Fluidity Properties Research Articles

Fluidity and mechanical properties of magnetic-field-enhanced steel fibre reinforced coral mortar

Fluidity and mechanical properties of magnetic-field-enhanced steel fibre reinforced coral mortar

Internal Curing Effects of Slag on Properties and Microstructure of Ambient-Cured Fly Ash-Based Geopolymer Mortar

The preparation of ambient-cured fly ash-based geopolymer mortar (FAGM) with high strength by utilizing the high chemical reactivity of slag is key to realizing the sustainable and efficient application of solid waste resources. This paper investigates the influence of different type S95 slag contents (0%, 5%, 10%, 15%, 20%, 25%, and 30%) on the fluidity, setting time, and mechanical properties of FAGM at ambient temperature. The direct method is first adapted to monitor the influence of slag on geopolymerization. The results indicate that slag has a minimal effect on the fluidity of the mortar, while the setting time decreases and compressive strength increases with higher slag content. For FAGM with 30% slag content, the setting time is reduced from 3160 min to 140 min, with a decrease of 95.6%, and a 3-day and 28-day compressive strength increase from 1.5 MPa and 34.7 MPa to 33.5 MPa and 73.4 MPa, with enhancements of 2170.2% and 110.3%, respectively. Slag also exerts an internal curing effect, raising the internal curing temperature and accelerating the geopolymerization process of fly ash, thereby improving the compactness of FAGM and reducing its porosity. This approach successfully enables the production of high-strength, ambient-cured FAGM.

Machine Learning Driven Fluidity and Rheological Properties Prediction of Fresh Cement-Based Materials.

Controlling workability during the design stage of cement-based material mix ratios is a highly time-consuming and labor-intensive task. Applying artificial intelligence (AI) methods to predict and optimize the workability of cement-based materials can significantly enhance the efficiency of mix design. In this study, experimental testing was conducted to create a dataset of 233 samples, including fluidity, dynamic yield stress, and plastic viscosity of cement-based materials. The proportions of cement, fly ash (FA), silica fume (SF), water, superplasticizer (SP), hydroxypropyl methylcellulose (HPMC), and sand were selected as inputs. Machine learning (ML) methods were employed to establish predictive models for these three early workability indicators. To improve prediction capability, optimized hybrid models, such as Particle Swarm Optimization (PSO)-based CatBoost and XGBoost, were adopted. Furthermore, the influence of individual input variables on each workability indicator of the cement-based material was examined using Shapley Additive Explanations (SHAP) and Partial Dependence Plot (PDP) analyses. This study provides a novel reference for achieving rapid and accurate control of cement-based material workability.

ДОСЛІДЖЕННЯ ГАЛУАЗИТУ ЯК НАНОСІЯ ДЛЯ ФОТОЗАХИСТУ АКТИВНИХ ФАРМАЦЕВТИЧНИХ ІНГРЕДІЄНТІВ У СКЛАДІ ТАБЛЕТОК

The paper presents the results of research into composite tablets based on halloysite nanotubes. It is shown that according to the determination of Repose Angle, Gaussner coefficients and Carr’s index, halloysite has similar fluidity properties to microcrystalline cellulose, which allows it to be used for the development of formulations of tablet forms of medicines. Tablets are made based on halloysite, microcrystalline cellulose, croscarmellose sodium, magnesium stearate and colloidal silicon dioxide. Such standardized parameters as disintegration time, hardness, brittleness, friability and tensile strength of tablets, which fully meet pharmaceutical standards to produce tablet forms of drugs, were studied. The photostability of moxifloxacin hydrochloride encapsulated in halloysite as part of the developed composite tablet was studied. Testing for the photostability of moxifloxacin hydrochloride was carried out by irradiating composite tablets with halloysite-encapsulated pharmaceutical ingredients with light in the visible and ultraviolet ranges. Determination of the change in the effective concentration of moxifloxacin hydrochloride was carried out in model solutions at pH 1.2(0.1 M HCl solution), 4.5 (acetate buffer) and 6.8 (phosphate buffer) by liquid chromatography. It was found that after photostability testing, the effective concentration of moxifloxacin hydrochloride decreased by no more than 3%, which indicates the feasibility of using halloysite as an effective nanocarrier for protection against photodegradation of active pharmaceutical ingredients.

Study on the properties of alkali-activated ferrochrome slag paste filling materials prepared from multiple industrial solid wastes

ABSTRACT The enormous utilization potential of industrial solid waste in cemented paste backfill (CPB) materials has attracted considerable interest. To solve the treatment challenges of ferrochrome slag (FS), a green ferrochrome slag cemented paste backfill materials (FS-CPB) composed of FS, desulfurization gypsum (DG) and granulated blast furnace slag (GBFS) was proposed in the study. The setting time, slump, uniaxial compressive strength (UCS), microstructure and leaching behavior of FS-CPB were systematically investigated. The results indicated that FS and DG showed retarding properties, while the setting time first decreased and then increased with the increase of polycarboxylate superplasticizers (PCE) and sodium silicate dosage. The slump was positively correlated with FS and sodium silicate dosage. However, the addition of DG and PCE can improve the fluidity properties. The optimum UCS values (3 d: 0.92 MPa; 7 d: 2.43 MPa; 14 d: 3.19 MPa; 28 d: 4.58 MPa) was obtained with 6% sodium silicate. Moreover, the primary hydration products of FS-CPB were ettringite, C-S-H gels and N-A-S-H gels. The leaching concentrations of total Cr and Cr(VI) satisfied the Class Ι water quality standard limits (≤1.5 mg∙L−1) in GB 8978–1996 and Class III water quality standard limits (≤0.05 mg∙L−1) in GB 14,848-2017, respectively. The research results in this paper can provide new options for cement substitutes in mining companies and guide the large-scale application of FS.

Spatially controllable fluid hydrogel with in-situ electrospinning PCL/chitosan fiber for treating irregular wounds

Skin injuries sustained during exercise are often irregular in shape and frequently accompanied by infections. Bacteria residing in the crevices of these wounds can lead to persistent infections. Routine wound monitoring, which requires removing the wound dressing to assess recovery, is inconvenient and increases the risk of infection. To address this, we prepared a polyvinyl alcohol/polyhydroxylated fullerenes ((PVA/PHF) hydrogel with good fluidity and photothermal antibacterial properties, which can penetrate into the crevices of irregular wounds. After the hydrogel was applied to the wound, the hydrogel was locally defined by the polycaprolactone/Chitosan (PCL/CS) membrane of in-situ electrospinning, which effectively killed bacteria, and the healing efficiency was increased by 240 % in the wound healing experiment. The PVA/PHF hydrogel exhibits excellent electrical conductivity, making it suitable for real-time monitoring of human body motion as a strain sensor. This capability provides doctors with an accurate basis for wound assessment. At the same time, the hydrogel can achieve self-healing within 1.5 s and withstand up to 2200 % tensile strain, which can be used for large-scale motion monitoring of the human body. This flowable hydrogel, capable of penetrating wound crevices, offers a dual function of both treatment and monitoring.

Effects of cement content, polypropylene fiber length and dosage on fluidity and mechanical properties of fiber-toughened cemented aeolian sand backfill

Effects of cement content, polypropylene fiber length and dosage on fluidity and mechanical properties of fiber-toughened cemented aeolian sand backfill

Experimental study on the effect of mixing parameters on the rheological behaviour and micro-flocculation structure of ultrafine Portland cement slurry

The penetration diffusion of ultrafine Portland cement (UPC) slurry is closely related to its rheological behaviour and micro-flocculation structure. To date, there has been a need for more research investigating the impact of mixing parameters on the macro-micro hydrodynamic behaviour of UPC slurries. In this study, a series of macroscopic rheomechanical characterisation tests and microscopic in-situ tests of the flocculation structure of UPC slurries under various mixing parameters were conducted systematically by using a rotational rheometer and a focused beam reflectance measurement (FBRM) system. The effects of mixing speeds and times on the macroscopic shear stress-shear rate curves, rheological patterns, rheomechanical parameters, and the distribution of micro-flocculated particles of UPC slurries were investigated. The results indicate that the macroscopic rheomechanical parameters and microscopic flocculation coefficient of UPC slurry exhibit a decrease with increased slurry mixing speed. However, a “decrease and then increase” trend is observed with increased slurry mixing time. The smaller the powder size of cement and the lower the water-cement ratio of the slurry, the more sensitive the rheomechanical properties of the slurry are to the influence of the mixing parameters. A positive correlation exists between the macroscopic rheomechanical properties of UPC slurry and its microscopic flocculation coefficient. Increasing the slurry mixing speed or prolonging the early mixing time can destroy the microscopic flocculation particles of UPC slurry, a reduction in the flocculation coefficient of the slurry, and an improvement in the macroscopic fluidity properties. The research findings provide a foundation for improving the effectiveness of UPC grouting in the engineering field.

Influence of mixing time and coarse aggregate content on the flowability, setting time, and mechanical properties of cemented backfill

Ensuring the even mixing of filling slurry is crucial for the performance of cemented backfill, and mixing time is a key factor in this process. This study comprehensively investigates the effects of mixing time and coarse aggregate content on the fluidity, setting time, and mechanical properties of coarse aggregate backfill through extensive experiments. The results indicate no significant regularity in the vibration diffusion of the filling slurry at different regions of the mixing shaft, and positional variations do not impact the slurry's fluidity. Vibration diffusion initially increases and then decreases with prolonged mixing time, suggesting an optimal mixing time of within 9 minutes. The setting time of the filling slurry shows no significant variation across different regions of the mixing shaft. However, the setting time decreases with longer mixing times and increases with higher coarse aggregate content. The uniaxial compressive strength (UCS) of the backfill improves with extended mixing time, particularly benefiting early UCS. Incorporating an optimal amount of coarse aggregate, around 60 %, also enhances the UCS. Both extending the mixing time and adding an appropriate amount of coarse aggregate help suppress the expansion of destructive cracks and reduce internal void structures, thereby improving the overall mechanical properties of the backfill.

Al-CeO2-Mg refiner on grain refinement, cast fluidity and mechanical properties of AZ91 alloy

Al-CeO2-Mg refiner on grain refinement, cast fluidity and mechanical properties of AZ91 alloy

Preparation and flame retardant properties of new mining fireproof gel

Coal spontaneous combustion (CSC) brings great danger to mine safety. Although traditional colloidal fire-fighting materials can reside at high fire source points, their permeability and fluidity are poor, and such materials focus on their water absorption, but pay less attention to water retention and resistance, which makes their fire-fighting effect not good. This paper proposed a new type of mining fire prevention colloid material (CPS-α), which had good solid water gel formation, viscosity, fluidity, and blocking properties to compensate for traditional colloids' shortcomings. According to the single-factor experiment, polymeric polyacrylamide (PAM) as the base material, sodium carboxymethyl cellulose (CMC) as the coagulant, modified starch (SS) as the flame retardant and reduced ascorbic acid were determined. After gel treatment, compared with raw coal, the critical temperature point of spontaneous combustion of coal was increased by about 28 °C, the time to reach the critical temperature point was delayed by 190s, and the characteristic temperature points were significantly increased; the overlap area of coal and water increases by about 20 % after adding gel, and the change slope of the diffusion coefficient of water decreases, which indicated that CPS-α had good flame retardant effect.

Mechanical properties, hydration behavior and shrinkage deformation of ultra-high performance concrete (UHPC) incorporating MgO expansive agent

To reduce the extremely high autogenous shrinkage deformation of ultra-high performance concrete (UHPC) caused by low water-to-binder ratio and high binder materials content, this work aimed to designed and prepared low shrinkage UHPC containing MgO-based expansive agents (MEA). The effects of UHPC with different reactivity of MEA (R-MEA and S-MEA) were compared in terms of fluidity, mechanical properties, hydration characteristics, shrinkage deformation, pore structure and microstructure. The results indicated that the incorporated of MEA decreased the fluidity and mechanical properties of UHPC, while the autogenous shrinkage deformation was compensated significantly. When 6 % R-MEA was incorporated, the flow and compressive strength decreased by 16 % and 7.9 %, respectively, but the autogenous shrinkage at 7 days also decreased by 70.1 % at the same time. The same amount of S-MEA showed lower compensation for the autogenous shrinkage of UHPC than R-MEA, but with the same reduction in compressive strength loss. This was due to the highly reactive R-MEA showed higher hydration degree and larger swell increment, which caused more compensation for shrinkage in UHPC, while it had slight adverse effect on the strength development. It is worth noting that the compensation effect of autogenous shrinkage is very limited when the doping is higher than 6 % for either MEA, but the loss of mechanical properties is serious. In addition, the microstructure showed that the crystal growth pressure of brucite forced the pastes to expand and thus resulted in increase on the porosity for UHPC. This study provides a feasible and effective way for mitigating the autogenous shrinkage of UHPC.

Utilization of biochar as a green additive in supersulfated cement: Properties, mechanisms, and environmental impacts

To promote the green development of building materials, this study develops a novel and sustainable method for incorporating coconut-derived biochar (BC) in supersulfated cement (SSC). Moreover, the solid waste desulfurized gypsum is used as a sulfate activator. The macroscopic experimental results show that the addition of 2 % biochar can reduce the fluidity of composites by 12.5 % but increase the 28-day compressive and flexural strength by 10.3 % and 19.1 %, respectively. Hydration heat analysis show that biochar can increase the maximum heat release of SSC. XRD patterns and TGA analysis indicate that 2 % biochar can improve the hydration degree of cement where the bound water content is increased by 8.9 %. SEM observations and 1H NMR spectrum suggest that although biochar can compact the microstructure, it increases the harmful and multiple harmful pores ratio. Furthermore, a comprehensive analysis considering greenhouse gas emissions, energy consumption, cost, fluidity, and mechanical properties is performed to evaluate the BC-SSC composites. The results prove that BC-modified SSC has significantly lower environmental pollution and resource consumption than ordinary Portland cement, but the cost may be increased.

Properties of Polymer-Modified Cement-Water-Glass Slurry.

The corrosion resistance of cement-water-glass dual-liquid slurry is poor. Improving its material properties is necessary. In this study, we examined the influence of water-based lotions on the fluidity, gelling time, and mechanical properties of a cement-water-glass dual-liquid slurry based on the mix proportion of the dual-liquid slurry commonly used in construction. The mixture ratio of a C-S (cement-water-glass slurry) dual-liquid slurry was adjusted by introducing a waterborne polyurethane lotion and a waterborne acrylic lotion to modify the traditional C-S dual-liquid slurry material. When acrylic acid is used as a modifying polymer at a dosage of 7.5%, the flowability and gelation time of the dual-liquid slurry are excellent, the compressive strength of the stone body decreases slightly, the flexural strength is improved to a certain extent, and the stone body's crack resistance during water loss is also enhanced. Moreover, the porosity of the stone body is low.

Enhancing fluidity and mechanical properties in Limestone Calcined Clay cements with one-third Portland clinker content

Limestone Calcined Clay Cements (LC3) are attracting considerable attention due to their low CO2 footprints and relatively fast hydration kinetics. LC3-50 formulations (approximately 50 % Portland clinker, 30 % kaolinitic calcined clay, 15 % limestone and 5 % gypsum) are being extensively investigated and the hydration chemistry, rheology, mechanical strength developments and durability performances are starting to be well established. LC3 binders with lower clinker factors are possible, offering an opportunity for further CO2 footprint reduction. However, these blends have been much less studied. This work contributes to fill this gap. Here, a LC3-35 binder (i.e. 35 % Portland clinker content) is investigated and its performances are compared to those of the original Portland cement (PC) and a standard LC3-50 binder. The effects of two superplasticizers and a strength-enhancing admixture are thoroughly investigated in mortars and pastes. Larger calcined clay contents result in an exacerbation of the slump retention problem, but this issue is solved by the use of a new superplasticizer. Moreover, the low mechanical strengths at early ages can be partly mitigated with a C-S-H nucleation seeding admixture. Employing the right admixtures, LC3-35 binders can develop strength values similar to those of neat PC and LC3-50 at 7 and 28 days. The laboratory X-ray powder diffraction results for LC3-35 pastes, when using the strength-enhancing admixture, show that C4AF exhibits an accelerated reaction rate, leading to the formation of larger amounts of AFt and AFm phases. Approximate mass balance calculations are carried out to estimate the metakaolin reaction degree. Finally, an environmental performance indicator is used to place the footprints of the reported binders within the LC3 landscape.

Versatile, modular, and customizable magnetic solid-droplet systems

Magnetic miniature robotic systems have attracted broad research interest because of their precise maneuverability in confined spaces and adaptability to diverse environments, holding significant promise for applications in both industrial infrastructures and biomedical fields. However, the predominant construction methodology involves the preprogramming of magnetic components into the system's structure. While this approach allows for intricate shape transformations, it exhibits limited flexibility in terms of reconfiguration and presents challenges when adapting to diverse materials, combining, and decoupling multiple functionalities. Here, we propose a construction strategy that facilitates the on-demand assembly of magnetic components, integrating ferrofluid droplets with the system's structural body. This approach enables the creation of complex solid-droplet robotic systems across a spectrum of length scales, ranging from 0.8 mm to 1.5 cm. It offers a diverse selection of materials and structural configurations, akin to assembling components like building blocks, thus allowing for the seamless integration of various functionalities. Moreover, it incorporates decoupling mechanisms to enable selective control over multiple functions, leveraging the fluidity, fission/fusion, and magneto-responsiveness properties inherent in the ferrofluid. Various solid-droplet systems have validated the feasibility of this strategy. This study advances the complexity and functionality achievable in small-scale magnetic robots, augmenting their potential for future biomedical and other applications.

Effect of Composition and Pouring Temperature of Cu-Sn on Fluidity and Mechanical Properties of Investment Casting

The composition and pouring temperature are important parameters in metal casting. Many cast product failures are caused by ignorance of the influence of both. This research aims to determine the effect of adding tin composition and pouring temperature on fluidity, microstructure and mechanical properties including tensile strength and hardness of tin bronze (Cu-Sn). The Cu-Sn is widely used as employed in the research is Cu (20, 22 and 24) wt.%Sn alloy using the investment casting method. Variations in pouring temperature treatment TS1 = 1000°C and TS2 = 1100°C. The mold for the fluidity test is made with a wax pattern then coated in clay. The mold dimensions are 400 mm long with mold cavity variations of 1.5, 2, 3, 4, 5 mm. Several parameters: increasing the pouring temperature, adding tin composition, decreasing the temperature gradient between the molten metal and the mold walls result in a decrease in the solidification rate which can increase fluidity. The α + δ phase transition to β and γ intermetallic phases decreases fluidity at >22wt.%Sn. The columnar dendrite microstructure increases with the addition of tin composition and pouring temperature. The mechanical properties of tensile strength decrease, hardness increases and the alloy becomes more brittle with increasing tin composition.

Evaluation of Fe Content on the Fluidity of A356 Aluminum Alloy by New Fluidity Index

AbstractElements that are deliberately added to aluminum alloys or are incorporated into the alloy later depending on the production process affect the final product properties. In addition, liquid metal cleaning is important in minimizing undesirable elements. Considering the production process, one of the most harmful impurities that is likely to pass into the alloy via diffusion for aluminum is the element, Fe. It is known that this is due to the fact that although Fe is highly soluble in liquid aluminum and its alloys, it has very little solubility in solids. Depending on the Fe content, mechanical properties, porosity and fluidity properties are affected in aluminum alloys. In this study, stainless and carbon steel rods were dipped into the melt at 700 °C and 750 °C for 1, 2 and 5 h. Castings were performed before and after degassing. Four-channel fluidity mold with different section thickness was used in the trials. Additionally, microstructure characterization was performed under varying casting conditions. Fluidity Index was proposed which is a single value measured from all fluidity values in different sections. When the results were examined, it was determined that the diffusion material, holding time, casting temperature and liquid metal cleanliness had an effect on the fluidity. Due to the increase in diffusion time, a decrease in fluidity was observed in both carbon steel and stainless steel. It was found that fluidity was significantly reduced when using stainless steel.

Improved ablation resistance of silicone/phenolic hybrid resin coatings with Zr-Si-O glass as anti-ablation layer

With the development of the new generation space vehicles, traditional phenolic resin (PR)-based coatings are no longer able to meet the increasingly harsh thermal environment. There is an urgent need to develop higher performance PR to ensure the flight safety of aircraft. Therefore, in this work, a novel hyperbranched polysiloxane containing Si-O-Zr bond was synthesized and then introduced into PR to develop homogeneous silicone/phenolic hybrid resin coatings. The TG results indicate that the introduction of Si-O-Zr bonds significantly improves the heat resistance of silicone. During ablation, the hyperbranched polysiloxane will undergo a ceramization to produce SiO2 and ZrO2 particles, both of which will subsequently generate a highly viscous Zr-Si-O glassy phase as anti-ablation layer. With the fluidity and self-healing properties, it can fill the gaps of the carbon layer and cover the surface of the carbon layer, giving the hybrid resin excellent ablative resistance. The linear ablation rate of the hybrid resin can be as low as 0.003 mm/s, which is an 80 % decrease compared to pure PR. The synthesized hybrid resin is expected to act as superior thermal protection coatings for the next generation of spaceflight.

Oxhide gelatin-regulated aramid nanofiber/liquid metal films with sandwiched structure for electromagnetic interference shielding

Liquid metal (LM) based electromagnetic interference (EMI) shielding materials with high conductivity and continuous deformation capacity are important needs for meeting modern advanced electronic equipment. However, an independent free-standing film with LM is difficult to achieve due to its unique fluidity properties. Here, a simple alternating filtration film-forming method was utilized to orderly construct a sandwiched EMI shielding film with LM stabilized by bio-based oxhide gelatin (gel) as the intermediate conductive layer, and two films of aramid nanofibers/oxhide gel (ANF/gel) as the external insulating protective layers. This design not only prevents LM from being exposed to environmental conditions, but also reduces the risk of chemical corrosion in practical applications. Under optimal LM addition conditions, the sandwiched film (0.3-3 L) exhibited better EMI shielding performance of 50.4 dB in the X-band than the blended film (0.7 dB), as well as excellent mechanical properties (tensile strength of 65.8 MPa, strain 8.6 %). More importantly, the sandwiched film still maintained reliable EMI shielding performance after being experienced largely physical deformation. This study provides a new solution for preparing LM-based EMI shielding composites, and is expected to arouse pursuit of high EMI shielding effects of bio-based gel while also paying attention to their safety.