Fluidity Of Slurry Research Articles

Preparation of water-quenched manganese slag and fly ash ultrafine mineral admixture and its application in UHPC

Abstract In this paper, S95 grade ultrafine mineral admixture (UMA) was prepared by water quenched manganese slag and fly ash 1:1 compound mechanical ball milling to a specific surface area of 714 m2/kg. Its activity index was 86.8% at 7d and 96.3% at 28d. The S95 UMA prepared by ball milling has the characteristics of small particle size, high specific surface and high activity. Mixing with powders of different particle sizes, such as cement and silica fume (SF), is helpful to improve particle gradation, reduce its pore structure and increase its compacting property for ultra-high performance concrete (UHPC) whose raw materials are fine aggregate. UHPC was prepared by using the obtained UMA based on orthogonal test. The effects of different factors on the workability, mechanical properties, hydration heat and microstructure of UHPC were studied. The results show that when the SF content is 10%, the mineral admixture content is 10%, the binder–sand ratio is 1.1, and the water–binder ratio is 0.17, the fluidity of UHPC slurry can reach 261 mm, the compressive strength of 7d and 28d age can reach 128 MPa and 154.6 MPa, respectively. The hydration heat release of cementitious materials in 3d was 139.8 J/g. In terms of solid waste resource utilization, S95 grade UMA prepared by water-quench manganese slag and fly ash can replace 10% SF for the preparation of UHPC. It can not only solve the utilization problem of high added value of water quench manganese slag but also reduce the preparation cost of UHPC to a certain extent.

Mechanical Properties of Fly Ash-Slag Based Geopolymer for Repair of Road Subgrade Diseases.

Fly ash-slag-based geopolymer is a grouting material with good fluidity and excellent mechanical and eco-friendly properties. The geopolymer can react chemically with the inert minerals of road subgrade under alkali excitation to form a good interfacial bond between road subgrade; therefore, it is suitable for the repair of weak road sections. In order to solve the problems such as the difficulty to store and transport the liquid activator of existing geopolymer grouting materials and to study the unclear mechanism of the influence factors on the fluidity and mechanical properties of geopolymer; the research on the mechanical properties of fly ash-slag based geopolymer was carried out in this paper. Experiments on the preparation of geopolymer and research on different ash-slag ratios under solid alkali excitation were studied. The influence of slag content and solid alkali content (NaOH, Na2SiO3) on the fluidity, compressive and flexural strength of fly ash-slag-based grouting materials was also researched on the basis of single-factor gradient tests. The results showed that the slurry fluidity decreased but the compressive strength gradually increased when the content of slag was increased from 20% to 50%. With the increase in alkali content (NaOH: 2-5%; sodium silicate: 0-6%), the slurry fluidity decreased and the compressive strength increased and then decreased. Combined with the analysis of the test results of Scanning Electron Microscopy (SEM), the microscopic structures of mechanical properties of geopolymer were investigated. Lastly based on ridge regression theory, a regression model was established to predict the mechanical properties of fly ash-slag-based geopolymer. The results indicate that fly ash-slag-based geopolymer has good mechanical properties and fluidity with proper contents of slag and alkali activator, which provide a reference for experiment research and engineering application.

Surface modification of garnet fillers with a polymeric sacrificial agent enables compatible interfaces of composite solid-state electrolytes.

The poly (vinylidene fluoride) (PVDF)-based composite solid-state electrolyte (CSE) has garnered attention due to its excellent comprehensive performance. However, challenges persist in the structural design and preparation process of the ceramic-filled CSE, as the PVDF-based matrix is susceptible to alkaline conditions and dehydrofluorination, leading to its incompatibility with ceramic fillers and hindering the preparation of solid-state electrolytes. In this study, the mechanism of dehydrofluorination failure of a PVDF-based polymer in the presence of Li2CO3 on the surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is analyzed, and an effective strategy is proposed to inhibit the dehydrofluorination failure on the basis of density functional theory (DFT). We introduce a molecule with a small LUMO-HOMO gap as a sacrificial agent, which is able to remove the Li2CO3 impurities. Therefore, the approach of polyacrylic acid (PAA) as a sacrificial agent reduces the degree of dehydrofluorination in the PVDF-based polymer and ensures slurry fluidity, promoting the homogeneous distribution of ceramic fillers in the electrolyte membrane and enhancing compatibility with the polymer. Consequently, the prepared electrolyte membranes exhibit good electrochemical and mechanical properties. The assembled Li-symmetric cell can cycle at 0.1 mA cm-2 for 3500 h. The LiFePO4‖Li cell maintains 91.45% of its initial capacity after 650 cycles at 1C, and the LiCoO2‖Li cell maintains 84.9% of its initial capacity after 160 cycles, demonstrating promising high-voltage performance. This facile modification strategy can effectively improve compatibility issues between the polymer and fillers, which paves the way for the mass production of solid-state electrolytes.

Study on Physical and Mechanical Properties of Micro-Cement Grouting Materials with Different Water-Cement Ratio

The water-cement ratio is one of the key parameters of grouting materials, which greatly affects the working performance and mechanical properties of grouting materials. This paper studies the physical properties, such as density, fluidity, consistency, bleeding rate, and stone rate, and the mechanical properties of flexural and compressive strength of micro-cement grouting materials with a water-cement ratio of 0.8:1, 1:1, 1.5:1 and 2.0:1 are investigated through a variety of indoor experiments. The results show that with the gradual increase of water-cement ratio, the density, consistency value, stone rate, flexural strength, and compressive strength of micro-cement grouting material gradually decrease, while the fluidity and bleeding rate of micro-cement slurry gradually increases. Although the slurry with a water-cement ratio of 1.5:1 and 2:1 has good fluidity, the high bleeding rate and the low stone body strength result in more water injected into the reinforced formation and low reinforcement strength. On the contrary, the slurry with a water-cement ratio of 0.8:1 has a low bleeding rate and high stone body strength, but low fluidity. The grouting performance and mechanical properties of the slurry with a water-cement ratio of 1:1 are relatively balanced. This study provides a basis for the subsequent on-site ultra-fine cement grouting project. A reasonable water-cement ratio can be selected according to the specific needs to ensure the reinforcement quality and safety of the grouting operation.

Study on the Performance and Mechanisms of High-Performance Foamed Concrete.

As a common building insulation material, foamed concrete has been widely used in engineering practice. However, the contradiction between compressive strength and thermal conductivity has become the main problem limiting the development and application of foamed concrete. Therefore, high-performance foam concrete (HPFC) with high compressive strength and low thermal conductivity was prepared by using graphene oxide (GO), fly ash, and polypropylene (PP) fiber as the main admixtures, and taking compressive strength, thermal conductivity, and microstructure as the main indices. Scanning electron microscopy, X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC) were employed to examine the mechanisms of HPFC. The results showed that when the content of fly ash was 25-35 wt%, PP fiber was 0.2-0.4 wt%, and GO was 0.02-0.03 wt%, the FC's compressive strength increased by up to 38%, and its thermal conductivity reduced by up to 3.4%. Fly ash improved the FC's performance mainly through filling, pozzolanic activity, and slurry fluidity. PP fiber enhanced the performance of FC mainly through bridging cracks and skeletal effects. The addition of GO had no significant impact on the type, quantity, or hydration reaction rate of the hydration products in these cement-based materials, and mainly improved the FC's microstructural compactness through template action and crack resistance, thereby improving its performance.

Review on Comprehensive Utilization of Magnesium Slag and Development Prospect of Preparing Backfilling Materials

China is the largest producer of the metal magnesium, which is the third largest metal after steel and aluminum, and magnesium slag (MS) discharged from magnesium production cannot be treated effectively at present. Large amounts of MS occupy the land, making the land salinized and polluting the groundwater, which will threaten the sustainable development of the inland areas of China. To realize the large-scale utilization of MS, this paper reviews the research on the comprehensive utilization of MS and proposes using MS to prepare backfill materials. Firstly, the source and physical and chemical properties of MS are introduced, and the hazards caused by MS are also pointed out. Then, the several utilization methods of MS are summarized, such as cement admixture, chemically activated cementitious materials, clinker sintering, etc. Thirdly, the effect of MS on the properties of cementitious materials and concrete is summarized, including condensation time, workability, mechanical properties, durability, etc. Finally, based on the cemented backfill mining method, MS replaces Portland cement and blast furnace slag (BFS) to prepare cementitious materials. The mechanical properties and fluidity of backfilling slurry composed of MS, gypsum, BFS, and tailings can meet the requirements of backfilling mining.

Effect of Compounding Retarder and PCE on the Early Properties and Hydration of High-Belite Sulphoaluminate Cement

To cope with the problem that the setting time and hardening time of high-belite sulphoaluminate cement (HBCSA) is too fast and not easily controlled, three common retarders, citric acid (CA), β-cyclodextrin (β-CD), and borax (B), were selected and compounded with polycarboxylate superplasticizer (PCE). Based on the cement slurry fluidity, fluidity loss, setting time, and mechanical properties of cement mortar, combined with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Zeta potential tests, the interaction and mechanism of different retarders and high-belite sulphoaluminate cement were studied. The results show that β-CD and CA can significantly delay the hydration process of HBCSA cement, effectively improve the fluidity loss, and make the dispersion more stable, but the strength of cement mortar decreases, which is not conducive to the development of strength. However, the addition of B has no obvious retarding effect on the HBCSA cement, and the dispersibility of the cement paste decreases. In microscopic tests, XRD and SEM tests verified that the combination of retarder and PCE had a certain inhibitory effect on the early hydration of HBCSA, and the zeta potential indicated that the addition of retarder would interact with PCE to improve the fluidity loss of HBCSA. In addition, when the retarders CA and B were, respectively, compounded with β-CD, the two would have a synergistic effect. The retardation effect is more obvious, and the time interval between the initial and final setting is shorter, which is more controllable. The initial fluidity is also improved under the auxiliary plasticization of cement paste by β-CD.

Development of solid waste-based self-insulating material with high strength and low thermal conductivity

Foam concrete as a thermal insulation material has been widely used to meet building energy conservation requirements. In this study, a low-clinker foamed concrete was prepared with an amount of solid waste, including fly ash, carbide slag, and glauber's salt, up to 80%. The effect of polycarboxylate superplasticizers (PCs) in the preparation process was examined to improve the mechanical properties of this particular system. The characteristic of hydration products and the pore structure was analyzed to illuminate the PCs influence on the hydration process. The outcomes demonstrate that the PCs can effectively improve the slurry's fluidity, enhance its compressive strength, and decrease its average diameter. Low-clinker foamed concrete's compressive strength reached 5.3 MPa, and its thermal conductivity reached 0.1556 W/(m·K). It was concluded that foam concrete has the potential to be widely used in green buildings due to its high strength and low thermal conductivity.

High-performance and high-precision Al2O3 architectures enabled by high-solid-loading, graphene-containing slurries for top-down DLP 3D printing

To date, obtaining the high-solid-loading Al2O3 slurry and overcoming the trade-off between high solid loading and printing accuracy and strength of printed green bodies to achieve high-performance and precision Al2O3 ceramic parts by DLP 3D printing remain challenging. In this study, an Al2O3 slurry with high solid loading of 60 vol% was developed through dispersant optimisation for top-down DLP 3D printing. Graphene was innovatively introduced during slurry fabrication to decouple the printing accuracy and strength of green bodies from such high solid loading. Simultaneously, graphene addition could considerably reduce slurry fluidity, thereby facilitating its coordination with top-down DLP. With 0.07 wt% graphene addition, the dimension deviations of printed green bodies improved from 90 to 880 µm to ≤ 70 µm, and the bending strength increased by 17.75%. High-performance and precise Al2O3 ceramic components with low sintering shrinkages were prepared. The density and microhardness were 99.7% and 18.61 GPa, respectively.

Preparation and experimental study of emulsion ice slurry under vacuum flash evaporation in solid adsorption

As a cold storage material, emulsion ice slurry is expected to increase the ice slurry's fluidity because of the emulsion's structural characteristics, which does not adhere to the wall of the cooling vessel. In this paper, surfactants were mixed in the water-oil mixture, and the emulsion with small particle size and high stability was optimized by the response surface method. The emulsion ice slurry was also prepared under vacuum flash evaporation by solid adsorption, and we studied the properties of the emulsion ice slurry under vacuum flash evaporation. The microstructures of pure water ice slurry and emulsion ice slurry under vacuum flash evaporation were observed by metallographic microscopy.

Characteristics of Pavement Cement Concrete Incorporating Steel Slag Powder

After thermal braising and magnetic separation, steel slag is often ground into steel slag powder (SSP), which contains active silica (SiO2) and can be used as a cementitious material to replace part of the cement and applied in concrete. However, there have been relatively few studies on the influence of SSP on the performance of pavement cement concrete (PCC). In this paper, SSP was used as an admixture to replace part of the cement in the cement paste, cement mortar, and PCC, to investigate the effect of SSP on the fluidity of SSP-cement slurry, the mechanical properties, and the durability of PCC. Results showed that SSP can lead to the secondary hydration reaction with Ca(OH)2 in the cement paste and affect the hydration products, morphology, pore characteristics, and strength of the cement paste. When the SSP mixing amount was less than 20% and up to 1.3% superplasticizer was added, the fluidity of the cement slurry could be optimized. For the samples with the SSP mixing amount of less than 20%, the concrete compressive strengths were greater than 50 MPa, and the flexural strengths were greater than 5.0 MPa. As the SSP mixing amount increased, concrete displayed a better anticarbonization performance. Finally, using 15% SSP, the best performance in terms of the concrete antipermeability (chloride ion diffusion coefficient and electric flux) and frost resistance was achieved.

Synthesis and property of EPEG‐based polycarboxylate ether superplasticizers via RAFT polymerization

AbstractPolycarboxylate ether superplasticizers (PCEs) with comb‐shaped molecular structures have attracted considerable attention in the area of admixtures for construction engineering. However, there are some contradictions in studying the relationship between the molecular structure and property of PCE due to its random structure based on traditional free radical polymerization, which is confused for designing and developing novel PCEs. In this article, a series of reversible addition fragmentation chain transfer (RAFT) polymerization‐based polycarboxylate ether superplasticizers (RPCs) were prepared by the copolymerization of acrylic acid (AA) and ethylene‐glycol monovinyl polyethylene glycol (EPEG). The chemical structure and composition of RPCs were characterized and their adsorption behavior and dispersion properties were conducted. The results demonstrate that the molecular weights of RPCs do not vary significantly with prolonging reaction time, and the actual monomer ratio in RPCs displays a significant change to the feed one due to the monomer reactivity and conversion at higher reaction temperature, which is different from conventional free radical polymerization. The dispersion and adsorption properties of RPCs to cement were evaluated by slurry fluidity tests and total organic carbon (TOC) experiments. The effect of polymerization temperature and time on the dispersion ability has been systematically studied. The results indicate that the dispersion ability and adsorption capacity of RPCs are closely related to their molecular structures. The dispersion ability of RPCs were enhanced with increasing carboxyl group density in a certain range of monomer molar ratios (≤6:1). This study will provide a new platform for designing and developing high‐performance and rational cost‐effective superplasticizers with well‐defined structure and controlled molecular weight.

Synergistic effect of surfactant and chlorine salt on dispersion of nano-SiO2 and performance of cement-based grout containing a large amount of bentonite

Nano-SiO2 (NS) is widely used to improve the performance of cement-based grouts. The workability and mechanical property of grouts are greatly affected by NS dispersion. In this paper, synergistic effect of surfactants and chloride salts on NS dispersion, as well as on performance of grouts including fluidity, mechanical and microscopic properties were systemically studied. The results showed that the synergistic effect of anionic surfactant (SDS) and chloride salt can effectively improve NS dispersion because of the massive formation of micelles that can encapsulate NS and the electrostatic repulsion between micelles. And the effect of CaCl2 was more significant than NaCl. Furthermore, fluidity of fresh slurry and mechanical property of hardened grouts were also improved by the synergistic effect. The mechanical property enhancement might be attributed to the filling effect of NS due to its improved dispersion, and to the matrix compaction associated with the formation of strätlingite and Friedel's salt.

Study on Rheological Mechanism of Cement-Coal Gangue Cementitious Material (CGCM) Slurry

To explore the rheological mechanism of cement-coal gangue cementitious material (CGCM) slurry, the effects of the activation temperature (500°C-900°C) of coal gangue on the initial fluidity, plastic viscosity (η0), and yield stress (τ0) of CGCM slurry were considered, the variation laws of rheological parameters of CGCM slurry at different hydration ages were compared, and the rheological equations of CGCM slurry were established in this study. The results show that the rheological law of the CGCM slurry conforms to the modified Bingham model, and the significant shear thinning occurs in the CGCM slurry at low-shear speed, and relatively weak shear thickening occurs in the CGCM slurry at high-shear speed; under the thermal activation temperature of 800°C, the pozzolanic activity of coal gangue reaches the highest, the hydration reaction is the fastest, and the initial fluidity of CGCM slurry at 800°C is the lowest; the plastic viscosity of CGCM slurry increases gradually with the increase of thermal activation temperature of coal gangue, and the yield stress of the CGCM slurry reaches the maximum at 800°C; the flow law of CGCM slurry has significant time-varying characteristics, and the plastic viscosity and yield stress of CGCM slurry increase gradually with the extension of hydration time. This study shows that the fluidity of coal gangue cement slurry has significant time-varying characteristics, which can provide effective theoretical support for the accurate application of coal gangue cement in grouting engineering.

Influences of CO2 Absorption under Ultrasonic Vibration and Water-Reducer Addition on the Rheological Properties of Cement Paste

Research shows that ultrasonic vibratory stirring can effectively increase CO2 absorption by cement slurry. However, with the increase in CO2 absorption, the fluidity of slurry begins to decrease. Adding water reducer to fresh cement paste can improve its fluidity. In order to reveal the influences of ultrasonic vibration and water-reducer addition on the rheological properties of cement pastes after absorbing various amounts of CO2, changes in the rheological properties of yield stress and plastic viscosity (PV) were analysed. The results show that ultrasonic vibration can effectively increase the shear stress and PV of cement paste. Moreover, shear stress and PV are positively related to the CO2 absorption amount. Meanwhile, a new rheological model of cement paste carbonated under ultrasonic vibration was established based on the basic principles of rheology. Microstructural changes in cement paste before and after water-reducer addition were observed by scanning electron microscopy (SEM). A microrheological model of cement paste carbonated under ultrasonic vibration and with water reducer added was constructed. It describes the influencing mechanisms of ultrasonic vibration and water-reducer addition on the rheological properties of carbonated cement paste. Next, a molecular model was constructed in which CO2 was added into a C-S-H gel. Changes in intermolecular repulsion in the CO2+ C-S-H gel structure and in the CO2− water-reducer molecular structure were analysed. Finally, the rheological mechanism was further analysed in terms of the dispersion effect of the C-S-H gel. The results will play a major role in improving the fluidity of cement paste.

A novel countermeasure for preventing scour around monopile foundations using Ionic Soil Stabilizer solidified slurry

A novel scour prevention countermeasure of using the Ionic Soil Stabilizer (ISS) solidified slurry was investigated in this study. The ISS-solidified slurry is composed of Ionic Soil Stabilizer, Dispersion Resistance Agent (DRA), silt (or silty clay) and distilled water. It can be placed on the seabed immediately after monopile was installed, or in the developed scour holes. In present study, the first type was adopted as the scour protection layer around monopile. The scour morphology and the performance of scour protection layer was firstly analyzed based on flume experimental results. Furthermore, the falling head permeability tests, Zeta potential tests and scanning electron microscope (SEM) tests were carried out to investigate the scour protection mechanism of ISS-solidified slurry. Finally, the performance of the ISS-solidified slurry as scour protection layer was remarked comprehensively. The results indicate that the ISS-solidified slurry for scour protection is favorable and cost-effectiveness. Compared with the untreated seabed, the ISS-solidified slurry layer can bear with the greater critical shear stress required for the initial scour. The DRA can keep the fluidity of ISS-solidified slurry within an appropriate range and facilitate the hardening process in water simultaneously, so the DRA is indispensable for ISS-solidified slurry when it is used as scour protection layer in field.

Investigating the Slurry Fluidity and Strength Characteristics of Cemented Backfill and Strength Prediction Models by Developing Hybrid GA-SVR and PSO-SVR

Investigating the Slurry Fluidity and Strength Characteristics of Cemented Backfill and Strength Prediction Models by Developing Hybrid GA-SVR and PSO-SVR

Fluidity Influencing Factor Analysis and Ratio Optimization of New Filling Slurry Based on the Response Surface Method

The filling mining method is important in realizing the green mining of mineral resources. Aiming at the problems of land resource occupation, environmental pollution, and rational utilization of coal-based solid wastes such as coal gangue, fly ash, and desulfurization gypsum, a new paste filling material was developed with coal gangue, fly ash, and desulfurization gypsum as raw materials. The microstructure of the raw materials was analyzed by XRD and SEM. Combined with the Box-Behnken experimental design, the effect of each component on the fluidity of the filling slurry was analyzed through the response surface analysis. The significance of each component on its bleeding and fluidity was determined, and the optimal ratio of the filling slurry was obtained. Experimental results show that the microcosmic morphology of coal gangue, desulfurization gypsum, and gasification slag presents an irregular block and rough particle surface; the microcosmic morphology of fly ash and bottom slag presents first out spherical or quasi spherical particles. Moreover, obvious sintering traces exist on the surface of the bottom slag. The main crystal mineral of coal gangue and fly ash is SiO2, the desulfurization gypsum is composed of Ca(SO4) (H2O) and Ca(CO3) crystal minerals, the gasification slag is composed of carbon and nitrogen compounds, and the main crystal mineral components in the bottom slag sample are SiO2 and AlxSiyOz compounds. The order of significance of each key factor on slurry fluidity is as follows: C (desulfurization gypsum) > D (gasification slag and bottom slag 1:1) > A (coal gangue) > B (fly ash). The order of the significance of each key factor on slurry bleeding is as follows: B (fly ash) > C (desulfurization gypsum) > D (gasification slag and bottom slag 1:1) > A (coal gangue). Considering the material preparation, field application, and other conditions, the mass percentage of each factor content of the new paste filling material is as follows: 49.5% coal gangue, 8.3% fly ash, 4.1% desulfurization gypsum, 6.2% gasification slag, and 6.2% bottom slag.

Lattice-structured SiC ceramics obtained via 3D printing, gel casting, and gaseous silicon infiltration sintering

In view of technical difficulties in preparing ceramics with complex shapes, gel casting combined with 3D printing was here adopted to prepare silicon carbide ceramic green body, and gaseous silicon infiltration sintering was used to prepare 3D lattice-structured ceramics. The preparation of the slurry, gel curing, and ceramic molding was investigated. Results demonstrate that the ratio of components affects the fluidity and stability of slurry. However, when volume fraction of the solid phase of the slurry reaches 56%, the viscosity of slurry is only 300 mPa s, and drying shrinkage rate of green body is 6.6%; these characteristics make slurry suitable for 3D complex model injection molding. Furthermore, both the temperature and the initiator affect gel curing speed. As the temperature and initiator content increase, the induction and gel time are rapidly shortened. When demolding at 300 °C and when gaseous silicon infiltration sintering is carried out at 1550 °C, a 3D lattice-structured ceramic with relative density of 87% and average compressive strength of 433 MPa can be obtained.

Lignocellulose particle size and rheological properties changes in periodic peristalsis enzymatic hydrolysis at high solids

Periodic peristalsis is an effective intensification method in high solids enzymatic hydrolysis. But the change law of slurry physical properties was not fully understood in periodic peristalsis enzymatic hydrolysis (PPEH) at high solids. This leads to the limitation of its application. Therefore, we studied particle size, viscosity and yield stress changes under periodic peristalsis. The D50 decreased by 42.59% and the viscosity decreased from 290.5 to 0.63 Pa s within 2 h under periodic peristalsis. The yield stress decreased from 245.9 Pa to 8.6 Pa and the fluidity of slurry can be pumped. Furthermore, the relationship between its physical properties and enzymatic hydrolysis efficiency and energy consumption was analyzed. And a method of calculating periodic peristalsis energy consumption was proposed. The energy consumption of periodic peristalsis is one-ninth of the stirring by calculation. These results provided guidance for its industrial application.