Fluidity Of Slurry Research Articles

Experiment and Numerical Simulation on Grouting Reinforcement Parameters of Ultra-Shallow Buried Double-Arch Tunnel

For an ultra-shallow buried double-arch tunnel with a large cross-section, the arching effect is difficult to form in surrounding rock, and grouting method is often adopted to reinforce the surrounding rock. Hence, examining the grouting reinforcement parameters is of great significance for potential failure and collapse prevention. The land part of Haicang undersea tunnel was selected as a case study; laboratory experiments, theoretical analysis, and numerical simulation were performed to determine the grouting solid strength and grouting reinforcement parameters. The effects of different water–cement ratios on slurry fluidity, setting time, bleeding rate, and sample strength were studied by laboratory experiments. A method was proposed to determine the shear strength parameters of grouted surrounding rock through the grout water–cement ratio and the unconfined compressive strength of the rock mass. Numerical simulations were performed for grouting reinforcement layer thickness and the water–cement ratios. The deformation and stability law of tunnel surrounding rock and its influence on surrounding underground pipelines were obtained considering the spatial effect of tunnel excavation and grouting reinforcement. The reasonable selection range of grouting reinforcement parameters was proposed. The initial setting time and bleeding rate of cement slurry increased with the increasing water–cement ratio, while the viscosity of cement slurry and sample strength decreased with the increasing water–cement ratio. The shear strength parameters of grouted surrounding rock were determined by the water–cement ratio of grout and unconfined compressive strength of rock mass before grouting. When the thickness of grouting reinforcement layer h = 1.5 m and the water–cement ratio of grout was suggested η = 0.85, the surface settlement, the deformation of the vault, and the deformation of the nearby pipeline all met the design. Moreover, the construction requirements were more economical. Research results can provide a reference for the selection of grouting reinforcement parameters for similar projects.

Hydrophobic Lightweight Cement with Thermal Shock Resistance and Thermal Insulating Properties for Energy-Storage Geothermal Well Systems.

This study assessed the possibility of using polymethylhydrosiloxane (PMHS)-treated fly ash cenospheres (FCS) for formulating a thermally insulating and thermal shock (TS)-resistant cementitious blend with calcium aluminate cement. To prevent FCS degradation in an alkaline cement environment at high temperatures, the cenospheres were pre-treated with sodium metasilicate to form silanol and aluminol groups on their surface. These groups participated in a dehydrogenation reaction with the functional ≡Si–H groups within PMHS with the formation of siloxane oxygen-linked M-FCS (M: Al or Si). At high hydrothermal temperatures of 175 and 250 °C, some Si–O–Si and SiCH3 bonds ruptured, causing depolymerization of the polymer at the FCS surface and hydroxylation of the raptured sites with the formation of silanol groups. Repolymerization through self-condensation between the silanol groups followed, resulting in the transformation of siloxane to low crosslinked silicon-like polymer as a repolymerization-induced product (RIP) without carbon. The RIP provided adequate protection of FCS from pozzolanic reactions (PR), which was confirmed by the decline in zeolites as the products of PR of FCS. Cements with PMHS-treated FCS withstood both hydrothermal and thermal temperature of 250 °C in TS tests, and they also showed improved compressive strength, toughness, and water repellency as well as decreased thermal conductivity. The lubricating properties of PMHS increased the fluidity of lightweight slurries.

Research on mechanical performances of composite cementitious material system in new bridge expansion joint UHPC material

In the bridge expansion joint repair project, in order to ensure the efficiency of the project, the repair material needs to have better flow properties and higher early strength. The introduction of sulphoaluminate cement will significantly change the properties of UHPC. Compared with ordinary Portland cement, the composition of its cement clinker mineral belongs to another physical and chemical system, which has excellent properties such as early strength, high strength, impermeability and corrosion resistance. Therefore, different groups of UHPC were prepared by changing the content of sulphoaluminate cement, and the fluidity test of each group of slurry and the compressive strength and flexural strength test of 1d, 3d, 7d, 28d were carried out to study the sulfur. The influence of aluminate cement content on slurry fluidity and early mechanical properties in order to obtain the optimal mix ratio of UHPC materials for new bridge expansion joints.

Adsorption Affinity of Linear and Aromatic Organic Anions Competing for Cationic Cement Surfaces.

Competitive adsorption of chemical admixtures onto cement is of critical importance in delivering bulk performance requirements of cement slurries employed in constructing high-performing structures, like oil wells. This challenge is complex to investigate, because of the many variables that include the heterogeneity, high pH, and ionic strength of cement fluids; the multiple crystalline phases present in unhydrated and set cement; and the high number of admixtures required to meet performance criteria in commercial operations. The purpose of this study is to relate chemical structures to relative adsorption behavior of admixtures onto cement when present together and classify such interactions as beneficial (synergistic) or detrimental (antagonistic). Adsorption characteristics of single admixtures were examined by total organic carbon analysis, FT infrared spectroscopy, scanning electron microscopy, calorimetry, and UV/vis spectrophotometry. Results show that the adsorption of single chemical admixtures follows the order of monomeric hydroxycarboxylate molecule > sulfonated linear polymer > sulfonated aromatic polymer > carboxylated/sulfonated linear polymer > carboxylated branched polyether polymers. The observed adsorption behavior of polymers correlates extremely well with the order for cement hydration retardation, with carboxylated polymers being the most powerful retarders. Results correlate closely with the proposed mechanism that sulfonated polymers adsorb onto aluminate phases, presumably the tricalcium aluminate phase; and the carboxylate polymers onto silicate phases, particularly the predominant tricalcium oxysilicate phase. The hydroxycarboxylic monomeric molecule was the strongest retarder of all and has the highest adsorption level, presumably on tricalcium oxysilicate. The competitive adsorption behavior in binary mixtures was studied by monitoring the displacement of a signaling polymer by a second admixture. Results indicate that, for similar functional groups, shorter polymers are competitively more strongly adsorbed than longer chain molecules and that the shorter chain polymers were not desorbed significantly by longer chain polymer molecules. Rheological measurements correlated admixture adsorption behavior to the observed slurry fluidity.

Effect of modified polyvinyl alcohol on fluidity of cement slurry

Select appropriate amount of dispersant to modify polyvinyl alcohol, and explore the influence of modified polyvinyl alcohol on the rheology of cement slurry by investigating the thickening time, initial consistency, free liquid and density, fluidity index and viscosity coefficient of cement slurry. The results show that the thickening time of cement slurry is the shortest when the dispersant parameter is 1.5%, and the rheology of cement slurry becomes better and better when the dosage of polyvinyl alcohol increases. When 1.5% polyvinyl alcohol is added, the rheology of cement slurry is good and the viscosity is low.

Study on the synthesis and properties of benzoate modified with hydroxyl-terminated of the side chains of polycarboxylic superplasticizer

By the esterification of benzoic anhydride (BA) with polyoxyethylene ether (HPEG), the modified macromonomer (BA-HPEG) with benzoate of HPEG was prepared. Then, BA-HPEG and HPEG were copolymerized with acrylic acid (AA) with an alkyd ratio of 2:1 to obtain three novel polycarboxylate superplasticizer BA-PCE-10, BA-PCE-20 and BA-PCE-30 with good flow retaining behaviors of cement mortars. The effects of the benzoate content in the copolymers on adsorption, dispersion, Zeta potential and hydrodynamic radius for cement suspensions were investigated to elucidate the governing dispersing mechanism. The absorption of the modified copolymers on the cement surfaces was controlled by COO― and hydrophobic phenyl content in copolymers and polymer conformation in solution. The fluidity of cement slurry increases with the adsorbed amount to increase dispersion effect. The copolymers grafted with benzoate exhibited a high dispersion performance than that of the unmodified molecule, which could be explained as the hydrophobic modified polycarboxylate superplasticizer mainly dispersing cement particles by the main repulsion of steric hindrance and electrostatic repulsion, so as to improve the dispersion performance of cement. The study shows that the flow retaining behaviors of polycarboxylate superplasticizer can be significantly improved by BA modified with hydroxyl-terminated of the side chains of polycarboxylic superplasticizer.

Mechanical experiments and precise simulation of a novel functional material: Electrically conductive roller-compacted concrete

<p indent=0mm>Electrically conductive roller-compacted concrete (ERCC) is a novel functional material, which can solve the problems of low efficiency of artificial snow removal and deicing on expressway and airport runway and the difficulty in temperature control of dam engineering structures. In this study, we designed ERCC and conducted an experimental study and numerical simulations on the designed ERCC. The improvement mechanism of surfactants on the fluidity of ERCC slurry and the effects of carbon-black dispersion were analyzed by scanning electron microscopy. Aiming at the large ERCC core-sampling specimen formed by rolling, macroscopic tests for mechanical properties and mesoscopic tests by X-ray computed tomography (XCT) were conducted. Based on the experiment, precise simulation of ERCC was performed by coupling the calculation methods of continuous and discontinuous mediums. We developed a mesoscopic model of ERCC based on real aggregate. The model overcomes the challenges of high cost of XCT models, low efficiency of discontinuous-medium calculation methods, and poor refinement of traditional sphere/polyhedral aggregate models in traditional continuous-medium calculation methods for concrete. The result shows that surfactants can significantly improve the effect of carbon-black dispersion on ERCC, and the forming quality of rolling construction technology is positive with compressive strength of <sc>22.85 MPa,</sc> splitting strength of <sc>1.72 MPa,</sc> elastic modulus of <sc>23.7 GPa,</sc> and pore volume ratio of 1.05‰. The mortar and interface strengths of ERCC were constant, whereas with an increase in the volume ratio of aggregates, the mechanical properties of ERCC could be improved. The precise simulation results are consistent with the statistical laws of concrete material characteristics in many practical projects, and they have better applicability than traditional meso-simulations of concrete.

Inorganic-organic composite solid electrolyte based on cement and Polyacrylamide prepared by a synchronous reaction method

Inorganic-organic composite solid electrolyte (CSE) has a high potential for future energy storage. Compared with ceramic-based CSE, cement-based CSE can be prepared at room temperature, which is conducive to incorporation of polymer into CSE. However, the content of polymer in CSE is limited to the small level, which hinders the performance of the electrolyte. In this work, a novel synchronous reaction method (SRM) is proposed to prepare CES, which can exceed the content limit of polymer remarkably. Through SRM, cement hydration and polymer polymerization are simultaneously carried out to solve the problem of cement slurry fluidity caused by the addition of polymer. Infrared and 1H-NMR spectra confirm that the CSE has been successfully prepared, and Polyacrylamide (PAM) can be detected in CSE. GPC results show that the molecular mass of PAM in the CSE increases with the monomer content. SEM results reveal that PAM and hardened cement are well combined and evenly distributed at the micro level. The microstructure, ionic conductivity and compressive strength of CSE change considerably with the polymer content. In general, with the increase of polymer content, the internal structure is gradually improved, also the ionic conductivity and compressive strength are improved remarkably. The multi-functionality results indicate that the CSE prepared by synchronous reaction method with 20 wt.% PAM shows the best combination of the ionic conductivity (10.52 mS/cm) and the compressive strength (53.78 MPa). An all-solid supercapacitor (ASS) was assembled by the solid electrolyte and rGO/Ni foam composite electrodes, which shows good electrochemical energy storage performance. Therefore, the solid electrolyte synthetized with SRM provides a promising way for the application of all-solid electrochemical energy storage.

Research on sustainable development of fine-grained material cement slurry

Sustainability has become a major focus of the cement industry, largely due to the carbon dioxide emissions associated with Portland cement production. In grouting engineering, ordinary cement slurry has high viscosity, poor fluidity and groutability and is prone to blockage. In this study, a cement slurry was designed using superfine cement (SC). Fine-grained ultrafine fly ash (UFA) waste was used, part of which is used to replace cement, and a certain amount of nontoxic mSiO2·nH2O (SH) is extracted from limestone waste and mixed with the commonly used admixture polycarboxylic acid water reducer (PAWR) to ensure its physical properties in practical engineering applications while reducing its viscosity, increasing its fluidity, and reducing the occurrence of clogging. To determine the optimal mix ratio of the cement slurries mixed with various materials, the characteristics of each material were analyzed through the single-factor test of the multiperformance test, and the orthogonal test mix ratio was designed based on the single-factor test results. Through the Taguchi grey correlation analysis method, the orthogonal test data were analyzed to find the optimal mix ratio. A performance test of the cement slurry with the optimal mix ratio was carried out, and its sustainability was analyzed. Combined with the Discrete Element Method (DEM) and the Voronoi Calculation Method (VCM) methods, UDEC numerical simulation software is used to simulate and analyze the general laws of cement slurry fluidity. The results show that the cement slurry with the optimal mix ratio of SH, SC, PAWR and UFA materials has good fluidity and groutability, has the characteristics of sustainable development, and can be applied to practical projects.

Effect of Different Activators on Rheological and Strength Properties of Fly Ash-Based Filling Cementitious Materials

In this paper, lime, gypsum, NaOH, and Na2SO4 are mainly used to study the activation degree and activation mechanism of fly ash, and L9 (34) orthogonal table is used for the orthogonal test. The influence of different activators on the rheological and strength properties of slurry was analyzed. The microstructure and hydration products of fly ash cement cementitious body were studied by SEM and XRD. The results show that the bleeding rate of slurry containing activator fly ash system is between 2.24% and 3.37%, which is much higher than that of pure cement slurry (9.25%). Therefore, the addition of this system can improve the fluidity of slurry, and the optimal scheme is a3b2c2d2. The results show that the compressive strength of cement with activator fly ash system is much lower than that of pure cement, but the increase of strength is between 31% and 85%, which is much greater than that of pure cement (35%–46%). The optimal scheme is A2B2C3D3 or A3B2C3D3 at 3 days and A1B3C2D3 at 28 days. According to the scanning results of SEM and XRD, the addition of activator can significantly improve the hydration degree of fly ash and form a more complex network structure without obvious gap.

Ceramic Molding Based on 3D Printing Technology

3D printing technology can also be described as an increase in the manufacture of materials. In the forming process, no traditional machine tools, fixtures and cutting tools are required. Parts models of arbitrary complex shapes can be manufactured quickly and accurately. In the experimental process, small printers are modified in the extrusion part and printed with water-based alumina slurry as ink. The water-based oxide slurry is mainly water medium and contains only a small amount of organic binder. The influence of pH value, solid content, plasticizer, binder, lubricant and dispersant on the fluidity of slurry is studied. The results show that the slurry has the best stability when the amount of dispersant is 0.4 wt%, plasticizer is 1.0 wt%, lubricant is 4.0 wt%, binder is 1.0 wt%.

Effect of polycarboxylate superplasticizer on fluidity and rheology of cement slurry containing silica fume

The effect of polycarboxylate superplasticizer on the fluidity and rheology of cement - silica fume - water paste was investigated. The changes of dispersion degree, yield stress and plastic viscosity of paste with different superplasticizer content were analyzed. The results show that the rheological properties of paste with different superplasticizer content conform to Herschel-Bulkley model. The shear thinning of the slurry is manifested as a typical yielding pseudoplastic fluid characteristic. When the content of superplasticizer is less than 1.0%, the plastic viscosity and yield stress decrease and the fluidity increase with the increase of plasticizer content. When the content of superplasticizer is more than 1.0%, the yield stress decreases slightly and the plastic viscosity increases with the increase of plasticizer content. The fluidity decreases with the increase of yield stress, and there is a good correlation between them.

Evaluation of Rheological Parameters of Slag‐Based Paste Backfill with Superplasticizer

The use of blast furnace slag‐based binders in cemented paste backfill (CPB) has become increasingly popular in China, due to its low cost and superior early‐age strength. Increasing the solid content can increase the strength of CPB, but it will lead to a decrease in its fluidity. As a chemical admixture that can improve CPB slurry fluidity, superplasticizer is gaining increased interest in the field of CPB. In this study, the effects of superplasticizer types and dosages, curing time, solid content, and binder content on the rheological properties of fresh CPB made of blast furnace slag‐based binder (Slag‐CPB) were studied. For Slag‐CPB samples, polycarboxylate (PC) has the best water‐reducing effect, followed by polymelamine sulfonate (PMS) and polynaphthalene sulfonate (PNS). In the absence of a superplasticizer, the shear yield stress and plastic viscosity of Slag‐CPB are lower than those of CPB made of ordinary Portland cement (OPC‐CPB). The water‐reducing effect of PC on OPC‐CPBs samples is stronger than that of Slag‐CPB samples. The degradation rate of the water‐reducing effect in slag‐based samples is higher than that in cement‐based samples. The effect of PC is affected by solid content and binder content. These results will contribute to a better understanding of the rheological behavior of Slag‐CPB with superplasticizer.

Enhancement of fluidity and slurry-phase hydrogenation reactivity of coal-oil slurry by preheating treatment

The effects of preheating treatment at temperatures from 200 to 350 °C on the viscosity–temperature properties and slurry-phase hydrogenation reactivity (SHR) of a coal-oil slurry (COS) prepared from Xinjiang lignite and fluid catalytic cracking slurry were studied. Moreover, the structural changes to the coal after preheating treatment were characterized to reveal the origin of preheating treatment effects. As the preheating temperature increased, the viscosity of COS increased, and the sudden increases in the COS viscosity at 160 °C and 240 °C disappeared, improving the fluidity of COS. Moreover, as the preheating temperature was increased, the SHR of the COS increased with increasing preheating temperature up to 300 °C, but decreased when a temperature of 350 °C was used. Structural characterization of the coal showed that increasing the preheating temperature up to 300 °C enhanced coal swelling, promoting expansion of the coal structure, which in turn increased its average particle size, specific surface area, and porosity. The increased release of light components in the coal, which had relatively high and stable contents of ortho-substituted aromatic rings and methyl and methine groups, was also observed with increasing preheating temperatures of up to 300 °C. The irreversible swelling of the coal induced by preheating treatment was responsible for the improved fluidity and enhanced SHR of the COS. However, the pyrolysis of coal occurring at 350 °C decreased the specific surface area and porosity of coal, causing a reduction in contact between the coal and catalyst sites and decreasing the SHR of COS.

Development of Quick-Solidifying Foamed Concrete for Mine Fires Extinguishment and the Basic Performances Tests

Coal mine fire has always been the main disasters in coal mining in various countries around the world, and several attempts have been made to develop many kinds of fire extinguishing materials and technology. Because of the salient features: high foaming factor(that means a small amount of raw materials can produce large-volume of foam concrete), widely source, eco-friendly and economical raw materials, cement-based inorganic foam concrete for engineering filling and coal mine fire extinguishing has become the first choice. But the shortcomings of traditional foamed concrete are obvious, short curing time, poor water retention capacity, foam burst easily, and can not be kept in the spontaneous combustion cavity area for a long time to accumulate and solidify; at the same time after the foam burst, the formation of cracks in the solidified body is sometimes not strict, and so on. So, traditional foamed concrete should be optimized and the aforementioned deficiencies could be overcome. The objective of this paper goes to propose quick-solidifying foamed concrete by laboratory test and to test these materials properties. The stability of the solidified body of the quick-solidifying foamed concrete, foamed concrete slurry fluidity, curability, shrinkage and cracking during solidifying, high temperature resistance and water resistance were tested and the laws and values of these characteristics were got. The results finally show the quick-solidifying foamed concrete developed in the paper with a good performance in implementation of high filling and fire prevention in big space of mine.

Effect of the cross-linker structure of cross-linked polycarboxylate superplasticizers on the behavior of cementitious mixtures

At present, several researchers mainly focus on the synthesis of new micro-cross-linking structure, or explore the effect of cross-linkers with different molecular weight and similar structure on the performance of cross-linked polycarboxylate superplasticizers. In order to explore the influence of the different molecular structure of the cross-linker on the performance of polycarboxylate superplasticizers, two kinds of cross-linked polycarboxylate superplasticizers were synthesized in this study. These two superplasticizers incorporated either a linear cross-linker triethylene glycol diethyl ether or a cyclic cross-linker 3,9-divinyl-2,4,8,10-tetroxyspiro[5,5] undecane as one of the monomers. Then the polymers were respectively coded as SPT and SPD. Furthermore, the dispersion performance of the cross-linked polymers was evaluated by cement slurry fluidity tests and scanning electron microscopy (SEM) characterization. Consequently, cementitious mixtures incorporating SPT had better dispersibility than those incorporating conventional comb-type polycarboxylate superplasticizers (SPC) and SPD. In addition, the XRD, thermogravimetric analysis (TGA), hydration heat, and setting time tests confirmed that SPT exhibited a stronger retardation effect on cement hydration than that was provided by SPD. It was also found that SPT enhanced the compressive strength of concrete, compared to SPC and SPD. This study provides a reference for the development of cross-linked polycarboxylate superplasticizer.

Research on the fluid characteristics of cemented backfill pipeline transportation of mineral processing tailings

With the deepening of underground resource exploitation, the application of cemented backfill pipeline transportation of mineral tailings has become the best option to reduce the risk of deep ground pressure and solid waste pollution. Research in this field is mainly centred on slurry fluidity experiments. However, the slurry transportation parameters, particle characteristics and complexity of the pipeline all cause uncertainty in the calculation of backfill pipeline transportation parameters. The conventional backfill loop test is expensive. Combining structural fluid tests with particle flow models, this paper presents a method to optimize backfill pipeline transportation parameters. The H-B model is employed to analyse the transportation resistance of backfill slurry along the line to establish the relation function between the resisting force and the parameters. Adoption of a custom function improves the accuracy of the inter-phase drag model and the erosion effect. This paper analyses the flow state of the high-concentration solid-liquid dense phase fluid in backfill gravity transportation to obtain optimized transportation parameters. The research results improve the accuracy of the calculation of the backfill pipeline transportation parameters, which can be effectively applied in the optimal design of high-concentration slurry backfill pipeline transportation.

Improvement of flexural and tensile strength of layered-casting UHPC with aligned steel fibers

In order to further improve flexural and tensile strength as well as ductility of ultra-high performance concrete (UHPC), this research developed an improved device for casting layered UHPC with better alignment of the fiber. The effect of fiber content (2% or 3%) and fiber type (straight fiber, end hooked fiber and combining the two fibers) on the flexural strength was first discussed. The optimal fiber content and fiber type were used to study the effect of fiber alignment on the mechanical performance of UHPC under flexural and direct tension loading. Through image analysis, the specific influence of fiber aligning on fiber orientation and dispersion in UHPC was analyzed in detail. The results showed that the vibration effect of the improved device significantly improved the slurry fluidity, and the movable mold provided additional drag force during the casting process to ensure the effectiveness of fiber aligning. Fiber aligning not only improved the ultimate tensile and flexural strength of UHPC, but also significantly improved the cracking strength and ductility of UHPC due to the orientation of fibers parallel to the casting direction after fiber aligning. However, the UHPC after fiber aligning showed anisotropy, and had a higher probability to develop diagonal cracks under tension. In addition, fiber aligning made the overall fiber dispersion uniform, while it led to the uneven fiber distribution at the interlayer boundary and the weak areas formed there.

Rheological Study on Cemented Coal Gangue Fly-Ash Backfill Slurry Associated with Fly Ash Impacts

The cemented coal gangue-fly ash backfill (CGFB) slurry has commonly been used to control subsidence damage caused by underground coal mining. This paper discusses the CGFB slurry rheological characteristic associated with the various percentage of the fly ash within the configuration of the mixture. A general description about CGFB slurry fluidity in the pipe transportation is provided. The physical, chemical and rheological characteristic of the CGFB have been determined in the test. The fly ash was mixed with 18%, 20% and 22% of solid concentration with respects to 12%, 10% and 8% for cement on various concentrated CGFB slurry ranges 76.05%, 78.05% and 80.05%. The tests verify the CGFB slurry exhibits non-Newtonian behavior in nature as Bingham plastic fluid. The experimental data show CGFB slurry rheological characteristic is noticeable influenced by the slurry solid concentration and the proportion of the fly ash, which affects the value of yield stress and viscosity. The lower value of the rheological parameters was observed on 22 % fly ash other than the 18 % case based on the same solid concentration of CGFB slurry.

Application of a Bentonite Slurry Modified by Polyvinyl Alcohol in the Cutoff of a Landfill

Soil‐bentonite cutoff walls are usually used to contain the contaminants of landfills. The pumpability, permeability, and adsorption capability of the slurry are all crucial to the performance of the cutoff wall. In this study, the effect of polyvinyl alcohol (PVA) was used to improve the performance of bentonite slurry. A series of lab tests were conducted to evaluate the pumpability, permeability, and adsorption capacity with different concentrations of PVA treatment. Results show that the addition of PVA can increase the fluidity and pumpable period of slurry, which facilitates the casting and grouting during construction. The addition of PVA also helps to reduce the permeability coefficient of slurry and improve the adsorption capability which enhances the cutoff performance of the walls.