Quantitative Formulation of Mechanism of Sintering Process during Creep Deformation of Refractory Concretes

This paper is concerned with quantitative formulation of the mechanism of the sintering process during secondary state creep deformation of refractory concretes. Investigated concretes varied in, both, chemical and mineralogical compositions. The sintering process during secondary state creep within refractory concrete has an isothermal character. Thus, an attempt was made to describe the mentioned process quantitatively. Creep was investigated at three different temperatures: 1200, 1300 and 1400 degrees C. Variations of the microstructure of concrete samples, exposed to constant static pressure and constant temperature during certain time-intervals, were investigated using a scanning electron microscope. Obtained results of the investigation proved that creep resistance is an irreplaceable method when the decision about the best possible type of refractory concrete for application in metallurgical furnaces is required

Influence of microstructure on properties of refractory concretes

Prеdmеt оvе dоktоrskе disеrtаciје је prоučаvаnjе uticаја mikrоstrukturе nа svојstvа vаtrоstаlnih bеtоnа prојеktоvаnih nа bаzi sintеtičkih аgrеgаtа (еlеktrо-tоplјеnоg kоrundа i kаlcinisаnоg bоksitа), visоkо-аluminаtnоg cеmеntа i аditivа. Оsnоvni cilј istrаživаnjа је utvrđivаnjе zаvisnоst izmеđu mikrоstrukturе i nајvаžniјih fizičkih, tеrmо-mеhаničkih i tеrmičkih svојstаvа i pаrаmеtаrа prоcеsа sintеrоvаnjа vаtrоstаlnih bеtоnа, јеr u litеrаturi pоstојi mаli brој pоdаtаkа о uticајu mikrоstrukturе nа svојstvа vаtrоstаlnih bеtоnа kојi kао аgrеgаtе sаdržе bоksit i kоrund. Prоučаvаnе su dvе sеriје vаtrоstаlnih bеtоnа, јеdnе sа kоrundоm kао аgrеgаtоm, а drugе sа bоksitоm kао аgrеgаtоm i šаmоtоm kао puniоcеm, pri čеmu је sаstаv u оbа slučаја mоdifikоvаn dоdаtkоm silikа prаhа i hеmiјskоg аditivа. U cilјu ispitivаnjа prоmеnа kоје sе оdigrаvајu pri visоkо-tеmpеrаturnој primеni bеtоnа, оčvrsli uzоrci su tеrmički trеtirаni nа: 110, 300, 800, 1000, 1300, 1500οC i оdrеđеnа su fizičkа svојstvа: zаprеminskа mаsа, upiјаnjе vоdе, prividnа pоrоznоst, čvrstоćа pri pritisku i sаviјаnju. Zа оdrеđivаnjе оblikа, vеličinе i rаspоdеlе vеličinе pоrа u strukturi bеtоnа kоrišćеnа је аnаlizа slikе pоmоću prоgrаmа Image Pro Plus. Таkоđе је primеnjеnа nеdеstruktivnа mеtоdа ispitivаnjа, mеtоdа brzinе ultrаzvukа, rаdi utvrđivаnjа zаvisnоsti pritisnе čvrstоćе i pоrоznоsti bеtоnа оd tеmpеrаturе tеrmičkоg trеtmаnа. Теrmičkа i tеrmо-mеhаničkа svојstvа, vаtrоstаlnоst i tеmpеrаturе оmеkšаvаnjа оdrеđеnе su nа оbе sеriје bеtоnа. Меhаnizаm i brzinа sintеrоvаnjа prоučаvаnе su u tоku оdrеđivаnjа tеčеnjа (creep-a) vаtrоstаlnih bеtоnа. Меtоdоm rеndgеnskе difrаkciоnе аnаlizе оdrеđеn је fаzni sаstаv bеtоnа tеrmički trеtirаnih nа rаzličitim tеmpеrаturаmа, а mеtоdоm skеnirајućе еlеktrоnskе mikrоskоpiје аnаlizirаni su dеtаlјi mikrоstrukturе uzоrаkа bеtоnа sušеnih nа 110οC i sintеrоvаnih nа 1000 i 1500οC. Еnеrgеtskоm dispеrziоnоm аnаlizоm u оdаbrаnim tаčkаmа priprеmlјеnih uzоrаkа аnаlizirаn је i оdrеđеn hеmiјski sаstаv nа zrnu аgrеgаtа i u cеmеntnој mаtrici. Rеzultаti ispitivаnjа su pоkаzаli dа bоksitni i kоrundni bеtоni svојim svојstvimа i pеrfоrmаnsаmа zаdоvоlјаvајu zаhtеvе industriјskе primеnе i ugrаdnjе u kоnstruktivnе еlеmеntе mеtаlurških аgrеgаtа prоgrаmirаnih zа rаd nа izuzеtnо visоkim tеmpеrаturаmа. Kоrundni bеtоni imајu bоlја svојstvа оd bоksitnih bеtоnа. Svојstvа оbе sеriје bеtоnа su pоbоlјšаnа primеnоm аditivа Litopix i silikа prаhа. Dоdаtаk silikа prаhа је uticао nа smаnjеnjе vоdо-cеmеntnоg fаktоrа, оmоgućiо је еfikаsniје pаkоvаnjе čеsticа pоlаznih kоmpоnеnаtа nа sоbnој tеmpеrаturi i fоrmirаnjе mulitа nа tеmpеrаturаmа primеnе, dоprinео smаnjеnju pоrоznоsti, pоvеćаnju pritisnе i sаvојnе čvrstоćе zа оbе sеriје bеtоnа. Kоd bоksitnih bеtоnа silikа prаh је dоprinео pоvеćаnju vаtrоstаlnоsti i vаtrоstаlnоsti pоd pritiskоm (Та i Те). Fоrmirаnjеm "lаnčаstih" tvоrеvinа hеmiјski dоdаtаk Litopix је оmоgućiо stаbilizаciјu strukturе bеtоnа, čimе је sprеčеnо pоgоršаnjе mеhаničkih svојstаvа bеtоnа i znаčајnо pоvеćаnjе pоrоznоsti. Kоrundni bеtоn sа dоdаtkоm silikа prаhа је pоkаzао nајbоlја tеrmо-mеhаničkа, mеhаničkа i tеrmičkа svојstvа оd svih ispitivаnih bеtоnа. Оvа dоktоrskа disеrtаciја prеdstаvlја dоprinоs prоučаvаnju fеnоmеnа vеzаnih zа prоcеs оbrаzоvаnjа mikrоstrukturе i fаznоg sаstаvа i njihоvоg uticаја nа svојstvа vаtrоstаlnih bеtоnа u zаvisnоsti оd tеmpеrаturе. Pоtvrđеnо је dа su svојstvа vаtrоstаlnih bеtоnа dirеktnо оdrеđеnа kаrаktеristikаmа mikrоstrukturе. Pritisnа i sаvојnа čvrstоćа su zаvisnе оd pоrоznоsti, vеličinе pоrа, vоdо-cеmеntnоg fаktоrа, zаprеminskе mаsе, čvrstоćе аgrеgаtа, pоrоznоsti u trаnzitnој zоni cеmеntnа mаtricа - аgrеgаt, prisustvа zаtvоrеnih pоrа, оblikа zrnа аgrеgаtа, hеmiјskоg sаstаvа kоmpоnеnаtа i fаzа kоје sе јаvlјајu u tоku tеrmičkоg trеtmаnа. Vаtrоstаlnоst i vаtrоstаlnоst pоd pritiskоm su tаkоđе funkciја pоrоznоsti, minеrаlоškоg sаstаvа kоmpоnеnаtа i kоličinе i vrstе upоtrеblјеnоg vеzivа. Теčеnjе је funkciја pоrоznоsti i vаtrоstаlnоsti kоmpоnеnаtа. Nа tеmpеrаturаmа iznаd 1300ºC pоrоznоst sе u mаlој mеri smаnjuје, а mеhаničkе kаrаktеristikе sе pоbоlјšаvајu, štо ukаzuје nа pоčеtаk prоcеsа sintеrоvаnjа. Sеkundаrnа fаzа creep-a se pokazala kao uspešna aproksimacija izotermskog procesa sinterovanja pod pritiskom. Rezultatima dobijenim metodom ispitivanja creep-a оdrеđеni su pаrаmеtri sintеrоvаnjа: brzinа sintеrоvаnjа, еnеrgiја аktivаciје i mеhаnizаm prоcеsа sintеrоvаnjа nа rаzličitim tеmpеrаturаmа. Меtоdа brzinе ultrаzvukа sе niје pоkаzаlа uspеšnоm u оpisivаnju prоmеnе pоrоznоsti i pritisnе čvrstоćе sа tеmpеrаturоm tеrmičkоg trеtmаnа, аli је zаklјučеnо dа sе оvа mеtоdа mоžе kоristiti pri prоvеri rеzultаtа dоbiјеnih dеstruktivnim mеtоdаmа i pri lоcirаnju оštеćеnjа u bеtоnu in-situ. Аnаlizа mikrоstrukturе skеnirајućоm еlеktrоnskоm mikrоskоpiјоm, еnеrgеtskоm dispеziоnоm аnаlizоm i rеndgеnskоm difrаkciјоm је pоtvrdilа rеzultаtе о uticајu mikrоstrukturе, оdnоsnо оblikа zrnа, vеličinе pоrа, prisustvа pоrа u trаnzitnој zоni zrnоmаtricа, prisustvа mulitа nа visоkim tеmpеrаturаmа i dr. nа svојstvа vаtrоstаlnih bеtоnа. Image Pro Plus mеtоdа zа аnаlizu slikе је pоtvrdilа rеzultаtе dоbiјеnе stаndаrdоm lаbоrаtоriјskоm mеtоdоm ispitivаnjа pоrоznоsti. Ispitivаnjа u оvој disеrtаciјi su pоkаzаlа dа sе prаvilnim оdаbirоm аgrеgаtа i аditivа i оdgоvаrјućim dizајnоm bеtоnskе mеšаvinе mоgu pоstići dоbrе pеrfоrmаnsе bеtоnа i sа trаdiciоnаlnim аgrеgаtimа (bоksit, kоrund), zа rаzliku оd skupih sintеtičkih аgrеgаtа (mulit, spinеl, siliciјum-kаrbid, itd.), kојi su uglаvnоm zаstuplјеni u vаtrоstаlnim bеtоnimа ispitivаnim u dоstupnој litеrаturi.This dissertation is concerned with investigation of influence of microstructure on refractory concrete properties. Refractory concretes were designed on basis of following components: synthetic aggregates - corundum and bauxite, high-aluminate cement and admixtures. Main goal of the investigation is to find correlation between microstructure and the most important concrete properties such are: physical, mechanical, thermo-mechanical properties and parameters of sintering process. There is insignificant number of papers in accessible literature that are concerned with theme of effect which microstructure has on corundum and bauxite based refractory concretes. Two groups of refractory concretes were investigated: first group contained corundum as aggregate and second group contained bauxite as aggregate and chamotte as filler. Concrete design was modified with admixtures: Litopix and silica fume. Hardened concrete specimens were thermally treated at following temperatures: 110, 300, 800, 1000, 1300 and 1500οC. Afterwards, following properties were determined: bulk density, water absorption, and apparent porosity, mechanical compressive and flexural strengths. Image Pro Plus program for image analysis was applied for determination of size and number of pores within concrete structure. Non-destructive investigation method (Ultrasonic Pulse Velocity technique) was used for determination of correlation between compressive strength and temperature, and also porosity and temperature. Refractoriness and refractoriness under load were investigated for both groups of concrete. Mechanism of sintering and rate of sintering process were investigated during secondary state creep. Phase composition of refractory concretes was investigated using XRD. Micro-structural changes on following temperatures: 110, 1000 and 1500οC were followed on SEM micro-photographs. Chemical composition of grains and cement matrix was determined with EDS. Investigation results showed that both corundum and bauxite based concrete can be used as lining of metallurgical plants, as well as other plants operating at high temperature. Corundum based concretes showed better properties than bauxite concretes. Properties of both groups of concrete were improved with application of admixtures. Silica fume decreased water-cement factor, improved "packing" of componential grains and enabled mullite formation at 1500ºC. Silica fume, also, decreased porosity and increased mechanical flexural and compressive strength of both bauxite and corundum concretes. In case of bauxite concretes, silica fume increased refractoriness and refractoriness under load. Litopix stabilized concrete structure by which degradation of mechanical properties was prevented. Corundum concrete with silica fume as admixture showed highest thermo-mechanical, mechanical and thermal properties. This dissertation represents contribution in global investigation of phenomena of micro-structural formation and its influence on properties and performances of concrete subjected to high temperature. It is confirmed that properties of refractory concretes are directly correlated to micro-structural characteristics: mechanical compressive and flexural strength are correlated with apparent porosity, size of pores, water-cement factor, bulk density, aggregate hardness, porosity of transition zone cement-aggregate, grain shape, chemical and phase composition, etc. Refractoriness and refractoriness under load are correlated with porosity, chemical composition of components and quantity and type of bonding agent. At temperatures above 1300ºC porosity started decreasing and mechanical properties started increasing, which indicated that sintering process occurred within structure of investigated concretes. Secondary state creep was successfully used as approximation of isostatic sintering under load. Results obtained during secondary state creep investigation were used in determination of rate of sintering, activation energy and mechanism of sintering Process Ultrasonic pulse velocity technique was not the right choice for description of correlation of mechanical properties/porosity and temperature. However this method is useful for in-situ determination of defects occurring within concrete elements in plants. SEM, EDS and XRD confirmed assumption about influence of microstructure on concrete properties: grain shape, pore size, presence of pores in transition zone, presence of mullite at high temperatures, etc. Image Pro Plus method successfully confirmed results obtained by standard laboratory method for investigation of porosity. Thus, conclusion is that Image Pro Plus method can be used in investigation of concrete microstructure. Investigations in this dissertation confirmed assumption that the right choice of aggregates, admixtures and appropriate concrete mix-design can "shape" supreme performances of refractory concrete, even with classic components such are corundum and bauxite

Correlation between mechanical properties and microstructure of refractory composites determined using non-destructive testing method

Cilj ovog rada je da se utvrdi veza između važnih mehaničkih svojstava i karakteristika mikrostrukture pomoću nedestruktivne ispitne metode - metode merenja berzine ultrazvuka, na uzorcima korundnih i boksitnih vatrostalnih betona. Ispitivani betoni se razlikuju po hemijskom i mineraloškom sastavu. Standardnom destruktivnom laboratorijskom metodom je određena mehanička čvrstoća pri pritisku na uzorcima koji su bili prethodno izloženi termičkom tretmanu na temperaturama: 110, 800, 1000, 1300 i 1500°C. Kada je uzorak vatrostalnog betona izložen uticaju povišene temperature i statičkog opterećenja dolazi do smanjenja pritisne čvrstoće i do sveukupne degradacije materijala (gustina i elastčna svojstva se smanjuju). Određivanjem mehaničkih svojstava betona može se ukazati ili se mogu pratiti promene koje se dešavaju unutar mikrostrukture materijala. Nivo površinske degradacije uzorka, nakon termičkih tretmana, je utvrđen pomoću optičkog mikroskopa i Image Pro Plus - kompjuterskog programa za analizu slike. Nedestuktivna metoda merenja brzine ultrazvuka je primenjena pri praćenju promene poroznosti unutar uzoraka vatrostalnog betona. Ultrazvučna metoda i analiza slike su pouzdane metode za karakterizaciju mikrostukturnih promena i defekata i veoma su korisne kada je potrebno utvrditi koji je tip vatrostalnog betona najpogodniji za određenu primenu.Aim of this paper is to establish the correlation between important mechanical properties and characteristics of microstructure using non-destructive testing method, i.e. ultrasonic pulse velocity, on the example of corundum and bauxite based refractory concretes. Investigated concretes are varying in chemical and mineralogical composition. Mechanical compressive strength of concrete samples after thermal treatment at various temperatures (110, 800, 1000, 1300 and 1500°C) was investigated using standard laboratory procedure. When refractory concrete sample is subjected to increased temperature and compressive load loss of strength and material degradation occurs (density and elastic properties of material are decreasing). Measurement of mechanical properties can indicate and monitor the changes in the microstructure. Level of surface deterioration after thermal treatment was determined using optical microscope and Image Pro Plus - program for image analysis. Nondestructive ultrasonic measurement was used as a means of monitoring of increasing porosity in refractory specimens. Ultrasonic pulse velocity technique and image analysis are reliable non-destructive methods for characterization of micro-structural defects and can be useful when type of refractory concrete is to be chosen for an application

Prevention of electrofilter ash toxic leaching by embedding in composite materials

Disposal of the fly ash may pose a significant risk to the environment due to the leaching of hazardous pollutants. The only sustainable solution for the pollution-prevention is the reapplication of fly ash as one of the components in construction material composites. There is a risk of leaching even when fly ash is built-in the construction composites and the goal of this investigation was to prove that leaching concentrations of toxic elements is in range assigned by actual regulations. Fly ash was applied in several composits: mortar, concrete and asphalt. The leachability of the potentially toxic elements from the fly ash based products was investigated. The leaching behavior and potential environmental impact of the 11 potentially hazardous elements was tracked: Pb, Cd, Zn, Cu, Ni, Cr, Hg, As, Ba, Sb and Se. A detailed study of physico-chemical characteristics of the fly ash is included. The overall results showed that most of the elements are more readily leachable from the fly ash in comparison with the fly ash based composites

Application of artificial neural networks in performance prediction of cement mortars with various mineral additives

The machine learning technique for prediction and optimization of building material performances became an essential feature in the contemporary civil engineering. The Artificial Neural Network (ANN) prognosis of mortar behavior was conducted in this study. The model appraised the design and characteristics of seventeen either building or high-temperature mortars. Seven different cement types were employed. Seventeen mineral additives of primary and secondary origin were embedded in the mortar mixtures. Cluster Analysis and Principal Component Analysis designated groups of similar mortars assigning them a specific purpose based on monitored characteristics. ANN foresaw the quality of designed mortars. The impact of implemented raw materials on the mortar quality was assessed and evaluated. ANN outputs highlighted the high suitability level of anticipation, i.e., 0.999 during the training period, which is regarded appropriate enough to correctly predict the observed outputs in a wide range of processing parameters. Due to the high predictive accuracy, ANN can replace or be used in combination with standard destructive tests thereby saving the construction industry time, resources, and capital. Good performances of altered cement mortars are positive sign for widening of economical mineral additives application in building materials and making progress towards achieved carbon neutrality by reducing its emission

Influence of the phase composition of refractory materials on creep

In this paper, the relationship between the creeping effect and mineralogical characteristics of the applied binding phase for various refractory materials (high-alumina materials, with high or low impurity content, tar bonded either magnesite or dolomite materials and silicate bonded chrom-magnesite materials) is presented. The mechanism of creeping is analyzed and the activation energy for creep for each investigated material is obtained and discussed. All investigated materials are creep sensitive under investigated conditions and have similar activation energies for creep except high-alumina refractories with a low impurity content

Correlation between microstructure, phase composition and mechanical properties of thermo-insulation bonding agents based on waste material

Konstrukcioni kompoziti - termo-izolaciona i/ili visoko-temperaturna veziva u kojima je leteći pepeo, kao potencijalno štetna materija za okolinu, kombinovan sa običnim i vatrostalnim cementom predstavlja jednu sasvim novu mogućnost za reaplikaciju ovog otpadnog materijala. U ovoj studiji, ispitivana su veziva spravljena na bazi dve vrste letećeg pepela dobijenog procesom sagorevanja uglja i dve vrste cementa - obični Portland cement i visoko-aluminatni cement. Promena u mineralnom sastavu kompozita uslovljena povećanjem temperature je analizirana pomoću XRD metode. Mikrostrukturne promene ispitivanih kompozita su utvrđene na osnovu rezultata skening-elektronske mikroskopije (SEM). Makro performanse - mehanička svojstva ispitivanih veziva su povezana sa promenama koje se dešavaju u mikrostrukturi materijala. Ispitivana veziva imaju odlične vrednosti pritisne čvrsoće, a SEM i XRD analiza je ukazala i na potencijalno dobra termo-izolaciona i vatrostalna svojstva ovih materijala.Building composites - thermo-insulating and/or high-temperature resistant bonding agents in which fly ash, as potentially environmentally harmful waste material, is combined with ordinary and refractory cement is new option for reapplication of this waste material. In this study, investigated bonding agents were based on two types of fly ashes from coal combustion process and cements - ordinary Portland cement and highaluminate cement. Change of mineral phase composition of the composites with increasing temperature was analyzed by means of XRD method. Microstructural changes within investigated composites were investigated by means of scanning electron microscopy (SEM). Macro-performance - mechanical properties of the investigated bonding agents was finally correlated with its microstructure. The investigated bonding agents showed excellent compressive strength, while SEM and XRD analysis indicated its valuable refractory and thermo-insulation properties

Doprinos Instituta IMS razvoju građevinskih materijala (kratak istorijat, pregled stanja i pogledi ka budućnosti)

Institut IMS ima lidersku poziciju među multidisciplinar-nim naučno-istraživačkim organizacijama u Srbiji i regionu. Visoko je pozicioniran u oblasti građevinarstva i inženjer-stva. IMS poseduje jedinstveni spoj naučno-istraživačkog rada i saradnje sa privredom kao vrlo važne karike u lancu primenljivosti i održivosti rešenja i rezultata istraživačkog rada. IMS je decenijama simbol znanja u oblasti građevi-narstva i industrije građevinskih materijala, što aktivno nastavlja kroz aktuelne i planirane naučno-istraživačke aktivnosti - razvojna istraživanja, realizaciju u privredi, primenu najnovijih saznanja i savremenih tehnologija

Analytical modeling of activation procedure applied in α-alumina thermo-mechanical synthesis

The impact of the mechanical processing parameters on the alumina grain-size distribution affiliated characteristics and on the γ to α phase transformation rate was investigated. The moderation in the alumina samples behavior has been correlated to the granulometric and mineralogical changes induced by activation via an ultra-centrifugal mill. The assessment of the activation process variables influence on the final quality of the product parameters was conveyed in order to optimize the mechanical treatment of the alumina, which otherwise could be regarded as either energetically or economically unsustainable procedure. The Response Surface Method, Standard Score Analysis and Principal Component Analysis were applied as means of the mechanical activation optimization. The r 2 values obtained by developed models were in range from 0.816 to 0.988. The established mathematical models were able to precisely predict the quality parameters in a broad range of processing parameters. The Standard Score Analysis emphasized that the optimal output sample was obtained using a sieve mesh of 120μm set of processing parameters (SS=0.96). Diverse comparison analyses disclosed that the optimal set of activation process parameters could reduce the negative effect of γ-alumina samples immanent properties on the final score, and furthermore to enhance the rate of γ to α transition which would improve energetic and economic sustainability of the alumina phase transformation procedure. © 2015 Elsevier Ltd and Techna Group S.r.l

Microstructural changes initiated by sintering of refractory concrete based on recycled bauxite aggregate

Concretes whose structure and final properties are shaped during thermal pre-treatment or during life-service at elevated temperatures can be applied as construction material for thermal insulation and/or refractory linings in high-temperatureoperating plants. Refractory concretes designed with waste raw materials show satisfying performances in comparison with standard concretes. Sintering initiates microstructural changes within concrete. Concrete microstructure further develops with increasing temperature. Change progression can be monitored by means of destructive and non-destructive tests: either by investigating change of compressive strength or apparent porosity of concrete samples. Destructive tests, in this study, were applied in compressive strength investigation, while non-destructive tests were performed for results comparison. Experiment has been conducted on corundum (standard) concrete and recycled bauxite (experimental) concrete. Samples underwent thermal treatment from 110 to 1500°C. Macroperformance of the final refractory concrete was correlated to the microstructural change detected by means of XRD and SEM analysis. Creep testing was conducted to prove sintering process. Results showed that recycled concrete has equal if not better properties in comparison with standard refractory concrete and can be used as thermoinsulation or refractory material. The results presented in this paper contribute to the idea of including other testing methods (i.e. nondestructive methods) in investigation of microstructural changes and sintering process of refractory concrete. At the same time results of this investigation highlight advantages of application of secondary raw materials in design of refractory materials. Although recycled aggregate concrete showed lower compressive strength and higher porosity than commercial concrete it should be noted that both porosity and compressive strength are within satisfying value range for high-temperature application, i.e. these concretes will not be used as structural materials but as thermal insulation linings. In such application refractoriness is the property which is more important than strength. Considering the fact that compressive strength is above 50 MPa (and above 20 MPa at 1500°c) these concretes should be able to withstand load induced by other constructive parts of furnace and slag. Refractoriness test showed that bauxite-based recycled concrete is highly resistible on increasing temperatures and creep test showed initiation of sintering process. Corundum concrete can be used for temperature above 1500°c. Due to the satisfying performances it is concluded that recycled concrete can be equally used as standard concrete. Even though it has slightly lower properties, accent should be on the financial and ecological benefit found in using of recycled material and savings of energy and natural resources