No description available.

Prova complementar para doutoramento, na Faculdade de Engenharia da Universidade do Porto

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Structural lightweight aggregate concrete is an important and versatile material, which offers a range of technical, economic and environmental-enhancing and preserving advantages and is designed to become a dominant material in the new millennium. For structural application of lightweight concrete, the density is often more important than the strength. A decreased density for the same strength level reduces the self-weight, foundation size and construction costs. Structural lightweight aggregate concrete generally used to reduce dead weight of structure as well as to reduce the risk of earthquake damages to a structure because the earthquake forces that will influence the civil engineering structures are proportional to the mass of those structures. In this study, structural lightweight aggregate concrete was designed with the use of natural perlite aggregate that will provide an advantage of reducing dead weight of structure and to obtain a more economical structural lightweight concrete by the use of perlite powder as a replacement of the cement. Six mixes were produced with different cement content and with or without perlite powder. Six mixes divided into two groups according to their cement content. First group had a cement content of 300 kg/m3 and second group had cement content of 500 kg/m3 / also the water/cement ratios of groups were 0.49 and 0.35 respectively. Moreover, each group had three sub-mixes with 0%, 20% and 35% of perlite powder as cement replacement. According to results of experimental study, it was concluded that natural perlite aggregate can be used in the production of structural lightweight aggregate concrete. Based on the strength and density results of experimental work, it is possible to produce lightweight concrete with 20 MPa-40 MPa cylindrical compressive strength by using natural perlite aggregate. Also, the use of perlite powder, which will provide economy, can reduce dead weight further and increase performance.

A RESEARCH REPORT SUBMITIED TO THE FACULTY OF ARCHITECTURE. UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG, FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING / This research project is an investigation into the effect of the grading of perlite lightweight aggregates on the resultant concrete strengths. Lightweight concretes are reviewed. Perlite, as a lightweight aggregate, is assessed. Grading theory for aggregates and in particular lightweight aggregate is analysed. A series of mix designs are proposed with manipulation of the grading of the perlite as the only variable. This is so that variations in compressive strength and density may be assessed in terms of the grading of the perlite. Those mixes are undertaken and tested for compressive strength and dry density. In this research project compressive strength is considered a benefit, while mass is considered a disadvantage. The performance of a lightweight concrete is assessed firstly in terms of the Power Factor. The Power Factor is the compressive strength divided by the dry density of a concrete. The performance of lightweight concretes produced with Perlite aggregate is assessed secondly in terms of the Cement Content factor. The Cement Content Factor is the Power Factor divided by the Cement Content. This factor has the effect of creating a common denominator of the cement content. An evaluation of the results yields the conclusions detailed in chapter Eight, the principal two being: • The optimal perlite grading tested was a monodisperse, single size fraction, of between 600 and 1180 microns. • The most practical measure for manufacturers to improve the performance of lightweight / Andrew Chakane 2019

The main objective of this investigation is to determine the effect of different physical and chemical parameters on the performance of biofilters, treating hydrophobic organic compounds. pinene was used as a model substance. Alpha-pinene is commonly found in wood, and therefore found at wood storage facilities and wood processing industries [1]. In this experiment two biofilter which were in equal size, were used. Both of them were filled with perlite for treating the alpha pinene contaminated air. One of the columns contained perlite partially coated with silicone oil to make the surface of perlite more hydrophobic. The filters were run at 5, 2.5 and 1.5 l min-1 air flow rate. The results showed that the silicone oil amended filter performed better at 2.5 l/min with a maximum removal rate of 20 g / (m3 h) in comparison with 15 g/ (m3 h) for the filter without oil. The efficiency was approximately the same for both filters at 1.5 and 5 l/min (40 compare to 35 g/m3 bed h). The flow rate was then set to 2.5 l/min once more. The results showed that the removal rate had increased to approximately 35 g/ (m3 h) and that the efficiency of both filters was approximately the same. The difference in results between the initial run and the later at 2.5 l/min is probably depending on that the microorganisms had become adapted to the α-pinene and that the microorganism communities developed differently in the two filters. / Syftet med denna studie var att undersöka om en ökning av biofilterytans hydrofobicitet kan förbättra effektiviteten med avseende på nedbrytning av en hydrofob förening såsom -pinen. En hydrofob yta skulle kunna medföra en ökning i adsorption av hydrofoba föroreningar vilket i sin tur skulle kunna öka tillgängligheten hos föroreningarna för mikroorganismerna. Försöken utfördes med hjälp av två biofilter fyllda med perlit. Ett filter fylldes med obehandlad perlit medan det andra filtret fylldes med perlit som blandats med silikonlja. Båda filtren ympades med mikroorganismer som växt på träflis. Dessa mikroorganismer är anpassade för att bryta ner -pinen då denna förening friges i stora mängder från trä. Resultaten visar att filtret innehållande perlit täckt med silikonolja var mer effektivt med avseende på nedbrytning avpinen under den första tiden av studien (de första 30 dagarna). Skillnaden i effektivitet mellan filtren minskade dock betydligt med tiden så att skillnaden inte var signifikant under resten av studien. Prover från vätskefasen från de båda filtren undersöktes i mikroskop. Dessa studier visade att olika mikroorganismer dominerade i de båda filtren. Filtret innehållande oljetäckt perlit dominerades av stavformiga bakterier medan filtret innehållande obehandlad perlit dominerades av kocker. Båda filtren innehöll en blandkultur av kocker och stavar. Dessutom växte svamp i båda filtren. Dessa resultat visar att en förändring av ytans hydrofobicitet inte bara kan leda till en ökad adsorption av förorening utan den kan också leda till att andra mikroorganismer får en dominerande roll i filtret. Den maximala nedbrytningshastigheten låg mellan 35 och 40 g pinen/(m3h) under hela studien förutom de 30 första dagarna oberoende av luftflödeshastighet (1,5 , 2,5 respektive 5 l/min). Den maximala nedbrytningshastigheten under inledningen av försöket var 15 g/(m3 h) för filtret innehållande obehandlad perlit och 20 g/(m3h) för filtret innehållande oljetäckt perlit. Luftflödet var 2,5 l/min under den inledande perioden. Ökningen i nedbrytningshastighet med tiden indikerar att mikroorganismerna anpassade sig till miljön. Den relativt konstanta nedbrytningshastigheten under resten av studien indikerar att det var de biokemiska reaktionerna som var hastighetsbegränsande och att masstransporten inte hade någon dominerande roll med avseende på att begränsa hastigheten.

<p>The main objective of this investigation is to determine the effect of different physical and chemical parameters on the performance of biofilters, treating hydrophobic organic compounds. pinene was used as a model substance. Alpha-pinene is commonly found in wood, and therefore found at wood storage facilities and wood processing industries [1].</p><p>In this experiment two biofilter which were in equal size, were used. Both of them were filled with perlite for treating the alpha pinene contaminated air. One of the columns contained perlite partially coated with silicone oil to make the surface of perlite more hydrophobic. The filters were run at 5, 2.5 and 1.5 l min-1 air flow rate. The results showed that the silicone oil amended filter performed better at 2.5 l/min with a maximum removal rate of 20 g / (m3 h) in comparison with 15 g/ (m3 h) for the filter without oil. The efficiency was approximately the same for both filters at 1.5 and 5 l/min (40 compare to 35 g/m3 bed h). The flow rate was then set to 2.5 l/min once more. The results showed that the removal rate had increased to approximately 35 g/ (m3 h) and that the efficiency of both filters was approximately the same. The difference in results between the initial run and the later at 2.5 l/min is probably depending on that the microorganisms had become adapted to the α-pinene and that the microorganism communities developed differently in the two filters.</p> / <p>Syftet med denna studie var att undersöka om en ökning av biofilterytans hydrofobicitet kan förbättra effektiviteten med avseende på nedbrytning av en hydrofob förening såsom -pinen. En hydrofob yta skulle kunna medföra en ökning i adsorption av hydrofoba föroreningar vilket i sin tur skulle kunna öka tillgängligheten hos föroreningarna för mikroorganismerna. Försöken utfördes med hjälp av två biofilter fyllda med perlit. Ett filter fylldes med obehandlad perlit medan det andra filtret fylldes med perlit som blandats med silikonlja. Båda filtren ympades med mikroorganismer som växt på träflis. Dessa mikroorganismer är anpassade för att bryta ner -pinen då denna förening friges i stora mängder från trä. Resultaten visar att filtret innehållande perlit täckt med silikonolja var mer effektivt med avseende på nedbrytning avpinen under den första tiden av studien (de första 30 dagarna). Skillnaden i effektivitet mellan filtren minskade dock betydligt med tiden så att skillnaden inte var signifikant under resten av studien. Prover från vätskefasen från de båda filtren undersöktes i mikroskop. Dessa studier visade att olika mikroorganismer dominerade i de båda filtren. Filtret innehållande oljetäckt perlit dominerades av stavformiga bakterier medan filtret innehållande obehandlad perlit dominerades av kocker. Båda filtren innehöll en blandkultur av kocker och stavar. Dessutom växte svamp i båda filtren. Dessa resultat visar att en förändring av ytans hydrofobicitet inte bara kan leda till en ökad adsorption av förorening utan den kan också leda till att andra mikroorganismer får en dominerande roll i filtret. Den maximala nedbrytningshastigheten låg mellan 35 och 40 g pinen/(m3h) under hela studien förutom de 30 första dagarna oberoende av luftflödeshastighet (1,5 , 2,5 respektive 5 l/min). Den maximala nedbrytningshastigheten under inledningen av försöket var 15 g/(m3 h) för filtret innehållande obehandlad perlit och 20 g/(m3h) för filtret innehållande oljetäckt perlit. Luftflödet var 2,5 l/min under den inledande perioden. Ökningen i nedbrytningshastighet med tiden indikerar att mikroorganismerna anpassade sig till miljön. Den relativt konstanta nedbrytningshastigheten under resten av studien indikerar att det var de biokemiska reaktionerna som var hastighetsbegränsande och att masstransporten inte hade någon dominerande roll med avseende på att begränsa hastigheten.</p>

Οι ορυκτοί πόροι είναι απαραίτητη συνιστώσα για τη βιωσιμότητα της οικονομικής ανάπτυξης και την ποιότητα ζωής, καθιστώντας τη διαθεσιμότητά τους πολύτιμo αγαθό και πλουτοπαραγωγική πηγή μίας χώρας. Η Ελλάδα είναι μία από της χώρες της Ευρωπαϊκής Ένωσης με σημαντικότατο ορυκτό πλούτο. Η μεγάλη ποικιλία των ορυκτών και μεταλλευμάτων που απαντώνται στην ελληνική επικράτεια, η ποιότητα, αλλά και η ποσότητά τους καθιστά την εκμετάλλευσή τους μια εξαιρετικά βιώσιμη και προσοδοφόρα δραστηριότητα. Ενδεικτικά αναφέρεται ότι η Ελλάδα, σε παγκόσμια κλίμακα, είναι η μοναδική χώρα παραγωγής χουντίτη, πρώτη χώρα στην παραγωγή περλίτη, δεύτερη χώρα στην παραγωγή κισσήρεως (ελαφρόπετρας) και μπεντονίτη, καθώς και πρώτη στην εξαγωγή προϊόντων λευκόλιθου/μαγνησίτη στην ΕΕ. Ο περλίτης, ο οποίος αποτελεί και αντικείμενο μελέτης της παρούσας εργασίας, είναι ένα υαλώδες όξινο ηφαιστειακό πέτρωμα, με κύριο χαρακτηριστικό την περλιτική του υφή και την ικανότητα του να διογκώνεται έως και είκοσι φορές του αρχικού του όγκου, χαρίζοντας του εξαιρετικές θερμομονωτικές και ηχομονωτικές ιδιότητες. Οι κυριότερες χρήσεις του περλίτη είναι σε οικοδομικές εργασίες, ως μονωτικό ή ως αδρανές συστατικό σε προκατασκευασμένο σκυρόδεμα, στην διήθηση, ως ενδιάμεσο διηθητικό φίλτρο κατά το διαχωρισμό υγρού στερεού, στην κρυογενετική, ως μονωτικό, καθώς εμποδίζει τη μετάδοση της θερμότητας, στην κηπουρική, ως προσθετικό στο χώμα για τη διατήρηση της υγρασίας, ως προσθετικό σε πλαστικά, απορρυπαντικά κτλ. Το πιο σημαντικό κοίτασμα περλίτη στον ελλαδικό χώρο είναι το κοίτασμα της Μήλου. Το νησί της Μήλου, είναι τμήμα του εξωτερικού μετώπου του νησιωτικού ηφαιστειακού τόξου του Νοτίου Αιγαίου και διέπεται από ασβεσταλκαλική ηφαιστειότητα. Τα πετρώματα που απαντώνται στο νησί είναι κυρίως ηφαιστειακά προϊόντα, με εναλλαγές πυροκλαστικών προϊόντων, χερσαίας απόθεσης και τοφφιτών, που έχουν αποτεθεί σε θαλάσσιο περιβάλλον. Στην παρούσα εργασία, αναλύθηκαν 15 δείγματα ρυολιθικών λαβών περλιτικής υφής, από τις περιοχές πλησίον των ηφαιστειακών κέντρων του Τράχηλα και της Φυριπλάκας, με βασικό σκοπό τη μελέτη των ορυκτολογικών και των χημικών χαρακτηριστικών τους, καθώς και το βαθμό της εξαλλοίωσης που έχουν υποστεί, λόγω των καιρικών συνθηκών. Τα δείγματα των ρυολιθικών λαβών περλιτικής υφής μελετήθηκαν τόσο μακροσκοπικά όσο και μικροσκοπικά, μέσω λεπτών τομών. Επίσης, πραγματοποιήθηκαν χημικές αναλύσεις και εξετάσθηκε ο βαθμός εξαλλοίωσής τους με τη χρήση της μεθόδου Isocon, ενώ προσδιορίστηκε και η κινητικότητα των στοιχείων κατά την εξαλλοίωση. Τέλος, με τη βοήθεια της υπέρυθρης φασματοσκοπίας FTIR και NIR προσδιορίσθηκε η παρουσία του περιεχόμενου νερού στα υπό μελέτη δείγματα, δίδοντας πληροφορίες για τις μεταβολές που παρουσιάζονται κατά την εξαλλοίωση του περλίτη, λόγω των καιρικών συνθηκών. / The mineral resources are a necessary component for the sustainability of economic development and quality of life , making their availability a valuable asset and resource of a country . Greece is one of the EU countries with important minerals . The wide variety of minerals and ores found in Greek territory , their quality, and their quantity, is making their exploitation a very viable and lucrative activity . Indicatively Greece , worldwide , is the only country producing huntite, first country in producing perlite, second country in the production of pumice stone and bentonite , and the first to export products of Magnesite in the EU. Perlite , which is the subject of study of this paper , is a glassy acid volcanic rock , with the typical perlitic texture and its ability to swell up to twenty times its original volume , is giving it excellent thermal and sound insulation properties . The main uses of perlite is in carpentry , as insulation or as an inert ingredient in precast concrete, in infiltration , as an intermediate filter at the solid liquid separation, in cryogenetics as insulation , because it prevents the transmission of heat , in horticulture , as an additive to soil to retain moisture , as an additive in plastics, detergents , etc. The most important ore perlite in Greece is the deposit of Milos . The island of Milos is part of the outer face of the volcanic island arc in the southern Aegean and governed by calc alkaline volcanism . The rocks found on the island is predominantly volcanic products , with alternating pyroclastic products of land deposition and toffiton, deposited in a marine environment . In this paper, we analyzed 15 samples of rhyolitic lavas with perlitic texture , from the areas near the volcanic centers of Trachilas and Fyriplaka , with main purpose to study the mineralogical and chemical characteristics, and the degree of alteration that have suffered because of weathering . The samples of rhyolitic lavas and perlitic texture studied both macroscopically and microscopically , through thin sections . Also , chemical analyzes were performed and examined the degree of alteration with the use of the method Isocon, while determining also the mobility of elements during alteration . Finally , with the help of infrared spectroscopy FTIR and NIR, we determined the presence of water content in the studied samples , yielding information about the changes that occur during the alteration of perlite , due to weathering. conditions .

Techn. Universiẗat, Diss., 2002--München.

Large Liquid Hydrogen (LH2) storage tanks are vital infrastructure for NASA. Eventually, air may leak into the evacuated and perlite filled annular region of these tanks. Although the vacuum level is monitored in this region, the extremely cold temperature causes all but the helium and neon constituents of air to freeze. A small, often unnoticeable pressure rise is the result. As the leak persists, the quantity of frozen air increases, as does the thermal conductivity of the insulation system. Consequently, a notable increase in commodity boiloff is often the first indicator of an air leak. Severe damage can then result from normal draining of the tank. The warming air will sublimate which will cause a pressure rise in the annulus. When the pressure increases above the triple point, the frozen air will begin to melt and migrate downward. Collection of liquid air on the carbon steel outer shell may chill it below its ductility range, resulting in fracture. In order to avoid a structural failure, as described above, a method for the safe removal of frozen air is needed. Two potential methods for air removal are evaluated here. The first method discussed is the connection of a vacuum pump to the annulus which provides pumping in parallel with drainage of LH2. The goal is to keep the annular pressure below the triple point so that the air continues to sublimate, thus eliminating the threat that liquefaction poses. The second method discussed is the application of heat to the bottom of the outer tank during tank drain. Though liquefaction in the annular space will occur, the goal of the heater design is to keep the outer shell above the embrittlement temperature, so that cracking will not occur. In order to evaluate these methods, it is first necessary to characterize some the physical properties and changes that take place in the system. A thermal model of the storage tank was created in SINDA/FLUINT (C&R Technologies, 2014) to identify locations where air can freeze. This model shows the volume that is capable of freezing air under varying conditions. It is also necessary to characterize the changes in thermal conductivity of perlite which has nitrogen frozen into its interstitial spaces. The details and results of an experiment designed for that purpose is outlined. All data, including operational data from existing LH2 tanks, is compiled and a physics-based evaluation of the two proposed air removal techniques is performed. Due to small pumping capacities at low pressure and the large quantity of air inside the annulus, the pumping option is not deemed feasible. It would take many years to remove a significant amount of air by pumping while maintaining the annular pressure below the necessary triple point. Application of heating devices is a feasible option. For a specific case, it is shown that approximately 105 kilowatts of power would be required to vaporize the air in the annulus and keep the temperature of the outer tank wall above the freezing point of water. Several engineering solutions to accomplish this are also discussed. There are many unknowns and complexities in addressing the problem of safely removing frozen air from the annulus of an LH2 storage sphere. The work that follows utilized: research, modeling, experimentation, analysis, and data from existing tanks to arrive at possible solutions to the problem. Heating solutions may be implemented immediately and could result in significant savings to the user.