Jaw Crusher Research Articles

Effects of recycled fine aggregates on properties of concrete containing natural or recycled coarse aggregates: A comparative study

Most of the past studies related to recycled concrete aggregates (RCA) dealt with only coarse RCA (CRCA), while there were many hesitations regarding incorporation of fine RCA (FRCA) into concrete. Therefore, the present study analyses the compatibility of FRCA with coarse natural aggregates (CNA) and CRCA based on their combined influence on concrete. In this study, the original concrete (produced on-site and tested in the laboratory) was broken down to 50–70 mm with a hand hammer, followed by more size reduction using a jaw crusher (maximum size∼25 mm). Further, they were graded into CRCA and FRCA as per IS 383. FRCA was used directly in concrete, but CRCA was ground further in an abrasion machine. 30%, 60% and 100% FRCA (as a replacement of fine natural aggregates (FNA) by volume) were utilised either with 100% CNA or 100% CRCA to study their effect on fresh properties (workability and density), mechanical properties (compressive, flexural and split tensile strength) and durability properties (water permeability and carbonation) of concrete. The properties of recycled concrete were mostly inferior to conventional concrete at each curing age (except for 90 days compressive strength of concrete incorporated with 30% FRCA). However, the performance gap between conventional and recycled concrete was reduced with an increase in curing age. The recycled concrete containing three different combinations of FRCA and CRCA (0% and 100%, 30% and 0%, 30% and 100%) satisfied IS 10262's target compressive strength criteria for M30 grade concrete. The density of RCA affected the concrete properties more than its water absorption. Also, the water permeability of recycled concrete (followed by its carbonation depth and compressive strength) was most influenced by incorporation of RCA. Conclusively, it was found that FRCA is more compatible with CNA at 30% FNA replacement and with CRCA at 60% and 100% FNA replacement.

OPTIMISATION OF LOCATION AND PERFORMANCE PARAMETERS FOR THE CRUSHING AND TRANSFER STATIONS IN THE DEEP OPEN PIT MINES

When designing the strip mining methods at the deep open pits at the stage of preliminary studies, it is necessary to determine the optimum number and succession of relocation of crushing and transfer stations while developing the open pit. This cuts the transport costs and reduces the number of dump trucks required. An analytical dependence has been established to determine the optimum number of transfer points with their uniform location along the length and height of the open pit working area. The features of changes in the basic technological parameters of truck operation, depending on the number of crushing and transfer stations, the open pit size and output are studied. The conditions for simultaneous use of several crushing and transfer stations, their optimum number and performance have been determined; the economic benefits of using the flowcharts with multiple transfer points have been estimated. Optimisation of the number of transfer points reduces the required capacity of each crushing and transfer plant of up to 10-20 million tons/year. Reducing the required capacity of transfer points makes it possible to equip them with primary jaw crushers.

Studies on Cent Percent Utilization of Recycled Coarse and Fine Aggregates in the Construction Industry

As a measure of conserving the resources and for creating eco-friendly environment, studies have been conducted on recycled demolished concrete aggregates (RCA) for their complete usage in the construction industry. The method adopted comprises improving the structure, physical and mechanical properties of RCA. The RCA that are obtained from impact jaw crusher, the surface of these aggregates is improved by processing it through miller machine by way of ball rotation action, where the surface defects and brittle fracture are removed without affecting the permanent mortar adhered on the aggregate, to these modified aggregates which are porous and weak in structure, the surface of the aggregates is subjected to various treatments to improve its structure. The techniques used are densification, hydrophobization, polymerization, and a combination of polymerization & densification. On these combinations, the various dosages of chemical treatments were applied and tested for their properties on coarse and fine aggregates. Finally, a combination of 2.5% of Lithium silicate treatment on coarse aggregates and 1 % colloidal silica treatment on fine aggregates has given satisfactory results in usage in concrete/cement mortar mass. On these combinations, the durability and microscopic studies (SEM, EDS, XRD) were done and it was observed that the combination has more association of silica with calcium and these resulted in more formation of C-S-H, and a dense interfacial transition zone. The aggregates applicability was tested in the field by using it for various civil works. All the tests and analyzed parameters indicate that the treated aggregates are future materials and act as a complete replacement for natural aggregates.

Shape Characterizing of Aggregates Produced through Different Crushing Techniques

The aggregate shape properties produced from the different crushing techniques influence the performance properties of the asphalt mixtures. The objective of this study was to classify the aggregates into spherical, flat, elongated and flat, and elongated shapes, collected from impact crusher and jaw crusher of two sources, and to calculate the shape parameters, such as aspect ratio, shape factor, form factor, sphericity, roundness, and angularity index. In addition, this study also investigated the effects of this classification on the Marshall stability and volumetric properties of asphalt mixtures prepared from the respective shape of aggregates. The results showed that the aggregate of different fractions (passing 37.5 mm and retained on 4.75 mm) produced from the jaw crusher of Margalla quarry showed better shape parameters. The spherical aggregates collected from all crushers showed 20–30% higher Marshall stability of the blends by improving the mechanical and volumetric properties of the asphalt mixtures.

Subsurface microstructural dynamic recrystallization in multiscale abrasive wear

This paper evaluates various subsurface microstructures of Hadfield steel worn in different abrasion systems. The abrasion systems are defined according to their abrasion conditions related with the following scales: macro (cone crusher); meso (jaw crusher test) and micro (scratch test) in order to relate the industrial and laboratory conditions. The subsurface microstructures were evaluated by Scanning Electron Microscope, Electron Backscatter Diffraction, X-Ray Diffraction, Focused Ion Beam and Transmission Electron Microscope. The observed wear effects to the surface of the cone crusher mantle are characterized by indentations, grooves, intergranular cracks and grain detachment. The subsurface microstructure of the multiscale abrasive wear conditions was composed of a topmost layer with ultrafine grains, a layer with deformation twins and slip bands. In the cone crusher and the jaw crusher, changes in the shape of the subsurface deformed grains after plastic strain were not observed, leaving deformation twinning as the primary strain mechanism. The cone crusher subsurface microstructure showed dynamic recrystallization characterized by ultrafine-grains, small grains with continuous network carbides in the grain boundary, acicular carbides and annealed twin. The analysis of the ultrafine grains formation considers the energy release at the abrasive/material interface and in the subsurface by deformation as responsible for nucleation and growth of ultrafine grains. The scratch test in {111}//ND grain has the subsurface with ultrafine-grains and deformation twins. The nano-hardness results show that the regions with ultrafine-grains have a higher hardness than the regions with deformed grains, where the plasticity was restored and the hardness of the subsuperficial layer had improved. The models of dynamic recrystallization induced by severe plastic deformation are discussed and correlated to the ultrafine-grains formation.

Evaluation of blast fragmentation effects on jaw crusher throughput

Evaluation of blast fragmentation effects on jaw crusher throughput

Determiantion of energy characteristics of material destruction in the crushing chamber of the vibration crusher

The crushing equipment is characterized by a significant energy-consuming system during the crushing workflow. The current trend in the development of such processes puts forward requirements for the development of new or improvement of existing energy-saving equipment. The essence of the solution to the problem in this work is determined by using resonant modes, which are inherently the most effective. The practical implementation of the resonance mode has been achieved taking into account the conditions for the interaction of the resonant vibration crusher with the material at the stages of its destruction. The degree of the stress-strain state of the material is taken into account, which was a prerequisite for identifying the potential for the development of a vibration load. Composed equations of motion based on a substantiated discrete-continuous model of a vibration crusher and processing material. An approach is applied to determine the stepwise destruction of the material with the determination of the required degree of energy. This methodological approach made it possible to reveal the nature of the process of material destruction, where energy costs at the stages of crack formation, their development and final destruction are taken into account. It was revealed that the greatest energy consumption during the operation of crushers goes into the kinetic energy of the crushing plates and the potential energy of deformation of the springs. The proposed model is common for any design of a vibration machine and its operating modes. The stable resonance mode has made it possible to significantly reduce the energy consumption for the course of the technological process of material grinding. The results obtained are used to improve the calculation methods for vibratory jaw and cone crushers that implement the corresponding energy-saving stable zones of the working process.

Modular design for optimum granularity with auto-generated DSM and improved elbow assessment method

To cope with an increasingly competitive market environment, manufacturers are utilizing modular technology to guide the production process, and a vital activity in the module partition is to determine the optimal granularity levels. A modular design methodology is developed for obtaining the optimal granularity of a modularized architecture in this paper. A relationship extraction solution is executed to automatically construct the design structure matrix (DSM) from the 3D CAD assembly model. Hierarchical clustering algorithm is implemented to form a hierarchical dendrogram with different granularity levels. An improved Elbow method is proposed to determine the optimum granularity level and corresponding modularity spectrum during the dendrogram process. The computational framework for hierarchical clustering and modularization with improved Elbow assessment operators is explained. Based on a existing literature example and a jaw crusher modular design case, comparative studies are carried out to verify the effectiveness and practicality of the proposed method. The methodology is characterized by running independently on the computer in data visualization format without human involvement, and the obtained result with optimized granularity favor further modular design work.

Selection of a structure of jaw crusher regulator

To control a crushing machine at various industrial enterprises, including the mining industry, different types of typical regulators are used. It should be taken into account that a modern jaw crushing machine is not only an element of a crushing and screening complex, but it is also a system in itself. Realizations of various typical regulators for the electrical protection subsystem are shown.

Investigation of the jaw crusher operation with backlash eliminators

The condition for the appearance of additional dynamic forces in the presence of gaps in the journal bearings of the jaw crusher is determined. The design of the backlash eliminator equipped with pneumatics is described. It was experimentally established that the use of pneumatic devices for backlash elimination in the interfaces of the moving links, using journal bearings, during the operation of the jaw crusher, reduce the magnitude of accelerations and, therefore, increase the reliability of the crusher as a whole.

Optimized magnetic separation for efficient recovery of V and Ti enriched concentrates from vanadium-titanium magnetite ore: Effect of grinding and magnetic intensity

We present an optimized magnetic separation process to improve the recovery of high-content vanadium and titanium concentrates from vanadium‑titanium magnetite (VTM) ore. The ore chunks were crushed using jaw crushers and then grinded in a laboratory rod mill for different grinding times and studied. Vanadium recovery was dependent on maximizing magnetite and ilmenite recovery. Ilmenite, which is the main source for titanium, existed in the stripes within magnetite; it got pulverized first during milling and remained as relatively coarse particles of magnetite. A grinding time of 15 min was determined as optimum for the grinding conditions of this study, based on the degree of liberation, the grade, and recovery of vanadium. The effect of varying magnetic intensities on the separation behavior of the pre-concentrates was analyzed through magnetic separation of the ground VTM samples. The grade and recovery attained for the vanadium concentrates were 1.12% and 63%, respectively. In addition to vanadium, titanium concentrates were also obtained by medium-intensity magnetic separation and the grade and recovery were 38% and 75%, respectively.

Micromechanical and multi-scale modeling of manganese containing slag comminution in the design of energy efficient secondary raw material beneficiation processes

Efficient separation of valuable metals from various slags is of great interest for the industry to effectively utilize valuable raw materials. Present work focuses on modeling the deformation and damage behavior of manganese containing slag materials at the microstructural level, which dictates the macroscopic material behavior and allows one to investigate possibilities to perform metal separation after comminution of the slags. The model includes finite element micromechanical description of the material behavior and slag microstructure. Computational micromodels are constructed based on direct input characterization data and statistically representative synthetic models. The damage model treats brittleness and ductility of the material together with phase specific material behavior, all relevant to comminution of the slag. Finally, a simplified jaw crusher simulation accounts for freeing materials, assisting the evaluation of empirical random breakage, all together with a microstructural particle study which is analyzed against micromechanical modeling. Crystal plasticity level simulations of surface deformation and hardening in jaw crusher are presented to couple macroscale crushing events with microscale deformation of wear parts. The work overall presents a workflow and proposes a methodology how digitalization and multi-scale material modeling can contribute to the development of efficient comminution means for hard to process secondary raw materials.

Целочисленный структурный синтез многоконтурных рычажных механизмов со сложными шарнирами для разных областей машиностроения

The article considers the problem of structural synthesis of various lever mechanisms with multiple joints. Structural synthesis of multi-link mechanisms, on the one hand, is the primary and most difficult, due to the large number of options for structural solutions and, on the other hand, it is the most important design stage. To solve the problem under study, a theorem of integer structural synthesis of multi-loop kinematic chains with multiple joints is proposed. On the basis of the theorem the entire finite sets of structural solutions for directed synthesis are determined at the level of inventions of various working multi-loop lever mechanisms with multiple joints of different multiplicity. An algorithm for the structural synthesis of multi-loop lever mechanisms of a given mobility with a variety of multiple joints is proposed. The effectiveness of the proposed algorithm is confirmed by examples of its application for an integer structural synthesis of a manipulator gripper, a jaw crusher, a rectilinear-guiding articulated lifting mechanism of the manipulator and a universal multi-point articulated clamping device, as well as by the results of experimental studies of their operating models.

Effect of Oxidation Behavior of (Nd,Dy)-Fe-B Magnet on Heavy Rare Earth Extraction Process

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the LME p rocess, Nd i s completely e xtracted a fter 6 h, w hile D y remains as D y2Fe17 and Dy-oxide. Because the decomposition rate of Dy2Fe17 is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.

Influence of the ore reduction method on the percolation leaching efficiency

This paper covers gold leaching from sulfide ores. The data on the silicate, mineral, and grain-size composition are presented for the ore studied. Agitation leaching studies were completed for the combined sample and direct cyanidation dynamics indicators are established for the material sample. For all material with the grain size class of 95 % passing –0.074 mm, the required agitation leaching duration is 9–10 hours; with the material sizes up to 2 mm, the leaching duration shall be at least 22 hours. In order to study the efficiency of using roller presses as an alternative to fine crushing, two percolation leaching tests were conducted for the ore size of –5 mm. The material for the first test was prepared by crushing in a standard jaw crusher and the material for the second test was prepared by crushing in a laboratory press with complex monolayer reduction. It has been found that ore reduction using high-pressure crushers, as compared to standard crushing equipment, allows increasing gold recovery during subsequent leaching by 13.52 %. At the same time, the consumption of sodium cyanide increases by 0.26 kg/t of ore.

Investigating the effects of feeding properties on rock breakage by jaw crusher using response surface method and gene expression programming

The present study investigates the effects of feeding properties on rock comminution by a laboratory-scale jaw crusher. For this purpose, detailed crushability tests were carried out on four different rock types to assess their degree of rock crushability (DRC). Various feeding sizes (9.5 – 19 mm) and quantities (500 – 1500 g) were adopted to reveal the choke feeding intensity during crushing actions. The efficiency of feeding properties was investigated through the response surface methodology (RSM). The RSM results demonstrated that the characterized feeding size (F80, mm) dominates the general size reduction, whereas the feeding quantity (mf, g) is associated with the crushing energy consumption and product flakiness. Therefore, the choke feeding intensity has a direct relation to the mf and F80. In addition, novel gene expression programming (GEP) models were employed to generate empirical formulations to predict the DRC parameters. The established GEP models have a satisfactory estimation capability. Therefore, the DRC of the investigated rocks can be optimized through the proposed GEP models based on the coupling variables of mf and F80.

Influence of technological load on the stability of synchronous anti-phase motion of the jaws of a vibratory crusher

Vibratory jaw crushers are based on the effect of self-synchronization of jaws and body, when its elements vibrate with frequencies that are in a rational relationship due to the influence of links already existing in the system. The technological load acting on the jaws of a vibratory crusher during its operation can have a significant effect on which operating mode of the crusher (synchronous antiphase or synchronous inphase) is implemented. This paper investigates the influence of the proposed crushing model on the dynamics of a vibratory jaw crusher. The model takes into account the elastoplastic properties of the rock being crushed and its one-way connection with the jaws. The destruction of the material, its movement along the crushing chamber and the change in the properties of the processed rock as it is crushing has been implemented. Conclusions are made about the influence of the processed rock on the implementation of the crusher operating modes.

Highlights on the properties of the soda-lime-silicate glass residue that enable its use as filler in ultra-high performance concrete

The exponential advancement of cutting-edge technologies in the scope of civil construction, seeks to give cement-based materials the eco-efficient potential linked to mechanical performance that enables different applications. This work aims to evaluate the glass residue regarding the pozzolanic potential through ABNT NBR 5752:2014, as well as to verify whether through the characterization tests of x-ray fluorescence, x-ray diffraction and laser diffraction granulometry, if it is viable of application as supplementary cementitious material (filler), in ultra-high performance concrete. The glass residue submitted to the tests proposed in this study, was crushed in a jaw crusher, milled in a bench ball mill at 47 rpm, and was sieved in a 75 µm opening mesh (ABNT nº 200 mesh). For the test of pozzolanic activity, CP II F-40 class cement, normal sand, water from the public supply network, and superplasticizer additive were used for the mix with 25% of the residue replacing cement, while for the other characterization techniques, the glass residue was applied in its processed form (after sieving), dry or wet. The evaluated glass residue did not reach the minimum rate of 75% established by ABNT NBR 5752:2014, achieving only 45.72%, being classified as non-pozzolanic, which indicates its inert behavior in the presence of calcium hydroxide. The characterization tests confirmed, based on the specialized literature on ultra-high performance concrete, its viability as a filler when adopted as an alternative raw material for presenting chemical and mineralogical composition, in addition to granulometric distribution, very close to those used in studies that demonstrated satisfactory results when using the glass residue as an input.

STUDY OF OVERBURDEN TUFF ROCKS AND DEVELOPMENT ON ITS BASIS OF LIGHTWEIGHT STRUCTURAL CONCRETE

Introduction. The work presents the research results on the development of technology for lightweight structural concrete based on overburden tuff rocks. To develop the technology of lightweight structural concrete, overburden tuff rock (Almaty region of the Republic of Kazakhstan) is used, which is formed during the extraction of volcanic tuff for the manufacture of facing tiles. Aim. Study of the basic physical, mechanical and chemical properties of tuff, development of lightweight structural concrete compositions. Methods. The overburden tuff rock is crushed in a jaw crusher and screened through a set of standard screens. As a result, aggregates from tuff of fractions were obtained: 0.16-5 mm, 5-10 mm, and 10-20 mm. The composition of tuff concrete was selected by calculation according to the standard procedure. After calculating the composition of tuff concrete, all raw materials: cement, aggregates, additives, and water are dosed and mixed. The concrete mixture is placed in a mold and compacted by vibro-compression on a vibrating table. Hardening of concrete samples is carried out in humid conditions for 7, 14, and 28 days and steaming in a steaming chamber for 12-16 hours. Results and Discussion. After hardening, the properties were determined: compressive strength, average density, and heat transfer coefficient of concrete samples according to standard methods. The tuff concrete grade is in the range of 15.0-20.0 MPa. The average density of tuff concrete is 1822-1910 kg/m3. The thermal conductivity coefficient (λ) is in the range of 0.66-0.75 W/m∙K. The possibility of manufacturing finishing tiles from tuff concrete by grinding and polishing its surface has been established. Based on tuff sand, with a grain size of 3-5 mm, concrete stones with dimensions of 390x190x188 mm with 2 technological voids were made by vibration pressing. The hollowness of the stone is 51% of its total volume, and the compressive strength grade is 2.5-3.5 MPa. Conclusions. As a research result, the main physical, mechanical and chemical properties of overburden tuff rocks as a filler for lightweight structural concrete were studied. The possibilities of manufacturing wall blocks and facing slabs have been established.

Analysis of vibrations for a vibrating jaw crusher when interacting with material

A model of a vibrating jaw crusher (VJC) with self-synchronizing unbalanced vibration exciters is considered with account of the impacts between the jaws and the material being processed. Numerical modeling is used to establish the influence of the initial gap between the jaws and the material and of the velocity recovery factor upon impact on the synchronization of vibration exciters rotation and jaw vibrations, on the excitation frequency ranges of stable periodic vibroimpact regimes, and on the impact velocities between the jaws. The analysis results indicate that a change in the conditions of contact between the jaws and the material being processed leads to a change in the frequency ranges of the stable antiphase synchronization of vibration exciters rotation, as well as in the excitation frequency ranges of steady single-period vibroimpact regimes for the motion of the system, considered as the main operating modes of the VJC. The impact-like nature of the interaction between the jaws and the material being processed suggests the possible multimodality of the system, which explains some of the effects observed in practice and manifested in changes in the periodicity of the vibroimpact regime and in the vibration mode of the jaws at a constant excitation frequency. Therefore, the vibroimpact-based model proposed for the VJC and its dynamics analysis results may be used to design and improve vibrating jaw crushers with the selection of reasonable design parameters and the most effective vibration excitation conditions. The work was carried out with the financial support of the RFBR, project No. 18-08-01491_a.