Fluidity Properties Research Articles

Experiment and numerical simulation study of polycarboxylate superplasticizer modified cemented ultrafine tailings filling slurry: Rheology, fluidity, and flow properties in pipeline

Understanding the rheological properties of cemented paste backfill is crucial for optimizing its flowability and ensuring the efficient transportation in mine site. Due to the superfine size, the high-concentration filling slurry prepared by ultrafine tailings (the mean size < 0.019 mm) usually exhibits poor flow performance. In this study, the polycarboxylate superplasticizer (PCS) was adopted as an additive to modify cemented ultrafine tailings filling slurry. Experiment tests and numerical simulation were conducted to investigate effects of PCS dosages, solid and binder contents on rheological, fluidity, and flow performance. Results indicate that the PCS modified filling slurry conforms to Bingham model and shows shear-thinning behavior. As PCS dosage increases from 0 to 0.30 wt%, the yield stress gradually decreases, whereas the plastic viscosity initially increases then decreases. The electrostatic repulsion and steric hindrance generated by PCS can disintegrate the floc structures formed by ultrafine particles, leading to more release of free water, and reducing interparticle friction, correspondingly, improving flowability of filling slurry. The optimal PCS dosage is determined as 0.15–0.25 wt% considering transportation requirement. For a given PCS dosage, the yield stress and plastic viscosity exhibit an exponential growth with solid content, while a continuous decline with binder content. Furthermore, the fluidity increases linearly and exponentially with PCS dosage for filling slurry at solid content of 59–62 wt% and 63 wt%, respectively. An exponential model is established to quantify the relationship between yield stress and fluidity, which provides a method for predicting rheological parameters. With addition of PCS dosage, the flow performance of filling slurry is enhanced significantly in transportation pipeline. The maximal flow velocities at the pipeline center increase, and those near the pipeline wall decrease. The findings afford a practical guidance for designing and optimizing materials proportions of PCS modified filling slurry to achieve the desired flowability in mine site.

Development of inorganic anticorrosive coatings for steel bars: Corrosion resistance testing and design

A densely structured three-dimensional geopolymer network could effectively impede the migration and diffusion of chloride ion. This study developed one kind of efficient and cost-effective and multi-component geopolymer coating (MGC) for inhibiting and delaying the corrosion of steel. The influence of alkali content, metakaolin replacement ratio, polyvinyl alcohol content, and titanium dioxide content on the fluidity, setting time, and rheological properties of MGC was investigated. Accelerated corrosion tests were carried out to determine the optimal formulation of MGC. The corrosion resistance of MGC prepared by different coating method was compared to commercial organic metal coatings, for which the salt spray test, adhesion test, and electrochemical impedance spectroscopy test were conducted. The results showed that the dip-coated specimen of MGC exhibited 63.8% decrease in mass loss, 59.5% decrease in adhesive strength loss, and 38.1% increase in impedance modulus compared to commercial organic metal coatings. Furthermore, the corrosion protection mechanism of MGC was elucidated by analyzing its microstructural characteristics including the functional groups formed on the surface of coated steel bars. In terms of cost, MGC reduced the total cost by about 15 times compared to commercial organic metal coatings.

Ternary particle composite synergistically enhances the fluidity and dielectric properties of filled thermal conductive epoxy resin

Abstract Particle-packed epoxy materials are widely used to improve the thermal conductivity of insulation materials. However, the addition of fillers increases the viscosity of the composite which reduces its operability, and is not conducive to the packaging of power electronic equipment such as electric transformers and reactors. Multi-scale particle compounding is one of the effective methods to enhance the co-processing performance of materials by reducing the friction between particles and epoxy matrix while forming an effective thermal conductivity network. Three types of spherical alumina sized around 4 μm, 38 μm, and 125 μm were used as fillers to study the fluidity, thermal conductivity, and dielectric properties of single-filled and ternary compounds. The results showed that the ternary particle composite reduced the viscosity of the precursor by up to 68.8%, achieving a synergistic improvement in operability, thermal conductivity, and electrical performance.

Effect of Dental Stone Fluidity Properties, Compatibility with Impression Materials, and Detail Reproduction after Incorporation of 0.2% Chlorhexidine Solution

Effect of Dental Stone Fluidity Properties, Compatibility with Impression Materials, and Detail Reproduction after Incorporation of 0.2% Chlorhexidine Solution

Feasibility study of replacing part of cement by igneous rock powder as cementitious material: based on mortar macroscopic properties and microstructure

To address the increasing demand for cement and promote sustainable development, the utilization of igneous rock powder as a supplementary material to partially replace cement has emerged as an effective strategy. In this study, the fluidity and mechanical properties of the igneous rock powder-cement (IRP-OPC) composite system were investigated, and the hydration product and microstructure of IRP-OPC were analyzed by using TG/DSC, N2 adsorption-desorption curve (BET) and SEM. The experimental findings demonstrate that the performance of the andesite powder-cement composite cementing system (AP-OPC) surpasses that of tuff powder-cement slurry (TP-OPC) and granite powder-cement slurry (GP-OPC). When the dosage of andesite powder (AP) is 5%–15%, the flowability, flexural strength and compressive strength of cement mortar are improved. When the dosage is 10%, the 28-day compressive strength is 48.3 MPa. Under the condition of low content (10%), part of Ca(OH)2 is fully consumed by active SiO2 in AP and reacts to form C-S-H. Hydration products and AP particles with small particle size are filled into the structural gap, which refines the pore structure of cement slurry, and the increase in compactness provides support for the development of strength in the later stage. The use of 5%–15% AP instead of OPC can improve fluidity and meet the strength requirements of P.O 42.5 Portland cement. This substitution not only reduces engineering costs but also enhances resource utilization.

Effect of Steel Slag on Hydration Kinetics and Rheological Properties of Alkali-Activated Slag Materials: A Comparative Study with Fly Ash.

The effects of steel slag (SS) and fly ash (FA) on hydration heat, fluidity, setting time and rheological properties of alkali-activated slag (AAS) pastes with different silicate modulus (Ms) values were comparatively investigated. The results show that the incorporation of SS shortens the induction period, increases the cumulative hydration heat, improves the initial fluidity and decreases the setting time at low Ms, but the opposite trend is found at high Ms. FA significantly retards the reaction, reduces the hydration heat, increases the fluidity and prolongs the setting time. The addition of SS or FA reduces the yield stress and plastic viscosity of AAS paste. SS improves the rheological properties of AAS paste more significantly than that of FA at high Ms. The yield stress and plastic viscosity of AAS paste with SS or FA rise with the increasing Ms and decline with the increasing water/binder (w/b) ratio.

Effect of aging level on the healing properties of an induction-heated ultra-thin wearing course and its mechanism

Electromagnetic induction heating can accelerate crack self-healing in asphalt concrete and extend its service life. In the maintenance project of existing pavements, induction heating and ultra-thin wearing course can be combined by paving functional induction heating wearing course. However, the ultra-thin wearing course is directly affected by the environment and loading, and undergoes aging in the service process. Thermo-oxidative aging is an irreversible and important mechanism that seriously affect the rheological and healing properties of asphalt. Therefore, the purpose of this work is to examine the impact of thermo-oxidative aging on the induction heating-healing of an ultra-thin wearing course mixture. Firstly, the AC-5 induction heated ultra-thin wearing course (IHUC) containing 1 % steel wool fiber by aggregate mass was prepared. Subsequently, the IHUC was aged to six different levels. Then, the induction heating and healing properties of the aged IHUC were evaluated. Simultaneously, the aged asphalt binder was extracted and its rheological characteristics and chemical alterations were studied. The outcomes showed that the heating rate of IHUC decreased, but the temperature gradient effect reduced at higher aging level. The optimal healing temperature of IHUC shifted to a higher temperature region and the healing rate decreased. Both heating cycles and thermo-oxidative aging reduce healing effectiveness, but the impact of heating cycles is less compared to aging. Rheology and chemical structure test results of extracted asphalt binder showed that the transformation of the molecular structure caused the fluidity and self-healing properties of asphalt were decreased. This ultimately decreased the healing rate of IHUC.

Performance study of new lightweight cementitious composites with glass beads as filler

Glass beads are a kind of inorganic lightener material with low density and high strength. They can be used to prepare lightweight cement composite and significantly improve traditional cement materials' fluidity, compressive, and flexural properties after setting. In this paper, a new lightweight cementitious hole sealing material was prepared by utilizing the excellent properties of glass beads, and the new lightweight cementitious composite drilled hole sealing material was quantitatively and qualitatively analyzed by flow test, uniaxial compression, nuclear magnetic resonance, and SEM experiments, to derive the effects of the substitution of different types of glass beads with different proportions of different types of glass beads on the material's fluidity, compressive strength, pore distribution, and microstructure. The results show that the new cementitious materials have better fluidity, in which the fluidity of the optimal group is increased by 8 % compared with that of pure cement mortar; the mechanical properties of the optimal group are significantly improved with the hollow glass beads acting as the aggregate, and the peak stress reaches 55.025 MPa; the peak stress can reach 60.191 MPa with the use of modified hollow glass beads acting as the aggregate; moreover, with the incorporation of hollow glass beads, the material is more compact, and the pore distribution and microstructure of the material is improved. In addition, with the incorporation of hollow glass beads, the densification of the material showed a trend of first enhancement and then a gradual decrease, while the densification of the material weakened after the incorporation of solid glass beads. Therefore, hollow glass beads are more suitable for improving and optimizing cementitious sealing materials. The research and development of this material are conducive to improving cementitious materials' sustainability and alleviating the cement production's environmental burden. At the same time, it provides a reference for the research and development of new high-quality cementitious materials.

High Strength Self-Compacting Concrete's (HSSCC) Fluidity and Mechanical Properties: An Experimental Study

High Strength Self-Compacting Concrete's (HSSCC) Fluidity and Mechanical Properties: An Experimental Study

Impact of coarse aggregate morphology andseparation distance on concrete properties based on visual learning

The morphology of coarse aggregates plays a significant role in concrete performances. This study conducted a quantitative analysis on the morphology of coarse aggregates using visual learning technology, aiming to explore their effects on fluidity, rheology and mechanical properties of fresh concrete. The parameters of flatness, angularity, roughness, roundness, sphericity and coarse aggregate separation distance (CSD) on concrete properties are discussed. The results showed that CSD, flatness and sphericity had the most significant effect on slump, with its weighting of 0.99, 0.96 and 0.94, respectively. Higher value of CSD, flatness and sphericity help to produce concrete with better flowability. The yield stress of concrete was mainly affected by roughness, roundness and CSD with weighting of 0.98, 0.87 and 0.76, respectively. Plastic viscosity was also affected by these factors with weighting of 0.96, 0.85 and 0.80, respectively. Aggregate roughness (weight 0.96) and roundness (weight 0.87) are the two significant factors influencing the compressive strength. Through numerical analysis, mathematical models correlating the morphological parameters coarse aggregates with the performance of concrete are established, which can provide some indications for the smart design of concrete mixture.

Preparing gypsum-based self-levelling energy storage mortar via fly ash cenospheres/paraffin used for floor radiant heating

In the underlayment of a floor radiant heating system (FRHS), using gypsum-based self-levelling mortar (GSM) with high fluidity and early strength properties could save labor force and material costs. Combining phase change materials (PCMs) with FRHS is a promising way to improve energy efficiency and provide a comfortable thermal environment. This paper investigates the feasibility of preparing gypsum-based self-levelling energy storage mortar (GSEM) by incorporating fly ash cenospheres/paraffin (FACP) into GSM. The selection of fly ash cenospheres (FAC) particle size, the pre-treatment of FACP, the additional amount of FACP, and the thermal performance of FRHS containing GSEM are investigated. Results show that the selection of FAC should consider the influence of strength, fluidity, thermal property, and possible economic and environmental impacts. FAC 2 with a particle size (D50) of 110.5 µm is considered to be a suitable choice. FACP pre-treated with 52.5 cement could decrease paraffin leakage and increase the mechanical strength and fluidity of GSEM. With the sand replacement ratio (Vf) increase, the mechanical strength of GSEM first increases and then decreases. When the Vf is 100%, the compressive strength and flexural strength of GSEM are 18.8 MPa and 4.3Mpa; the thermal conductivity decreases by about 15.8% and the specific heat capacity increases by about 53.5%. For FRHS, the matching between the supply water temperature and the plate thickness should be considered in the design. Compared with the GSM plate, the GSEM plate could reduce about 2.4℃ temperature fluctuation, and the time at a comfortable temperature is extended by 60.8%. This finding indicates that the prepared GSEM could be applied to FRHS and has good potential to provide a comfortable thermal environment for buildings.

Investigation of the Effects of Filling Speed, Casting Temperature and Metallurgical Quality on Fluidity of Lamellar Graphite Cast Iron at Different Section Thicknesses

AbstractIn this study, the fluidity properties of the alloy were investigated at different casting temperatures, different section thicknesses, and varying casting parameters of lamellar graphite cast iron materials. To achieve our goal, we utilized sand molds that were created with specific parameters including pouring temperature, metallurgical quality, section thickness, and fluidity test model. These molds were used for casting. Thus, the effect of fluidity properties in changing casting conditions and liquid metal advance distances at determined section thicknesses was investigated. Modeling was carried out with FlowCast casting simulation software by determining the liquid metal advance distance depending on the section thickness in the castings made in sand molds under changing casting conditions. The fluidity and advance distance of the liquid metal was determined comparatively with experimental and modeling techniques under the changing casting conditions in the parameters determined in this study. When the outcomes were examined; it was observed that different liquid metal advance distances occur at different cross-section thicknesses depending on the changing conditions.

Supramolecular polymers form tactoids through liquid–liquid phase separation

Liquid–liquid phase separation (LLPS) of biopolymers has recently been shown to play a central role in the formation of membraneless organelles with a multitude of biological functions1–3. The interplay between LLPS and macromolecular condensation is part of continuing studies4,5. Synthetic supramolecular polymers are the non-covalent equivalent of macromolecules but they are not reported to undergo LLPS yet. Here we show that continuously growing fibrils, obtained from supramolecular polymerizations of synthetic components, are responsible for phase separation into highly anisotropic aqueous liquid droplets (tactoids) by means of an entropy-driven pathway. The crowding environment, regulated by dextran concentration, affects not only the kinetics of supramolecular polymerizations but also the properties of LLPS, including phase-separation kinetics, morphology, internal order, fluidity and mechanical properties of the final tactoids. In addition, substrate–liquid and liquid–liquid interfaces proved capable of accelerating LLPS of supramolecular polymers, allowing the generation of a myriad of three-dimensional-ordered structures, including highly ordered arrays of micrometre-long tactoids at surfaces. The generality and many possibilities of supramolecular polymerizations to control emerging morphologies are demonstrated with several supramolecular polymers, opening up a new field of matter ranging from highly structured aqueous solutions by means of stabilized LLPS to nanoscopic soft matter.

Research on the strength prediction for pervious concrete based on design porosity and water-to-cement ratio

Abstract The strength prediction of pervious concrete is hard to implement for the mix design due to the porous structure. This work studied the influence of the water-to-cement ratio on the fluidity, viscosity, and mechanical properties of cement paste. Then, the porosity, permeability, and compressive strength of the pervious concrete with various porosities were investigated, and the test results were fitted and analyzed. The result indicates that as the water-to-cement ratio increases, the viscosity of the cement paste reduces and the fluidity increases. The water-to-cement ratio has a negative linear relationship with net slurry strength. The porosity and permeability of pervious concrete fluctuate in accordance with the same rule as the water-to-cement ratio changes. The compressive strength of pervious concrete with varying design porosities increases initially, then declines as the water-to-cement ratio rises. According to the linear fitting analysis, when the water-to-cement ratio is constant, the permeability and compressive strength of pervious concrete have a positive and negative linear relationship with the design porosity, respectively. By analyzing the fitting results and combining the volume method of pervious concrete, a calculation method for mix proportion design is proposed to predict the strength of pervious concrete.

Effects of Dosing and Mechanical Activation on the Performance of Reservoir Sediment-Cement Composite Cementitious Material

To solve the problem of reservoir sediment accumulation, this paper intends to study the feasibility of preparing reservoir sediment-cement composite cementitious material by partially replacing cement with reservoir sediment. Using the single factor test method, the replacement rate of reservoir sediment and mechanical activation time were selected as variables to explore the effects of water requirement of normal consistency, setting time, mortar fluidity, and mechanical properties of mortar specimens. The results show that with the increase of sediment replacement rate, the water requirement of normal consistency of composite cementitious material paste increases, the setting time increases, the fluidity of mortar decreases, and the mechanical properties of mortar specimens decrease significantly. With the increase of mechanical activation time, the water requirement of normal consistency decreases, the setting time decreases, the fluidity of mortar increases, and the mechanical properties of the mortar specimen increase. The microcosmic results show that mechanical activation can promote the formation of C-S-H gel in reservoir sediment, and fill each other with unreacted reservoir sediment particles, resulting in a denser microstructure. The purpose of this paper is to provide theoretical support for the preparation of reservoir mud-cement composite cementitious material.

Investigation into the alkali-activation of lithium slag: A sustainable alternative to conventional cement with optimized mechanical properties

Utilizing lithium slag as a precursor for alkali-activated cementitious materials offers a sustainable alternative to conventional cement, addressing both environmental pollution and land-use challenges posed by lithium slag waste. Additionally, this practice reduces energy consumption and CO2 emissions associated with cement production. This study presents a novel methodology involving high-temperature calcination and mechanical grinding to enhance the reactivity of lithium slag. Analytical techniques, such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), were employed to elucidate the mechanisms behind lithium slag's increased reactivity. Subsequently, these activated materials were used to formulate alkali-activated lithium slag cement composites (ALC). Various factors, including the calcination temperature, water-to-cement ratio, NaOH concentration, and lithium slag content, were investigated for their effects on the fluidity and mechanical properties of the mortar. Analytical techniques including XRD, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), FTIR, and thermogravimetric analysis (TGA)/derivative thermogravimetry (DTG), were used to explore the hydration mechanisms. Results indicate that the optimal calcination temperature for lithium slag was 700 °C, while the optimal NaOH concentration was 1 mol/L. ALC exhibited robust mechanical properties, with compressive, flexural, and fluidity measures reaching 37.66 MPa, 10.13 MPa, and 200 mm, respectively. Predominant hydration products were found to be N-A-S-H and C-A-S-H. The production cost of 1 ton of ALC is $49.8, which is roughly 70% of the cost of producing 1 ton of OPC. Additionally, the total CO2 emissions and energy consumption of producing ALC amount to 60.56% and 64.95% respectively, compared to the total CO2 emissions and energy consumption of producing 1 ton of OPC.

Enhancement of magnetic activation on the backfilling performance of coal gangue-based composite materials

ABSTRACT The large accumulation of coal gangue has resulted in significant environmental contamination and detrimental impacts. Utilizing it as a filler material in coal mining operations may successfully address this issue. It may be used to efficiently alleviate this issue by filling up coal mines. The wettability of magnetized solution on the coal gangue surface and the phase composition, microstructure, and pore structure of hydration products of coal gangue-based composite material (CGCM) at different ages were analyzed by means of contact angle (CA), X-ray diffraction (XRD), thermogravimetry (TG/DTG), mercury intrusion (MIP), and scanning electron microscopy (SEM) in order to control the fluidity and mechanical properties of backfilling materials. Simultaneously, an investigation was conducted on the slump expansion, setting time, and compressive strength of composite filler materials derived from magnetized coal gangue. The findings indicate that the application of a magnetic field reduces the interaction force among the molecules in the mixing water. Consequently, this leads to an improvement in the wettability of the coal gangue particle surface. Thus, the fluidity of the backfilling slurry is improved. The permeability and diffusion characteristics of magnetized water surpass those of regular water, The rate of dissolving and hydration reactions of the cementitious active material in the slurry is increased, resulting in a noticeable reduction in the setting time of the slurry. In the backfilling body, magnetized mixing water can encourage the formation of dicalcium silicate (C2S), tricalcium silicate (C3S), and Ca (OH)2. Higher amounts of C-S-H gel and Aft are produced by the pozzolanic action with SiO2, which enhances the pore structure. Thus, the mechanical qualities of the filler body are enhanced. The study findings provide novel insights into the coal gangue backfill mining and offer an environmentally friendly and efficient approach for the large-scale processing and exploitation of coal gangue.

Remarkable improved strength and ductility in brittle eutectic high-entropy alloy via a novel spheroidization and recrystallization strategy

Eutectic high-entropy alloys (EHEAs), as a classification of high-entropy alloys (HEAs), have received worldwide interest due to superior fluidity and attractive properties. However, other than the FCC + B2 EHEA system, most other reported EHEA systems show inherent brittleness during tensile loading at room temperature, which limits their advanced engineering application. In this work, a novel spheroidization + recrystallization (SR) strategy for synergistic strengthening and plasticizing of the brittle CoCrFeNi2(V6B3Si)0.149 was proposed. The superior combination of strength and ductility was achieved by tailoring spherical M3B2 + recrystallized FCC duplex phases. Based on this strategy, the yield strength and elongation were improved from 565 ± 15 MPa and 2.3 % ± 0.3 % to 841 ± 24 – 1278 ± 20 MPa and 14.7 % ± 0.5 % – 22.5 % ± 1.2 %, with an increase of 48 %–126 % and 539 %–878 %, respectively. The synergistic increment in the strength and ductility of SR-FCC+M3B2 EHEAs exceeds all reported further strengthened FCC + B2 EHEAs. Meanwhile, such simple thermo-mechanical processing is suitable for large-scale industrial production. The high strength results from the back stress provided by the dual heterogeneity of FCC grain sizes and soft FCC/hard M3B2. The good ductility is attributed to the dislocation movement path released by spheroidized M3B2 and a more uniform stress distribution caused by the recrystallized FCC. This work provides a new strategy for synergistic strengthening and plasticizing of the brittle EHEAs to meet industrial reliability requirements.

The Influence of Chemical Admixtures on the Fluidity, Viscosity and Rheological Properties of Ultra-High Performance Concrete

The Influence of Chemical Admixtures on the Fluidity, Viscosity and Rheological Properties of Ultra-High Performance Concrete

Review of researches on strength model of foamed concrete

Compared with ordinary concrete, foamed concrete has the advantages of light weight, high fluidity, good thermal and sound insulation properties. It has been initially applied in the construction industry. As the most basic research content of foamed concrete, the strength prediction model has received widespread attention from scholars. In this paper, the existing foamed concrete strength prediction models were summarized. The development status of the traditional empirical model based on theory or experiment and the artificial intelligence model based on computer technology were analyzed, and the advantages and disadvantages of each model were described comprehensively. The following conclusions can be drawn: ①Porosity is an important factor affecting the density and compressive strength of foamed concrete. Considering pore structure and volume composition will be more convenient and accurate to predict the strength. ② As for gel-space ratio model, considering the contribution of different hydration products produced by the cementitious materials to the strength is helpful to improve the accuracy of the prediction model. ③ The artificial intelligence model overcomes the shortcomings of less factors in the empirical model and large amount of experiments with high cost, which makes the strength prediction more effective and precise. This paper provides a train of thought for further research on the strength prediction model of foamed concrete. The development of foamed concrete strength prediction model can provide theoretical guidance for the design of foamed concrete, and is of great significance for promoting the application of foamed concrete in various occasions.