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Valorisation of wastewater treatment plants and aggregates processing sludge for lightweight aggregates production

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The processing of new waste-based lightweight aggregates is described. Main components are sludges generated from potable water filtration/cleaning operations and clay-based by-products from cutting process of igneous rocks. The complete characterization of residues is reported, including physical and chemical parameters, and their thermal behaviour. Several mixtures were designed, prepared, and fired at different temperatures, trying to use the materials such as they are available. First we attempted to reproduce typical properties of common lightweight aggregates based on natural resources, such as clays. Then, a further approach was followed, involving the production of aggregates with improved mechanical strength, In this attempt, the firing cycle seems to play an important role. The bulk density of this new aggregate is some-what higher but still low due to the formation of an internal cellular structure made of closed pores and an external shell that is partially vitrified. Microstructural evolution was also evaluated (by SEM) while the expansive behaviour of the most promising formulations was studied by hot stage microscopy.
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Washing aggregate sludge from a gravel pit, fly ash of the Aliaga thermal power plant (Teruel, Spain) and used motor oil from cars have been physically, chemically and mineralogically characterized. They were mixed, milled and formed into pellets, pre-heated for 5 min and sintered in a rotary kiln at 1150 °C, 1175 °C, 1200 °C and 1225 °C for 10 min and 15 min at each temperature. The effect of raw material characteristics, heating temperatures and dwell times on loss on ignition (LOI), bloating index (BI), loose bulk density (ρb), apparent and dry particle density (ρa, ρrd), voids (H), water absorption (WA24h) and compressive strength (S) had been determined. All mixtures showed bloating potential taking into consideration the gases released at high temperatures, two of which were located inside and close to the “area of bloating”. The products obtained were lightweight aggregates (LWAs) in accordance with norm UNE-EN-13055-1 (ρb ≤ 1.20 g/cm3 or particle density ≤2.00 g/cm3). LWAs manufactured with 75%:25% and 50%:50% proportions of washing aggregate sludge:fly ash, heated at different temperatures and dwell times, were expanded LWAs (BI > 0). They showed the lowest loose bulk density, the lowest dry and apparent particle density, the lowest water absorption and the highest compressive strength. It was possible to establish three groups of LWAs depending on their properties in comparison to Arlita G3 and/or F3, a commercially available lightweight aggregate manufactured in Spain. Our LWAs could have the same or similar applications of these commercial products, such as insulation, geotechnical applications, horticulture, gardening and/or prefabricated lightweight structures and insulation lightweight concretes.
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The aim of this research is to assess the possible use of Italian zeolitic rocks for the production of lightweight aggregates. In particular, both the expansion at high temperature and the technological features of fired products were investigated. Fifteen zeolite-bearing volcanoclastites from Northern Sardinia and three zeolitized tuffs from Campania and Tuscany (Sorano and Campanian ignimbrites and Neapolitan Yellow Tuff) were taken into account. The firing expansion turned out to be mainly dependent on the chemical composition (especially SiO2 and fluxing oxides such as Fe2O3, Na2O, K2O, MgO and CaO) and the water content (largely related to the zeolite amount) of the raw materials. Other relevant parameters were the temperature of maximum expansion (ranging between 1350 and 1500 °C, without additives) and soaking time (between 2 and 5 min). Some products are highly impervious to water (water absorption below 1%) and exhibit a considerable firing expansion (>100% in volume), a low bulk density (0.5–0.7 g·cm−3) and fair technical properties (loose weight and strength of particles). These encouraging results make some of the investigated tuffs interesting raw materials for the production of lightweight aggregates.
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Aim of this research is an evaluation of the zeolitized facies of Campanian Ignimbrite as raw material for the production of lightweight expanded aggregates (LEA). A commercial product (Cab70) was used as reference for this rock. Tests were carried out on “pure” samples or mixed with an industrial waste mud (DPM — Dried Polishing Mud) deriving from a porcelain stoneware tile polishing process. This mud contains SiC, a phase known to act as bloating enhancer. Raw materials were subjected to mineralogical (XRPD–RIR method) and chemical (XRF) analyses. Bloating upon heating was measured (Leitz heating microscope) on Cab70, DPM and on three mixtures having the following Cab70/DPM ratios: 85/15 (Mix1); 70/30 (Mix2); 50/50 (Mix3). LEA production was assessed both in static (muffle kiln) and in dynamic (rotating kiln) conditions by firing pellets, 3–8 mm in size, between 1220–1380 °C. The unit weight of the single particle was determined on fired and unfired products. All materials evidenced a decreasing density with temperature whereas the same parameter decreases with DPM increasing content. Cab70 LEAs never dropped below 0.90 g/cm3, even at the highest temperature, whereas DPM LEAs range between 0.86 g/cm3 (at 1260 °C) and 0.46 g/cm3 (at 1380 °C). A direct but not linear relationship between DPM content and density was evidenced. Among the three mixtures, Mix2 showed the lowest DPM content able to produce the strongest density reduction. To get LEAs with the same density the rotating kiln required temperatures generally 60–80 °C higher than those of the muffle kiln. This difference should be related to the different thermal insulation of the two systems during firing. Two sets of LEAs were massively produced in dynamic conditions from Cab70 (at 1380 °C) and Mix2 (at 1300 °C). These latter showed better technical performances in terms of unit weight of the single particle (0.81 vs. 0.98 g/cm3), bulk unit weight (460 vs. 565 kg/m3), water absorption coefficients (1.4 vs. 5.5% after 24 h) and compressive strength of the particles (2.9 vs. 0.6 MPa). Differences in pore shape, dimension, abundance and spatial distribution were observed by SEM between the two sets. The technical features of these LEAs were comparable to some expanded clays, with similar grain size, commercialised in Italy.These results are worth interesting as they reveal new perspectives of application both for a rock characterized by a low exploitation cost and widely available in central-southern Italy, as well as for an industrial waste produced in high amount but not recycled at all.
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In this article, a new briquette fuel (SC), which was produced by the mixture of coal fines (25.9%), sewage sludge (60.6%), lignin (4.5%), tannic acid (4.5%) and elemental silicon (4.5%), was provided. Then, in a high temperature electric resistance tubular furnace, the total emissions of NO2 and NO, effects of combustion temperature, air flow rate and heating rate on NOx (NO, NO2) emissions of SC were studied during the combustion of SC; furthermore, effects of additives on hardness were also analysed, and the X-ray photoelectron spectroscopy was applied to investigate the reduced NOx emission mechanism. The research results showed that, compared with the characteristics of briquette fuel (SC0) produced only by the mixture of coal and sewage sludge (the ratio of coal to sewage sludge was the same as that of SC), the Meyer hardness of SC was 12.6% higher than that of SC0 and the emissions of NOx were 27.83% less than that of SC0 under the same combustion conditions. The NOx emissions of SC decreased with the adding of heating rate and increased with the rise of air flow rate. When the temperature was below 1000 °C, the emissions of NOx increased with the elevated temperature, however, further temperature extension will result in a decreasing in emissions of NOx. Furthermore, the X-ray photoelectron spectroscopy results proposed that the possible mechanism for the reduction of NOx emissions was nitrogen and silicon in SC to form the compounds of silicon and nitrogen at high temperatures. © The Author(s) 2015.
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Currently, Taiwan's major source of gravel for construction purposes is its river systems; however, over exploitation could potentially deplete this source. To address this problem and reduce dependence on natural aggregate exploitation, this article investigates artificial lightweight aggregates (ALWAs) synthesized from industrial waste such as sewage sludge and sewage‐sludge‐derived ash. The ALWAs were synthesized from the sewage sludge and ash using Na2CO3. The sodium carbonate helps produce the required viscous glassy phase (needed for ALWA sintering) at a lower co‐melting temperature than would otherwise be possible. Water absorption, apparent porosity, bulk density and compressive strength of the ALWAs were tested to assess resource‐recycling feasibility. The required dosages of Na2CO3 were 16 and 22 wt % for conditioned sludge and ash, respectively. The dosed sludge sample required preheating at 400°C for 0.5 h, followed by sintering at 900°C for 5 min. The ash sample required sintering only at 900°C for 15 min. The sludge‐derived ALWAs gave the following percentages 2.84%, 3.31%, 1.20 g/cm3, and 13.0 MPa for water absorption, apparent porosity, bulk density, and compressive strength, respectively. The corresponding values for ash‐derived ALWAs were: 4.85%, 6.55%, 1.41 g/cm3, and 87.3 MPa, respectively. The characteristics of ALWAs derived in this study were then compared to those of commercially available lightweight aggregates—Lytag and Arlita F7. The characteristics mentioned above of the former were superior than those of the latter except that the value ofdensity was an interval value between Lytag and Arlita. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 740–748, 2013
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The relationships between fracture energy and compressive strength of sphere have been theoretically studied from the viewpoint of fracture mechanics using experimental results of crushing of spheres. Two kinds of glassy and five kinds of natural materials were examined. Specimen diameter ranged, from 0.5 to 3 cm. Combining the above with the size effect of strength reported in the previous papers, the authors obtained a new equation for the change in fracture energy with size.The specific fracture energy increased with a decrease in size and, with natural materials, when size was less than 500, μm, the specific fracture energy increased rapidly. Even if the kinetic energy of a particle with a size of 100 μm was converted completely into fracture energy, the impact velocities required to fracture were calculated to be 13 ∼ 225 m/s for the samples used in this report.
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The microstructure and mineralogy of lightweight aggregates manufactured with washing aggregate sludge, sewage sludge and a clay-rich sediment have been studied. The mineralogical analysis revealed the neo-formation of plagioclase and pyroxene group minerals and a minor presence of gehlenite. Some relationships may be established: (i) heating temperature and dwell time affect the formation of new porosity; (ii) the disappearance of pyroxenes could produce changes in the density of the solid material in the lightweight aggregates; (iii) when an external glassy film is not present, water absorption values depend on the size and number of each type of pore.
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New dense and porous ceramics are developed using two formulation approaches. These are ceramics with remarkable content of mullite, corundum and ZrO2 - tetragonal and monoclinic in crystalline phase and porous (average size of pores up to 150-350μm) spinel-enstatite/forsterite ceramics. To promote the phase development by high-temperature synthesis of these ceramics the mineral raw materials - illite clay and illite clay together with dolomite are used. Bulk density for mullite (corundum) - zirconia ceramics is increased by equal addition of illite clay (8.2 wt.%) as well as ZrOc and especially ZrO2 +Y2O3 to starting mullite mixtures. Contrary the addition of different kind and amount of illite clay together with dolomite trends to formation of spinel - enstatite (forsterite) ceramics and decrease the bulk density to the value up to 0.35 g/cm3. The XRD results indicate that ZrO2 monoclinic/tetragonal incorporation in mullite (corundum) structure realizes through the liquid phase. Development of the spinel MgAl2O4 and enstatite MgSiO2 crystalline phases along with the sufficient amount of glassy phase in microstructure and even distributed pores are proper for spinel-enstatite (forsterite) ceramic samples.
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Deriving in ancient Greece as keramikos, the term potters clay was only reconfirming the recognition of clay as man's earliest utilitarian raw material. Clay is no doubt man's first manufacturing and construction raw material and fortunately, through the miracle of fire, the first lasting chronicler of his own origin and early history.Oddly enough, millennia later, the material still occupies leading positions in the construction and manufacturing areas with each generic end-use accounting annually for about one billion dollars of salable product in the U.S. alone. Needless to say, clay ceramics are proven products.The longevity of clay in the ceramics industry stems in part from its variable and some times unique physical and chemical properties and in part to its ubiquitous occurrence and relatively inexpensive produced value. Clay properties of interest to the ceramics industry are plasticity and moldability, of course, but also chemistry, color, refractoriness, solubility and corrosion resistance, electrical properties and the many possible variations on these and other properties afforded by the essentially two-dimensional morphology of the individual clay platelets.In addition to construction (brick, tile, sewer pipe, cement, fiberglass, roof granules, paint, etc.) and manufacturing (refractories, kiln furniture, sanitary ware pottery and dinnerware) clays are used in the calcined form as fillers, carriers, extenders and grogs.Chemistry, because of its basic relationship to both the chemical and physical properties of clay, has been the subject of continuous studies over the past few decades and is responsible for most of advances in processing which have taken place. Color body removal and the elutriation of objectionable salts have led to more or less sophisticated slurrying and the beneficiation which this medium affords. In particular, the water washing, first initiated by the kaolin industry and now extended to ball clays, and high-energy magnetic filtration have noticeably improved the quality of clay and broadly expanded its market in the ceramics industry.At the present time, ceramics markets are under pressure in several areas. Refractories have followed the downturn in American steel production. Although stabilizing, this industry continues at reduced levels which threatens to become the new norm. Likewise, dinnerware and tile production in the U.S. have declined because of foreign competition.
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Two conditions necessary for bloating which have long been recognized are (1) that a material must produce a high temperature glassy phase with a viscosity high enough to trap a gas and (2) that some substance must be present that will liberate a gas at a temperature at which a glassy phase has formed. By utilizing a large number of chemical analyses of bloating and nonbloating clays, the author was able to define the limits of bloating on a composition diagram. The “area of bloating” on this diagram showed the desirable compositions of clays which satisfy the first necessary condition for bloating. As a test of the area of bloating, silica and alumina were added to nonbloating clays to give them compositions conforming to paints within this area. When fired these mixtures bloated. Tests showed that of all the accessory minerals of the Decorah shale, hematite, pyrite, and dolomite are the only ones which could dissociate and produce a gas at the proper temperature. Fractions of the shale which apparently contain only illite also bloated. It was discovered that many igneous rocks whose compositions fall within the area of bloating on the composition diagram produced good bloats when ground and cast into briquettes. Aphanitic rocks such as rhyolites, trachytes, and dacites should be investigated as possible raw materials for lightweight aggregate.
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The applications of the clay minerals in the various process industries engineering, petroleum discovery, recovery and refining, and others, are closely related to their structure and composition. Important characteristics relating to applications of clay minerals are particle size, surface chemistry, particle shape, surface area, and other physical and chemical properties specific to a particular application such as viscosity; color; plasticity; green, dry and fired strength; absorption and adsorption; abrasion; and others.
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The Rupelian Boom clay has been investigated with respect to its bloating characteristics. In industrial practice, it was found that too much organic matter has a negative impact on bloating and that iron compounds have to be added to facilitate the expansion process. Laboratory experiments on selected samples have revealed that during heating reduction of iron oxides to metallic iron occurs. Due to the complex nature of the raw material — resulting in various mutually interfering reaction mechanisms — thermodynamic calculations have been carried out to determined the energetic most favourable reactions. It was concluded that an excess of residual carbonaceous matter causes a reduction of the iron oxides at too low a temperature. Gases can freely escape before a high viscosity melt is formed. Therefore, preheating in an oxidizing atmosphere at temperatures below 400°C — in order to burn out the fine organic matter and pyrite — might be beneficial for the bloating process. The oxidation of coarse organic matter can subsequently generate the gases which reduce the iron oxides preferably present as ferric iron. As a result, the addition of extra iron oxides could be decreased.
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Mechanical-strength measurement methods for differently shaped solid catalysts, such as crushing, knife-edge cutting and three-point bending have been discussed. The strength data were correlated by Weibull distribution. Experimental results show that, except for the crushing strength test on extruded catalysts, all strength tests have a single fracture mode, and the strength failures are due to brittle fracture, originating from tensile stress concentration at the edges of the existing flaws in the catalyst pellets. The suitability of different test methods for spheres, tablets and extrudates, respectively, are discussed. It is concluded that the crushing test is a satisfactory method for spheres, and crushing and cutting tests are both suitable for tablets, while cutting and bending tests are appropriate for extrudates.
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Smectite-rich claystone–marlstone samples from 12 outcrops located in the Southern Atlas domain of Tunisia were investigated with regard to manufacture of lightweight aggregates (LWAs). The clayey materials mainly consist of smectite, kaolinite and illite, together with quartz, calcite, dolomite and feldspars as accessory components. 10–12 mm pellets were prepared from wet paste and initially heated to 600 °C, 700 °C or 800 °C (depending on the raw material) for at least 2 h in order to avoid any explosion of the aggregate. The pellets were then subjected to a quick firing process at 1180 °C. The addition of 15% of quartz sand (< 250 μm grain size) to the raw materials was found to improve some required pre-treatments and give better expansion properties to some of the aggregates. The addition of 1% used automobile oil to the clay and quartz sand mixtures caused the formation of more gas and a drop in bloating temperature. The obtained LWAs were characterized by physical properties such as apparent density, mechanical resistance, water absorption and expansion. The laboratory results were comparable to those of two commercial LWAs from France (Argidécor®) and Portugal (LECA®) and provide new openings for the utilization of Tunisian claystone in civil engineering work or in agricultural applications.
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The microstructures and mineralogical compositions of lightweight aggregates (LWAs) manufactured with washing aggregate sludge (WS), fly ash (FA) and used motor oil (UMO) have been studied. Most LWAs with WS and FA exhibited an external layer and a glassy core with isolated pores. LWAs with WS and UMO did not present external shells or signs of bloating. Iron oxides, within the external layer, and pyrrhotite, in the inner glass, were observed. The mineralogical analyses revealed the neo-formation of plagioclase and pyroxene, along with minor gehlenite. Some relationships could be established: (i) the presence of larger pores is related to a decrease in the dry particle density values, (ii) when the LWA lacks the external layer, the water absorption values were dependent on the size and amount of each type of pore (open or closed), and (iii) the neo-formation of Ca-plagioclase and the consumption of quartz improved the compressive strength values.
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This study presents the results of the different tests carried out on fly ash lightweight aggregates produced with three different kinds of binders: Lime, Portland cement and Pozzolan Portland cement. The elaboration process used for the aggregates consisted in an agglomeration system by agitation under cold bonded hardening conditions. The tests carried out were a physical characterization of the aggregates, the determination of mechanical properties with a crushing test and, finally, the study of the microstructure of the aggregates with scanning electron microscopy (SEM) and dispersive energy X ray (EDX). From the point of view of mechanical strength, the results indicate that the best kind of aggregate is the one made with a 5% Pozzolan Portland cement. This result was confirmed by the microstructure analysis, which shows that this kind of aggregate presents the highest hydration speed. El estudio presenta los resultados obtenidos de ensayos realizados sobre áridos ligeros de cenizas volantes fabricados con tres tipos de conglomerantes: cal, cemento Portland puro y cemento portland puzolánico. El proceso de fabricación empleado para la elaboración de los áridos consistió en un sistema de aglomeración por agitación bajo condiciones de endurecimiento enfrío. Los ensayos efectuados comprenden la caracterización física de los áridos, la determinación de las propiedades mecánicas por medio de un ensayo de trituración y, finalmente, el estudio de la microestructura de los áridos con técnicas de microscopía de barrido (SEM) y energía dispersiva de rayos X (EDX). Desde el punto de vista de resistencia mecánica los resultados indican que el mejor tipo de árido es el fabricado con un 5% de cemento portland puzolánico. Este resultado se confirma con el análisis de la microestructura que demuestra que este tipo de árido presenta la mayor velocidad de hidratación.
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The preparation, characterization, preheating mechanism and bloating mechanism of ultra-lightweight ceramics (ULWC) manufactured by dehydrated sewage sludge (DSS) and clay were studied. Three experiments were designed to investigate the addition of DSS, the effect of preheating treatment and sintering treatment, respectively, and then the optimum conditions for preparing ULWC were determined. Chemical components, especially ratios of carbon content to iron oxide content (C/Fe-ratios), were used to explain the preheating mechanism; physical forces (surface tension and bloating force) combined with C/Fe-ratios were used to explain the bloating mechanism. The characterizations (physical properties, microstructure properties and toxic metal leaching properties) of ULWC that were prepared under the optimum conditions were tested. The results showed that the optimum addition of DSS was 20-30 wt.%, and the pellets which preheated at 400 degrees C for 20 min and sintered at 1150 degrees C for 10 min were beneficial to produce ULWC. Property tests of ULWC showed that ULWC was light (with a bulk density of 330.80 kg m(-3)), waterproof (with a water absorption of 5.30 wt.%), nontoxic (contents of toxic metal leaching test were all below the detection limit) and suitable for practical civil engineering.
Article
Washing aggregate sludge from a gravel pit, sewage sludge from a wastewater treatment plant (WWTP) and a clay-rich sediment have been physically, chemically and mineralogically characterized. They were mixed, milled and formed into pellets, pre-heated for 5 min and sintered in a rotary kiln at 1150 degrees C, 1175 degrees C, 1200 degrees C and 1225 degrees C for 10 and 15 min at each temperature. The effects of the raw material characteristics, heating temperatures and dwell times on the loss on ignition (LOI), bloating index (BI), bulk density (rho(b)), apparent and dry particle densities (rho(a), rho(d)), voids (H), water absorption (WA(24h)) and compressive strength (S) were determined. All the mixtures presented a bloating potential taking into consideration the gases released at high temperatures. The products obtained were lightweight aggregates (LWAs) in accordance with Standard UNE-EN-13055-1 (rho(b)<or=1.20 g/cm(3) or particle density<or=2.00 g/cm(3)). LWAs manufactured with 50% washing aggregate sludge and 50% clay-rich sediment were expanded LWAs (BI>0) and showed the lowest apparent particle density, the lowest water absorption and the highest compressive strength. It was possible to establish three groups of LWAs on the basis of their properties in comparison to Arlita G3, F3 and F5, commercially available lightweight aggregates manufactured in Spain. Our LWAs may have the same or similar applications as these commercial products, such as horticulture, prefabricated lightweight structures and building structures.
Article
The large volumes of wastes generated by industrialised society has led to efforts to find practical uses for these wastes, whilst also offsetting the consumption of natural resources. This paper describes the use of an innovative rotary kiln to produce synthetic aggregates from a variety of waste streams. The main waste used was a quarry fines which was blended with either paper sludge, clay, or a dredged harbour sediment. The different combinations were extruded and fired in the kiln to produce a material suitable for natural aggregate replacement. Two of the synthetic aggregates produced were tested by incorporation in to concrete as coarse aggregate replacement. The concrete 28-day compressive strengths achieved were above 40 N mm(-2) and compared favourably with control concretes made with natural aggregates and a commercially available lightweight aggregate (Lytag). Leaching tests have also been carried out to assess the potential environmental impact of utilisation. Although not finalised, these tests have also given favourable results.
Article
In this study, artificial lightweight aggregate (LWA) manufactured from recycled resources was investigated. Residues from mining, fly ash from an incinerator and heavy metal sludge from an electronic waste water plant were mixed into raw aggregate pellets and fed into a tunnel kiln to be sintered and finally cooled rapidly. Various feeding and sintering temperatures were employed to examine their impact on the extent of vitrification on the aggregate surface. Microstructural analysis and toxicity characteristic leaching procedure (TCLP) were also performed. The results show that the optimum condition of LWA fabrication is sintering at 1150 degrees C for 15 min with raw aggregate pellets fed at 750 degrees C. The rapidly vitrified surface envelops the gas produced with the increase in internal temperature and cooling by spraying water prevents the aggregates from binding together, thus forming LWA with specific gravity of 0.6. LWA produced by sintering in tunnel kiln shows good vitrified surface, low water absorption rate below 5%, and low cylindrical compressive strength of 4.3 MPa. In addition, only trace amounts of heavy metals were detected, making the LWA non-hazardous for construction use.
Article
Metal sludge from industrial wastewater treatment plants was mixed with mining residues to be recycled into lightweight aggregate (LWA) through sintering at different temperatures. The physical properties of the LWA thus obtained were examined by scanning electron microscopy analyzer (SEM) coupled with an energy dispersive X-ray analyzer (EDX). The sequential extraction method combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) was employed to determine the concentration and distribution of hazardous toxic elements in the metal sludge-based artificial LWA. The results show that the leaching concentrations of Cd, Cr, Cu, and Pb present in the non-sintered raw aggregate pellets reached 7.4, 68.0, 96.0, and 61.4 mg/l, respectively, far exceeding the regulatory threshold. Sintering at 1150 degrees C for 15 min results in stronger chemical bonds being formed between the elements. Hence, after the first three steps of sequential extraction, the concentrations of Cr, Cu, and Pb reached 2.69, 1.50, and 1.88 mg/l at 1150 degrees C, while the final residues had total concentrations of 96.1, 88.4, and 60.6 mg/kg, respectively, with Cd undetected in both phases. The concentration levels fell within the regulatory threshold, indicating that the LWA fabricated from recycled metal sludge contains elements that are toxic and hazardous but not leached. Having no harmful effect on the environment, the metal sludge-based artificial LWA is not only safe but also practical with good physical properties.
Article
The objective of this study was to investigate the recycling of the fine sediments of Shih-Men Reservoir to manufacture lightweight aggregate. By qualitative and quantitative analysis of the fine sediment and sintered aggregate through soil test, X-ray fluorescence, X-ray diffraction and scanning electron microscopy, a strategy of recycling fine sediment as aggregate for other similar material is proposed. The test results indicate that such fine sediment can be classified as low plastic clay, and clay of such chemical composition is located in the Riley's 'area of bloating'. The particle density of sintered lightweight aggregate decreases when the sintering temperature increases especially above 1200 degrees C due to phase transformation and formation of a vitrified layer on the surface through subsequent dehydration, bloating and collapsing stages. Our findings show that the fine sediment of Shin-Men Reservoir could be a suitable raw material for making expanded lightweight aggregate sintered at 1200 to 1300 degrees C for 10 to 12 min by a programmable furnace and a diffusion process.
Caracterización de los residuos y estériles generados en las graveras del río Jarama y sus aplicaciones en la industria cerámica
  • I Blanco García
I. Blanco García, Caracterización de los residuos y estériles generados en las graveras del río Jarama y sus aplicaciones en la industria cerámica (PhD thesis), Univ. Complutense, Madrid, 2004.
Production of lightweight aggregates from waste materials
  • M H Weinecke
  • B P Faulkner
M.H. Weinecke, B.P. Faulkner, Production of lightweight aggregates from waste materials, Miner. Eng. 54 (11) (2002) 39-43.
Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierce-Shale. United States Geological Survey Professional Paper. US Government Printing Office
  • L G Schultz
L.G. Schultz, L.G. Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierce-Shale. United States Geological Survey Professional Paper. US Government Printing Office, Washington, DC, 1964, 391-C, 1-31.
Gas-producing agents in production of lightweight aggregates
  • S K Chopra
  • K Lal
  • V S Ramaahandran
S.K. Chopra, K. Lal, V.S. Ramaahandran, Gas-producing agents in production of lightweight aggregates, J. Appl. Chem. USSR 14 (5) (1964) 181.
  • S A Optiroc Áridos Ligeros
  • La Arcilla Expandida
Optiroc Áridos Ligeros S.A. La Arcilla Expandida, in: Arlita. Arcilla Expandida. Manual General, 2000, pp. 5-29.