Rheological Index Research Articles

Improving thermal cracking and fatigue cracking performance of hard asphalt binders with bio-renewable additives

Traditional hard asphalt, due to its low cost and excellent mechanical properties, is considered a favorable material for resisting permanent deformation under high-temperature conditions. However, its limited stress relaxation ability at medium and low temperatures significantly impairs its capacity to meet the cracking resistance requirements. To address the limitation, this study synthesized three green and sustainable bio-renewable additives derived from high oleic rapeseed oil. These additives aimed to improve the performance of hard asphalt at medium- and low-temperature conditions, thereby broadening its potential for application in green and low-carbon construction practices. Bending Beam Rheometer (BBR) tests were conducted to determine the critical low-temperature difference (ΔTc) to evaluate the thermal cracking resistance of bio-modified hard asphalt. The effects of the bio-additives on fatigue cracking resistance of hard asphalt were investigated using rheological indices, crossover frequencies, Glover-Rowe (G-R) parameters, and Linear Amplitude Sweep (LAS) tests. The results indicated that bio-additives effectively alleviated the stress in hard asphalt and reduced the asphalt’s susceptibility to thermal cracking by improving the flexibility and stress relaxation of the hard asphalt at low temperatures. Furthermore, the bio-additives substantially improved the ductility and toughness of hard asphalt at intermediate temperatures by lowering its strain sensitivity and increasing its fatigue cracking resistance. Additionally, the high oleic rapeseed oil-based derivatives notably reduced hard asphalt binder’s cracking induced by aging. Among the three bio-additives, acrylated epoxidized high oleic rapeseed oil (AEHORO) and epoxidized high oleic rapeseed oil (EHORO) were noticed to exhibit the most significant improvements in thermal cracking resistance and anti-aging properties, demonstrating superior load-bearing capacity at low temperatures. Overall, the developed bio-additives significantly improved both the thermal cracking and fatigue damage resistance of traditional hard asphalt, thus expanding its applications in pavements for various regions.

Research on the Rheological Properties and Diffusion Law of Coal-Based Solid Waste Geopolymer Grouting Material.

The rheological properties and diffusion law of coal-based solid waste geopolymer grouting material (CGGM) slurry were investigated by rheological property test and diffusion theory model derivation. Based on the power-law fluid constitutive equation, a theoretical model of slurry diffusion in an inclined fissure aquifer was established, and the effect of slurry grouting time on the slurry diffusion distance under different fissure widths, fissure inclination angles, and grouting pressures were analyzed. The results show that when coal gangue:cement:fly ash = 5:4:1, sodium silicate modulus 2.0, sodium silicate content is 10%, CGGM slurry's bleeding rate of 1%, the liquidity of 227 mm, the initial and final setting time is 412 min and 825 min, respectively, to meet the requirements of the grouting project. CGGM slurry is a typical viscosity time-varying power-law type fluid, and the slurry diffusion distance is positively correlated with the grouting pressure, fissure width, fissure inclination angle, and negatively correlated with the rheological index. The established theoretical model can provide a reference for the parameter design of CGGM slurry in grouting construction.

Numerical Thermal Analysis of Greased Rolling Bearing Considering Surface Topography and Plastic Deformation

ABSTRACTIn numerical studies of grease lubrication, thermal effect is often neglected and surface plastic deformation is almost not considered. This paper has developed a deterministic thermal plasto‐elastohydrodynamic lubrication (PEHL) model for grease‐lubricated rolling bearing. The influence of tangent modulus, rheological index and texture orientation on lubrication characteristics and temperature rise is analysed. The results show that increasing the rheological index of grease and decreasing the wavelength factor are obviously positive for improving lubrication behaviour. Since surface plastic deformation in the EHL state is at nanoscale, film thickness, friction coefficient and temperature rise of solid surfaces decline slightly with the decrease of tangent modulus.

Effect of polycarboxylate superplasticizer and temperature on the rheological properties of seawater-mixed ferric-rich sulfoaluminate cement-based composite slurries

In this study, the effects of polycarboxylate superplasticizer (PCE) and temperature on the rheological properties of seawater-mixed ferric-rich sulfoaluminate cement-based composite (FR-SCC) slurries were investigated. The results show that the viscosity of seawater-mixed FR-SCC slurries initially decreases and then stabilizes as PCE content increases. Moreover, PCE improves the shear-thinning behavior and the stability of the slurry. As temperature increases, the shear stress and rheological index of the slurry increase, while the consistency coefficient decreases. Furthermore, a constitutive equation is established to describe the rheological behavior of seawater-mixed FR-SCC slurries at different temperatures.

Exploring the effect of self-combustion gangue powder particle distribution on rheological behavior and hydration mechanism in cement-based systems

Solid waste-based mineral admixtures are widely employed as a partial replacement for Portland cement due to their superior performance and minimal carbon and environmental footprint. This study involves the production of self-combustion gangue powder (SCGP) with varying particle sizes achieved through crushing, screening, and grinding. The SCGP is subsequently blended with cement to form a self-combustion gangue powder-cement (SCGP-C) system with diverse particle size distribution. Rheological tests and hydration exothermic tests were conducted to investigate the rheological behavior and degree of hydration of the SCGP-C mixed system. The results show that SCGP enhances the plastic viscosity and thixotropy of the mixed slurry. However, when a finer SCGP (d50=1.36 μm) was used to replace 15 % of the cement for the same mass, the yield stress and rheological index of the slurry were reduced by 28.1 % and 15.4 % respectively compared to the control group, while the closed-packing of the SCGP-C system was obtained. When the cement was replaced by 15 % SCGP (mass substitution), the yield stresses of finer and coarser SCGP (d50=18.24 μm) and pure cement slurries were increased by 289.1 %, 67.3 %, and 29.2 %, respectively, at T=60 min compared to T=0 min. This suggests that the fineness of SCGP has a greater effect on the yield stresses of mixed slurries over time. Mixed slurries with different finenesses of SCGP all prolonged the hydration induction period and reduced the total exothermic heat of hydration. Incorporating 15 % finer SCGP extended the induction period of the mixed slurry by 27 min and increased the peak value of the main hydration curve. Appropriate incorporation of SCGP helps to improve the fluidity and early strength of mortar in the SCGP-C system and promotes the physical filling effect and the positive role of SCGP volcanic ash in the cement system.

Research on the Effect of Static Pressure on the Rheological Properties of Waxy Crude Oil

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

Finding possible diagnostic markers for differentiating benign and malignant thyroid tumors on example investigate of rheological properties1.

The functioning of the thyroid gland is a multi-component process that in some conditions may undergo alterations. The thyroid gland is part of the endocrine system that produces the iodine-containing hormones thyroxine and triiodothyronine. Thyroid hormones, control metabolism and energy, growth processes, maturation of tissues and organs, regulation of blood flow, and, therefore, providing vital functions of the body. The role of thyroid hormones in the regulation of blood flow is determined by the intensity of their production and the quantity in the blood. Presumably, in case of oncological and non-oncological diseases of the thyroid gland, the fluidity of the blood, which depends on the rheological properties, will be different. Our aim was investigating rheological characteristics for studying of changes of rheology in patients with thyrotoxicosis, with benign tumor pathology of the thyroid gland, with thyroid cancer and finding possible diagnostic markers for differentiating benign and malignant thyroid tumors. In this regard, we examined, using modern methods accepted in clinical practice, a standard list of recommended diagnostic tests in the group of patients (thyrotoxicosis: n = 25; benign tumor: n = 47), thyroid cancer: n = 35) and control group (n = 15), and with new original methods, parameters that describe the rheological properties of the blood, such as blood rheological index, volume, thickness, surface area of erythrocytes, erythrocyte aggregation index, deformation index, plasma viscosity, hematocrits. Against the background of relative changes in the studied values, it is necessary to pay attention to the fact that erythrocyte aggregation in patients with a benign form and control, as well as in patients with a malignant form and control, differ significantly from each other, in addition, there is a significant difference between aggregation in the group of patients with benign and control aggregation. malignant forms of the disease. It is significant that aggregability differs in patients with thyrotoxicosis and in controls. This indicates that erythrocyte aggregation is particularly informative. The blood rheological index most clearly demonstrated the difference between benign and malignant forms of the disease. Significantly changed compared to control in various forms of thyroid diseases. Additional diagnostic markers for differentiating benign and malignant thyroid tumors may be consideredeerythrocyte aggregation index and blood rheological index.

Study of some components of the influence and formation of blood flow in patients with "slow flow".

"Slow flow" is one very important concept in modern fundamental and clinical biomedicine. Slow coronary flow is indicative of delayed filling of the terminal coronary artery vessels, occurring in the absence of significant coronary stenosis. This group patient of patients exhibits a high incidence of disability and represents a significant financial and material burden for the state and the healthcare system in general. The primary objective of our study was to examine patients with slow coronary flow. We studied the standard parameters recommended by the international health care system (electrocardiography (by Medica QRS-12, Germany), through the electrical activity of a patient's heart by the electrical impulses (beating) of the heart; HC1(Germany); coagulogramma by Coatron M1 (Germany), troponin by AQT 90 (Germany); general blood test we used automatic human counting device HC1(Germany). Also, we investigate the original parameters (non-standard parameters, which we use in this pilot study) that we were first studied for this diagnosis and non-standard parameters. A general blood test showed that patients with slow flow had a higher blood leukocyte count than the control group, but the amount of hemoglobin was normal, the hematocrit was much higher than in the control group, and the platelet count was close to the lower limit of clinical standards.We obtained details of blood flow by coagulation situation, such as prothrombin time, prothrombin index, international normalized ratio, activated partial thromboplastin time, thrombin time, fibrinogen, and rheological properties such as index of erythrocyte aggregability, index of erythrocyte deformability, plasma viscosity, in silico blood rheological index. Blood flow can be considered as a superposition of vortices with similar frequencies and wave vectors that change after bifurcations or other obstacles in the vascular network. These factors together determine the conditions for structuring the flow of moving blood. Disruption or alteration of these factors results in slow flow. It has been found that the speed of blood flow in the coronary arteries depends on changes in the number and function of red blood cells. Slow flow is directly influenced by the aggregation and deformation of red blood cells, their number, and plasma viscosity. Consequently, the rheological status plays a crucial role in determining blood flow and its velocity.

Intermittent hypoxia training does not change erythrocyte aggregation indicators in young, healthy men.

The increasing popularity of hypoxic training as a training method to improve physical performance indicates the need to study the effects of this type of intervention on blood morphological and rheological indices, since the adaptive changes that follow such training mainly affect blood indices. In this study, the effects of a 4weeks of intermittent hypoxic training on blood morphological and rheological indicators in physically active men were assessed. Forty-eight young, physically active men, participated in the study. Participants were randomly divided into three groups: two training groups and a control group without intervention (CTRL). Each group consisted of 16 participants. Training groups performed interval training (three times per week, 4weeks, 12 workouts) under different conditions: in hypoxia (IHT; fraction of inspired oxygen (FiO2) = 14.4%) or in normoxia (NT; FiO2 = 20.9%). The control group performed only two workouts 4weeks apart. Blood was taken during the first and last training session at rest, and 3minutes after training. After the last training session, there was a significant increase in mean corpuscular volume and a decrease in mean corpuscular haemoglobin concentration measured at rest only in the IHT group. There was also a significant decrease in resting aggregation amplitude for the IHT and CTRL groups. There was no difference in change of post-exercise plasma volume between first and last training session. The applied intermittent interval training in conditions of normoxia and hypoxia had no significant impact on resting aggregation parameters. This suggest that training under hypoxic conditions does not cause adverse rheological changes.

Evaluation of cracking susceptibility of asphalt binders modified with recycled high-density polyethylene and polypropylene microplastics

The use of recycled plastics as modifiers for asphalt binder have gained attention in recent years. Studies have confirmed the enhancement in the rutting resistance of asphalt binder with the addition of these types of plastics, however there are controversies with regards to their long-term cracking performance. The long-term cracking performance of asphalt binder is directly influenced by their rheological properties. This study evaluated the fatigue performance of recycled High-Density Polyethylene (rHDPE) and recycled Polypropylene (rPP) modified asphalt binders using several rheological indices including the Superpave intermediate-temperature PG (G*sin δ), fatigue life (Nf), complex modulus (G*), phase angle (δ), the Glover-Rowe (G-R) parameter, the crossover temperature (Tδ=45°), the rheological index (R-value), the peak shear stress, failure strain and the yield energy, as well as a newly developed monotonic cracking index (MCI). Additionally, the influence of the process of mixing plastic with asphalt at high temperatures and shear rate on the cracking performance was also investigated. Results indicated that long term cracking performance were not consistent across all rheological indices. While Nf indicated improved overall cracking performance with the addition of rHDPE and rPP, G*sin δ, G-R parameter, R-value, Tδ=45°, and MCI indicated susceptibility to cracking with the addition of these recycled plastics.

Linking Chemical Structure to the Linear and Nonlinear Properties of Asphalt Binders

The study described in this paper aims to establish the relationship between the chemical composition and rheological properties of asphalt binders in both the linear viscoelastic (LVE) and nonlinear viscoelastic (NLVE) domains. Two asphalt binders with different penetration grades were subjected to four distinct aging treatments of varying severity, resulting in changes in their chemical fingerprints. Chemical characteristics of the asphalt binders were analyzed using thin-layer chromatography (TLC), Fourier Transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Frequency sweep tests were conducted to evaluate the LVE behavior of the asphalt binders, while multiple stress creep recovery (MSCR) tests were employed to assess their NLVE properties. With regard to the LVE properties, rheological index ( R) and zero shear viscosity (ZSV) derived from the Christensen-Anderson-Marasteanu (CAM) model exhibited high correlations with FTIR and molecular weight distribution (MWD) parameters. Additionally, the polydispersity index (PDI) displayed a stronger correlation with LVE-based parameters. Findings from the MSCR tests revealed that the sensitivity of the percentage recovery ( %R) to chemical composition, as opposed to nonrecoverable creep compliance ( Jnr), can be largely attributed to the degree of nonlinearity. Furthermore, it was observed that lower molecular weight molecules exert a greater influence on %R in the nonlinear domain. Finally, it was found that Jnrslope is a more reliable parameter than Jnrdiff for assessing the effects of chemical makeup on stress and temperature sensitivity.

Rheological properties of seawater-mixed seashell powder calcined slag cement slurries: Effect of polycarboxylate superplasticizer and temperature

In this study, the effects of temperature and a polycarboxylate superplasticizer (PCE) on the rheological properties of seawater-mixed seashell powder calcined slag cement (SCSC) slurries were examined, revealing the mechanism of action of the PCE in them. The results showed that the shear stress and viscosity of the seawater-mixed SCSC slurries tended to decrease and then increase with increasing PCE content, reaching a minimum value at 0.8% PCE content, reducing the viscosity by 31.8% compared to the SCSC slurry without PCE. Temperature variations did not change the flow pattern of the seawater-mixed SCSC slurries; however, the rheological parameters were greatly affected. The viscosity, shear stress, and consistency coefficient decreased gradually with increasing temperature, whereas the rheological index exhibited the opposite trend.

Macro-micro correlation analysis of rheological characteristics for composite modified asphalt

Purpose This study aims to investigate the micro mechanism of macro rheological characteristics for composite modified asphalt.Grey relational analysis (GRA) was used to analyze the correlation between macro rheological indexes and micro infrared spectroscopy indexes. Design/methodology/approach First, a dynamic shear rheometer and a bending beam rheometer were used to obtain the evaluation indexes of high- and low-temperature rheological characteristics for asphalt (virgin, SBS/styrene butadiene rubber [SBR], SBS/rubber and SBR/rubber) respectively, and its variation rules were analyzed. Subsequently, the infrared spectroscopy test was used to obtain the micro rheological characteristics of asphalt, which were qualitatively and quantitatively analyzed, and its variation rules were analyzed. Finally, with the help of GRA, the macro-micro evaluation indexes were correlated, and the improvement efficiency of composite modifiers on asphalt was explored from rheological characteristics. Findings It was found that the deformation resistance and aging resistance of SBS/rubber composite modified asphalt are relatively good, and the modification effect of composite modifier and virgin asphalt is realized through physical combination, and the rheological characteristics change with the accumulation of functional groups. The correlation between macro rutting factor and micro functional group index is high, and the relationship between macro Burgers model parameters and micro functional group index is also close. Originality/value Results reveal the basic principle of inherent-improved synergistic effect for composite modifiers on asphalt and provide a theoretical basis for improving the composite modified asphalt.

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives.

In the practical application of hydraulic rotating machinery, it is essential to thoroughly explore drag reduction and rheological characteristics of drag-reducing additives to optimize machinery efficiency and reduce equipment consumption. This paper combines simulation and experimental approaches to investigate the drag-reduction performance and rheological properties of drag-reducing additives. Numerical simulations are initially conducted to investigate the shear-thinning properties of drag-reducing fluid and explore variations in drag-reduction rate. Turbulent phenomena characteristics are described by analyzing turbulent statistical quantities. Subsequently, the rheological behaviors of polyethylene oxide (PEO), cetyltrimethyl ammonium chloride (CTAC), and their mixed solutions under different conditions are scrutinized using a rotational rheometer. The findings indicate that the drag reduction effect amplifies as the rheological index n and characteristic time λ decrease. The numerical simulations show a maximum drag reduction rate of 20.18%. In rheological experiments, a three-stage viscosity variation is observed in single drag-reducing additives: shear thickening, shear thinning, and eventual stabilization. Composite drag-reducing additives significantly reduce the apparent viscosity at low shear rates, thereby strengthening the shear resistance of the system.

Do different chemical and rheological properties act as effective and critical indicators for efficiency evaluation of rejuvenated bitumen?

This study investigates the impacts of rejuvenator type/dosage and the aging degree of bitumen on the chemical and rheological properties of rejuvenated bitumen, and propose critical chemo-rheological indicators for evaluating rejuvenation efficiency. Moreover, the potential connections between essential chemical and rheological indices of rejuvenator-aged bitumen blends are explored. Results indicate that chemical indices show linear relationships with rejuvenator dosage and vary depending on the rejuvenator type and aging level of bitumen. All rejuvenators can regenerate certain rheological parameters of aged bitumen to varying degrees, but cannot restore the crossover modulus (Gc). Various rheological indices exhibit different correlations with rejuvenator dosage and sensitivity degrees to the discrepancy in rejuvenator type and aging degree of bitumen. Critical chemical and rheological indicators are proposed based on their sensitivity levels to influence factors, with the aromaticity index (AI), carbonyl index (CI), and sulfoxide index (SI) as effective chemical indices and the complex modulus (G*), crossover frequency (fc), and high-temperature master curve area (AMH) as critical rheological indices for rejuvenation efficiency evaluation. The study finds that the magnitude of rejuvenation efficiency for four rejuvenators is Bio-oil > Engine-oil > Naphthenic-oil > Aromatic-oil, and the linear correlations between the critical chemical and rheological indices, together with their rejuvenation percentages, are significantly affected by the rejuvenator type and aging level of bitumen.

Laboratory short-term aging of crumb rubber modified asphalt: RTFOT temperature optimization and performance investigation

Improper disposal of substantial scrap tires can result in significant environmental issues, such as air pollution, water resources, and soil contamination. The scrap tires can be turned into valuable materials by preparing tire rubber powder into Crumb rubber modified asphalt (CRMA). This method can effectively reduce environmental pollution and achieve the concept of energy conservation, environmental protection, and low-carbon. However, during the production process of CRMA mixtures, the elevated construction temperature may induce more severe short-term aging of the mixtures. The standard laboratory short-term aging scheme of asphalt binders, the Rolling Thin Film Oven Test (RTFOT), cannot simulate the short-term aging of CRMA due to the increase in construction temperature. Besides, the determination methods and indices of RTFOT aging temperature are still unclear and inconsistent. In this study, three CRMA binders were treated by RTFOT with five temperatures, and the short-term oven aging (STOA) protocol was conducted on CRMA mixtures with three types of gradations. Firstly, the chemical and rheological performance of CRMA binders and mixtures were investigated by conducting Gel permeation chromatography (GPC), Fourier transformation infrared spectroscopy (FTIR), Dynamic shear rheology (DSR) tests, and Bending beam rheometer (BBR) test. Then, the equivalent aging temperatures were determined to optimize RTFOT temperatures by comparing the chemical indicators of binders and mixtures. Finally, the correlations of chemical and rheological indices were established, and the rheological properties of aged asphalt in mixtures were predicted. The analysis results indicate that suitable RTFOT temperature is not only related to the technical routes and viscosity of CRMA binders, but also relevant to the mixture gradations. Binders with higher viscosity need elevated RTFOT temperatures from 173 °C to 193 °C, especially simulating short-term aging of mixtures with higher air voids. The swelling and degradation of crumb rubber contribute to the enhancement of the anti-aging performance. The aging index (AI) can reflect the anti-aging performance of CRMA binders, and the variation of AI can validate the rationality of the optimized RTFOT temperatures.

Slip Backflow of Polymers in Elastic Fractures for Subsurface Heat Recovery

This research delves into the complexities of backflow phenomena in finite-length and flat-walled fractures with elastic walls, specifically focusing on power-law fluids, whose shear-thinning behavior distinguishes them from Newtonian fluids. We model the backflow process under the lubrication approximation and by incorporating the linear Navier slip law. We numerically examine the influence of parameters such as slip length, fluid rheology, and external pressure on the backflow propagation of the carrier fluid. Our findings underscore the significant role played by the rheological index in determining the fracture closure rate. Additionally, our investigations highlight the marked effect of external pressure variations on pressure distribution within the fracture. Notably, the friction coefficient at the fracture walls, as denoted by a dimensionless slip number, exhibits limited influence on the fundamental dynamics of the problem. These insights advance our understanding of power-law fluid backflow and have wide-ranging applications across various engineering disciplines.

Research on slurry diffusion and seepage law in mining overburden fractures based on CFD numerical method

It is of great theoretical significance and engineering application value to research the diffusion law of slurry in mining fractures of rock strata to enrich grouting theory and improve grouting sealing effect. In this paper, the law of grout diffusion in fractures under different working conditions is systematically explored and analyzed, and a numerical simulation scheme of grout diffusion in a single slab crack is established. Then, the diffusion law of grouting slurry in crack under different rheological index and different consistency index is further investigated. The results show that the diffusion time of grouting slurry has no relation with the rheological index. The grout pressure at the same point increases with the increase of rheological index. When the rheological index increases by 0.1, the grout pressure increases by about 12.5%. The closer the grouting mouth is, the more the grouting pressure is affected by the rheological index. There is little relationship between the diffusion time of grouting slurry and consistency index. The grout pressure at each measurement point increases with the increase of the consistency index. When the consistency index increases by 1, the grout pressure increases by about 15% on the basis of the origin. The closer the grouting mouth is, the more the grouting pressure is affected by the consistency index. In engineering practice, when grouting slurry with large rheological index or consistency index exists, it is necessary to moderately increase the grouting pressure value.

Effect of pre–shearing regimes on rheological parameters of cement paste

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

Alterations of Body Composition, Blood Morphology and Fibrinogen Concentration after Vibration Therapy in Older Adult Women: A Randomized Controlled Trial.

Vibrotherapy is one of the methods of physical therapy. Vibration, like various forms of physical activity, affects metabolic processes and health. The aim of this study was to assess the influence of thirty vibration sessions on body composition, hematologic and rheological indexes of blood, and protein and fibrinogen concentration in elderly women's blood. The study included 69 women, aged 60-70 years (mean age 64.6 ± 2.9), who were randomly and parallel assigned into: the vibrotherapy group 1 (G1) that took part in vibrotherapy on the Knees module, the vibrotherapy group 2 (G2) that took part in vibrotherapy on the Metabolism module, and the control group (CG) without interventions. In all patients, the following assessments were performed twice-baseline and after thirty vibrotherapy sessions: an assessment of body composition, a complete blood count with a hematology analyzer and erythrocyte aggregation by a laser-optical rotational red cell analyzer; total plasma protein and fibrinogen concentrations were established, respectively, by biuret and spectrophotometric methods. Intergroup (between groups) and intragroup (within each group) changes were statistically evaluated. After applying thirty vibration sessions, a decrease in body composition parameters (BM, body mass G1, p < 0.05; G2, p < 0.001 and FFM, fat free mass G1, p < 0.05; G2, p < 0.05) was confirmed in both intervention groups and BMI, body mass index in G2 (p < 0.05). It was found that, in G2, changes in erythrocyte aggregation indexes (T ½, half time kinetics of aggregation, p < 0.05 and AI, aggregation index, p < 0.05) and decrease of fibrinogen concentration (p < 0.05) took place. A series of thirty vibration sessions did not cause significant alterations in blood morphological parameters; therefore, vibrotherapy did not disturb hematological balance. Vibration sessions had a positive effect on BM, BMI, AG and fibrinogen concentration in the studied women, indicating the usefulness of this form of activation in older adults. Due to a decrease in FFM observed in the study, vibrotherapy should be employed in conjunction with physical exercise and other forms of physical activity in the group of older adults.