Black Granite Research Articles

Dynamic response analysis of linear motion stage with track roller guides

This paper aims at characterizing the role of preload, friction and mass on the dynamic response of the linear motion stage used in the laser marking machine for black granite. A single-axis linear motion stage model was realized in Creo Parametric® CAE software. The mechanism design option was used to create a virtual mechanism with simulation entities for stiffness, friction, mass, damping, and motors. The experimental design was accomplished using Minitab® software to create the Taguchi orthogonal array. The simulation experiments with different values of preload, friction, and mass were conducted. The results show that increasing the linear bearing preload reduced the settling time. Increased elastic deformation increased bearing rigidity, which ultimately helped reduce vibrations and hence settling time. Furthermore, lower levels of friction reduced sticking and slipping, which led to reduced vibration levels and therefore a lower settling time.

Action of Urine on Stone-Built Heritage

Due to its resistance and durability, stone is the material most used in construction by humanity. The aim of this study was to investigate the action of urine on granites. Accelerated alteration tests were performed on Grey Itaquera, Pink Itupeva, and Black Piracaia granites – stones from the São Paulo State, Brazil, which were widely used in the historical built heritage of the São Paulo state. The test was performed with 30 cycles of partial immersion of nine samples in artificial urine solution and the sanitising of the specimens, totalling 60 consecutive days of testing. In the first 24 hours, the samples were partially immersed in urine; in the following 24 hours, the samples were sanitised in three different groups: A) without washing; B) washing with natural water; C) washing with a 5:1 solution of natural water with bleach. The alterations induced in the specimens were evaluated by spectrophotometry, P-wave velocity, and scanning electron microscopy. The main results obtained were chromatic alterations and crystallisation of salts on the three types of granite. The study concluded that urine is a substance that can cause moderate alterations in the aesthetics and structure of granitic stones.

Characterisation of the tensile performance of bonding agents for the restoration of heritage dimension stone from southeast Australia

Through this research, we measure the direct tensile strength of three important southeast Australian heritage dimension stones and compare the results with published values. The three stones are Sydney Sandstone, Victorian Bluestone and South Australian Black Granite. This information is crucial for stone masons when they are selecting and cutting stone for construction projects, as they need to ensure that the stone they use and the repair will be strong enough to withstand the loads and stresses it will be subjected to in its final location. Results show that direct methods of testing provide tensile strengths that are 30–63% of the indirect methods. When the direct tension to compressive strength ratio is considered, results of 2–7% are calculated for these stones. This is significantly less than the typically assumed 10% for intact rock. Three masonry bonding agents have been selected to determine their capacity to re-bond the dimension stone. Highly variable results were achieved, with re-bonded tensile strengths ranging from 6% to 104% of the intact strength. This variability is most likely related to the heterogeneity of the stones and the surface preparations. Based on these outcomes, it is recommended that stone masons carefully consider the product that is used for restoration works and that test samples be prepared to confirm capacities.

Effectiveness of thermal energy storage material and forced convection on the regeneration of liquid desiccant using hybrid solar still - An experimental study

Hybrid solar still has been investigated to desalinate the saline water and regenerate the weak liquid desiccant. An influence of thermal energy storage material (waste pieces of black granite) and forced convection (12 V direct current fan) was studied in terms of the water desorbed from the weak liquid desiccant and distilled water output from the saline water in two cases of the experiment. A 40% weight concentrated calcium chloride for Case-I and a 42% weight concentrated lithium chloride for Case-II as a weak liquid desiccant were used for the study and flown over the upper basin, whereas a saline water depth of 1 cm was maintained in the lower basin. The total daily desorbed water for Case-I was 761.33 ml/m2 and 796.00 ml/m2 for Case-II from the weak liquid desiccant. The total daily distillate output achieved for Case-I was 302.67 ml/m2 and 284.00 ml/m2 for Case-II. An increase in the concentration of liquid desiccant for Case-I was 2.42% and 1.37% for Case-II. When hybrid solar still will be used as a regenerator in the liquid desiccant-based solar cooling system, the regenerated liquid desiccant can able to adsorb the latent heat load of 0.1251 kW/d for Case-I and 0.1304 kW/d for Case-II from the humid air. For the bright sunshine hours, the daily average overall efficiency of 20.98% for Case-I and 27.76% for Case-II was obtained for the hybrid solar still.

Simulated Acidic Weathering of “Black Granites”: an Assessment using Regression Analysis

A number of “black granites” were tested using simulated acidic weathering (H2SO4, HNO3, H2SO4/HNO3 and HCl, at pH = 3,00), freeze resistance and relative loss of brightness. The same plates of these granites remained immersed in each acidic solution over eight weekly cycles. The pH data from residual acid solutions were plotted versus timing of the experimental cycles in XY diagrams for interpretation as log-linear regressions. The global set of data, transcribed in a ternary diagram, shows a distinctive area highlighting the best commercial granites. In addition to these granite coatings, the proposed methodology allows easy and accurate identification of their best performances.

The effect of notches on breakdown pressure during hydraulic fracturing at various stress regimes

High stress environments are becoming more common as the trend and need to develop deeper block cave mines economically and safely continue. Hydraulic fracturing (HF) is considered to be a powerful tool in the success of hard rock block cave mines as it assists with caveability, economic recovery, and seismic risk mitigation. Therefore, determining critical design parameters such as breakdown pressure and the impact of notching on this parameter is paramount for designing and implementing a successful preconditioning campaign. To better understand the impact of notches on the breakdown and propagation pressure, a series of lab experiments were undertaken with variations in stress regime, stress magnitudes and the presence and number of notches were evaluated. This enabled us to explore the impact of confining pressure and spacing of notches on the breakdown and fracture propagation pressures. Various types of samples including Adelaide Black Granite, Engineered plastic (PMMA) were tested to give ranges and balance for homogeneity and real-world mining applications. We observed the fracture initiation and propagation through breakdown pressures along with acoustic emission measurements. The experimental results confirm that increasing confining stress on a sample increases the breakdown pressure. The works also validate the non-impact of axial stresses and the variation of tensile strength on a sample on the breakdown pressure.

Selective visualization techniques for elemental mapping analysis of granite stones by field emission scanning electron microscopy and energy dispersive spectroscopy (FESEM-EDXS)

Image analysis using an advanced technology of a field-emission scanning electron microscope intrinsically equipped with energy-dispersive X-ray spectroscopy (FESEM-EDXS) used to observe the microstructure of black galaxy, emerald pearl, and baltic brown granites. Current study includes characterization of grain patterns, and chemical composition of the granites stones. FESEM – EDXS analysis performs a vital position in the great analysis of objects and is one of the satisfactory techniques that fall beneath non-destructive testing (NDT). The present work aimed to discuss the optical characteristics of minerals, distribution surface patterns and its chemical composition of the granite stone types. The surface pattern of the grains and their chemical composition were found to indicate differences in the three mineral images. It shows that Baltic brown granite contain high concentration of Si (29.3 wt%) compared to Black galaxy granite (24.7%) and Emerald pearl (18.6 wt%). It is suggested that these three (3) types of granite samples represent high concentration of O and it can be classified that SiO2 (silica) is the main compound. Oher elements found such as Al and Fe also has their own role in granite stone physical characteristics. Therefore, the study has provided insight view on granite image and elemental mapping analysis as well as its colours and texture properties. A better understanding on the physicochemical of the granite has been achieved.

Augmenting the productivity of tubular solar still using low-cost energy storage materials

Productivity improvement is one of the high-priority areas in the development of solar stills. The present work describes the use of some low-cost energy storage materials such as sand, gravels, and black granite as potential candidates to improve the productivity of the tubular solar still (TSS). The experimental studies have been carried out at Nagpur (21.1241° N, 79.0023° E) to investigate the effects of these materials on the productivity of the TSS. Three separate TSS experimental setups have been made for each energy storage materials. These include (a) 5kg of fine sand (0.125-0.25-mm grain size), (b) small gravels (20-30mm), and (c) black granite (5-mm thickness) placed in the absorber basin of individual TSS setup, separately. The experiments have been performed by varying basin water depth at 0.5cm, 1cm, and 2cm, for each case. The results show that for water depth of 0.5cm, productivity of TSS-Black granite is enhanced by 10.5% and 34.88% as compared to TSS-Gravel case and TSS-Sand case, respectively. Thermal efficiency and exergy efficiency of TSS-Black granite at 0.5-cm water depth is enhanced by (32.4%, 9.8%) and (92.1%, 21.9%) as compared to TSS-Sand case and TSS-Gravel case, respectively. Furthermore, it has been estimated that the cost of production of freshwater using TSS-Black granite is lowest among all selected combinations.

Investigation and performance analysis of solar still with energy storage materials: An energy- exergy efficiency analysis

Researchers have attempted different Energy storage materials (ESM) in solar stills (SS) to improve distillate yield. In this experimental work, an attempt was made to increase the distillate yield & efficiency of SS, using good absorbing and heat transfer capacity of ESM. A comparison was made between a conventional solar still (CSS) and a solar still with energy storage materials (SSWESM) in this experiment. Different energy storage materials like black color glass ball (BCGB), black granite (BG) and white marble stone (WMS) were used in equal quantity during experimental work. CSS and SSWESM had daily distillate yield of 1.4 kg/m2 and 2.5 kg/m2, respectively. The ESM boosts water evaporation during the day and releases heat at night, resulting in a higher distillate yield than CSS. Meanwhile, the exergy efficiency (ƞexe) of CSS and SSWESM were 4.99% and 12.55% respectively. Also the SSWESM gives 72.6% more daily efficiency (ƞ) than CSS.

‘Our own law is making us beggars’: Understanding experiences of governed, mine-side communities in Mutoko district, Zimbabwe

There is rising interest in connecting global value chains with sites of extraction to ensure that mineral resources, wherever extracted, are governed to benefit communities. Despite commitments by policymakers and African intergovernmental bodies to governance that does not disenfranchise communities, voices of those affected remain peripheral to mining industry operations. In this article we ask how the extraction of black granite used in grand buildings in the West is experienced by mine-affected people in Zimbabwe's Mutoko District. We seek to bring forth voices of those affected by mineral extraction including its governance processes, to produce an account of mining anthropology rooted in Habermas's lifeworld concept. We show how communities continue to shoulder multiple burdens of black granite extraction without getting its rewards: Broken bridges, damaged roads, dirty air, hazardous living environments and loss of land are some of the key experiences. And the current governance regime characterised by outdated laws, dishonesty, and intimidation of the governed allows the burdens of black granite mining to perpetuate. In conclusion, we note how the marginalised lifeworld contains knowledge, capacity and experiences that must be fully accounted for in reshaping the governance of extraction for the benefit of mine-side communities.

Diamond tool wear monitoring by sensory analysis in milling of absolute black granite

Diamond tools suitable for machining operations of natural stones can be divided into two groups: cutting tools, including blades, the circular blades and the wires, and the surface machining ones, involving mills and grinders, that can be of different shapes. For the stone sawing process, the most adopted tool type is the diamond mill, whose duration and performance are influenced by various elements such as: the mineralogical characteristics of the material to be machined; the working conditions such as the depth of cut, the feed rate and the spindle speed; the production process of the diamond segment and the characteristics of both the matrix and the diamond, such as the size, the type and the concentration of the diamonds and the metal bond formulation hardness. This work allows to indirectly assess the wear of sintered diamond tools by signal analysis (in time and frequency domain) of the cutting force components acquired in the process. The results obtained represent a fundamental step for the development of a sensory supervision system capable of assessing the tool wear and hence to modify the process parameters in process, in order to optimize cutting performance and tool life.

Nuclear Radiation Shielding Characteristics of Some Natural Rocks by Using EPICS2017 Library.

Radiation leakage is a serious problem in various technological applications. In this paper, radiation shielding characteristics of some natural rocks are elucidated. Mass attenuation coefficients (µ/ρ) of these rocks are obtained at different photon energies with the help of the EPICS2017 library. The obtained µ/ρ values are confirmed via the theoretical XCOM program by determining the correlation factor and relative deviation between both of these methods. Then, effective atomic number (Zeff), absorption length (MFP), and half value layer (HVL) are evaluated by applying the µ/ρ values. The maximum μ/ρ values of the natural rocks were observed at 0.37 MeV. At this energy, the Zeff values of the natural rocks were 16.23, 16.97, 17.28, 10.43, and 16.65 for olivine basalt, jet black granite, limestone, sandstone, and dolerite, respectively. It is noted that the radiation shielding features of the selected natural rocks are higher than that of conventional concrete and comparable with those of commercial glasses. Therefore, the present rocks can be used in various radiation shielding applications, and they have many advantages for being clean and low-cost products. In addition, we found that the EPICS2017 library is useful in determining the radiation shielding parameters for the rocks and may be used for further calculations for other rocks and construction building materials.

Brackish water desalination using black granite as heat storage medium under arid climatic conditions

Brackish water desalination using black granite as heat storage medium under arid climatic conditions

Application for Prediction of Waviness in Water Jet Cutting of Granite

Granite has broad applications as construction material, architectural stone, a decorative stone, bridges and counter-tops. Black pearl granite is excavated in large blocks providing slabs of suitable sizes. Machining of rocks with conventional method has low surface finish and incorporates cost in final finishing. Abrasive water jet cutting is used for precise cutting of granite. Burst occurs at the other side of the material which is undesirable. The burst has to be minimum for high production and minimum wastage of cost. The experiments were carried on Black pearl granite. By using Taguchi method a L27 Orthogonal Array was formed for deciding number of cuts. Input parameters such as traverse speed, abrasive flow rate and standoff distance were varied whereas water pressure and abrasive size were constant and burst area was the response which is to be calculated. After experimentation, with the help of ImageJ software area of burst is calculated for each cuts. Thereafter with the help of data acquired, coding was done in ANFIS in order to predict the burst area. The motive behind this is to increase the precision of machining and to reduce the cost behind the finishing of granite.

The Wall

The Wall Colder than the reception coming home Stateside is this black granite to my touch. Colder than the corpses of all I nursed there who yet died. Colder than the fire of missies spit forth from mortars, AKs, rockets. Colder than the political terrorism that sent us there. Colder than the hearts of those who came home survivors of ‘Nam” and colder yet is the black granite reminder.

Effect of cost-free energy storage material and saline water depth on the performance of square pyramid solar still: a mathematical and experimental study

Low productivity of single-slope solar still is the main barrier for its worldwide usability. An attempt has been conducted to enhance the distillate yield of single basin square pyramid solar still using thermal storage material in basin. The experiments were conducted with two identical single basin square pyramid solar stills under the climate of location (20.61° N 72.91° E), one with small pieces of black granite as a thermal storage material and other without black granite. With and without thermal storage, the effect of saline water depth (30 and 20 mm) was investigated on the performance of still. Compared to still without thermal storage, yield of 1430.40 mL m−2 (13.96% higher) and 1380.40 mL m−2 (6.63% higher) was obtained at water depth of 30 mm and 20 mm for the still with thermal storage. The daily average efficiency of 18.69% (11.35% higher) and 18.58% (5.09% higher) was obtained at water depth of 30 mm and 20 mm for the still with thermal storage. The higher yield was achieved at water depth of 30 mm than the 20 mm for the still with thermal storage, whereas the higher yield was achieved at water depth of 20 mm than the 30 mm for the still without thermal storage. Transient model for the still with and without thermal storage was developed, and the results were compared with experimental outcomes and good agreement was observed.

Efficacy of forced condensation and forced evaporation with thermal energy storage material on square pyramid solar still

Authors have attempted to investigate the impact of thermal storage material, forced condensation and forced evaporation on the performance of square pyramid solar still. The experimentation was conducted in three sets. First set was carried out with and without thermal storage (black granite) and variable water depth (20 mm and 30 mm). The daily yield of 1430.40 ml/m2 (13.96% higher) was obtained for the still with thermal storage at water depth of 30 mm. The second set was conducted for studying the impact of forced condensation and forced evaporation with thermal storage on the performance of still at 30 mm water depth. Compared to the still with forced condensation, increment of 33.24% was observed in daily yield for the still with forced evaporation. The effect of forced evaporation and thermal storage on yield and efficiency was compared with the still without augmentation at 30 mm water depth in third set. The daily yield of 2253.6 ml/m2 (61.48% higher) and the efficiency of 27.04% (61.53% higher) were achieved for the still with forced evaporation and thermal storage. The still with forced evaporation and thermal storage at water depth of 30 mm has proved most productive, efficient and economic.

Epoxy Granite Properties using Indian Origin Granite

Precision machine tools are expected to operate at higher machine speed to produce precise products. Hence, its structures must have high structural stiffness and high damping along with dimensional and geometrical stability. Granite is the material used for metrological and precision machine manufacturing applications. Granite is also used in some of the high accuracy machine tool manufacturing. Considering the natural properties and limitations of granite a new emerging material named Epoxy Granite is evolved. In this paper, Epoxy Granite properties using Indian Black granite are studied. In particular, the maximum load-bearing and density of epoxy granite are focussed. Also, the combination which is best suited for the applications can be easily dragged out. Density is compared with maximum load-bearing and their relation is also put forward to simplify the selection process of epoxy granite.

A cohesive grain based model to simulate shear behaviour of rock joints with asperity damage in polycrystalline rock

A cohesive grain based model is proposed to simulate the fracture behaviour of polycrystalline rocks. The model was employed to characterize the cracking response of both inter- and intra-grain contacts in the grain based model (GBM). The model was implemented in distinct element codes and its ability to mimic the mechanical and failure behaviour of polycrystalline rocks was demonstrated through calibration of several granitic rocks including Adelaide black granite, Eibenstock II granite, and Aue granite. The calibrated model of Aue granite was used to assess the effect of joint roughness coefficient (JRC) on asperity damage and shear mechanism of rock joints (i.e. grain crushing) under constant normal load (CNL) and constant normal stiffness (CNS) conditions. The bond-break in intra-grain contacts contributed to asperity damage in form of grain crushing. The numerical observations showed that under CNS condition asperity damage increased with increasing initial normal stress and JRC, and rough rock joints exhibited more dilative response.

Experimental investigations on the thermal properties of Jalore granitic rocks for nuclear waste repository

The main objective of this study is to analyze the thermo-physical properties of the potential host rock (golden, red, white and black Jalore granitoid) for the construction of a nuclear waste repository in India. The thermal properties of Jalore granitic rocks were determined using the transient plane source (TPS) technique in the temperature range from 25 °C to 250 °C. The dilatometric tests for thermal expansion and the thermal strain were carried out. The results indicate that the thermal conductivity, thermal diffusivity, mass loss and elastic wave velocity of Jalore granite decreases gradually as the temperature increases from 25 °C to 250 °C. The thermal expansion increases with the increasing temperature, and there is a good exponential growth relation between temperature and thermal strain. Additional laboratory tests including thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope (SEM) have also been conducted to investigate the temperature evolution inside the rock specimens. The results show that the feldspars have a low and isotropic thermal expansion that do not affect the molecular structure as much in red and white granite, while on the other hand, thermal stresses are confined in quartz crystal, resulting in intense intragranular cracking for golden and black granite. This research in terms of measurement of thermal parameters subjected to below damage threshold temperature (≥ 250 °C) as well as the method of analyzing the results are novel for primary importance for the construction of nuclear waste repository applications in Jalore granitoid.