Granite Gravel Research Articles

Erosion Wear Behavior of HVAF-Sprayed WC/Cr3C2-Based Cermet and Martensitic Stainless Steel Coatings on AlSi7Mg0.3 Alloy: A Comparative Study

The paper presents a comparative study of the erosion wear resistance of WC-10Co4Cr, Cr3C2-25NiCr and martensitic stainless steel (SS) coatings deposited onto an AlSi7Mg0.3 (Al) alloy substrate by high-velocity air‒fuel (HVAF) spraying. The influence of the abrasive type (quartz sand or granite gravel), erodent attack angle, thickness, and microhardness of the coatings on their and Al substrate’s wear resistance was comprehensively investigated under dry erosion conditions typical for fan blades. The HVAF-spraying process did not affect the Al substrate’s structure, except for when the near-surface layer was 20‒40 μm thick. This was attributed to the formation of a modified Al-Si eutectic with enhanced microhardness and strength in the near-substrate area. Mechanical characterization revealed significantly higher microhardness values for the cermet WC-10Co4Cr (~12 GPa) and Cr3C2-25NiCr (~9 GPa) coatings, while for the SS coating, the value was ~5.7 GPa. Erosion wear tests established that while Cr3C2-25NiCr and SS coatings were more sensitive to abrasive type, the WC-10Co4Cr coating exhibited significantly higher wear resistance, outperforming the alternatives by 2‒17 times under high abrasive intensity. These findings highlight the potential of HVAF-sprayed WC-10Co4Cr coatings for extending the service life of AlSi7Mg0.3-based fan blades exposed to erosion wear at normal temperatures.

PROPERTIES OF CONCRETE AND FIBER-REINFORCED CONCRETE FOR BASES OF ROAD CLOTHES BASED ON SECONDARY AGGREGATES WITH HETEROGENEOUS COMPOSITION

The problem of disposal of concrete scrap of dismantled building structures is relevant for most countries of the world. For Ukraine, this problem is even more acute due to the significant amount of destruction caused by hostilities and rocket attacks. In current research the properties of concrete and fibre-reinforced concrete for the bases of road clothes based on natural and secondary aggregates were compared: granite river gravel, secondary crushed stone with a heterogeneous composition, quartz sand and secondary sand from recycled reinforced concrete structures. CEM III/A slag Portland cement with a blast furnace slag content of 65% and a polycarboxylate type superplasticizer were used. Three series of samples were studied: without fibre; with glass fibre ANTI-CRAK HP 12 (length 12 mm, diameter 0.017 mm, equivalent thread diameter 0.3 mm) in the amount of 1 kg/m3; with polypropylene fibre BeneSteel 55 (length 55 mm, equivalent thread diameter 0.48 mm) in the amount of 4 kg/m3. In each series, concrete on granite gravel and quartz sand, concrete on secondary crushed stone and quartz sand, concrete on secondary crushed stone and secondary sand were studied. The workability of all mixtures was equal to S1. Due to the use of different types of aggregates and fibres, the W/C of concrete mixtures differed significantly. Concretes on secondary aggregates had a higher W/C than on natural aggregates. When using the Anti-Crak HP 12 fibre, the mobility of mixtures with equal W/C increased by 5.5 – 6.9 %. When using BeneSteel 55 fibre, W/C increased by 10.6 – 15.5 %. The type of aggregate had a significant effect on the average density of concrete. When using secondary crushed stone and quartz sand, the average density decreased by 3.8 – 4.6 %. When using secondary crushed stone simultaneously with secondary sand, the average density of concrete decreased by 5.2 – 8.5 %. When using Anti-Crak HP 12 fiber, the average density of concrete decreases by 2 %, when using BeneSteel 55 fibre – up to 4.1 %. Concretes on secondary crushed stone with heterogeneous composition and quartz sand had 4 % higher compressive strength and 2 % higher tensile strength in bending than concretes on granite gravel and similar sand (29.8 MPa and 3.18 MPa, respectively). When secondary crushed stone is used simultaneously with secondary sand, the compressive strength of concrete is only 1.1 % lower than the strength of concrete on natural aggregates, and the tensile strength in bending is 10 % lower. This confirms the possibility of effective use of these concretes for arranging of bases of road clothes. The high-quality performance of secondary aggregates in concrete explains due to their better adhesion to the cement-sand matrix. Dispersed fibre reinforcement with Anti-Crak HP 12 has a positive effect on the compressive strength of concrete on all types of aggregate and increases the tensile strength of concrete on natural aggregates. The use of BeneSteel 55 fibre was not effective due to a significant increase in the W/C of the mixture when it was introduced. In general, taking into account the economic factor, dispersion reinforcement of concrete on secondary aggregates with the types of fibres used in the research is not advisable.

STRENGTH OF CONCRETE FOR BASES OF ROAD CLOTHES ON DIFFERENT TYPES OF SECONDARY GRAVEL AND SAND

The task of developing of concrete for the bases of road clothing using secondary concrete aggregates is relevant for an economic and ecological reasons. The properties of concrete were compared with different types of coarse aggregate of 8-16 mm fraction: granite river gravel, secondary crushed stone from recycled reinforced concrete structures, secondary crushed stone from recycled brickwork and ceramic tiles. Three types of sand with a fraction of 0-4 mm were also used: quartz, secondary sand from recycled reinforced concrete structures, secondary sand from recycled brickwork. 2 series of experiments were conducted. During the first series of experiments Portland cement CEM II/B-S 32.5 R and superplasticizer Soudal Soudaplast was used (1% from weight of cement). For the second series of experiments Portland cement CEM II/B-S 42.5 R and superplasticizer Berament HT28 was used (1.2% from weight of cement). The mobility of all mixtures was equal to S1. Concretes with Berament HT28 superplasticizer had a lower W/C ratio of mixture than concretes with similar aggregates composition and Soudal Soudaplast superplasticizer. The use of secondary crushed stone requires an increasing of the W/C ratio of the mixture. The simultaneous use of secondary sand additionally increases W/C. Due to the lower W/C, the concretes of the second series have a higher average density than the similar concretes of the first series of the experiment. Concretes based on granite gravel and quartz sand have the highest average density (2369-2465 kg/m3). When using secondary crushed stone from reinforced concrete structures, the average density decreases by 3-5%. When using secondary crushed stone from brickwork and ceramic tiles – decreases by 8-9%. Concretes based on secondary crushed stone and sand from reinforced concrete structures have a 6-9% lower average density compared to concretes on granite gravel. Concretes based on secondary crushed stone and sand from recycled brickwork and ceramic tiles have the lowest average density – from 2015 to 2061 kg/m3. Due to the use of higher grade cement and a more effective superplasticizer, the strength of the concretes of the second series of the experiment at the age of 3 days was 69-190% higher than the strength of similar concretes of the first series, at the age of 28 days – higher by 67 to 147%. When using quartz sand, concrete based on secondary crushed stone from reinforced concrete structures has the greatest strength. At the age of 3 days up to 17.97 MPa and 30.33 MPa, at the design age (28 days) up to 32.07 and 53.41 MPa for the first and second series, respectively. The lowest strength (about 16 MPa in the first series of experiments and 27 MPa in the second) had concretes using only low-strength secondary aggregates from recycled brickwork and ceramic tiles. In general, all the studied concretes on secondary aggregates were characterized by sufficient strength for their use in the bases of hard road clothes.

Modelling and Parametric Analysis of Conventional Still By using Passive Control Techniques

: The present paper deals with experiments performed on a conventional single slope solar still with various quantities of saline water (20kgs, 30 kgs and 40 kgs) and also deals with experiments conducted in a modified still which is directly placed on ground without insulation at the sides and bottom of the still. Further a modification is made to a still by removing insulation so that heat stored in the earth surface is utilized to heat the saline/sea water during the evening hours. Initially experiments are performed for 20 kg, 30 kg, 40kgs of saline water using conventional still to get the optimized quantity. From the results it is observed that there is an increase of 18.5% in the yield when earth heat is used and 28% when 25 mm depth of granite gravel is used in addition to earth heat. Further the study is extended to compare the analytical and experimental cumulative yield for three different quantity of saline water.

CONCRETES ON SECONDARY CRUSHED STONE AS A PROMISING MATERIAL FOR THE RIGID PAVEMENT BASE

In the course of research, the efficiency of application of plasticizers of different type in concretes for bases of highways on secondary crushed stone is defined. In studies of concrete compositions, the type of crushed stone, secondary or granite, changed, which allowed to compare the properties of concrete on secondary crushed stone with the properties of concrete of similar composition on granite crushed stone. In addition, the type of sand changed: Bilyaevsky or Voznesenski quarry. As modifiers used additive lignosulfonate or superplasticizer polycarboxylate type MC-PowerFlow 3200. All concrete mixtures had equal mobility P2, which was provided by variation W/C (water-cement ratio). It was found that the concrete on the secondary crushed stone is characterized by a significantly higher W/C mixture due to greater porosity and damage to the surface of the coarse aggregate. The average density of concrete on secondary crushed stone is 4.2-4.4% lower compared to the average density of concrete on granite crushed stone. The average density of concrete on the larger sand of the Voznesenski quarry is 25-30 kg/m3 higher than the average density of concrete on similar gravel and finer sand of the Bilyaevsky quarry. In composites based on CEM III/A and using lingosulfonate additives, the compressive strength of concrete on secondary crushed stone is 12-13% lower compared to the strength of concrete on granite crushed stone and similar sand. However, when using the more efficient MC-PowerFlow 3200 additive, the difference in concrete strength on secondary and granite crushed stone is only 5.4% (29.8 MPa and 31.4 MPa, respectively). The strength of concrete on the sand of the Voznesenski quarry is 4-6% higher than the strength of concrete on similar gravel and finer sand of the Bilyaevsky quarry. It was found that the tensile strength when bending concrete on secondary and granite gravel when using the additive MC-PowerFlow 3200 was 2.75 MPa and 2.87 MPa, respectively, which differs by only 4%. Thus, the tensile strength of bending concrete on secondary crushed stone was almost no different from the tensile strength of similar concrete on granite crushed stone. This can be explained by the peculiarities of the aggregate with a porous surface, which is characterized by high adhesion to the cement-sand matrix. In general, the strength of concrete on secondary crushed stone using slag-containing cements allows them to be used effectively for road bases.

Multi-scale particle morphology evolution in rotating drum tests: Role of particle shape and pore fluid

During the downslope long-distance movement of debris avalanches, particles interact with each other in various modes, by rolling, sliding and colliding with each other. During transport, grains may undergo breakage, changing in size and shape. However, research on debris avalanches at the grain scale remains limited, in particular, the evolution of grain morphology at different scales, from the overall form down to surface roughness, with runout distance. This paper investigates the evolution of particle morphology of granite gravel particles during long distance travel using a rotating drum, Micro-Deval apparatus, together with three-dimensional (3D) image analysis with a 3D laser scanner. The effects of particle shape and pore fluid (dry, saturated with water or slurry) on the evolution of particle morphology during transport were investigated. It was found that while the gravel was strong enough to resist the fragmentation that could be induced by the inter-particle actions during testing, the corners and edges became rounded, and the general form and surface roughness remained unaffected by the particle interactions. The more angular the grains, the easier the corners to be abraded during interaction. The change of local roundness of the grains was amplified in water-saturated conditions and suppressed in a slurry-saturated medium. The viscosity of the pore fluid, rather than initial particle shape, was critical in controlling the particle morphology evolution.

PREPARATION OF CONCRETE BASED ON GLASS WASTE

PREPARATION OF CONCRETE BASED ON GLASS WASTE

Comeback, and: For Anjoli Roy, and: Coyote, Gravel, and: Isolate, and: Dream of a Beached Whale

Comeback, and: For Anjoli Roy, and: Coyote, Gravel, and: Isolate, and: Dream of a Beached Whale Rajiv Mohabir (bio) Comeback Returning to Bellingham Bay,humpbacks lunge into krillclouds. Cetacean resurgence stuns August mackerel shoals, northernblooms now at silver capacity.Whalers once drove rorquals to markets as lamp oil and umbrellas.What is a body but to be rendered— In 1907 five hundred white menshook East Indians from prayer, broke dholak drums, pushed outwho they called Hindu Hordes. We are still being flensedof papers, striped to the quickin public. And yet, in America's thieved straits I sing dark-bodied chutney. Listen, the Salish Salt again hums.Off Semiahmoo Bay, see a cowteach her yearling to blow [End Page 49] a toroidal vortex. Despitewhale irons, ruin, despiteexpulsion, Get Out scrawled on our temple walls, we return.To our summer qawwali kirtan, we return, whileflukes beat the drum-skin sea. For Anjoli Roy What is nostalgia but a ship's keeninginto a capelin shoal, silver as springgrief. The sun somewhere hiding under cloudcover, so steel light glows from the photoyou hold of which shapes you have tried to befor others. Like Mary searched, whatdeity rests behind stone—the dyinggod is a winter tree. A crown of leavesfirst brown then gone. But like any seasonof whales, a comeback arrives soon. The treecoronated in emerald. The cornersof your house must first fill with ghost shadows.Without absence what value has cloudlesslight? Without silence can whale song return? [End Page 50] Coyote, Gravel I strip down to my erectionremembering the thirty-something who cruised me at the urinal—I am a lonely fool. Yesterday I followed a coyotebehind a pile of granite gravel. Who is foreign here?This coyote adapting to human waste, or the stonesthat don't recall being a cliff— Which of us coils poemsunable to recall to page the trade winds' balm?Magical thinking corrals me to the epic in whichthe god is god and not hewn stone—My god, I want to be led. [End Page 51] Isolate come night I let in the colduntil the ti plant frosts and brownsand I am cruel to imprison him in Bostonfor lusting after self-reflection * I have stopped listeningto music for a seasonthe drum beats a pulse of grief into me * a friend saysgrieving cultural loss is real grief I've mortared mineinto a house Papered the walls with hypotheticals Each morning I lift my blindsastonished by gray untilI am window-like neither inside nor outunable to control what moves meor stirs beyond casement [End Page 52] * A supine red breastbrush strokedthe feather's each vein matte and soft the window cracked lets inthe breeze of morningsong Dream of a Beached Whale A hurricane strands a humpbackthat croons from land, soonto bloat in surf, unable to bearthe weight of meat, lungs goredby rib. Beneath, copepods and powdered mollusk shellsperform their diatom orchestrain tiny voice, as salt packs themtighter together. You uttera spell of letters: mysticetes, and corals sprout from your pharynx.Clown fish scintillate in anemoneas if to say, O eye, be drawn bythe wild, fire-color you will be.Your body opens into a coral reef, triggerfish and wrasse playamongst the polyps of your chestuntil you roll back onto the beachnext to the other vertebraed creature.Your voice carries its noise [End Page 53] to swirl in starlight long afteryou shake into clay and teemwith microbial life. Burningin the tryworks of blubber, ashorein sun, helpless you voice too, the fire song that steams in airas a shadow cry. One day you willluminesce until you bleach into rockdust. But now, you can do nothingyourself except dissolve, balaena beside you, melodious elsewhere,but guttural here. Not mysticalballerina a name masked in cognates;you ask, Balma, is this my voice orthe rorqual's? Water, wave, grit of whelk and conch...

Geoelectric survey of the Granite Gravel aquifer, Llano Uplift, Central Texas, to determine locations for water wells

An electrical geophysical survey was completed within a small area of the Llano Uplift of central Texas to determine locations to install two water wells in the Granite Gravel aquifer (GGA). Electrical resistivity tomography (ERT) was performed along two 188-m long profiles that intersected at the approximate center of a 100-m by 100-m self-potential (SP) map. The ERT survey was completed to map two-dimensional (2D) electric resistivity distributions in the GGA and the underlying Precambrian Town Mountain Granite (TMG) bedrock, whereas SP mapping was performed to delineate apparent streaming potential anomalies at the land surface that appeared correlated to the subsurface resistivity distributions, which exhibited strong lateral heterogeneity in the upper 35 m of the weathered layer that comprises the GGA. The depth to TMG bedrock, as shown by the resistivity distributions, varied substantially over relatively small profile distances and surface areas; however, the general electrical structure showed resistivity increasing with depth, beginning with a thin electrically conductive layer at the surface characterized by resistivity in the range of about 30–100 Ω-m, followed by a resistivity increase to 300–500 Ω-m at a depth that coincided with the water-table depth observed in the installed water wells. Resistivity of the TMG bedrock was generally greater than 500 Ω-m and exceeded 1000 Ω-m in some locations of the tomograms. Electrical structure beneath the survey area, as shown by the 2D resistivity distributions beneath the ERT profiles, delineated a relatively thick weathered section of GGA that spatially aligned with a conspicuous negative anomaly observed in the SP map after electrode-drift and terrain corrections were made. The combination of ERT and SP mapping guided selection of locations for two productive water wells within the small survey area despite substantial heterogeneity in the weathering profile of the GGA beneath the survey area.

Innovative Multistage Constructed Wetland for Municipal Wastewater Treatment and Reuse for Agriculture in Senegal

This paper reports on the performance of using a multistage constructed wetland (CW) to treat municipal raw wastewater and an analysis of its suitability for agricultural irrigation. The pilot plant consists of two stages of vertical flow CWs plus one stage of a horizontal CW built in 2018 with different local materials at the Gaston Berger University Campus, Saint Louis (Senegal). Each CW stage is composed of several filters with different type of media (silex, granite, or river gravel), filtering media depths, and macrophytes (Phragmites and Typha). The physicochemical and microbiological indicators were monitored over six months at each bed inlet and outlet to evaluate the efficiency and achievements of the Senegalese, European, and WHO regulations/recommendations for disposal or reuse in irrigation. This study demonstrates the viability of this new multistage CW design to treat raw municipal wastewater and produce an effluent of good quality suitable for reuse in agriculture. The removal of organic matter, suspended solids, and nutrients was very high (>95% for SS, BOD5 and N-NH4+, >90% for COD and P-PO43−), as was the reduction of microbiological indicators (fecal coliform reduction >5 log units and helminth egg removal of 100%). First, trends related to the influence of design (the type of gravel, filter depth, and type of macrophyte), operational modes, and the CW treatment efficiency were determined. The use of non-crushed gravel and Typha spp. seemed to provide better removal rates. On the contrary, no differences were found between the use of silex or granite gravel. For the studied Senegalese conditions under dry and hot climates, the preliminary results indicate that no resting periods are necessary for vertical flow CWs (VFCWs), thus resulting in a reduction in construction and operation costs. The main outcome of our study is evidence that multistage CWs can provide robust, cost-effective treatments, as well as allow for safe water reuse, which is imperative in areas with severe water scarcity and endemic microbiological waterborne diseases.

Provenance and depositional mechanism analyses of the Yangtianba Formation, northwestern margin of the Yangtze Block, southwestern China

The Yangtianba Formation in the northwestern Bikou Terrane preserves sedimentary archives for the Early to Middle Neoproterozoic tectonic evolution of the northwestern margin of the Yangtze Block (YB). However, its provenance and depositional mechanism are still matter of debates. This paper presents geochronological and petrographic studies of two granite gravel samples and one coarse-grained sandstone sample as well as facies analysis of the conspicuous Yangtianba Formation conglomerates (YFC). The weighted average 206Pb/238U ages of the two granite gravels are 743 ± 6 Ma and 762 ± 4 Ma, respectively. The detrital zircon U-Pb ages of the sandstone sample peak at ca. 880 to 740 Ma, close to the depositional age of the Yangtianba Formation. Together with the dominantly angular to subangular morphology and clear oscillatory or broad zoning of these detrital zircons, the Yangtianba Formation is likely sourced from the Early to Middle Neoproterozoic igneous rocks. Facies analysis of the YFC shows they are stacked bundles of fining- and thinning-upward units of conglomerates-sandstone, suggesting a decreasing supply of coarse clastic materials from the episodic mass flow (debris flow) in the submarine channels rather than tillites. Combining with the previous work, the Yangtianba Formation probably mainly sourced from the Neoproterozoic igneous rocks in the Micangshan-Hannan area in the northwestern margin of the YB and is subaqueous sediment gravity flow deposits rather than glacial-marine deposits. These findings favor the model that the northwestern margin of the YB may be an active continental margin setting during the Early- to Middle- Neoproterozoic (ca. 835 to 720 Ma).

Performance analysis of conventional triple basin solar still with evacuated heat pipes, corrugated sheets and storage materials

Present research article examines the experimental analysis of conventional triple basin solar still (CTBSS) with evacuated heat pipes (EVHPP), corrugated sheets (CS) as absorber and sensible heat storage materials (SHSM). Nearby available materials like pebbles and granite gravel have taken as storage materials in current research work. Corrugated sheets (CS) used to enhance surface area and distillate output both in the present investigation. The investigations have carried out in three cases like (CTBSS), CTBSS with EVHPP and pebbles and CTBSS with EVHPP and granite gravel., From the six-month investigations, it has been found that the maximum distillate output obtained from the lower basin of CTBSS as compared with remaining two. Also, the present system obtained 19 kg/m2/day average distillate output for CTBSS with EVHPP and granite gravel.

Hardening of carbonate filled concretes in different conditions

At Tashkent chemical-technological institute, a study is being conducted to obtain strong concrete based on carbonate aggregates. These studies were conducted on flexible concrete mixes and aggregates up to 40mm in size, so the strength of the concrete did not exceed 40 kG/cm2 as a rule. Experiments show that in non-high-grade concrete, the strength of the limestone aggregates has a relatively small effect on the strength of the concrete. For example, the difference in the strength of concretes made of Baishevsk limestone and granite gravel does not exceed 5%, while the strength of the filler rocks differs by 10 times. Their results show that fillers made from ordinary limestone and carbonate wastes of the soda plant, despite the low strength of the rocks (average from 15 to 100 kG/cm), based on their structure, texture and chemical-mineralogical composition, at normal cement consumption, 150–300 kG/cm and has been shown to provide a higher strength concrete yield.

Removal of Al, Ga, As, V and Mo from alkaline wastewater using pilot-scale constructed wetlands.

The study was initiated to evaluate constructed wetland technology as a method for treating alkaline (pH 8.0-8.6) drainage high in Al, Mo, V, As and Ga originating from bauxite residue storage areas. Pilot-scale horizontal flow constructed wetlands were operated over a 40-week period using three filter materials (granitic gravel, bauxite and alum water treatment sludge), and half of the wetlands were planted with Phragmites australis and the other half left unplanted. Gravel was the least effective medium for removing the target elements, while of the two active media, water treatment sludge was more effective than bauxite. Plants removed only small amounts of elements into their above- and below-ground dry matter (0.4-4.9% of that added). Nonetheless, the presence of plants greatly increased the effectiveness of all three media since their presence decreased effluent pH values by 0.5-1.3 pH units and that of the filter media by 0.4 pH units. Removal of elements followed the order Al > Ga > V > As > Mo. For planted wetlands, total elemental removal ranged from 18 to 98% for gravel, 80 to 99% for bauxite, and 93 to 99% for water treatment sludge. The lowest removal was for Mo (ranging from 18% for gravel to 93% for water treatment sludge) and the highest for Al (ranging from 98% in gravel to 99% in water treatment sludge). A sequential fractionation scheme for As, V and Mo on filter material at the end of the experiment showed that for bauxite and water treatment sludge, V and As were concentrated in the NaOH extractable fraction while Mo was concentrated in the less strongly adsorbed NaHCO3 extractable fraction. It was concluded that a constructed wetland with water treatment sludge as an active filter material is an effective technology for removal of the target elements from the alkali drainage.

Performance of Phragmites Australis and Cyperus Papyrus in the treatment of municipal wastewater by vertical flow subsurface constructed wetlands

The use of constructed wetlands to treat municipal wastewater reduces energy consumption and therefore economic costs, as well as reduces environmental pollution. The purpose of this study was to compare the purification capacity of domestic wastewater using two species of plants sown in subsurface constructed wetlands with vertical flow built on a small scale that received municipal wastewater with primary treatment. The species used were Phragmites Australis and Cyperus Papyrus. For this purpose, a constant flow of 0.6 m3 day−1 was fed from the primary lagoon to each of the two wetlands built on a pilot scale with continuous flow. Each unit was filled with granite gravel in the lower part and with silicic sand in the upper part of different granulometry, the porosity of the medium was 0.34, with a retention time of 1.12 days and a hydraulic load rate of 0.2 m day−1. To analyze the purification capacity of wastewater, physical, chemical and biological parameters were monitored during three months. Samples were taken at the entrance and exit in each experimental unit. The results obtained in the experimental tests for the two species of plants, indicated that the Cyperus Papyrus presented a greater capacity of pollutants removal as biochemical oxygen demand (80.69%), chemical oxygen demand (69.87%), ammoniacal nitrogen (69.69%), total phosphorus (50%), total coliforms (98.08%) and fecal coliforms (95.61%). In the case of Phragmites Australis retains more solids. The species with greater efficiency in the treatment of municipal wastewater for this study was Cyperus Papyrus.

Synthetic granite composite for precision equipment structures

The structure is a component that plays an extremely important role in the equipment’s performance, it must withstand efforts without compromising the function, receive and transfer heat, dampen vibrations and position the elements, as well as promote ergonomics and aesthetics. In lightweight and precision equipment’s the raw material used must also allow thin walls, rigid, resistant and low density. The objective of the present work is the development of a synthetic granite composite for manufacturing of equipment’s structures. For this, an abundant Brazilian granite, a high strength epoxy resin and segmented carbon fibers were selected as materials. Test specimens, with maximized packing with granite gravel less than 2.0 mm were fabricated and tested for tensile strength, compression, flexural, damping, hardness, dilatometry, thermal conductivity and density. The maximized composition supported flexural stresses above 42 MPa, without fiber reinforcement and 51 MPa with carbon fiber reinforcement. The damping coefficient was about 7 times higher than cast iron, coefficient of thermal expansion of 1.4E-05 m/m.K, thermal conductivity coefficient of 1.2 W/m.K and density of 2.1 g/cm³. The developed composite showed potential for refining structures, with ease of molding of thin-walled elements, use of inserts, re-machining, providing economical manufacture of single parts, and is still able to perform the function with high damping coefficient and low weight. Keywords: Synthetic granite, composite, machine structure, damping

Annual performance analysis of various energy storage materials in the upper basin of a double-basin solar still with vacuum tubes

ABSTRACTA double-basin solar still with vacuum tubes showed impressive distillate output due to getting potable water from lower and upper basins. But it is also true that distillate output of the upper basin is lower compared with that of the lower basin. Hence, work is required to increase distillate output of the upper basin. In the present work, the upper basin was used with various energy-absorbing materials like black granite gravel, pebbles and calcium stones. The main purpose of using absorbing materials is to store excess energy during sunshine hours and release during off-sunshine hours. Therefore, the distillate output of the upper basin is increased compared with a still with only an upper basin. Hence, continuous work on a double-basin solar still with vacuum tubes (DBSWVT) by putting above energy absorbing materials is carried out during clear sky days of July 2014 and in June 2014. For comparison of a still with energy-absorbing materials, experimental readings of three days of May 2014 (1st, 5th and 9th) are chosen to determine the performance output of the present still with the said energy-absorbing materials. At last, yearly average distillate output of DBSWVT is carried out with said energy absorbing materials, cost of potable water/INR, energy payback time found 0.509 and 109 days. Also, on comparison with other researchers’ work in terms of percentage increment in distillate output 229.2% increment was found compared with a passive solar still.

Ca. 850 Ma magmatic events in the Tarim Craton: Age, geochemistry and implications for assembly of Rodinia supercontinent

The origin of magmatic episodes between final assembly and initial breakup of Rodinia is crucial for deciphering geodynamic transition and continental crust growth processes. However, few igneous rocks were identified during the quiescent time from 900 Ma to 830 Ma in the Tarim Craton. Along its northwestern margin, our field investigations identified abundant granitic debris in the Cryogenian Qiaoenbrak Group. Zircon U-Pb age determination revealed crystallization age at ca. 850 Ma. Detrital zircon crystals within Cryogenian to Ediacaran clastic rocks and schists of the basement Aksu Group also contain a major population having crystallized at ca. 860–840 Ma. Thus, we suggest that a hitherto unknown major magmatic event occurred ca. 850 Ma ago in northern Tarim. Granite gravels exhibit typical fractionated granite features, with high values of SiO2 (73.1–75.7 wt%), alkali oxides (Na2O + K2O = 7.8–8.7 wt%) and Na2O/K2O (avg. 1.3 wt%), and low values of P2O5 (≤0.04 wt%) and A/CNK (0.87–1.01), together with Rb, Th, U and K enrichment, and depletion in Nb, Ta, Sr, P, Ti and Eu, negative Eu anomalies (δEu = 0.21–0.74) and fairly low Ga/Al ratios. Including detrital crystals, ca. 850 Ma zircon crystals display a large range of εHf(t) values from −17.0 up to +11.6. Elemental and zircon Hf isotopes suggest that granites were derived from melting of juvenile lower crust, with addition of reworked upper crust and mantle-derived melts. We propose (1) before ca. 850 Ma, arc-continental collision setting related to southward accretionary assembly along Tarim margin, (2) progressive assembly of Tarim Craton, and (3) position of Tarim Craton within Rodinia supercontinent probably closer to North India Block than to Australia at ca. 850 Ma.

Organic Matter and Nutrients Removal in Tropical Constructed Wetlands Using Cyperus ligularis (Cyperaceae) and Echinocloa colona (Poaceae)

In tropical countries like Colombia, a large variety of available aquatic plants have yet to be investigated for phytodepuration processes. The aim of this study was to assess the effect of Cyper-us ligularis and Echinocloa colona¸ two local plants of Colombian Caribbean region, on removal of dissolved organic matter (COD) and nutrients (N-NH4 +, N-NO3 − and P-PO4 −3) from domestic wastewater. Experiments were conducted in replicate pilot-scale Horizontal Subsurface Flow Constructed Wetlands (HSSF CWs) (0.66 m2). Four wetland treatment units were installed in parallel. Two were planted with C. ligularis and the other two remained with E. colona. The experimental system was connected to a 0.76-m3 primary sedimentation tank that fed experimental wetland treatment units. Wetlands were filled with granite gravel (~8 mm and 0.4 of porosity). During a period of 4 months, each treatment unit received a continuous loading at the rate of 42 L day−1 and a hydraulic retention time of 2.3 days approximately. Wastewater samples from influent and effluents were collected three times each week in order to monitor temporal/spatial changes in removals efficiencies of COD, N-NH4 +, N-NO3 −, and P-PO4 −3. Results showed that removals of COD, N-NH4 +, and N-NO3 − were not significantly different between treatments (p > 0.05). Nevertheless, P-PO4 −3 removal for E. colona was significantly higher than C. ligularis (p < 0.05), showing that this plant can assimilate important amounts of P. Further investigations must be conducted to evaluate the potential of native aquatic macrophytes for phytodepuration.

Experimental Study on the Workability of Self-Compacting Granite and Unwashed Gravel Concrete

This study deals mainly with the mix proportions using granite and unwashed gravel as coarse aggregate for self-compacting concrete (SCC) and its workability, by considering the water absorption of unwashed gravel aggregate. Mix proportions for SCC were designed with constant cement and fine aggregate while coarse aggregates content of granite-unwashed gravel combination were varied in the proportion 100%, 90%/10%, 80%/20%, 70%/30%, 60%/40%, 50% /50%, represented by SCC1, SCC2, SCC3, SCC4, SCC5 and SCC6. 100% granite (SCC1) serves as the control. The workability of the samples was quantitatively evaluated by slump flow, T500, L-box, V- funnel and sieve segregation tests. Based on the experimental results, a detailed analysis was conducted. It was found that granite and unwashed gravel with SCC1, SCC2 and SCC3 according to EFNARC (2002) standard have good deformability, fluidity and filling ability, which all passed consistency test. SCC1, SCC2 and SCC3 have good passing ability while all mixes were in the limit prescribed by EFNARC (2002). It can be concluded that the mix design for varying granite-unwashed gravel combination for SCC presented in this study satisfy various requirements for workability hence, this can be adopted for practical concrete structures.