Granite Processing Research Articles

Investigation on the current situation of occupational disease hazards in stone processing enterprises in Weihai City

Objective: To analyze the occupational disease hazards in stone processing enterprises in Weihai City to provide scientific basis for occupational disease prevention. Methods: From January 2021 to December 2022, 107 stone processing enterprises in Weihai City were selected to collect the detection status of occupational hazard factors in the workplace through on-site investigation and on-site monitoring of occupational hazard factors. The diagnostic reports on occupational diseases and suspected occupational diseases of 780 workers were collected through the Occupational Diseases and Hazard Factors Monitoring Information System of the Chinese Center for Disease Control and Prevention, the occupational health monitoring files of the occupational health examination institutions and the information data of the occupational disease diagnosis institutions. The differences between the measurement data were analyzed by Chi-square test or Fisher exact probability method. Results: 107 stone processing enterprises were mainly focused on granite processing, and the average free silica content in granite was 32.92% (12.78%-47.84%). The over-standard rate of silica dust was 0.31% (6/1920), and the over-standard rate of noise was 86.20% (1324/1536). Among them, the noise intensity of cutting position was the highest[120.5 dB (A) ]. The over-standard rates of noise in cutting, water grinding, dry grinding (polishing) and material preparation (forklift transportation) were 98.05%, 89.55%, 70.00% and 42.62%, respectively, and the differences were statistically significant (P<0.05). Among 780 workers, 31 cases (3.97%) of suspected silicosis were detected, and 13 cases (1.67%) were diagnosed with silicosis. 51 cases (6.54%) of suspected occupational noise deafness were detected, and 11 cases (1.41%) were diagnosed with occupational noise deafness. Conclusion: Silicon dust and noise in some positions of stone processing enterprises in Weihai City exceed the standard, and supervision should be strengthened, prevention and control measures should be implemented to protect the occupational health of workers.

Quantitative characterization of granite failure intensity under dynamic disturbance from energy standpoint

Abstract Quantitative evaluation of rock dynamic disaster intensity is a challenging and difficult task in the field of earth science. In this article, the dynamic compression tests of granite under different impact velocities are carried out, and the energy evolution characteristics of the dynamic failure process of granite are analyzed. The dynamic fracture characteristics of granite were studied by using computed tomography and section scanning equipment. The results show that the energy dissipation and energy accumulation mechanism of granite under dynamic loading are fundamentally changed with the increase of impact disturbance strength, which leads to the transformation of the failure mode from the tension-type sheet crack under low-speed impact to the complex network crack coupled by tension and shear under high-speed impact. At the same time, the greater the impact velocity, the larger the macroscopic crack density, the more uneven the particle distribution on the fracture section, the greater the roughness, and the higher the rock mass fracture degree. In accordance with the results, the energy distribution ratio is proposed to quantitatively characterize the coupling effect of energy dissipation and energy accumulation in the dynamic failure process of granite and to reflect its dynamic failure intensity. The higher the energy distribution ratio, the stronger the energy coupling effect and the more intense the dynamic failure of the rock mass.

Effect of Granite Fly Ash on Mechanical Properties of Basalt and Glass Fiber Reinforced Polymer Composite

The granite processing industry generates a substantial volume of residual granite waste daily. This residue is collected through a filtration process during the drying and heating stages of concrete mixture production. Utilizing this residue, known as granite fly ash (GD), offers a promising avenue for mitigating adverse effects due to this waste material. The present study undertakes an experimental investigation into the potential utilization of granite fly ash as a filler to enhance the mechanical properties of basalt/glass composites (BFRC/GFRC). The research focuses on assessing the density and tensile characteristics of the developed fibre-reinforced polymer (FRP) composites. Composite samples were fabricated by incorporating GD at varying loadings, i.e., 1 wt.%, 3 wt.%, and 5 wt.%. The FRP laminates were produced using hand lay-up and vacuum silicon mold curing techniques. The outcomes show a slight increase in density, in which a maximum of 7% increment at 5 wt% of GD in BFRC. Meanwhile, tensile properties displayedsignificant enhancements, especially FRP with 3 wt.% GD content, for both BFRC and GFRC. Notably, the addition of 1 wt.% GD resulted in a 9% increase in tensile strength and a substantial 27% increase in modulus for the BFRC composite. In summary, the study underscores the advantageous influence of GD incorporation, particularly within the 1 wt.%, 3 wt.%, and 5 wt.%, on the mechanical properties of both BFRC and GFRC composites.

Characterization of Marble and Granite Processing Waste and its Utilization in Brick Production: Case of Saba and Semayata Dimensional Stone Companies, Tigray, Ethiopia

In Ethiopia, the marble and granite dimension stone industries have been growing significantly in the last decade and have become a part of the flourishing construction industry. Accordingly, the amount of quarrying and processing has increased significantly. This has contributed to increased waste of time. Semayata and Saba Dimensional Stone plc are the leading dimension stone-based companies located in the Wukro and Adwa areas, respectively in the Tigray region are involved in producing tiles and slabs of marble and granite. Due to its processing techniques and its highly alkaline nature, marble, and granite wastes in the Adwa and Wukro areas have become causes for environmental problems. Consequently, the demand for the recycling of waste has come to the forefront due to both environmental and financial considerations. Keeping this in view, a study was conducted on the waste generated by the Saba and Semayata processing units. The study aims to characterize wastes; and discuss the possibilities of using marble and granite wastes as an alternative raw material in the production of bricks. Based on the chemical, physical, and mechanical properties, the waste can be used to produce bricks without modifying and adding other contents.

A laboratory investigation for assessing the effectiveness of wastewater treatment using flocculation process in building stone processing industry on stone surface quality and abrasive tool wear

In this study, the effect of presence and concentration of two synthetic polymeric flocculants with different charging mechanisms (anionic and cationic) on surface quality and abrasive tool wear in polishing process of building stones was investigated. The polishing tests were performed in laboratory scale on two stone samples (granite and marble). An index, entitled improvement index (I) was defined for evaluating the effectiveness of flocculants on surface quality and abrasive tool wear. The results revealed that flocculation process had a noticeable effect on enhancement of surface quality and reduction of abrasive tool wear for both stone samples. The cationic flocculant was more effective for granite sample and anionic flocculant was more effective for marble sample. The granite particles mainly exhibit negative surface charge while the marble particles have positive surface charge in the pH range of wastewater used for polishing tests. Therefore, charge neutralization mechanism plays a major role in flocculation process of granite and marble samples. It was found that the use of flocculation process for treatment of wastewater in stone processing plants leads to increase of abrasive tool lifespan and more high-quality products.

Temperature-dependent acoustic emission characteristics and statistical constitutive model of granite under uniaxial compression

Understanding the temperature-dependent mechanical behavior and fracture characteristics of granite is crucial for many engineering projects. In this study, the real-time temperature curves of granite specimens were obtained during the heating and cooling process, and the thermal treatment tests were conducted. The physical properties of the specimen before and after thermal treatment, including mass, volume, and P-wave velocity, were measured. The acoustic emission (AE) signal in the uniaxial compression is monitored. The results indicate that the physical properties of granite deteriorate with temperature, while the mechanical properties show two effects of thermal strengthening and thermal weakening. This phenomenon is comprehensively analyzed by literature statistical data and optical microscopic observation. Furthermore, the AE characteristic is strongly dependent on temperature. High temperature induces more AE ring count to appear in the early stage of loading. As the temperature increases, the crack initiation stress decreases and the table crack propagation stage becomes longer. The attenuation of high-frequency signals and the enhancement of low-frequency signals are related to the development and interaction mechanism of thermally-induced crack and stress-induced crack. At 600 °C, the global b-value increases significantly. Meanwhile, the evolution of dynamic b-value helps explain the failure process of granite under axial load after thermal treatment. In addition, a new thermo-mechanical damage statistical constitutive model of granite considering temperature effects is proposed by introducing AE parameters. The main advantages of this model can well fit the nonlinear behavior of granite in the early loading stage after thermal treatment, and reflect the failure process of granite before the peak value.

Thermal-damage effects on fracturing evolution of granite under compression-shear loading

Shear-dominant instability disasters in high-temperature conditions pose a significant challenge for deep underground rock projects, necessitating a thorough understanding of rock fracture evolution and the impacts of thermal damage. To investigate how thermal damage influences shear fracturing behavior and geophysical responses, experiments were conducted on thermally-treated granite under compression-shear loading conditions. The detailed failure process was meticulously monitored using integrated acoustic emission (AE), electric potential (EP), and digital image correlation (DIC) techniques. The effects of thermal treatment on the patterns of AEs, EPs, and DIC strain fields during the loading process were analyzed. Micromechanics related to the influence of thermal treatment on mechanical properties and geophysical responses were explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM). By defining damage variables through multiparameter analysis using AE, EP, and DIC, the study delved into predictive insights on the failure process of thermal-damage granite. The results indicate that the physical properties of granite undergo significant changes as the treatment temperature increases, with the peak stress gradually decreasing and the plastic characteristics increasing. These changes can be attributed to thermal damage, which causes internal water escape, expansion of mineral particles, and crack formation. Additionally, increasing the thermal treatment temperature leads to a decrease in both AE and EP intensity, as well as a reduction in the occurrence of high-magnitude AE events, while the cumulative AE count rapidly increases during the plastic stage. Notably, thermal treatment induces significant alterations in mineral composition, intergranular fractures, and the formation of a gradual zigzag crack path, resulting in the intensified development of shear microcracks. This observation is supported by the varying of AE characteristic parameter AF/RA and the analysis of DIC displacement decomposition. Moreover, the three defined damage variables exhibit accelerated growth prior to catastrophic failure, with the order of precursor occurrence observed as AE, DIC, and EP. However, the occurrence of the precursor time for these three geophysical signals becomes earlier with increasing treatment temperature. These research findings shed light on the mechanism of compression-shear failure of thermal-damage rock and provide valuable references for predicting precursors of the shear-dominant instability disasters such as induced earthquakes.

Variscan lithotectonic units of the Suchý massif in the Strážovské vrchy Mts., Western Carpathians – products of sedimentary, tectonometamorphic and granite forming processes

The present geological investigation of the Pre-Alpine structure of the western part of Strážovské vrchy Mts (the Suchý massif; Western Carpathians) has distinguished three lithologically distinct Variscan lithotectonic units, which originated (1) in the deeper parts of oceanic basin (prevailingly metapelites with different content of organic matter, metabasalts, metacarbonates?); (2) sediments of the continental slope (flyschoid sediments with a predominance of greiwacke sediments; both VmD0); (3) a unit of continent basement primarily of pre-VmD0 granitic composition (orthogneiss). These rock sequences of differing geotectonic provenances were amalgamated and metamorphosed in the pre-intrusive (Pre-Mississipian) stage; pre-VmD2). Regarding the Variscan polyorogenic evolution, Variscan processes in Tatricum represent the Meso-Variscan evolution (VmD). The maximum P-T conditions of orogenic (regional) metamorphism (up to 610 °C and 7.5–8.5 kbar) were not sufficient for more extensive anatexis. Field observations indicated that the production of a limited volume of granitoid melts occurred mainly at the contacts of amalgamated lithotectonic units. Probably due to the heat, produced by the hot line below the collisional orogen and contributing also to unroofing processes (in orogenic phase VmD2) there started new granitization process. This stage of Mississippian VmD2 granite formation is associated with the emplacement of various types of granitoid magma, encompassing the oldest granodiorites with frequent schliers, representing a poorly differentiated and poorly mobile crystal slurry (present in the SE part of the territory). In the highly evolved collision phase, masses of leucogranites intruded comformably with the deformation plan in the metamorphic complexes, interacting with surrounding metamorphic rocks in shallower crustal conditions and causing their contact metamorphic overprint (up to 590 °C and 3–4 kbar). The syn-deformation character of leucocratic granites is proved by the orientation of biotite flakes parallel to the deformation plane of surrounding metamorphites. Part of leucogranites, especially in the central parts of the bodies, is omnidirectional. The stress field acted not only during the intrusion of the leucogranite magma, but also in the subsolidus stage. The final stage of this process is the formation of large bodies of pegmatites in extensional VmD2 fractures oriented at a large angle to the main stress component. The texture of the grey blocky K-feldspar pegmatites and the lack of H2O-bearing minerals point to pneumatolytic fracturing in a subsequently opened environment in VmD2. The final stage of VmD2 is represented by intrusions of I-type granodiorites with indications of magma mixing, or mingling. The chemical dating of monazites in granitoids allowed to date individual phases of granitization process in the range of 360–345 Ma, which youngest ages correspond with the formation of pegmatites. Dating of monazite in metamorphic rocks points to their thermal overprint during granitization process (360–350 Ma), having already earlier metamorphic overprint (380–370 Ma). The scenario of placement of granitoid intrusions is consistent with the decompression regime (in VmD2) after the end of VmD1c crustal thickening until the fracturing of the crustal block with of I-type magma intrusions of deeper origin. After this period, the exhumation of crystalline blocks, partial diaphtoresis and later surface erosion continue until the Lower Triassic. The re-submergence of the crystalline complexes is associated with a low degree of Alpine metamorphic reworking.

Research on the damage process of granite under pulse laser irradiation

Laser rock-breaking technology is a new type of non-contact rock-breaking technology, which is one of the most promising technologies to replace the traditional methods. At present, the research on laser rock-breaking technology mainly focuses on the rock-breaking mechanism and parameters optimization under the continuous laser, while the research on the law of damage process of rock under the pulse laser is relatively lacking. Therefore, in this paper, pulse laser rock-breaking tests with laser power (400W and 800W) and irradiation time (4s, 8s, and 12s) were carried out. The damage morphology and quality of the rock before and after the tests were measured and compared, and the damage performance of the rocks under different powers was analyzed. The test results show that the diameter of the ablation pit of 800W is 2.5% larger than that of 400W on average at the same moment. The depth of the ablation pit of the former is about 1.5 times that of the latter, and the mass damage of the former is about twice that of the latter. On this basis, a three-dimensional model of pulse laser rock-breaking based on the discrete element method was established, and the evolution law of granite ablation pits and cracks under pulse laser irradiation was investigated. The simulation results show that the diameter and depth of the ablation pits increase with time, and in general, both show a non-linear growth pattern with time. The crack development is dominated by radial development at the early stage, and the radial development rate is 3.1 times the development rate of the axial direction. The volume of thermal cracking damage increases exponentially with time, and the overall damage form of the rock tends to thermal cracking damage with time. The results of this study are of guiding significance for pulse laser rock-breaking drilling.

Analysis of Pore Characterization and Energy Evolution of Granite by Microwave Radiation

To study the dynamic response of granite to different levels of microwave power, an intelligent microwave rock-breaking instrument is used to irradiate different power from three directions. The servo universal testing machine is used to carry out a uniaxial compression test on the granite after microwave damage to analyze the strength damage characteristics and the degree of pore damage. Pore fractal characteristics are analyzed based on nuclear magnetic resonance to establish the microwave damage degradation model. In parallel, the energy evolution process of granite under the influence of various power levels is analyzed using the theory of energy dissipation. Simultaneously, based on the energy dissipation theory, we analyze the energy evolution process of granite under the action of different powers. The results show that with higher microwave power, the peak strength and modulus of elasticity show a linear decreasing law. The degree of fragmentation is more obvious, showing the damage characteristics with two big ends and little in the middle. The higher the power, the greater the porosity and the more sensitive the micropore becomes to microwaves. Additionally, the damage degradation model established to evaluate the microwave damage of the rock showed that it was feasible. The higher the power, the lower the total energy, elastic energy, and dissipation energy, and the granite is gradually transformed from elastic deformation to plastic deformation. The elastic energy ratio decreases, the dissipation energy ratio increases, and the degree of damage becomes more and more serious. This study provides theoretical support for exploring the mechanical behavior and mechanism of microwave-assisted rock breaking and is of great practical significance.

Cracking process and microstructural characteristics of granite under heating–cooling alternations

Studying the damage correlation mechanism of rocks subjected to heating–cooling alternations is of important significance for deeply understanding the permeability increase mechanism of reservoirs during heat extraction from hot dry rocks and assessing the reservoir stability. By carrying out the uniaxial compression test, Brazilian splitting test, nuclear magnetic resonance test, and scanning electron microscopy test on granite after heating–cooling alternations, the evolution laws of physical and mechanical properties as well as the microstructures of granite were studied. In addition, the multi-scale response characteristics and the damage correlation mechanism of granite after heating–cooling alternations were analyzed. Research results show that, when the heat treatment temperature rises to 600 °C, the physical and mechanical parameters, including the wave velocity, strength, and elastic modulus, reduce abruptly. The heat treatment temperature exerts more significant influences on the physical and mechanical properties of the granite than the heating–cooling alternation cycles. Both the temperature and alternation cycles are beneficial to the microcrack development and propagation, while the temperature more significantly affects the development degree of microcracks. Under the external load, the microscopic defects in the granite after heating–cooling alternations guide the propagation of macrocracks and cause more serious damage to the microstructures in the granite, exhibiting more complex failure modes. The results provide a theoretical basis for fracturing technology and stability evaluation of high-temperature reservoirs.

Experimental Investigation on the Effects of Tool Geometry and Cutting Conditions on Machining Behavior during Edge Finishing of Granite Using Concave and Chamfered Profiling Tools.

Granite edge finishing through grinding is a common process in the granite processing industry, crucial for achieving the final desired shape and edge quality of products. This study focuses on the granite industry, specifically delving into the significance of grinding and polishing for improving aesthetics and extending material longevity. The experimental design entails a comprehensive factorial experiment plan involving two workpiece materials (white and black granite samples) and two cutting tool edge shapes (chamfer and concave), each with two grit sizes: G150 and G600. The cutting conditions varied and consisted of variations in spindle speeds (1500, 2500, 3500 rpm), feed rates (500, 1000, 1500 mm/min), and lubrication modes (wet/dry). The results uncover intricate relationships among these parameters and part quality, underscoring the pivotal role of tool geometry in achieving superior surface finishes and in controlling the cutting forces. These findings contribute to a nuanced understanding of the dynamic interplay between tool characteristics, material properties, and machining conditions within the granite industry.

Time-delayed failure process of granite and its energy evolution and acoustic emission characteristics

Time-delayed rockbursts during underground engineering construction seriously endangered the engineering safety. In this paper, an experiment of rock time-delayed failure is designed and conducted, and the associated energy evolution laws and acoustic emission (AE) characteristics were analyzed. There is an obvious time effect of granite time-delayed failure under true triaxial conditions. There are two calm periods in granite time-delayed failure process. The failure modes can be divided into two categories, i.e., time-delayed failure I and time-delayed failure II. In the load maintenance stage, the total energy continues to increase, the elastic strain energy didn’t change significantly, and the dissipated strain energy increases rapidly. For time-delayed failure I, when the AE hits rises sharply, it reached its maximum subsequently, and the first small peak of absolute energy appeared. On the eve of the rockburst, the AE hits began to rise gradually, and the absolute energy was with a small protrusion. For time-delayed failure II, when the AE hits rises rapidly, it reached a high level. The small peak of absolute energy appeared. In the eve of the rockburst, the hits showed a steep increase trend and reached its maximum, the absolute energy also presented a rapid rise trend. The research results have certain reference value for the early warning and control of the time-delayed rockbursts in underground engineering.

An analytical dynamic force model for sawing force prediction considering the material removal mode

Diamond circular saw blades are indispensable tools in the industry of granite processing. Accurate prediction of sawing force is essential for optimizing the processing in advance. In this study, the calculation method for uncut chip thickness and instantaneous chip thickness was improved based on granite sawing characteristics. Furthermore, an analytical prediction force model was proposed in view of deep and intermittent grinding, which comprehensively considers the characteristics of diamond grits (including grit size, location distribution, and protrusion height) and material removal mode. The error between the predicted results and the experimental results is <12 %, indicating that the model can accurately predict the cutting force. The proposed analytical model provides a method to optimize the sawing parameters without the need for extensive experiments. This model can also extend to calculate parameters such as energy consumption and carbon emissions in the stone processing industry.

Effect of weakening characteristics of mechanical properties of granite under the action of liquid nitrogen

Liquid nitrogen fracturing and hot dry rock geothermal development are both emerging technologies in the field of energy. However, during the extraction of geothermal energy, it can cause the evolution of geological fractures, leading to the diffusion of groundwater and pollutants, thereby causing environmental pollution issues. Currently, geothermal energy has become a focal point in the global development of renewable energy. However, traditional hydraulic fracturing methods used in harnessing geothermal resources suffer from limitations such as limited fracture creation, uncertain initiation points, and environmental pollution. In contrast, liquid nitrogen has emerged as a promising reservoir stimulation technique, exhibiting significant effects on rock fracturing. In this study, we conducted three-point bending tests on granite samples subjected to liquid nitrogen treatment at temperatures of 300°C, with varying numbers of cooling cycles. Changes in fundamental mechanical parameters were analyzed. Additionally, through acoustic emission monitoring, we studied the variations in characteristic parameters of acoustic emissions under different cooling cycle conditions. Furthermore, based on the theory of energy evolution, we analyzed the energy evolution process during sample failure under different cooling cycle conditions. Using a compact scanning electron microscope, we observed changes in the microstructure of granite and analyzed the influence of cooling treatment on its surface characteristics and failure modes, thereby revealing the thermal damage process of granite. Moreover, by employing a non-metallic ultrasonic testing analyzer, we scanned the fracture surface morphology of granite and investigated the variations in fracture surface morphology features and surface roughness parameters caused by cooling treatment. The results indicate that liquid nitrogen cooling treatment can more effectively reduce the mechanical properties of rocks, and this effect is further enhanced at high temperatures. Under the condition of 300°C, after undergoing different cycles of liquid nitrogen cooling, granite will exhibit a more diverse macroscopic and microscopic structural failure characteristics, consistent with the expected formation of fluid flow channels in high-temperature rock formations.

Influence of the loading rate on the evolution characteristics of AE and MS signals during granite failure

To explore precursor rock failure information near a tunnel excavation boundary under different excavation rates, biaxial compression tests of granite failure under different loading rates were conducted, and the acoustic emission (AE) and microseismic (MS) signals produced by granite failure were monitored and analyzed. The results indicate that loading rate has an important effect on the evolution of AE and MS signal characteristic parameters. Hence, a multi-parameter rock failure warning method based on AE and MS according to different loading rates was proposed, which provides the scientific basis for safety warning of deep engineering. A damage evolution equation based on AE and MS is established to quantitatively describe the damage process of granite under different loading rates. Moreover, it is confirmed that there are vast variations in the sensitivity of AE and MS signals to the formation of cracks of different sizes. Therefore, combining AE and MS signals to monitor the granite failure process will help to reveal the mechanism of granite failure and improve the accuracy of granite failure prediction.

Impacts of different cooling methods on the dynamic tensile properties of thermal-treated granite

Hot dry rock (HDR) is a kind of clean, renewable energy and has received widespread attention worldwide in recent years. It is significant to explore the dynamic tensile properties of thermal-treated granite using different cooling methods for mining HDR. In the current work, a series of tests were performed containing ultrasonic testing and Split Hopkinson Pressure Bar (SHPB) tests on granite at different temperatures (25, 200, 400, 500, 600, and 800 °C) after different cooling methods (including natural, water, and liquid nitrogen cooling). Then the dynamic tensile properties, thermal shock damage, and energy evolution process of granite using different cooling methods were compared and analyzed. The high-speed camera and Digital Image Correlation (DIC) technology were used to analyze the tensile failure mode and the failure mechanism under different thermal treatment and cooling conditions. According to the experimental results, with the increasing thermal treatment temperature by adopting the three cooling methods, the P-wave velocity, dynamic tensile strength, and final absorbed energy of granite decreased, and thermal shock damage increased. In addition, the effect of liquid nitrogen cooling on thermal-treated granite was the most obvious among the three methods, followed by water cooling and natural cooling. Moreover, with the increasing treatment temperature, the time for the occurrence of central cracks in the specimen after impact was prolonged, and the areas of the shear failure zone and tensile failure zone increased; the influence of different cooling methods was also evident (natural cooling < water cooling < liquid nitrogen cooling). The experimental findings were expected to offer a reference for understanding the dynamic tensile properties and failure mechanism of thermal-treated granite after rapid cooling. By studying the degree of deterioration of rock dynamic properties by different cooling methods, the exploitation efficiency of geothermal wells can be improved.

Study on phase evolution and mechanical properties of reconstructed granite

In this paper, reconstructed granite with enhanced mechanical properties is prepared by re-melting and re-sintering granite wastes based on the formation process of natural granite. The sintering process, phase composition, and mechanical properties are deeply investigated. The optimal synthesizing process is sintering granite wastes at 1090 °C for 2 h with a preloading pressure of 25 MPa. Reconstruction results in excellent mechanical properties with a Vickers hardness of 5.30 GPa, a bending strength of 64.84 MPa, and an elastic modulus of 68.77 GPa, which are superior to those of natural granite (Vickers hardness of 3.64 GPa, bending strength of 23.40 MPa, and elastic modulus of 58.77 GPa). The sintering process plays a decisive role in improving the mechanical properties, which not only regulate the phase composition and refine the grain size but also effectively decrease the formation of cracks. This work not only clarified the mechanism between the phase evolution and mechanical properties of reconstructed granite but also proposed a viable way to dispose granite wastes for natural resource recycling.

Integration of machine learning models and metaheuristic algorithms for predicting compressive strength of waste granite powder concrete

The utilization of Granite Powder (GP), a by-product of granite processing, has arisen great attention due to environmental challenge posed by its casual disposal. To promote reasonable use of GP in concrete and obtain optimal ratio design of Granite Powder Concrete (GPC), this study explored four advanced machine learning models (Support Vector Machine (SVM), eXtreme Gradient Boosting (XGB), Random Forest (RF), and Multi-Layer Perceptron (MLP)) integrated with two novel metaheuristic algorithms (Salp Swarm Algorithms (SSA) and Ant Lion Optimizer (ALO)) to predict the compressive strength of GPC. The models consider seven effect factors on the compressive strength: cement, water, fine aggregate, granite powder, superplasticizer, coarse aggregates, and curing age. The comprehensive score ranking system was utilized four evaluation metrics to assess models’ performance: Coefficient of Determination (R2), Variance Accounted For (VAF), Mean Absolute Error (MAE), and Mean Square Error (MSE). In addition, Taylor diagrams and Regression Error Characteristic (REC) curves were used to compare the performance of the models. The results showed that the XGB-based hybrid model outperformed the other methods, with an optimal model of ALO-XGB achieving a high level of accuracy in predicting compressive strength. Furthermore, the study highlights the importance of understanding the interplay between various factors and their effect on the mechanical properties of GPC, which can inform the development of more sustainable and environmentally friendly building materials.

Feasibility of granite processing waste as a fill material in geotechnical applications

India is the third largest granite producer worldwide, and an increasing trend in its export has been seen year by year. Granite is generally sold in dimensional and finished form. Large quarried granite blocks are processed to get a finished dimensional granite in processing industries. Processing comprises sawing, grinding and polishing operations. In processing operations, about 30 to 35 per cent of the mass of large granite blocks is left as fine Granite Processing Waste (GPW) in the form of slurry. Dumping of GPW is of major concern for the processing industries; it is often unscientifically dumped. Disposal of GPW in an unscientific manner causes adverse effects on humans and the environment. Delightful results are obtained in previous studies addressing its use in concrete, mortar building blocks and stabilization of expansive soils. GPW has the potential to serve as a fill material in geotechnical applications. However, a comprehensive characterization of GPW addressing its use as a fill material is significantly lacking. The current study intends to characterize GPW in light of its application as a non-conventional fill material in place of natural materials. Based on geotechnical and geoenvironmental tests carried out on GPW involving grain size analysis, Atterberg limits, hydraulic conductivity, swelling potential, compaction characteristics, surface morphology, chemical composition, elemental and mineralogical composition, pH and organic content analysis, it can be inferred that GPW is comparable to conventional fill materials.