Segregation Of Mixtures Research Articles

Effects of cement paste viscosity on the properties of lightweight expanded polystyrene concrete

Lightweight expanded polystyrene concrete (EPS-C) offers several advantages, including low density, sound resistance, and good thermal insulation. These characteristics are contributed by the use of expanded polystyrene (EPS) with a closed cellular structure, which is non-absorbent, hydrophobic, and low-density (around 6.9 kg/m³). Since EPS is much lighter than cement paste, the viscosity of the paste plays an important role indirectly affecting segregation and the properties of EPS-C mixtures. This paper presents the experimental results of the viscosity and its influence of cement paste on both the segregation of the concrete mixture and thecompressive strength of EPS-C. The research revealed that a viscosity of cement paste below 50 mPa.s resultsin segregation of the concrete mixture. As the viscosity increases, the degree of segregation decreases. However, when the viscosity exceeds 180 mPa.s, using a viscosity-modifying admixture becomes a good solution to prevent segregation in EPS-C mixtures. Therefore, the optimal viscosity range for the binder paste to ensure the concrete mixture does not segregate is between 50 and 180 mPa.s.

Experimental study on the combined influence of particle shape, density, and size on segregation behavior in binary and ternary granular mixtures

Segregation of granular materials is a common experience; however, a few studies consider the segregation of granular mixtures characterized by variations in particle shape. Additionally, many particle systems in industry and geophysics consist of nonspherical particles. In the present study, we conducted a series of experiments to investigate the influence of particle shape, density, and size on the dynamic characteristics and segregation behavior in binary and ternary granular mixtures. Our experimental findings demonstrated a noteworthy correlation between the final steady-state segregation intensity and the proportion of non-spherical beans and cube-shaped particles in a ternary granular mixture. Specifically, the presence of beans, which are larger than the other particles, in a binary and ternary granular mixture increased the size-induced segregation phenomenon. Conversely, the steady-state segregation intensity decreased as the proportion of cube particles, which were less dense but of the same volume as the other materials, increased in a ternary granular mixture, indicating a mitigation of density-induced segregation. The study also discusses the relationship among the dynamic angle of repose, dynamic properties, and segregation behavior arising from the effects of shape, size, and density in binary and ternary granular mixtures.

Temporal Coherence Shapes Cortical Responses to Speech Mixtures in a Ferret Cocktail Party.

Segregation of complex sounds such as speech, music and animal vocalizations as they simultaneously emanate from multiple sources (referred to as the "cocktail party problem") is a remarkable ability that is common in humans and animals alike. The neural underpinnings of this process have been extensively studied behaviorally and physiologically in non-human animals primarily with simplified sounds (tones and noise sequences). In humans, segregation experiments utilizing more complex speech mixtures are common; but physiological experiments have relied on EEG/MEG/ECoG recordings that sample activity from thousands of neurons, often obscuring the detailed processes that give rise to the observed segregation. The present study combines the insights from animal single-unit physiology with segregation of speech-like mixtures. Ferrets were trained to attend to a female voice and detect a target word, both in presence or absence of a concurrent, equally salient male voice. Single neuron recordings were obtained from primary and secondary ferret auditory cortical fields, as well as frontal cortex. During task performance, representation of the female words became more enhanced relative to those of the (distractor) male in all cortical regions, especially in the higher auditory cortical field. Analysis of the temporal and spectral response characteristics during task performance reveals how speech segregation gradually emerges in the auditory cortex. A computational model evaluated on the same voice mixtures replicates and extends these results to different attentional targets (attention to female or male voices). These findings are consistent with the temporal coherence theory whereby attention to a target voice anchors neural activity in cortical networks hence binding together channels that are coherently temporally-modulated with the target, and ultimately forming a common auditory stream.

Segregation and mixing of binary mixtures of spherical particles in a bubbling fluidized bed

Abstract This work reports a CFD-DEM study on the segregation and mixing of binary mixtures of particles in a bubbling fluidized bed. A simplified mixing index was applied to determine the instantaneous mixing state in the bed, with which the effects of superficial gas velocity and initial packing state on the fluidization behavior were further discussed. For the well-mixed initial conditions, the mixing index decreases with fluidization time until a dynamic equilibrium between segregation and mixing is achieved. In contrast, the mixing index first increases and then decreases with fluidization time for completely-segregated initial conditions. However, the final equilibrium between segregation and mixing will not be affected by initial packing states for a given superficial gas velocity. Moreover, the bubbling behavior shows a marked impact on segregation and mixing, i.e., mixing is enhanced during the formation and grow-up of bubbles, while segregation is strengthened during the eruption of bubbles. This makes it possible to improve the fluidization of binary mixtures of particles based on the bubbling behaviors in the fluidized bed.

Pattern dynamics of density and velocity fields in segregation of fluid mixtures.

We present comprehensive numerical results from a study of model H, which describes phase separation kinetics in binary fluid mixtures. We study the pattern dynamics of both density and velocity fields in d = 2, 3. The density length scales show three distinct regimes, in accordance with analytical arguments. The velocity length scale shows a diffusive behavior. We also study the scaling behavior of the morphologies for density and velocity fields and observe dynamical scaling in the relevant correlation functions and structure factors. Finally, we study the effect of quenched random field disorder on spinodal decomposition in model H.

A new method for determination of segregation stability of pumped ready‐mixed concrete: Rapid wet‐sieved test

AbstractIn the process of pumping, the segregation of concrete mixture will lead to the difficulty of construction, and even the possibility of pipe blocking. There is a lack of a quickly evaluation for on‐site construction. In order to solve this problem, a rapid wet‐sieved test was proposed in this study and then its feasibility was evaluated based on concrete mixes with different water–cement ratios. Subsequently, the influence of sand ratio on the segregation degree of concrete was investigated. The test results show that a combination of 2.36 mm screen size and 20 s vibrating time did the best. The wet‐sieved mortar content and stratification degree were increased by 4.6%–25.2% and 0.3%–17.9% by pumping, respectively. With the sand ratio increasing from 0.40 to 0.60, the pumping pressure decreased by 51.9%. The linear fitting correlation between pumping pressure and wet‐sieved mortar content (0.96) is better than that between pumping pressure and stratification degree (0.85), which indicates that the proposed test method can reliably characterize the degree of segregation during the pumping of ready‐mixed concrete.

Effects of pellet-sinter interaction parameters on component segregation and bed porosity considering flow velocity and mixture composition: A DEM study

Bed permeability is a crucial factor in blast furnace performance which depends on the material distribution achieved through charging. Since a homogeneous bed of pellet and sinter is recommended, it is crucial to understand whether segregation of the pellet-sinter mixture occurs during charging. The Discrete Element Method is useful in this regard; however, simulations of pellet-sinter mixture charging currently lack credibility since pellet-sinter interaction parameters have not yet been calibrated and validated. Determining pellet-sinter interaction parameters will require significant efforts, so it is useful to know whether mixture segregation and the resulting bed permeability are sensitive to these parameters. In this work, we investigate to what extent the restitution coefficient, sliding friction coefficient and rolling friction coefficient between pellet and sinter affect segregation during bed formation and the resulting permeability in terms of porosity using a simplified charging setup. The investigation is done for different mixture compositions and flow velocities, and analysis settings including sample size and sampling directions. We conclude that all parameters affect segregation and porosity, regardless of the composition and velocity. Hence, all mixture parameters including the interaction parameters between the components must be carefully calibrated when developing a model for predicting permeability.

Analyzing the potency of Viscosity Modifying Agents on the Characteristics and Static Segregation of Fresh and Hardened Fluid Concrete

Self-compacting concrete (SCC) represents a recent advancement in the field of concrete technology due to its ease of handling and placement. In order to regulate the internal integrity of the concrete, a supplementary mixture component is employed. The term used to refer to this particular component is a viscosity-modifying agent (VMA). Different quantities of VMA were incorporated into the concrete mixture in order to evaluate its performance in both the fresh and hardened states. This study focused on the impact of VMA (Viscosity Modifying Agent) on various characteristics of concrete mixes. Specifically, the features under examination included flowing time, slump flow, flow time into a 500-mm diameter, and resistance to vertical segregation. In contrast, a measurement was conducted on the compressive strength of the cured concrete. The utilization of the column of segregation test allows for the identification and assessment of static segregation in SCC mixtures. This test offers a direct quantitative determination of the stability of segregation in fresh concrete. The purpose of this experiment is to determine the precise quantity of coarse aggregate with a diameter above 8 mm present within a specimen of 300 mm in height. This can be achieved by conducting sedimentation tests at a specific time interval of 30 minutes after the pouring of concrete. The research results indicate that the addition of VMA had a substantial impact on the rheological characteristics of the concrete mixture. It effectively stabilized the mixture, minimized static segregation, and improved the compressive strength when compared to the reference mixture without VMA. Furthermore, a comprehensive illustration of the segregation phenomenon is provided by the column of static segregation tests.

An Experimental Analysis of Lean Binary Mixture Segregation in a Continuous Liquid Fluidized Bed

This study examined the phenomenon of particle segregation in lean-phase binary mixtures, with a specific focus on the effect of particle size variations while flowing over a continuous liquid fluidized bed (LFB). The experimental configuration included a cylindrical column with a 72 mm internal diameter and 3 m vertical height. The binary mixture considered for this investigation was made up of solid materials that were rich in flotsam and jetsam. The study encompassed various factors, including liquid velocity, solid feed rate, and feed composition, in order to examine the separations containing flotsam and jetsam. A segregation index was calculated for each of the various combinations. On the other hand, the fluidization of the blend consisting of two solid components displayed notable differences in its behavior when compared to the reported effects of particle separation in any of the mixtures. Empirical correlations have been employed to establish relationships between variables, particularly with respect to solid entrainment and top and bottom product purity levels.

Overview of drum mixer designs suppressing segregation of bulk mixture

The mixing process is used in various areas of production to produce different types of bulk mixtures. These include agricultural mixtures, semi-finished products, bone cements and others. This process is the movement of particles of bulk material components in the space of the working capacity. Mixers of various types are used to set the components of the mixture in motion. One of the most common types of mixers are drum mixers. The main challenge that must be addressed when developing a mixer design is to reduce the segregation that occurs when mixing two or more components of a mixture. Segregation is associated with different particle sizes and densities of the various components. The object of the study is the designs of drum mixers developed in the last decade. All considered designs are divided into three groups, differing in the method of eliminating segregation. The subject of the study is the design features of these mixers. The results of the work were the determination of the most suitable method for eliminating segregation - the use of additional mixing elements in the center of segregation of the mixture, and based on this method, the development of two new designs of drum mixers. The first mixer with sectional radial separators allows you to repeatedly separate the mixture and move the particles of its components relative to each other. This allows you to reduce the degree of segregation of the mixture. The second mixer developed not only extends the residence time of the mixture particles in the drum, but also allows for the creation of crossing and recirculating flows of material. This also helps reduce or prevent segregation.

Towards compartmentalized micelles: Mixed perfluorinated and hydrogenated ionic surfactants in aqueous solution

HypothesisAqueous solutions of mixtures of hydrogenated and perfluorinated ionic surfactants are known to display anomalous aggregation behavior due to the mutual phobicity between hydrogenated and perfluorinated chains. Despite all efforts, different experimental limitations prevented so far a definite interpretation of the existing experimental results: both intermicellar and intramicellar segregation remain acceptable possibilities. MethodThe potential for segregation of mixtures of fluorinated and hydrogenated ionic surfactants in water was assessed using atomistic molecular dynamics simulations. Aqueous mixtures of hydrogenated and perfluorinated ionic surfactants were studied: mixtures of anionic surfactants (sodium dodecylsulfate (SDS) + sodium perfluoro-octanoate (SPFO)) and catanionic surfactants (decyltrimethylammonium bromide (DeTAB) + SPFO) were simulated. FindingsThe mixture of anionic surfactants, SDS + SPFO, exhibits clear intramicellar segregation between fluorinated and hydrogenated chains, displaying hydrogenous-rich and fluorous-rich regions. Compartmentalized micelles are thus clearly formed. The simulation results also suggest the possibility of intermicellar segregation. Conversely, catanionic mixtures of DeTAB and SPFO in water solution assemble into a large oblate structure, containing all available molecules in the simulation box, resembling a double layer membrane or a vesicle wall. In this case mixing between fluorinated and hydrogenated surfactants is dictated by charge alternation.

Experimental study on rolling segregation of cement stabilized macadam

Indoor simulated mixing building storage bin unloading, forming conical piles. The effects of falling distance, mixing time and water content on rolling segregation of cement-stabilized macadam were analyzed by three indexes, including repose Angle of pile, key sieve passing rate and cement dosage. The results show that the segregation of mixture can be increased significantly with the increase of drop distance. The separation degree of the mixture can be effectively controlled by controlling the unloading distance within 70 cm. Mixing time has little effect on the Angle of rest and gradation segregation of the mixture, but has significant effect on the distribution uniformity of cement. Indoor mixing time should reach more than 45 s. When the mixing water content is less than the optimal water content, the segregation of the mixture is serious. When the moisture content increased to 1.5 %, the mixture showed obvious bleeding phenomenon. The mixture shall not be lower than the optimal moisture content before the crushing is completed, and the moisture content increase shall not exceed 1.5 % of the optimal moisture content as far as possible.

Assessment of pellet mixture segregation during machine capsule filling

Assessment of pellet mixture segregation during machine capsule filling

Mechanistic evaluation of segregation in HMA mixtures

Segregation in hot mix asphalt (HMA) mixtures is defined as the separation of the coarse aggregate particles in the mixtures from the rest of the mass. Segregation can be a result of aggregate stockpiling and handling, production, storage, truck loading practices, construction practices, and equipment adjustments. Segregation is usually evaluated visually, which is considered as a subjective method with no definite limits and depends on the evaluator’s opinion.This study uses two mechanistic surface texture indicators, i.e., mean texture depth (MTD) that is measured using sand patch method and mean profile depth (MPD) using laser texture profilometer to evaluate if a road section is segregated or not.The sand patch method is standardized in ASTM E965 -15 (2019) “for Measuring Pavement Macrotexture Depth Using Volumetric Technique”. MPD is covered by the international standards ASTM E1845-15 “Standard Practice for Calculating Pavement Macrotexture Mean Profile Depth”.Using both measured MTD values at grid point crossings, and average MPD values at 25 m intervals in the wheel paths, in addition to the use of statistical analysis of the obtained data, assuming that the obtained data are normally distributed and finding the 95% probability limits of the MTD and MPD values, it is possible to prove the closeness of the obtained texture depth indicator data, homogeneity of the road section, and that the segregation is only present at very limited localized locations.

A mass transfer cavitation model for the numerical flow simulation of binary alkane mixture segregation

Based on the Rayleigh bubble dynamics equation a mass transfer model for cavitation of binary alkane mixtures is presented. Raoult's and Dalton's law, simple mixing rules, and an accurate Equation of State are utilized. The model is implemented into an in-house CFD code. For solver validation pure species literature cases are taken. The method is applied to a lighter n-octane/n-heptane and a heavier n-dodecane/n-heptane mixture in a rarefaction tube and a hydrofoil test case. Segregation of the species is observed during cavitation due to their different mass transfer rates. While for the lighter mixture, mass transfer of both species only moderately deviates, a significantly higher mass transfer of n-heptane compared to n-dodecane is observed for the heavier mixture, where the saturation pressure differs two orders of magnitude between the mixture ingredients. The strong segregation of the heavier mixture is associated with a predominant amount of n-heptane in the vapor phase. As a consequence, vapor composition is strongly affected by the volatilities of mixture ingredients.

Real-time identification of asphalt mixture segregation during paving process using digital imaging technique and Four-side static moment

The uniformity of the asphalt mixture is severely affected by aggregate segregation during the paving process, and there are many studies that indicate that segregation may lead to early pavement damage. This study aims to develop a real-time asphalt mixture segregation identification algorithm during paving process based on digital imaging technique and the static moment method. Static moments of the aggregate particles relative to the four boundaries of the image were calculated as an evaluation parameter, and the dispersion coefficient between the static moment of segregated asphalt mixture and the value of uniform asphalt mixture was calculated to quantify the degree of segregation. The algorithm was applied in a filed construction project in Yunnan, China. Comparing the result from the proposed algorithm with the sand patch test shows that the proposed algorithm is capable of detecting the segregation of an asphalt mixture in real-time and that it is accurate in identifying the degree of segregation. In addition, the proposed algorithm is more accurate than the sand patch test for areas where the gradation meets the standard but the distribution of the aggregate particles is not uniform.

Waste valorization in fluidized bed reactor: Statistical assessment of particle segregation in binary mixtures of sand and Tetra Pak residues

The fluidized bed reactor is an alternative for aluminum recovery and waste valorization of polyolefins from the polyethylene/aluminum composite (LDPE/Al). The sand is typically added as an inert particle into the fluidized bed to enhance heat and mass transfer. Such addition, however, can lead to particle segregation and compromise the reactor start-up. As a research novelty, this paper uses a 33-factorial experimental design with three central points to assess particle concentration uniformity in a fluidized bed composed of LDPE/Al and sand mixtures. A statistical procedure permits an evaluation of the factors effect of the LDPE/Al mass fraction (XC% w/w), the air velocity ratio (V/Vmf), and the diameter ratio of LDPE/Al and sand (dC/dS) on the bed mixing index (IM). Results show that only the dC/dS and V/Vmf ratio affects the IM. Data analysis reveals that fluidized beds reach axial particle uniformity with 0.67 dC/dS, 10 % V/Vmf, and 15% wt. LDPE/Al composite. The statistical model developed accurately predicts the IM, with an error of less than 15%. Such results allow applying a fluidized bed for waste-derived fuels, aluminum recovery from carton packaging wastes, and energy saving of 0.745 MWh per each ton of recovered carton package annually.

Determination of optimum VMA utilization dosage in cementitious systems: In terms of rheological and flowability properties

In mixtures such as self-compacting concrete (SCC) and 3D printing concrete (3DPC) having a high amount of binder, utilization dosage of water-reducing admixture (WRA) is increased to provide the rheological requirements. In such a case, in addition to the increase in cost, the presence of a high dosage of WRA in the system can cause segregation in the SCC mixture and a decrease in the buildability capacity of the 3DPC mixture. However, the addition of viscosity-modifying admixture (VMA) to the mixture together with the WRA reduces the risk of bleeding and segregation in SCC mixtures and increases shape stability and buildability in 3DPCs. Nevertheless, it was emphasized that these properties were seriously affected by the VMA dosage. It was aimed to determine the optimum VMA utilization dosage by examining the effect of dosages of VMA on the rheological properties and flow performance of paste mixtures in this study. Paste mixtures containing 4 different dosages of VMA (0%, 0.2%, 0.4% and 0.6%) were prepared. In all mixtures, the w/c and the WRA dosage were 0.35 and 0.2%, respectively. The rheological properties of the mixtures were evaluated by measuring the dynamic yield stress (DYS), final viscosity value and structural build-up (Athix) parameters. In addition, flowability of mixtures was also examined. DYS value of all mixtures decreased with the increase in VMA utilization dosage. The highest viscosity and Athix values were measured in the mixture containing 0.4% VMA. However, the lowest DYS, viscosity and Athix values were determined in the 0.6% VMA-containing mixture. Flowability of the mixtures generally increased with the increase of VMA utilization dosage. The optimum VMA usage dosage was chosen to be 0.4% in terms of rheological properties.

Study on radial segregation of whole and broken rice in an indented cylinder separator

Indented cylinder separators are often used to complete the grading of rice, but there is radial segregation which affects the screening performance. To clarify the cause of its radial segregation, the rice data required for simulation were first obtained through experiments, and then discrete element method (DEM) was used to analyze the segregation process of whole and broken rice at low filling levels. The results showed that with the intensification of segregation, the screening efficiency decreased gradually. Increasing the filling level will increase segregation. Segregation core to form in the center of the left half of the bed. The radial segregation mechanism of whole and broken rice is “percolation”, which is the result of a combination of particle size and shape driving forces. This study is helpful to improve the screening efficiency of rice and provides some reference for exploring segregation of multi-component mixture with multi-attribute differences.

Axial segregation of granular mixtures in laterally shaken multi-trapezium channels

Axial segregation of granular mixtures in laterally shaken multi-trapezium channels