Sands Processing Research Articles

The simulation of the fine crushing process of basalt-manufactured sand and its morphology's effect on the early age evolution of concrete ITZ

The availability of river sand is gradually decreasing, and it is an inevitable trend for manufactured sand to replace river sand as a sustainable resource. However, the current parameters for the fine crushing process of manufactured sand are insufficiently clarified, leading to poor morphology in the resulting manufactured sand. This significantly impacts the performance of concrete. Therefore, the properties of basalt, which is abundant in Gansu, China, were analyzed in this paper. And using basalt as the parent rock and a cone crusher as the crushing equipment, the basalt-manufactured sand fine crushing process was simulated using Rocky DEM4.5 software based on the discrete element method. Finally, the particle morphology of basalt-manufactured sand was quantitatively studied using digital image processing and profilometer, revealing the influence of morphology on the performance evolution of the concrete interface transition zone. The results showed that the basalt is classified as a highly abrasive and basic-alkaline rock, and its internal composition exhibits an intergranular-intercryptic structure. After the basalt is crushed in the cone crusher, the particle size is primarily concentrated within the range of 1.18∼4.75 mm. The energy required for the crushing of a single basalt particle is typically below 2000 J, with only a few particles exceeding this range due to multiple crushing. The morphology of the basalt sand can be effectively improved according to the parameters provided in this paper. Moreover, the flow of free water to the interface transition zone of concrete is proportional to the roughness of manufactured sand.

Generalized mathematical model applied to a silica sand laboratory-controlled mill: Derivation of simplified ceramic ball entrance flux, ball wear consumption, and mass distribution functions

A laboratory-controlled milling process of silica sand was carried out using aluminum oxide balls of three different sizes. The ball wear kinetic equations were experimentally obtained from the evolution curves of the ball diameter as a function of the operating time. From a generalized model, the ball entrance flux and ball wear consumption were calculated using exact two-parameter solution functions. One-parameter ball entrance flux and ball wear consumption functions were proposed to perform calculations that accurately describe the values provided by the two-parameter functions. In addition, a compact form of the ball mass distribution function is found. This set of simplified equations can be suitable for fast calculations in the milling industry.

Progress of joint process research on purification of high purity quartz sand

High-purity quartz sand is an important raw material for semiconductors, photovoltaics, aerospace and other cutting-edge fields, high-quality natural crystals can no longer meet the urgent demand for high-purity quartz in the domestic market, and it is imperative to accelerate the realisation of high-quality quartz purification technology from non-quality mineral sources. This paper summarises the joint process flow in the unused scenario, and outlines the main methods for the purification of quartz sand in China at present, including pretreatment, ultrasound-assisted leaching, chlorination roasting, etc., from the point of view of the joint process, and puts forward the problems that exist in these methods, so as to provide certain references for the research on the purification process of high-purity quartz sand in China.

Flexural and fracture characterization of UHPGC notched beam with various glass sand replacement ratios and steel fiber contents

The preparation process of quartz sand (QS) can cause serious environmental pollution, which is particularly important to find a new replacement material for QS in cement-based construction materials. In this study, an economical and environmentally friendly ultra-high performance glass sand concrete (UHPGC) was prepared by partially replacing QS in conventional ultra-high performance concrete (UHPC) with glass sand (GS) ground from waste glass. The effects of material composition characteristics including water-binder ratio (W/B), GS replacement ratio, and steel fiber content on the flexural and fracture characteristics of UHPGC notched beams were investigated based on response surface method (RSM) and acoustic emission (AE) monitoring. The results indicate that the GS replacement rate presents almost no effect on the tensile strength and flexural toughness of the specimens while reducing the water-binder ratio or increasing the steel fiber content can significantly improve the flexural tensile strength of UHPGC notched beams. UHPGC notched beams show the best performance when the W/B is 0.17, the steel fiber content is 3 %, and the GS replacement rate is 50 %. By analyzing and comparing the AE parameters and fracture modes, the discrepancies in flexural and fracture properties of UHPGC notched beams with variable material composition characteristics can be elucidated. Among them, the low water-binder ratio or high steel fiber content has a significant effect on the fracture characteristics and fracture process of the specimens, while the GS replacement rate exhibits negligible effect.

Evolution characteristics of calcareous sand force chain based on particle breakage

Abstract Calcareous sand is easily broken under external force, which brings great difficulties to island reef engineering. Based on the particle flow program, a discrete element model that can reproduce the results of laboratory tests is established, the large principal stress method is introduced to identify the particle force chain, and the bond strength between particles is increased to obtain an unbreakable model with the same initial conditions, and different confining pressures are compared and analyzed. The evolution law of the force chain of the following two models establishes a macro-meso cross-scale analysis in the deformation process of calcareous sand, explores the internal mechanism of the crushing of calcareous sand particles. The results show that particle breakage plays an important role in the evolution of the force chain. Particle breakage will reduce the probability of the force chain on both sides of the axis, forcing the probability of the axial force chain to rise steadily. The macroscopic deviatoric stress is the external manifestation of the probability of the axial force chain on the meso level. The faster the probability of the force chain in the direction of the potential shear band increases, the more obvious the shear band is.

Vertical coherence of coherent structures during sand and dust storms: A multi-height synchronous observation study

An experiment was conducted on the Qingtu Lake Observation Array (QLOA) to measure wind and dust information at various wall-normal heights during the sand and dust storm (SDS) process. According to the indicators of the non-stationary features in the flow field, the SDS process can be divided into three stages: ascending, stabilizing, and descending. Based on this division, the Hilbert–Huang transform (HHT) is employed to extract dominant flow structures, which carries a significant portion of the turbulent kinetic energy. Moreover, the HHT spectrum of stream-wise velocity component reveals that the scales of the dominant structures are approximately hundreds of meters in the horizontal direction, and hence suggests the presence of large and very large-scale coherence during the SDS. The hypotheses of Townsend [The Structure of Turbulent Shear Flow (Cambridge University Press, 1976)] and Davenport [“The spectrum of horizontal gustiness near the ground in high winds,” Q. J. R. Meteorol. Soc. 87, 194–211 (1961)] are utilized to demonstrate the vertical coherence of turbulence, which suggests the wall-similarity and evolution of inner/outer interactions for coherent structures during the SDS. Finally, the coherence spectrum [γL2=exp(−2c1Δz/λx)] and the linear transfer kernel [|HL2|=exp(d1−d2Δz/λx)] are parameterized, where c1, d1, d2 are fitting parameters, Δz is wall-normal offset, and λx refers to streamwise wavelength, to illustrate the evolution of the interactions between near-wall and outer regions during the SDS, which highlights the strong connections during the stabilizing stage. In general, the present study analyzed horizontal and wall-normal structures for a comprehensive SDS process, and thus, these findings present abundant features of wall-attached eddies which further be used to improve/enrich existing near-wall models.

Performing A Discrete Element Method Simulation Using A Linear Vibrating Screen for the Sieving Performance Analysis of Sand Particles

In order to respond to the strategic deployment of ecological protection and high-quality development of the Yellow River Basin, to solve the problem of separating river sand mixtures in the lower reaches of the Yellow River, and to improve the screening efficiency of river sand separation by linear vibrating screen, a large amount of literature is consulted, which show that the main factors affecting the screening efficiency and the screening quality during the screening process of linear vibrating screen are: the vibration frequency, the amplitude, and the inclination angle of the screen surface. Therefore, this paper takes sand as the research object, simulates the screening process of sand under different parameters in linear vibrating screen based on the discrete unit method (EDEM) , uses Hertz-Mindlin with JKR contact model, by changing the parameters of vibration frequency, amplitude, screen surface inclination angle, observes its impact on the screening performance and changes in the screening process of the material, and obtains the optimal screening efficiency with the screening efficiency of sand as a measure. As a measure, the vibration parameter set of optimal screening performance was obtained. Through analyzing the simulation results, it is found that the optimal vibration parameters of linear vibrating screen are: vibration frequency f =25Hz, amplitude A =4mm, screen surface inclination angle φ=4°, and the screening efficiency can reach 95. 77%. The results of this study show that the discrete element method has a good reliability for different process parameters to produce screening efficiency, and the study can provide a corresponding reference for the selection of vibrating screen parameters.

Research Status and Development Trend of Mechanized Sand Production Process and Equipment Optimization

With the continuous development of engineering construction industry, the demand for sand used in construction is increasing, the traditional natural sand is increasingly in short supply, and the demand for mechanical sand is increasing. The vertical shaft impact sand machine is an important equipment machine in the production process of mechanical sand. The rotor in the vertical shaft impact sand machine is the core part of the normal work of the sand machine. Studying the rotor in the vertical shaft impact sand machine can improve the efficiency and stability of the sand machine in the sand making process. Compared with the research results at home and abroad, the type and research direction of rotor structure are summarized, and the development trend of vertical shaft impact sand making machine is proposed.

Microbial Chaff Reinforcement: Preparation and Performance Study of a Soil Stabilizer

The fungus bran is the waste of the fruiting body of edible fungi, which is rich in a variety of protein and fiber, amino acids, polysaccharides, enzymes, and other nutrients, and has high reuse value. In this study, the fungus bran produced by desert Tremella was used as the raw material to prepare the fungus bran which could provide plant nutrients and water retention function. After 7 days of experiments, it was found that the sand fixation material had good water retention performance and significantly increased the aggregate performance of the sand. The results of FTIR and SEM analysis showed that the sand chaff was involved in the agglomeration process of sand, and the sand and the chaff were well combined, with a better spatial network structure and surface morphology. Therefore, it is a great prospect to explore the reuse of solid waste of fungal bran in desert afforestation.

Extraction of high activity bacterial urease and its application to biomineralization of soil

Biomineralization based on bacterial enzyme induced carbonate precipitation (BEICP) process is a promising alternative to cement-based ground treatment technology. The bacterial urease used in BEICP process is usually ultrasonic extracted from urease-producing bacteria. To efficiently extract urease with relatively higher activity from bacterial cells, the ultrasonic extraction parameters of urease were optimized in this study. Next, a series of bacterial urease extraction tests and sand column treatment tests were conducted to investigate the effects of vibration amplitude, upper temperature limit, and cooling method on the urease extraction process and biomineralization of sand. The results show that the upper temperature limit is an important factor affecting the extraction efficiency and the activity of the extracted urease solution, and the optimum upper temperature limit is 50 °C. The results indicate that increasing vibration amplitude could improve the extraction efficiency, but it hardly affects the urease activity (UA) under the optimal temperature. Continuous cooling could effectively simplify the operation and further improve the efficiency of urease extraction. Under the same urease activity of biotreatment solution, there is no marked difference in calcium carbonate content (CCC) and unconfined compressive strength of biomineralized sand columns prepared by urease solution extracted with different vibration amplitudes and upper temperature limits. The results of this study could provide a reference for application of BEICP technology of urease extraction to large-scale soil treatment.

Quality assessment standards and production technology of artificial sand based on hydraulic concrete construction specifications

Natural sand and gravel resources are a local resource. Natural sand and gravel are non-renewable in a short time and are not suitable for long-distance transportation. After decades of mining, sand and gravel resources in some areas have been exhausted. The transportation distance of natural sand and gravel is getting farther and farther, and accordingly, the price of natural sand and gravel continues to rise. At the same time, continuous and disorderly mining has caused serious damage to the environment and resources. During the construction of large and medium-sized water conservancy and hydropower projects in China, due to the lack of surrounding natural aggregates, most projects use artificial aggregates. In the current national standards for water conservancy projects, the content of artificial sand and gravel powder is clearly defined. Based on the “Hydraulic Concrete Construction Specifications” (SL677-2014), this article summarizes the particle shape, gradation and surface structure of artificial sand, and also calculates the theoretical gradation of artificial sand. To find out the impact of stone powder content on the performance of artificial sand, different levels of stone powder content need to be selected for research and analysis to clarify the impact of artificial sand powder content on concrete properties. Research shows that for concrete made from artificial sand, increasing the aggregate content with a particle size less than 0.075 mm can significantly increase the compressive strength of the concrete. In artificial sand, the content of stone powder will affect the workability, polishability, durability, permeability and water release of concrete. In the artificial sand and gravel production process system, crushing and sand making equipment are the most important sand and gravel production equipment. The research results provide theoretical reference for the application of artificial sand in concrete and the update of artificial sand production technology and equipment.

Improvement of Gold-Bearing Sand Mining and Processing at Structurally Complex Placers

Improvement of Gold-Bearing Sand Mining and Processing at Structurally Complex Placers

Assessing sand sedimentation in drilling slurry using particle methods for ground excavation management

In the construction of cast-in-place concrete piles, residual sand portions in the drilling slurry that are not completely removed can significantly influence the strength and characteristics of the concrete piles. Understanding the sedimentation behavior of these sand portions during concrete placement is crucial to ensure pile quality. However, directly observing this process in real-time at construction sites is challenging, making it difficult to accurately assess the impact of the sand portions. When predicting the sedimentation of sand particles in drilling slurry, the conventionally used Stokes' equation can only express one-dimensional motion of a single particle size, but to accurately capture the real phenomenon, three-dimensional behavior must be considered. In this study, a numerical simulation method based on the particle method (MPS method) was used to visually evaluate the sedimentation process of sand in the drilling slurry. By modeling the drilling slurry and sand particles using the MPS method, the complex three-dimensional settling behavior of sand particles in the drilling slurry at both laboratory and full scales was successfully represented, demonstrating the effectiveness of this modeling approach. The MPS method allows for the analytical visualization of the three-dimensional sedimentation behavior, enabling real-time observation and quantitative evaluation of the sand sedimentation process. Using this method, the temporal evolution of the settling process of sand components in the drilling slurry can be tracked, providing valuable insights into factors that influence the quality of concrete piles. The results of this study demonstrate the potential of the MPS method for visually evaluating the settling behavior of sand components in drilling slurry. This approach offers a more accurate and reliable method for assessing the impact of residual sand on the strength and characteristics of cast-in-place concrete piles. By enhancing the understanding of this process, more effective foundation techniques can be developed to improve the safety and stability of structures built on soft ground, particularly in earthquake-prone regions where fine particles such as clay and silt pose additional challenges to construction practices.

Enhancing Mechanical Properties and Microstructures of Mass-Manufactured Sand Concrete by Incorporating Granite Powder.

The production of manufactured sand and stone processing can cause dust pollution due to the generation of a significant amount of stone powder. This dust (mainly granite powder) was collected and incorporated as a cement replacement into mass-manufactured sand concrete in order to enhance the mechanical properties and microstructures. The heat of the hydration was measured by adding the granite powder into the cementitious material system. The mechanical properties, autogenous shrinkage, and pore structures of the concrete were tested. The results showed that the mechanical strength of the concrete increased first and then decreased with the increase in granite powder content. By replacing the 5% cement with the granite powder, the 28 d compressive and flexural strength increased by 17.6% and 20.9%, respectively. The autogenous shrinkage was mitigated by the incorporation of the 10% granite powder and decreased by 19.7%. The mechanism of the granite powder in the concrete was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The porosity decreased significantly within the 10% granite powder. A microstructure analysis did not reveal a change in the type of hydration products but rather that the granite powder played a role in the microcrystalline nucleation during the hydration process.

Shape Effect of Rockfall Impacting Sandy Soil Cushion Layer–Reinforced Concrete Slab Composite Structure

The impact effects of falling rocks on sand–reinforced concrete slab composite protective structures involve several factors. Among them, the existing codes are unable to consider the effect of rockfall shape and the angle of contact between the rockfall and the object on the impact force as well as the depth of penetration. Based on extensive field investigation, this paper proposes a shape factor to simplify the rockfall into an ellipsoid and determines the shape and dimensions of the rockfall by three-dimensional axis length. Besides, a coupled SPH-FEM numerical calculation model is established and validated through comparison with a large-scale outdoor test of a rockfall impact protection structure. Finally, the effects of rockfall shape and impact angle on the symbolic parameters including impact force, impulse and energy in the impact process are revealed. The findings indicate that the maximum force and displacement of the midpoint of the bottom of the reinforced concrete slab have relative errors within 5.0 % when compared to the model test, confirming the precision of the models discussed in this paper. For the same rockfall, the peak force decreases with the impact angle increasing; taking the same volume of spherical rockfall as the reference, under the same rockfall pattern, the peak impact force and impulse amplification factor decreases with the increase in contact attitude angle. Additionally, the scaling effect becomes more pronounced when the shape factor of the rockfall is smaller; under the same shape factor, the impact depth of the cushion layer is the smallest when the attitude angle is 45°, and the maximum when the impact angle is 90°; the SPH-FEM coupling algorithm could reasonably reproduce the pit-forming process of sand and soil, and it is very effective in simulating the flow effect of soil particles under impact.

Soil Amendment and Tillage to Reduce Phosphorus Loss in Coastal Western Australia

Phosphorus (P) runoff is a major factor contributing to water quality decline in waterways and waterbodies of coastal Western Australia (WA). Soils with naturally low P retention or those with increased P saturation from P application have higher risk of P loss via leaching or runoff. Substantial research has been carried out to minimise P loss via leaching and runoff through modifications of soil P retention capacity. We review literature of P retentive soil amendments, natural clays and tillage of soil to lift clay to the surface to increase P retention and reduce P loss from poorly retentive sandy soils and P stratified soils, and which have been tested for efficacy and safety. This review includes published research, previously unpublished trial data, research in unpublished reports and published research in limited circulation with particular emphasis on the Swan Coastal Plain due to unabated P loss and limited uptake of soil amendment in the region to combat it. Key findings are that amending leaching sands with bauxite residue from alumina refining, neutralised used acid (NUA from mineral sands processing) and clay, as well as tillage or mixing of P stratified soils have been shown to be very effective at reducing P loss. Increases in plant productivity have been found, depending on conditions such as soil pH and soil test P. For the materials tested, soil amendment did not lead to undue uptake of trace elements or concerning levels of radiation. Trials of NUA have shown Mn is close to acceptable limits or slightly exceeds them and is the subject of further research to determine application rates and field conditions required to minimise Mn or other contamination. The P retentive effect of soil tillage is restricted to soils with high P levels in the soil surface and higher P retention below the surface, reachable by soil tillage equipment.

On the durability of domestic and foreign slurry pumps in the processing of diamond-bearing sands and ores (review)

On the durability of domestic and foreign slurry pumps in the processing of diamond-bearing sands and ores (review)

Numerical Study on Effect of Aggregate Moisture on Mixing Process.

During the concrete mixing process, the transition of aggregates from a dry to a moist state introduces a crucial dynamic that significantly influences particle interaction, consequently impacting mixing homogeneity. In this paper, based on the discrete element method, the effect of aggregate moisture on the mixing process of sand and stone was investigated. The interaction between dry particles was described by the Hertz-Mindlin model, while the interaction between wet particles was calculated by the linear cohesion model considering the liquid bridge force. Additionally, a functional relationship between the moisture content and the parameters of the linear cohesive contact model was established. The results show that the numerical method can be employed to simulate the mixing process. Notably, when the moisture content of pebbles ranges from 0% to 0.75% and that of sand ranges from 0% to 10.9%, the linear cohesion model is deemed suitable. The standard deviation of the mixing homogeneity of wet particles is lower than that of dry particles for short mixing time, indicating that a small amount of liquid enhances mixing homogeneity. However, moisture has no obvious effect on mixing homogeneity for a long mixing time. This nuanced understanding of the interplay between moisture, particle interactions, and mixing duration contributes valuable insights to optimize concrete mixing processes.

A numerical study on load effects of low-rise buildings in a wind-blown sand environment

The transportation process of wind-blown sand, represented by sandstorms, occurs frequently in arid and semi-arid regions. The combined action of wind and sand impact load in a wind-sand environment poses a serious threat to the safety of construction, transportation and other engineering structures. However, most of the current structural designs only considers the effect of wind, and there is little detailed research on the surface load distribution of structures caused by sand impact, which leads to uncertainty in the safety assessment of engineering structures in wind-sand areas. In this paper, low-rise buildings which are easily damaged in strong wind-sand environments are taken as the research object. A numerical model of coupling turbulent wind field and particle motion was then established, and the reliability of the numerical simulation results was verified through wind tunnel experiments. Finally, the wind-sand movement around the low-rise building model and the load distribution characteristics on the building surface are simulated under different wind speed and sand concentration conditions. The results show that the edges and corners of engineering structures are subject to more severe particle erosion-abrasion. As the sand concentration increases in the flow field, the wind speed and the wind load acting on the structures weakens. Whereas the sand impact load increases with the increment of wind speed and sand concentration. The increased effect of sand particles on the total load can be considered by amplifying the wind load shape coefficient on the windward side. This study is helpful to understand the mechanism of sand wind-induced damage on low-rise buildings, and provides basic tools and a theoretical basis for the wind and wind-blown sand resistance design and performance optimization of engineering structures.

Numerical simulation of the bentonite-bonded sand mould compaction process using micro-mechanical parameter relationships

ABSTRACT Commercial software packages for FEM analysis have been used to numerically simulate the behaviour of the complex systems of bentonite-bonded sand mould under pressure and subjected to stress distributions and to predict their performance. The Drucker-Prager model and the Mohr-Coulomb model are two well-known mathematical models used to describe the plastic non-linear behaviour of the soil. Conducting direct shear tests on varying densities of sand can provide the individual parameters necessary for the simulation of the moulding process. A new approach is based on making relationships between micro-mechanical parameters and changes in sand density during the compaction process. COMSOL Multiphysics is a popular software tool used to implement FEM simulations. The steps involved drawing geometry, inserting material properties, mesh generation and time-dependent density, and solving the model. The boundary conditions depend on the particular problem being analysed, which defines the external forces and constraints acting on the structure. The use of a coarse mesh and stationary study may be a computationally efficient approach for the evaluation of the compaction process of green sand. The study found that the maximum displacement value is 6.1*10−3 mm, the maximum volumetric strain value is 8.88*10−5, and the von Mises stress is 4.14*103 N/m2.