequency heat treatment. And track the gelation and structural evolution of the curing process system. The results showed that the combination of isothermal aging, heating and high frequency were expected to be a simple strategy for low temperature curing or shortening the curing time of resin. The conversion α of the curing process was described by the evolution of storage modulus G'. The curing process can be described by autocatalytic model, and the fitting data are in good agreement with the experimental data. The model can be used for process optimization and further development of urushiol based materials.

Photothermal Self-Excitation of a Phase-Controlled Microcantilever for Viscosity or Viscoelasticity Sensing

This work presents a feedback closed-loop platform to be used for viscosity or viscoelasticity sensing of Newtonian or non-Newtonian fluids. The system consists of a photothermally excited microcantilever working in a digital Phase-Locked Loop, in which the phase between the excitation signal to the cantilever and the reference demodulating signals is chosen and imposed in the loop. General analytical models to describe the frequency and amplitude of oscillation of the cantilever immersed in viscous and viscoelastic fluids are derived and validated against experiments. In particular, the sensitivity of the sensor to variations of viscosity of Newtonian fluids, or to variations of elastic/viscous modulus of non-Newtonian fluids, are studied. Interestingly, it is demonstrated the possibility of controlling the sensitivity of the system to variations of these parameters by choosing the appropriate imposed phase in the loop. A working point with maximum sensitivity can be used for real-time detection of small changes of rheological parameters with low-noise and fast-transient response. Conversely, a working point with zero sensitivity to variations of rheological parameters can be potentially used to decouple the effect of simultaneous external factors acting on the resonator.

Rheological and electrical behavior of core–shell conduit comprising PCL-chitosan-gelatin/Al2O3 nanofibers and gellan-agar/poly aniline-graphene

In the field of neural regeneration, a channel guidance conduit with the potential of self-electrical stimuli would be considered a suitable candidate. In this study, the core–shell conduit structure composed of PCL-chitosan-gelatin-Al2O3 (shell) and gellan-agar-polyaniline-graphene (core) was fabricated. For nanofiber fabrication, the co-electrospinning technique was utilized and in-situ chemical oxidative polymerization was the method of polyaniline-graphene synthesis. The morphology, chemical, and structural behavior of electrospun nanofibers were characterized using SEM, EDX, FTIR and XRD. Polyaniline-graphene nanocomposite properties were studied with FTIR and XRD. Also, output voltage, rheology, gelation time, and swelling demeanor were evaluated. The successful synthesis of PCL-chitosan-gelatin-Al2O3 nanofibers and polyaniline-graphene was detected using FTIR and XRD spectra. The piezoelectricity property of core–shell conduit demonstrates that the output voltage of the structure has been increased from 339 to 480 mV with 0 and 1.5 (wt.%) of polyaniline-graphene samples respectively. The changes in rheological parameters (complex viscosity, storage, and loss modulus) in the cases of polyaniline-graphene nanocomposite incorporation have been observed. The MTT assay of PC12 cells in contact with neural conduit did not show any specific toxicity. Obtained results depict that the thermosensitive gellan-agar- polyaniline-graphene-filled PCL-chitosan-gelatin-Al2O3 nanofibers would be a possible candidate as a conduit.

ERYTHROCYTES AGGREGABILITY AND INTRACARDIAC HEMODYNAMICS IN PATIENTS WITH ATRIAL FIBRILLATION

According to the World Health Organization the morbidity of atrial fibrillations is 1-2% of the general population, which is extremely high number due to the severity of the disease. The frequency of morbidity will increase by about 2.5 times (1). Namely, the unfavorable epidemiological picture of atrial fibrillation makes the project relevant. There are numerous studies, although intracardiac hemodynamics and hemorheologycal parameters and their role in the course of atrial fibrillation have not been studied; We have studied the hemorheological profile in patients with atrial fibrillation. Changes of rheological parameters and hemodynamics were assessed against the background of rhythm disturbances. We examined 50 patients (women-22, men - 28, the average age of 65±10) and 20 healthy volunteers. We have studied the Index of the Erythrocytes aggregability, which is the area of aggregated erythrocytes divided by the full area of the erythrocytes. These new innovative methods “Georgian Technique” is created by Georgian scientists and they are famous in the world as direct, numeral and exact [G. Mchedlishvili, 2004; N. Maeda, 2010; M. Mantskava M., 2011]. Also, all patients the studies: ECG, ECHOcardioscopy was performed. After statistical processing of the material, it was found that erythrocytes aggregability is highly impaired in patients with permanent and persistent forms of atrial fibrillation. Mean value of EAI is 41.7 ± 10.4 compared to the control group, where the average EAI value is within 25.6 ± 1.2. The Index of erythrocytes aggregability (EAI) are significantly increased in inverse proportion to the decrease of the left ventricular ejection fraction. A negative correlation was revealed between the Index of erythrocytes aggregation and the left ventricular ejection fraction (R=0.4); According to the obtained data, changes of rheological parameters deepen in the wake of disruption of intracardiac hemodynamics; This confirms the notion that a small blood vessel is the "target" in the case of atrial fibrillation. From hemodynamic mechanisms rheology plays an important role. They are determinants of hemodynamic processes in the body (2).

The effect of plant components on the rheological properties of chopped semi-finished products from mulard meat

This article presents the results of an analysis to assess the effect of plant components on the rheological properties of chopped semi-finished products from mulard meat. Flour-ground talkan oatmeal, pea flour, white sesame flour and kelp algae were used as vegetable components. During the experiment, the analysis of changes in general deformation, plastic deformation, elastic deformation and modulus of elasticity was carried out. The nature of the change in the criterion of stickiness (adhesion) and consistency according to its five descriptors describing the consumer properties of products was also considered. The results of the study indicate a positive dynamics of changes in rheological parameters when plant components are introduced into the recipe. The analysis of the data obtained allows to establish 4% white sesame flour and 5% kelp as the recommended dosage for adding to the recipe of chopped semi-finished products from mulard meat.

Rheological properties of magnesium phosphate cement with different M/P ratios

Magnesium phosphate cement (MPC) with unique advantages of quick setting and high early-strength has been used as grouting materials. The rheological properties of MPC, being vitally important for site operation, need to be studied further. Dead burnt magnesia (MgO) and phosphate (ADP) are the main raw materials for preparing MPC. This study measured the rheological properties with different M/P ratios, and the mechanisms of M/P ratio were studied by characterizing the zeta potential, 1H NMR relaxation signal, water film thickness, mineral changes and electrical impedance. Experimental results indicate that both the yield stress (τ0) and plastic viscosity (η) decrease firstly and then increase gradually with increasing the M/P ratio from 2.5:1 to 4.5:1. Higher M/P ratio decreases the interparticle water film thickness and accelerates the initial hydration rate remarkably, which is responsible for the change in rheological parameters. Low field NMR, TG-DTG analysis and Nyquist plots confirm the quicker initial hydration in MPC with higher M/P ratio. The change in hydration products is very slight during the rheological property measurements. Nyquist plots show that the MPC paste with lower M/P ratios has more compact microstructure and lower porosity at several hours. In a word, initial hydration rate is the most important factor influencing the rheological properties of MPC, and the separation distance among solid particles is the secondary factor.

Correlation of the effectiveness of dispersing agents with different liquefaction mechanisms

Effective borehole sealing depends on many properties of the cement slurry. The rheological parameters are the most important. Designing the cement slurry with the required values of plastic viscosity, yield point or consistency coefficient contributes to the efficient performance of the cementing procedure and allows for effective filling of the cemented space outside the tubing. In order to adjust rheological parameters to technological requirements, dispersants are used. The operation of these plasticizers or superplasticizers is related to their chemical structure, which determines their liquefaction mechanism. Therefore, in order to properly select a fluidizing agent, it is beneficial to become familiar with its mechanism of operation, thanks to which it will be possible to use the optimal amounts for a given cement slurry recipe. The publication discusses the effectiveness of dispersing agents depending on their liquefaction mechanism. The research work carried out consisted in the modification of the cement slurry with the use of sodium salts of polycondensates of naphthalene sulfonic acids and a polymer dispersant based on carboxylates. Amounts of dispersant ranging from 0.05% (bwoc) to 1.0% (bwoc) were used. The rheological parameters described by means of five rheological models, i.e. Newton, Bingham, Ostwald de Waele, Casson and Herschele-Bulkley, were tested for the cement slurries. The main goal of the work presented in the article was to conduct a correlation analysis of the change in rheological parameters of slurries modified with dispersants belonging to different groups depending on their liquefaction mechanism. Thanks to this, it was possible to indicate the effectiveness of the dispersing additives depending on the amount of the fluid used belonging to a specific group. The work carried out is helpful in determining the optimal amount of dispersing agent depending on its type (mechanism of action).

Study of the Effect of Aggregate Geometry Characteristics on the Rheology of Asphalt Mortar Using Newly Developed Material Rheological Property Test Analyzer and Aggregate Image Measurement System

Abstract A new rheometer developed in the laboratory and the Aggregate Image Measurement System (AIMS) were used to study the effect of aggregate geometry characteristics on the rheological properties of asphalt mortar. AIMS was used to investigate the geometry characteristics (angularity index and Form 2-D) of two aggregates including steel slag and basalt. The results showed that steel slag had a better Form 2-D and angularity index, representing a better particle distribution and shape property. A material rheological property test analyzer was applied to evaluate the rheological properties of pure and styrene-butadiene-styrene (SBS)-modified asphalt and their asphalt mortars at 20°C and 40°C, and then the data were modeled through the simulation software. As a kind of rigid body, the addition of aggregate had a great influence on the rheological properties of asphalt. The experiment results indicated that, after the addition of aggregate or SBS, the rheological model of asphalt samples was still Burges model accompanied by the change of rheological parameters. As a kind of temperature-sensitive material, temperature was the most important factor for determining the rheological properties of asphalt. The addition of SBS promoted the elastic deformation of asphalt and restrained the viscous deformation of asphalt. The effect of aggregates with high Form 2-D and angularity index on the rheological properties of asphalt was weaker.

Effect of laboratory aging on chemistry and rheology of crumb rubber modified bitumen

Aging during construction and in-service substantially changes the chemical composition and physical properties of bitumen thereof influences the performance of asphalt pavements. The modification of bitumen by crumb rubber modifier (CRM) significantly increases the complexity of the aging mechanism and is expected to improve the aging resistance of bitumen. This study aims to investigate the effects of laboratory short-term and long-term aging on the chemistry and rheology of crumb rubber modified bitumen (CRMB). Neat bitumen and CRMB with four different CRM contents were studied. Fourier transform infrared spectroscopy and dynamic shear rheometer were employed to measure the change in the chemical composition and rheological properties of binders at different aging states. Bitumen hardening, which was rheologically revealed by the frequency sweep and multiple creep recovery test results, was also reflected in the growth of carbonyl and sulfoxide functional groups. In addition, the aliphaticity and aromaticity indices of binders before and after aging were also investigated. CRMB binders showed improved aging resistance compared to neat bitumen as reflected by the decreased carbonyl and sulfoxide indices as well as the lower change in rheological parameters. Higher resistance against aging was achieved when increasing the CRM content. The results also highlight the correlation between chemistry and rheology of bitumen. Among six selected mechanical parameters of binder, the non-recoverable creep compliance and percent recovery show better correlations with the combined chemical aging index (sum of carbonyl and sulfoxide indices) than the parameters derived from the linear viscoelastic region.

Wheat grain storage at moisture milling: Control of protein quality and bakery performance

To maintain grain quality and prevent loss, effective storage systems are required. To enable wheat flour of a certain quality to be extracted from grain, stored dry wheat must be humidified prior to milling. With the aim of reducing post-harvest drying stage costs for subsequent grain rehydration, the objective of this study was to optimize the wheat grain storage steps while maintaining the protein quality and baking performance using response surface methodology. A mixed 2 and 3 level design (3 factors) was used to optimize the independent variable (factors) values of grain moisture content (12% and 15%), temperature (14, 26, and 38°C) and storage time (4, 8, and 12-months). The quality of grain, flour, and baking performance were evaluated. It was possible to maintain the gluten protein quality at a low temperature and grain moisture. All of the flour evaluated provided a good baking performance, and there were no significant differences in specific volumes of treatments. Practical applications Dried wheat needs to be humidified before milling, a process named “water tempering” to enable suitable wheat flour extraction. New approaches could be aimed at improving grain quality and optimizing the post-harvest processing, to secure financial and environmental sustainability. One approach to reducing costs and post-harvest optimization is the storage of wheat with an adequate moisture level for use in the milling process, which would reduce costs in the post-harvest drying stage prior to subsequent grain rehydration. Our results showed only minor changes in rheological parameters with the different conditions studied, and these had no influence on the baking performance of samples evaluated.

Rheological studies and optimization of Herschel–Bulkley parameters of an environmentally friendly drilling fluid using genetic algorithm

The Herschel–Bulkley rheological parameters of an environmentally friendly drilling fluid formulated based on an Algerian bentonite and two polymers—hydroxyethyl cellulose and polyethylene glycol—have been optimized using a genetic algorithm. The effect of hydroxyethyl cellulose, temperature, pH and sodium chloride (NaCl) on the three-parameter Herschel-Bulkley model was also studied. The genetic algorithm technique provided improved rheological parameter characterization compared to the nonlinear regression, especially in the case of drilling fluids formulated with sodium chloride making it a better choice. Furthermore, the oscillatory test offered more reliable yield stress values. The rheological parameters were found to be very sensitive to different conditions. Yield stress and consistency index increased with increasing the hydroxyethyl cellulose concentration, reaching maximum at a temperature of 65 °C and decreased with decreasing pH and also when adding sodium chloride to the drilling fluid. The flow index changed inversely to yield stress and consistency index. The physical origins of these changes in rheological parameters were discussed and correlation between variation in rheological parameters and bentonite suspension properties were concluded. Based on these results, it is recommended to use the proposed formulation of drilling fluid at high temperature and when the formation of alkaline pH is encountered due to the gelation mechanism and to select the optimum concentration of NaCl to avoid degradation of the rheological parameters.

Development of hydrophilic gels containing coenzyme Q10-loaded liposomes: characterization, stability and rheology measurements

Objective: The aim of this study was to develop, characterize and evaluate stability of a gel containing coenzyme Q10 (Q10)-loaded liposomes, and enhance the stability of Q10 in the nanocarrier-containing gel compared to the conventional gel.Methods: Q10-loaded liposome dispersions prepared from unsaturated or saturated lecithin, were characterized for particle size, polydispersity index (PDI), zeta-potential, pH value, oxidation index, Q10-content and morphology, and incorporated into carbomer gel. Liposome gels and liposome-free gel were analyzed for flow properties, pH values, Q10-content, and liposomes size and PDI (liposome gels), 48 h after preparation and in predetermined time intervals during 6 months storage at different temperatures in order to predict their long term stability.Results: Liposomes were of small particle size, homogeneous, negatively charged, and their incorporation into gel did not significantly change (p > .05) their particle size and PDI. All gels revealed non-Newtonian, shear-thinning plastic flow behavior during storage with no marked changes in rheological parameters. Storage of gels did not significantly influence the pH value (p > .05), while it significantly decreased Q10-content (p < .05). Q10 was significantly more (p < .05) stable in liposome gel containing unsaturated lecithin liposomes (G1) than in gel containing saturated lecithin liposomes (G2) and liposome-free gel (G3).Conclusions: Q10-loaded liposome gel G1 was the optimal formulation, since during storage at different temperatures, it did not show significant increase in liposome size and PDI, it provided significantly higher stability for Q10 than other gels and its pH value was suitable for skin application. Due to limited Q10-stability it should be stored at 4 °C.

Effect of superplasticizers on the rheological properties of fly ash incorporated cement paste

The rheology is a study of flow of matter. Rheological behavior of cement paste changes with composition of cement, amount of mineral and chemical admixtures, family of superplasticizer, temperature etc. This paper explores the influence of superplasticizer dosage, superplasticizer family and mineral admixture dosage on the rheological behavior of cement paste. For this purpose cement pastes were prepared at a water cement ratio of 0.37 using OPC and different percentage of fly ash (15, 25, 35) and different dosages of superplasticizer (one from each family). Four families of superplasticizer used for this study are polycarboxylate ether, sulphonate melamine formaldehyde, sulphonate naphthalene formaldehyde and lignosulphates. Rheological tests were performed in a coaxial cylinder viscometer (Brookfield DV-II). Saturation dosage of the superplasticizers in the cement paste mixes with different percentage of fly ash replacement were obtained through marsh cone and mini slump tests on cement paste. Cement pastes were placed in the sample chamber of coaxial cylinder viscometer and shear stress produced measured with known shear rate ranging from 30 S to 65 S-1 applied to the fluid through the spindle. Rheological parameters like yield stress and plastic viscosities were calculated using Bingham and Herschel bulkley model. Change in rheological parameters of the cement paste with fly ash replacement percentage, superplasticizers dosage and family were measured and comparison is made

Numerical simulation of dynamic segregation of self-consolidating concrete (SCC) in T-box set-up

A CFD software was used to simulate free surface flow of SCC in the T-Box test. In total, seven simulations were developed to study the effect of rheological parameters on the non-restricted flow performance of SCC in both horizontal and vertical directions. Different suspending fluids having five plastic viscosity values between 10 and 50 Pa.s, three yield stress values between 14 and 75 Pa, one density of 2500 kg/m3, and one shear elasticity modulus of 100 Pa were considered for suspension of 178 spherical particles of 20-mm diameter and 2500 kg/m3 density. The results of the simulations are found to correlate well to changes in rheological parameters of the suspending fluid. Plastic viscosity was shown to be the most dominant parameter affecting flowability and dynamic stability compared to the yield stress. A new approach was proposed to evaluate performability of SCC based on a trade-off between flowability and dynamic stability.

Effect of modification with 1,4-α-glucan branching enzyme on the rheological properties of cassava starch

Steady and dynamic shear measurements were used to investigate the rheological properties of cassava starches modified using the 1,4-α-glucan branching enzyme (GBE) from Geobacillus thermoglucosidans STB02. GBE treatment lowered the hysteresis loop areas, the activation energy (Ea) values and the parameters in rheological models of cassava starch pastes. Moreover, GBE treatment increased its storage (G′) and loss (G″) moduli, and decreased their tan δ (ratio of G″/G′) values and frequency-dependencies. Scanning electron microscopic studies showed the selective and particular attack of GBE on starch granules, and X-ray diffraction analyses showed that GBE treatment produces significant structural changes in amylose and amylopectin. These changes demonstrate that GBE modification produces cassava starch with a more structured network and improved stability towards mechanical processing. Differential scanning calorimetric analysis and temperature sweeps indicated greater resistance to granule rupture, higher gel rigidity, and a large decrease in the rate of initial conformational ordering with increasing GBE treatment time. Pronounced changes in rheological parameters revealed that GBE modification enhances the stability of cassava starch and its applicability in the food processing industry.