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Pattern recognition techniques are applied to various morphological descriptors to monitor the formation and propagation of surface defects of materials subjected to thermal shock. A low-cement high-alumina castable was synthesized, cured, sintered, and exposed to thermal stability testing using the water quench test. After a certain number of thermal shock cycles, photographs of the samples’ surfaces were taken and subjected to image analysis. The influence of the sintering temperature on the morphology of the detected defects was studied using principal component analysis (PCA) as a pattern recognition technique that is the most informative for extracting possible differences. The morphological descriptors of the defects correspond to the previous results regarding the influence of sintering temperature on the structure of a castable during thermal shocks.

Secondary sulfur obtained as a by-product in the oil refining process is a major problem as an environmental pollutant. One of the possibilities of environmental protection is the use of sulfur obtained in this way as a component of sulfur concrete. Mixing of sulfur with suitable additives can provide longer working lifetime of sulfur concrete, as well as maintenance of the former physical, chemical, and mechanical properties of concrete. Such mixtures are usually called modified sulfur or sulfur cement. Secondary sulfur produced in the oil refining process by the Klaus process (approval of crude oil) cannot be used in this form. In order to be ready for the use of sulfur concrete and asphalt, it is necessary to modify elemental sulfur from cyclic to chain form, obtaining of modified sulfur whose application is as a binding agent in a concrete instead of portland cement is described in this paper. Influence of dicyclopentadien, an organic additive, on sulfur modification has been studied in this research. Microstructure and mineral analysis of modified and unmodified sulfur cement binding are performed using polarized and scanning electron microscopes and X-ray diffraction spectrometer.

To provide the quality required for its use, raw kaolin must be subjected to certain processing procedures like delamination which is applied to the layered structure materials. The aim of this research is to determine the possibility of performing delamination in the extruder and to estimate the effects of this process on the physico-chemical properties of kaolin. The results showed that delamination can be efficiently realized in the extruder by shearing densely packed layers under the influence of friction force and added Na2CO3 electrolyte. The crystal structure of the system was thus disrupted. This was confirmed by the Hinckley index (HI) decrease and by the dilatometric characteristics changes during heating. The particle size was reduced and, furthermore, new adsorption centers were formed, which led to an increase in the total cation exchange capacity (CEC). The plasticity of kaolin decreased with the increasing delamination degree, as well as the amount of water required for plastic processing, which is favorable in drying ceramic products.

This work presents a grinding process of monoammonium phosphate (MAP) as an active component in a powder fire extinguisher (PFE). The aim was to determine the grinding time for reaching the optimal particle size of MAP necessary for permanent fire extinguishing. MAP grinding was performed by using a laboratory ceramic ball mill and a vibrating cup mill. The grinding process was controlled by sieving using a 100 µm sieve at precisely defined time intervals. The efficiency of a PFE depends on the share of the -100 µm fraction of the active component, which has to exceed 60 %. The optimal grain size with 64 % of fraction of particle size -100 µm was obtained after 33 min of grinding of ≈3000 µm mm grain size MAP by using a ball mill (single-stage grinding). In two-stage process, by grinding the same initial MAP sample (≈3000 µm) in the vibro mill for 10 min, powder with the upper limit grain size of 300 µm and the mean grain diameter of 120 µm was obtained. This sample with a reduced size was further ground in the ceramic ball mill yielding 67.5 % of the fraction of particle size -100 µm after 19 min. The total time of the two-stage grinding process was 29 min. By analyzing the grinding time of MAP required to get the lowest required share of the fraction of particle size -100 µm that provides the effectiveness of formed PFE it can be concluded that 64 % of this fraction was obtained after 33 min of single-stage grinding, while only after 26 min in the two-stage process. Thus, the grinding time was reduced by 7 min indicating certain energy savings. Stability and hydrophobicity of the obtained PFE were achieved by coating with magnesium stearate (MgSt) at the content of 2 % in a ball mill for 15 min. The coating was confirmed by the standardized procedure for verification of PFE hydrophobic properties in contact with water drops. To obtained PFE had component mass ratios of MAP:AS:CC:QS:MgSt=55:20:18:5:2 (AS-ammonium sulfate; CC-calcium carbonate, QS-quartz sand) and was further characterized by chemical and granulometric analyses. The fire extinguishing efficiency of the PFE was tested in controlled conditions, whereby fires were initiated by burning solid materials and flammable liquids. In both cases, immediate elimination of flames was achieved, thus proving the efficiency of the PFE obtained in this work for practical applications. U radu je prikazan postupak mlevenja monoamonijum fosfata (MAP) kao aktivne komponente u praškastom sredstvu za gašenje požara (SGP). Cilj je bio da se utvrdi vreme mlevenja MAP koje je potrebno za dobijanje optimalne granulacije za potpuno gašenje požara i eliminisanje plamena. MAP je mleven u laboratorijskom keramičkom mlinu sa kuglama i vibro mlinu sa prstenastim radnim elementima. Proces je kontrolisan prosejavanjem na situ 100 μm. Utvrđeno je da se mlevenjem granula MAP veličine ≈3000 μm u laboratorijskom mlinu sa kuglama optimalna krupnoća od 64 % frakcije čestica veličine -100 μm dobija nakon 33 min mlevenja. Za postizanje iste finoće proizvoda u dvostepenom mlevenju vreme je skraćeno na 26 min (10 min u vibro mlinu i 16 min u mlinu sa kuglama). Stabilnost i hidrofobnost SGP je postignuta oblaganjem magnezijum stearatom (MgSt) pri udelu od 2 % u mlinu sa kuglama u trajanju od 15 min. Efikasnost gašenja je testirana na poligonu u realnim uslovima. Na tačno određenom mestu za testiranje, u kontro-lisanim uslovima, izazvan je požar paljenjem čvrstih materijala i zapaljivih tečnosti. U oba slučaja je došlo do trenutne eliminacije plamena. Na taj način je potvrđena efikasnost formiranog SGP i mogućnost njegove upotrebe u praksi.

The problem of subsidence and damages on buildings above mining works is an inevitable consequence of underground coal mining in large mining basins. Significant development of various methods for prediction of the displacement parameters of the undermined terrain took place in the period from the middle of the last to the beginning of this century. In this paper, a new mathematical model of the stochastic Pataric-Stojanovic method for the predictive subsidence calculation is developed. A case study, as an example for the practical application of the proposed stochastic method, is given for the underground coal mine “Rembas”- Resavica, Serbia. An original MITSOUKO program package, supported by spatial analyses in the Geographic Information System (GIS), was developed for the predictive subsidence calculation based on the stochastic method proposed by the authors Pataric and Stojanovic. The comparative analysis of predicted and measured subsidence values confirms the possibility of using this stochastic method for predictive subsidence calculation in practice, which is a necessity of modern mining.

According to the official definition, approved by the European Geothermal Energy Council (EGEC), geothermal energy is energy accumulated as heat below the surface of solid soil. Geothermal energy is thermal energy generated and stored in the Earth. It is generally defined as the part of geothermal heat that can be directly utilized as heat or converted into other types of energy. Geothermal resources vary by location and depth towards the Earth's core. Their use is possible for different purposes depending on their temperature. This paper presents the harnessing geothermal resources for electricity generation. There are three main types of geothermal power plants: dry steam plants, flash steam plants, and binary cycle plants. Dry steam plants pipe hot steam from underground into turbines, which powers the generator to provide electricity. Flash steam plants pump hot water from underground into a cooler flash tank. The formed steam powers the electricity generator. Binary cycle plants pump hot water from underground through a heat exchanger that heats a second liquid to transform it into steam, which powers the generator. In all mentioned systems the used fluids are recycled. It can be concluded that geothermal power plants work similarly to other power plants, but providing the steam for starting the turbine from the earth's interior. The fact that used fluids return to the ground makes geothermal energy resources renewable. Prema zvaničnoj definiciji, koju je odobrilo Evropski savet za geotermalnu energiju (European Geothermal Energy Council- EGEC), geotermalna energija je energija akumulirana kao toplota ispod površine čvrstog tla. Geotermalna energija je toplotna energija koja se generiše i skladišti u Zemlji. Generalno se definiše kao deo geotermalne toplote koji se može direktno koristiti kao toplota ili pretvoriti u druge oblike energije. Geotermalni resursi se razlikuju u zavisnosti od lokacije i dubine u odnosu na jezgro Zemlje. Njihova primena moguća je za različite svrhe u zavisnosti od njihove temperature. Ovaj rad prikazuje upotrebu geotermalnih resursa za proizvodnju električne energije. Postoje tri osnovna principa rada geotermalnih elektrana: suva para (dry steam), separisanje pare (flash steam) i binarni (binary cycle). Postrojenja na suvu paru izbacuju vruću paru iz unutrašnjosti Zemlje u turbine, a ona napaja generator koji daje električnu energiju. Postrojenja sa separisanjem pare pumpaju toplu vodu iz iz unutrašnjosti Zemlje u hladniji rezervoar. Nastala para pokreće generator električne energije. Postrojenja sa binarnim ciklusom pumpaju toplu vodu iz unutrašnjosti Zemlje kroz izmjenjivač toplote čime se greje drugi fluid i pretvara u paru koja pokreće generator. U svim pomenutim sistemima korišćeni fluidi se recikliraju. Može se zaključiti da geotermalne elektrane rade slično kao i druge elektrane, ali paru za pokretanje turbine obezbeđuju iz unutrašnjosti Zemlje. Činjenica da se korišćeni fluidi vraćaju u zemlju čini geotermalne izvore energije obnovljivim.

Electric power in Serbia is predominantly provided by thermal power plants. All of eleven existing thermal power plants in Serbia use coal, mainly lignite in the electricity production process thus generating about 6 million tons of fly ash per year. The estimated amount of fly ash from thermal power plants accumulated in Serbian landfills exceeds 200 million tons. On the other hand, during the last decades, respecting the principles of ecologically sustainable development has been imposed on industries, and one of them is the construction industry. Due to the presence of amorphous SiO2 and Al2O3, fly ash as pozzolanic material is convenient for the production of concrete and mortar. Consequently, multiple positive effects can be expected by the proper consumption of fly ash- reducing landfills and improving concrete properties. The idea of this study is to analyze the possibility of recycling fly ash from a thermal power plant by replacing a part of common mineral filler- limestone in the production of self-compacting concrete (SCC). Properties of conventional SCC with limestone and compositions with different fly ash content were compared. Considering that requirements for SCC should be satisfied and all properties remain or enhance in the case of fly ash addition, this study proved that all designed concretes can be used for structural applications. Električnu energiju u Srbiji pretežno obezbeđuju termoelektrane. Svih jedanaest termoelektrana u Srbiji koriste ugalj, uglavnom lignit u procesu proizvodnje električne energije, čime se godišnje generiše oko 6 miliona tona letećeg pepela. Procenjena količina letećeg pepela iz termoelektrana akumulirana na deponijama u Srbiji prelazi 200 miliona tona. S druge strane, poslednjih decenija poštovanje principa ekološki održivog razvoja nametnuto je industrijama, a jedna od njih je i građevinska. Zahvaljujući prisustvu amorfnog SiO2 i Al2O3, pepeo kao pucolanski materijal pogodan je za proizvodnju betona i maltera. Zbog toga se pravilnom upotrebom letećeg pepela mogu očekivati višestruki pozitivni efekti- smanjenje deponija i poboljšanje svojstava betona. Ideja ovog istraživanja je analiziranje mogućnosti recikliranja letećeg pepela iz termoelektrane tako što će delimično zameniti uobičajeni mineralni punioc- krečnjak u proizvodnji samozbijajućeg betona (SCC). Upoređena su svojstva konvencionalnog SCC sa krečnjakom i kompozicija sa različitim sadržajem pepela. S obzirom da je u slučaju dodatka letećeg pepela potrebno da budu zadovoljeni zahtevi za SCC, kao i da svojstva betona ostanu ista ili poboljšana, ova studija je pokazala da se sve dizajnirane smeše mogu koristiti za konstrukcijske primene.

Due to the Portland cement chemical reaction, which always takes place in a hardening concrete, a certain amount of heat is released. This heat should be quantified, as it can harm or aid the concrete itself, depending on the concrete components, structure element, ambient and building site conditions. There are number of possible setups for the monitoring of heat of hydration, two of which have been applied in the case presented in this paper. Four concretes were monitored with the use of the two stated techniques for 24 hours. First technique used is thermo-vision camera which monitored the surface, and the second is thermosensor - used for monitoring of interior of fresh concrete hardening mass. The potential of the applied setup lays in the ease of installation, low price, and possibilities of mass application, which could substantially aid the monitoring and prevent concrete failure.

Sodium carbonate is a well-known material for being used as a good sorbent of carbon dioxide from the atmosphere, and as such has gained increasing importance in environmental protection. In order to enhance its sorption ability, mechanochemical activation of sodium carbonate was carried out in this study while the occurred changes after the activation and the relaxation time in a controlled environment were monitored. Activation was performed in a vibro-mill from 1 to 28 min. Based on the results of specific surface area, obtained by BET, the samples activated for 2 and 7 min were chosen and placed in a moist carbon dioxide atmosphere for 96 h, a period called the relaxation time. Differential thermal and thermogravimetric analyses were applied with the aim of determining the changes that occurred on the activated samples during the relaxation period. The decomposition temperature change of activated Na2CO3 samples, as well as mass loss and conversion level of Na2CO3 to NaHCO3 were monitored depending on activation and relaxation time periods. The conversion reactions of sodium carbonate to sodium bicarbonate under the specified environment of carbon dioxide and moisture were also studied, and the thermodynamic data such are changes in enthalpy, entropy, and Gibbs energy at the temperature range of 0–160 °C are given.

In this study the resistance of cordierite and zircon to the cavitation erosion was investigated with the aim of possible spreading their application. Cavitation erosion test was applied using standard ultrasonic vibratory set up with stationary sample. Weight loss and image analysis measurements including morphological analysis of the formed pits were used for monitoring degradation during the cavitation erosion testing. The obtained results were discussed in order to compare and analyze degradation mechanism and the resistance of the investigated materials to cavitation erosion. Cordierite sample underwent less serious degradation, characterized by continual forming of new pits, while zircon degradation progressed by growth and merging of already formed pits.

Pulse-reverse power modes are used in galvanotechniques in order to obtain coatings with better characteristics in terms of gloss, adhesion, tracking sharp edges and uniform distribution of deposits on complex shape objects, compared with the coatings produced by constant current modes. Pulse-reverse modes also allow the use of a higher current density, and thus the production speed of electroplating cells increases. Systems for standard electroplating of copper, silver and gold are optimised by the suitable choice of duration and intensity of the pulses. It is shown that coatings with satisfactory quality can be deposited using higher current density, different modes of pulsed current in a very short period of time, without expensive and often dangerous additives in the electrolyte. Parameters of the model for certain electrochemical systems were determined by modelling and computer simulation, so the system behaviour under different circumstances becomes predictive.

Using domestic zeolite from Igroš as row material for ceramic samples for application in condition of cavitation erosion. Samples based on talc with 15 % of zeolite, from Igroš, sintered at 1200oC were used in this investigation. The ultrasonic vibratory cavitation set up with stacionary specimen was used. Mass loss was measured and degradation level of the samples using image analysis and Young modulus of elasticity. Obtained results showed good resistance of the sample to the cavitation erosion, which give the possibility for possible future application of ceramic samples based on talc and yeolite in different conditions where cavitation erosion is expected. U radu su prezentirani rezultati istraživanja korišćenja domaćeg zeolita sa ležišta 'Igroš' za izradu keramičkih uzoraka i primenu u uslovima dejstva kavitacije. Za ispitivanja su korišćeni uzorci talka sa 15% zeolita iz domaćeg ležišta IGROŠ (Brus) sinterovani na 1200oC. Za određivanje otpornosti na dejstvo kavitacije korišćena je ultrazvučna vibraciona metoda sa stacionarnim uzorkom. Gubitak mase i nivo degradacije površine uzoraka praćeni su primenom analize slike i Jungovog modula elastičnosti. Rezultati ispitivanja pokazali su dobru otpornost keramike na dejstvo kavitacije na bazi talka i zeolita što ukazuje na mogućnost primene u različitim oblastima industrije gde se očekuje prisustvo razaranja pod dejstvom kavitacije.

The occurrence of subsidence caused by the underground coal mining may be a complex process that causes damage to the environment. In the last century, there was a significant development in prediction methods for calculating the surface subsidence. In this paper, a new prediction method has been developed to calculate subsidence by combining a stochastic model of the ground movements and Geographical Information System (GIS). All the subsidence calculations are implemented by an original program package MITSOUKO, where the components of the GIS are used to fulfil the spatial analysis. This subsidence prediction technique has been applied to calculate the ground movements resulting from excavating 21 mining panels that are mined successively in the coal mine ''Rembas''-Resavica, Serbia. Details of movement were sequentially predicted and simulated in terms of years exploitation. Predictive calculation of the undermined terrain displacement parameters by the stochastic method and integration into the GIS is a powerful risk management tool.

This study analyzes the feasibility of valorizing industrial by-product, fly ash from a thermal power plant as a partial replacement of mineral filler-limestone for the production of self-compacting concrete (SCC). Three types of SCC mixtures with different portions of fly ash and the reference mixture with limestone were designed. The synthesized SCCs in the fresh state were examined for density, entrained air content, flowability (Slump flow, Slump flow time (t500), V-funnel time (tv)), passing ability (L-box), and segregation resistance, while hardened state testing included: density, compressive and flexural strength, static modulus of elasticity, water permeability, resistance against freezing in the presence of de-icing salt, and SEM analysis. Taking into account the obtained results it can be concluded that the addition of fly ash has a positive impact on the concrete properties and that the optimal content of fly ash is 20 % with respect to the total filler mass.

Self-compacting concrete (SCC) contains fine mineral fillers such as limestone powder. The idea of this study was to partially replace limestone with waste sulfur since it is hydrophobic, insoluble in water and therefore chemically inert and to compare the properties of produced concrete samples. Fresh concrete properties included: slump-flow, t500, V-funnel time, L-box ratio, segregation ratio, density, and entrained air content. Hardened concrete was tested for compressive, flexural and bond strengths, ultrasonic velocity, dynamic elasticity modulus, dynamic Poisson’s ratio, and microstructure. Flowability and segregation increased, while bulk density, compressive and flexural strength, dynamic elasticity modulus and ultrasonic velocity slight declined. Times t500 and V-funnel time, L-box ratio and entrained air changed insignificantly. Considering that all properties should remain or improve in case of waste valorization and the criteria should set to satisfy requirements for SCC, this study proved that all mixtures can be used for structural applications. Efectos del contenido de residuos de azufre en las propiedades del hormigón autocompactante. El hormigón autocompactante (SCC, del inglés Self-compacting concrete) contiene cargas (fillers) minerales finas como polvo de piedra caliza. La idea de este estudio fue reemplazar parcialmente la piedra caliza por contenido de residuos de azufre, ya que es hidrófobo, insoluble en agua y, por lo tanto, químicamente inerte, y comparar las propiedades de las muestras de hormigón producidas. Las propiedades analizadas en el hormigón fresco incluyeron: flujo de asentamiento, t500, tiempo del embudo en V (V-funnel time), relación de caja en L (L-box ratio), relación de segregación, densidad y contenido de aire ocluido. En el hormigón endurecido se analizó la resistencia a compresión, flexión y adherencia, velocidad ultrasónica, módulo dinámico de elasticidad, coefi ciente dinámico de Poisson y microestructura. La fluidez y la segregación aumentaron, mientras que la densidad aparente (bulk density), la resistencia a la compresión y la flexión, el módulo de elasticidad dinámica y la velocidad ultrasónica disminuyeron ligeramente. Los tiempos t500 y el tiempo del embudo V, la relación de la caja L y el aire ocluido cambiaron de manera insignificante. Considerando que al valorizar residuos, se deben conseguir propiedades similares o mejoradas, y que los criterios deben establecerse para satisfacer los requisitos de SCC, este estudio demostró que todas las mezclas se pueden utilizar para aplicaciones estructurales.

High-temperature materials are used in a wide range of industries and applications such as gas turbine engines for aircrafts, power and nuclear power plants, different types of furnaces, including blast furnaces, some fuel cells, industrial gas turbines, different types of reactors, engines, electronic and lighting devices, and many others. Demands for high-temperature materials are becoming more and more challenging every year. To perform efficiently, effectively and at the same time to be economically viable, the materials used at high temperatures must have certain characteristics that are particularly expected for applying under such extreme conditions, for example, the strength and thermal resistance. In the present review, some important requirements that should be satisfied by high temperature materials will be discussed. Furthermore, the focus is put on refractory concretes, ceramics, intermetallic alloys, and composites as four different categories of these materials, which are also considered in respect to possibilities to overcome some of the current challenges. U visokotemperaturske materijale spada široki spektar materijala koji se koriste u industriji, za primenu poput turbina za motore i avione, termo i nuklearne elektrane, različite tipove peći uključujući visoku peć, gorivne ćelije, turbine za različiite namene u industriji, razne vrste reaktora, motora, uređaja u elektronici i osvetljenju, kao i mnoge druge. Svake godine zahtevi za visokotemperaturske materijale postaju sve izazovniji. Da bi se ostvarila efikasnost i efektivnost, i da bi se istovremeno postigla ekonomska održivost, materijali koji se koriste na visokim temperaturama moraju zadovoljiti određene zahteve i imati svojstva koja se očekuju u tako ekspremnim uslovima, kao što su, na primer čvrstoća i otpornost na povišene temperature. U ovom preglednom radu razmatrani su neki od značajnih zahteva koji moraju biti zadovoljeni za visokotemperaturske materijale. Rad se odnosi na vatrostalne betone, keramiku, intermetalne legure i kompozite, kao četiri različite kategorije ove vrste materijala. Navedeni materijali su razmatrani u pogledu mogućnosti prevazilaženja nekih trenutnih izazova.

The cold spray technique was employed in this study to produce pure nickel (Ni) and nickel-Inconel 718 powder deposits on duplex stainless steel substrates. High quality coatings were manufactured using nitrogen as the propellant gas. The coatings exhibited satisfactory Inconel 718 (In718) retention within the Ni matrix due to the highly ductile binder phase necessary for fabrication. The characterization of the coating microstructures was implemented by means of X-ray diffraction, electron microscopy, energy-dispersive X-ray spectroscopy, and microhardness testing. In addition, the erosion resistance of both coatings was evaluated by performing cavitation erosion tests, with the analysis of the eroded surfaces revealing different erosion mechanisms for each coating. The results demonstrated the efficiency of the cold spray technique for use in the production of metal-metal matrix composite coatings and the potential of In718 use in applications which demand enhanced cavitation erosion resistance. This is the peer-reviewed version of the article: Surface and Coatings Technology, 2020, 382, 125195, [https://doi.org/10.1016/j.surfcoat.2019.125195] The published version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3274]

Throughout its historical development, mining has faced the problem of moral and material responsibility due to various types of endangerment and damage to the environment. As a result of the underground coal exploitation, a movement of the rock massif above the coal seam, and changes on the terrain surface due to the process of massif stabilizing take place. The process occurs in space and time, from the moment of balance disturbance in the massif, i.e., the beginning of excavation, during excavation, and after the final excavation of deposit, when the equilibrium state is reestablished in the massif. The character and intensity of these movements and principles according to which they are performed, depend on numerous natural and mining-technological conditions, and are specific to each individual coal deposit. Deformations on the terrain surface in the sinkhole occur in the horizontal and vertical directions. Their values serve to determine the vulnerability level of individual objects on the terrain surface. On the basis of the Patarić-Stojanović stochastic method for the predictive subsidence and deformations calculation, an original MITSOUKO program package, supported by the spatial analyses in the Geographic Information System (GIS), was designed. A case study in Sladaja village influenced by the underground exploitation in the coal mine "Rembas"-Resavica, one of the biggest Serbian coal mines, has been chosen. The data processed in the GIS provided determining the module, sense, and direction of the displacements, sinking velocity, and possible effects of subsidence on facilities.

The intent in this paper is to define how the batch equilibrium results of copper removal from a synthetic solution on natural zeolite can be used for prediction of the breakthrough curves in the fixed-bed system for both a synthetic solution and wastewater. Natural zeolite from the Vranjska Banja deposit, Serbia, has been fully characterized (XRD, chemical composition, DTA/TG, SEM/EDS) as a clinoptilolite with cation exchange capacity of 146 meq/100 g. The maximum adsorption capacity (qm) in the batch of the mono-component system (synthetic copper solution) obtained using the Langmuir isotherm model was 7.30 and 6.10 mg/g for particle size below 0.043 and 0.6&ndash, 0.8 mm, respectively. Using the flow-through system with the 0.6&ndash, 0.8 mm zeolite fixed-bed, almost double the adsorption capacity (11.2&ndash, 12.2 mg/g) has been achieved in a saturation point for the copper removal from the synthetic solution, compared to the batch. Better results are attributed to the constant high concentration gradient in flow-through systems compared to the batch. The complex composition of wastewater and large amounts of earth alkaline metals disturb free adsorption sights on the zeolite surface. This results in a less effective adsorption in flow-through systems with adsorption capacity in breakthrough point of 5.84 mg/g (~0.95 &times, qm) and in a saturation point of 7.10 mg/g (~1.15 &times, qm).

Mining induced the ground subsidence and consequently, damages on objects above excavation works is a serious problem all over the world. In this paper, a new approach for subsidence and deformation prediction based on the stochastic Pataric-Stojanovic method is presented. Since the calculation using the equations of this method is very complex, the original computer program package with the title MITSOUKO has been purposely designed. The MITSOUKO program enables calculating at any point of the land surface and representing the results owing to the possibility of their integration and further processing in the Geographical Information System (GIS). The components of the GIS are used to realize the spatial analysis.

Mechanical shock of zircon based ceramic induced by cavitation erosion testing was investigated in this study. Several parameters were followed in order to determine level of material degradation during the cavitation erosion testing. Mass loss was taken as a conventional criterion for material degradation, while the level of surface degradation was evaluated by image and thermal imaging analyses. Results show high cavitation resistance of zircon ceramics and their suitability when vigorous cavitation erosion environment is expected. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR 33007, Grant no. III 45012, Grant no. TR 35002 and Grant no. OI 172060]

The purpose of this study was to investigate possible application of refractory concrete in conditions of cavitation effect where the metal materials are usually applied. Also, influence of different sintering temperatures on cavitation resistance of refractory concrete was analyzed. As the refractory concrete, low cement castable was synthesized, cured, and then sintered at three different temperatures: 1100, 1300, and 1600 degrees C. Mass loss and surface degradation of investigated samples were monitored for 3 h during the exposure to the cavitation erosion. The results show that the samples sintered at 1100 degrees C are not suitable for application in conditions of cavitation since they were significantly destroyed only after 30 min of testing. On the other side, the samples sintered at 1300 and 1600 degrees C exhibited very good cavitation resistance, since they were stable during 360 min of cavitation testing with the damage level below 30% compared to the original surface.

Serbian lignite from Kolubara deposit was used as a low cost adsorbent for removal of copper ions (Cu2+) from aqueous solutions. Lignite was subjected to the elementary and technical analysis as well as BET and FTIR analysis due to complete characterization. Basic comparison between lignite and activated carbon was also done. As a method, batch adsorption procedure was applied. Adsorption efficiency was studied as a function of the initial metal concentration, pH of the solution, contact time, and amount of the adsorbent. Optimum removal of copper ions was achieved at pH values of 5.0. About 90% of copper cations were removed in 5 min of contact time from the solution with the lowest copper concentration (50 mg Cu2+/l) regardless adsorbent amount, while the same effect of adsorption was achieved in 60 min in case of solutions with higher concentrations of copper. It was concluded that the effect of adsorbent amount on adsorption kinetics is evident but not crucial. It was proved that the experimental results of copper adsorption fit well to a Langmuirian type isotherm which was used to describe monitored adsorption phenomena. The calculated adsorption capacities of lignite for copper adsorption decrease with increasing adsorbent amount. The study proved that tested lignite is very efficient adsorbent material, especially in case of low copper concentration in aqueous solution where the usual methods are either economically unrewarding or technically complicated. This behavior can be explained by FTIR spectrum despite a small specific surface area of lignite. Namely, many bands (peaks) are attributed to the functional groups that they are involved in chemisorption and ionic exchange, basic mechanisms of copper adsorption. (C) 2011 Elsevier B.V. All rights reserved.

Sulfur concrete was prepared by using the following initial components: sand as an aggregate, modified sulfur binder, and alumina as a filler. Portland cement concrete was made of the same aggregate, cement and water. The durability of prepared concrete samples was tested in 10% solution of HCl as a function of immersion time. The changes in mechanical strength and mass of the samples were periodically measured. Sulfur concrete exhibited limited mechanical strength and mass loss, while physico-mechanical properties of Portland cement concrete regressed rapidly. The image analysis used for surface destruction monitoring, performed by Image Pro Plus Program for determination of damaged surface area and original surface area before acid resistance testing, showed the similar results. Based on the image analysis results, model for predicting the mechanical strength degradation during durability testing was presented. The fact that calculated and experimental strength values were not far apart proved the validity of the proposed model.

The purpose of this study was to investigate the mechanical properties and level of cavitation damage to alumina-based low-cement castable. The effects of temperature treatment on some of the mechanical properties (strength, Young's modulus of elasticity) will be discussed. Cold crushing and flexural strength were determined using the standard laboratory procedures for destructive testing. The nondestructive methods such as ultrasonic measurements and image analysis were used for measuring the elasticity modulus and level of surface deterioration caused by cavitation testing. Cavitation damages in the alumina-based refractory specimens were induced by the modified vibratory cavitation setup. The rise of temperature treatment from room temperature to 1600°C resulted in strength increase by almost four times, with a slight drop occurring at 800°C. The values of Young's modulus were around 20 GPa at all stages of temperature treatment, with an obvious decrease at 800°C and 1200°C. Because the results show that the sintered low-cement castable exhibited very good resistance to the cavitation erosion, this material can be successfully used in the conditions where the cavitation resistance is needed.

Sulfur concrete was prepared by using the initial components: sand as an aggregate, modified sulfur binder, and talc, alumina, microsilica, and fly ash as fillers. Portland cement concrete was made from the same aggregate and fillers and portland cement. The durability of the prepared concrete samples was tested in the following aggressive solutions: 10% HCl, 20% H2SO4, and 3% NaCl as a function of time. Changes in mass and strength of the sulfur concrete were monitored periodically during the immersion time of 360 days in above solutions. These changes were used as a measure of deterioration level. It should be highlighted that the samples with the ash and especially talc exhibit higher durability in the solutions of HCl and H2SO4 than the samples with alumina and microsilica. In the solutions of NaCl all samples have shown excellent durability while the samples with talc were the best. Portland cement concrete samples lost 20% of mass after two months and showed degradation of mechanical properties. By usage of sulfur for sulfur concrete production, a huge environmental problem regarding storage of waste sulfur from oil refining processes is solved. On the other hand, sulfur concrete with its low price has an excellent quality for the application in aggressive environments unlike the more expensive PCC.

During sintering of the 2MgO-2Al2O3-5SiO2 system, cordierite, an attractive ceramic material because of its properties, is obtained. Effects of mechanochemical activation of stoichiometric mixtures, performed to investigate possibilities of lowering cordierite formation temperature during sintering, were monitored by thermogravimetric and differential thermal analyses. Specific surface areas of the mechanically activated powder mixtures were determined by the BET method. Kinetics of the specific surface area increase was analyzed using the Boltzmann model. It was confirmed that with activation time increase, temperatures of phase transformations were shifted to lower values and, according to FTIR analysis no significant changes occurred during material aging. According to the obtained results, it may be concluded that since mechanochemical activation has an influence on the treated powder mixture, lowering of the cordierite formation temperature during the sintering process is expected.

The analized material was high alumina low cement castable sintered at three different temperatures. Influence of initial material anisotropy on the thermal shock resistance as well as changes of anisotropy level during the thermal shock were studied. Water quench test was used as an experimental method for the thermal stability testing. Surface anisotropy was analysed by image analysis and structural anisotropy using ultrasonic measurements. The results pointed out that the highest homogeinity and the lowest surface and structural anisotropy was for the samples sintered at 1600oC. Surface anistoropy had prevailing infuence on behavior of material during the thermal shock, but the structural anisotropy should not be neglected. [Projekat Ministarstva nauke Republike Srbije, br. TR 33007]

Coating materials are widely used in refractory lining to prevent different deleterious effects such are reactions on the mold-metal contact surface, abrasion from liquid metal or alloy, gasses, slags, and other materials in contact with the coating. In this paper, behavior of cordierite based coating exposed to the cavitation erosion was investigated. Cordierite samples sintered at 1200 and 1400 degrees C were used for the tests. Mass loss, level of surface degradation obtained using image analysis and thermal imaging analysis were applied for the cavitation erosion evaluation. Results showed that the cordierite samples can be successfully used in conditions where the cavitation resistance is required. This is the peer-reviewed version of the article: Pavlović, M., Dojčinović, M., Martinović, S., Vlahović, M., Stević, Z.,& Volkov-Husović, T. (2016). Non destructive monitoring of cavitation erosion of cordierite based coatings. Composites Part B-Engineering, Elsevier., 97, 84-91. [https://doi.org/10.1016/j.compositesb.2016.04.073] The published version: [https://cer.ihtm.bg.ac.rs/handle/123456789/1858]

Two major deposits of diatomaceous earth (diatomite) in the region of the Balkan Peninsula, the Kolubara basin (Serbia and Montenegro) and the Vesje deposit (Former Yugoslav Republic of Macedonia), were selected for detailed investigation of their possible application in preparation of beer filter aids. Chemical, mineralogical and structural properties of diatomite samples were analyzed with the aim of predicting the filtration efficiency. Results of beer filtering compounds preparation are presented in this paper. The parameters of crushing, drying, calcination and classification are also defined. Beer filtration tests proved diatomites to be satisfactory and not causing any degradation of filtration process or beer quality. Technological flow scheme for obtaining the beer filter aids is proposed in the paper.

Thermal power plants in Serbia use lignite for electrical power production The secondary product of coal combustion is fly ash in the amount of 17%. Fly ash causes the pollution of air, water and soil, and also cause many human, especially lung diseases. Secondary sulphur is a product of crude oil refining. The aim of this study was to investigate the use of sulphur as a bonding material in ultra fine particle agglomeration (smaller than 63 ?m) in fly ash. The agglomeration should make the ash particles larger and heavy enough to fall without flying fractions. The experiments showed that during the homogenization of the ashes and sulphur from 150 to 170 ?C in a reactor with intensive mixing, an amount of 15% sulphur was sufficient to bond particles and cause agglomeration without visible flying fractions.

Low level laser (LLL) was applied to induct destruction of the low cement high alumina refractory concrete (LCC) samples. Three different series of samples were used in the experiment: a reference one dried at 105 degrees C, sintered at 1300 degrees C and sintered at 1600 degrees C. Level of destruction during time interval from 5 to 25 min was monitored by measuring surface and depth of damage. Obtained results shown that minimal level of destruction was observed for the samples sinteted at 1600 degrees C for the whole time interval.

The purpose of this study was to investigate behavior and degradation level of refractory concrete sintered at different temperatures during the thermal stability testing. Alumina based low cement castable was synthesized, cured, and then sintered at 1100, 1300, and 1600 degrees C with dwell time of 3 h. Prepared samples were subjected to the water quench test. Behavior of the refractory concrete and determination of surface and internal degradation level during the testing were monitored by ultrasonic measurements and image analysis. Overall material degradation was determined by measuring the strength degradation of samples using the standard laboratory procedure. The samples sintered at 1300 degrees C showed the best behavior under thermal shock, since they withstood 110 cycles of water quench without breaking. It was evident that during the thermal shock, surface and interior of the samples sintered at 1600 degrees C behave differently compared with those sintered at 1100 and 1300 degrees C.

Gradevinski materijali dolaze u fokus interesovanja u vreme kada otpad, bilo industrijski, bilo komunalni, dobija na znacaju kao potencijalna sirovina. Verovatan razlog za to je osnova gradevinskog materijala- cement, koji u svom sastavu ima i veliki broj uslovno otpadnih materijala koji mogu da vode poreklo od sastojaka ili od energenata koji se koriste za njegovu proizodnju. S jedne strane, primarna primena gradevinskih materijala sve se više širi, ali pored njih i alternativni materijali dobijaju svoje mesto. Modifikacija konvencionalnih gradevinskih materijala uglavnom se vrši korišcenjem nekih od sekundarnih sirovina iz razlicitih industrijskih procesa. Generalno gledajuci, gradevinski materijali i njihovi proizvodi znacajni su akceptori otpadnih materija ukoliko mogu u potpunosti da izvrše njihovu imobilizaciju, pri cemu mora biti ispunjen uslov da ne dolazi do degradacije osnovnih svojstava samog materijala. Danas se najveci broj istraživanja u svetu odnosi na korišcenje pepela iz termoelektrana i ostalih velikih insineratora u cilju dobijanja kvalitetnog gradevinskog materijala široke primene. Prateci slicnu koncepciju, u ovom radu prikazana je i analizirana mogucnost korišcenja sekundarnog sumpora kao alternativnog sastojka betona. Sumpor cesto predstavlja zapostavljen otpad, iako je veliko pitanje da li kolicina proizvedenog sekundarnog sumpora na svetskom nivou premašuje kolicinu pepela kome se pridaje veliki znacaj. Zahvaljujuci tehnološkoj revoluciji, došlo je do vracanja sumpora u atmosferu preradom nafte, prirodnog gasa i II ruda, što predstavlja reverzibilan proces prirodnom uklanjanju sumpora iz atmosfere. Tako se kao nusproizvodi dobijaju sumpor i sumporna kiselina koji danas predstavljaju ozbiljan ekološki problem. Zbog toga je bilo neophodno razmatrati alternativne nacine valorizacije sumpora i sumporne kiseline u realnom procesu (large scale). U tom slucaju, rešenja se mogu naci u korišcenju pomenutih vrsta sekundarnog sumpora u proizvodnji dubriva, imobilizaciji otpadnih materijala prevodenjem u nerastvorna jedinjenja i kao dodatak odgovarajucim gradevinskim materijalima...

In order to predict service life of the sulfur–polymer composite, the samples were subjected to the induced destruction using 10% hydrochloric acid solution. Control specimens were prepared using Portland cement binder. Sulfur–polymer composite showed limited mechanical strength and mass loss, while physico-mechanical properties of Portland cement composite regressed rapidly. The Image Pro Plus software was used for surface destruction monitoring. The simulations for composites were applied to the previously reported model for predicting the mechanical strength degradation during durability testing, based on the image analysis results. The results proved that the time gradient of structural change was useful for quantification of service life, therefore it can be accepted as a parameter that represents service life.

Durability of sulfur concrete with different fillers, as well as Portland cement concrete, was tested in the solutions of HCl, H 2 SO 4 , and NaCl. Regarding mass changes, in the solutions of HCl and H 2 SO 4 sulfur concrete with talc and fly ash exhibited higher durability, while in NaCl samples with alumina and microsilica were better. The type of filler did not affect durability regarding compressive strength. Strength loss was higher in the solution of HCl comparing to H 2 SO 4 , while negligible in NaCl which is in accordance with apparent porosity increase. Portland cement concrete after two months lost 20% of mass.

Lifetime prediction for construction material is essential and very often crucial for determination of impact on material application and service. Many models based on different parameters were used to monitor materials behavior subjected to different extreme conditions such as thermal shock and erosive wear. In this chapter, image analysis for lifetime prediction of refractory concrete, more precisely low cement high alumina castable, during the thermal shock and cavitation erosion was studied and discussed. Generally, analyzed material has the properties that depend on sintering temperature but usually is a material with very high strength, density, hardness, and good thermal stability resistance. Usage of image analysis for lifetime prediction of refractory concrete during the thermal shock and cavitation erosion were the goals of this study. Thermal stability was investigated using most common experimental method, water quench test. Destruction of samples during the testing was monitored by image analysis. Results obtained from the image analysis of samples surface and bulk give proof that the level of degradation induced by extreme conditions can be monitored by this way. Values of degradation level were used for lifetime modeling expressed as strength degradation, and correlated to the experimental values. Based on the models for strength degradation using degradation level as variable, model for lifetime was proposed. Similar approach was applied in case of monitoring the degradation level caused by cavitation erosion experiments. The fluid dynamic system of the experimental methodology used to produce ultrasonic erosive wear. Mass loss and level of material degradation were measured before and during the experiment. Level of degradation, that is average erosion area were monitored by using Image Pro Plus program for image analysis. Obtained results showed that after 180 minutes sample exhibited excellent erosion resistance compared to metallic and ceramic samples. Level of surface degradation did not overcome 8 % compared to the original surface.