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Bartie, Neill J. "The effects of temperature, slag chemistry and oxygen partial pressure on the behaviour of chromium oxide in melter slags." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16255.
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Thesis (MScIng)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: This thesis details results obtained in an experimental study conducted to determine the effects of operating temperature, oxygen partial pressure, bulk chromium oxide content and bulk FeOx/MgO ratio on the solubility of chromium oxide in melter type slags in the platinum industry. Two PGM-containing layers in the Bushveld Complex in South Africa, the Merensky and UG2 reefs, are currently being mined for the extraction of base metals and platinum group metals (PGM). While the Merensky reef is a pyroxenitic layer, the UG2 reef is a platiniferous chromitite seam. Due to a gradual depletion in Merensky ore reserves, platinum producers have been moving towards the processing of more UG2 concentrates, which are higher in chromium oxide content. The technical difficulties associated with the smelting of concentrates with high chromium oxide contents is a matter of concern. The formation of chromite spinels in melts increases liquidus temperatures and viscosities and subsequently hampers tapping of slags and mattes from furnaces. Bottom build-up from the smelting of high chromium oxide containing concentrates could reduce effective furnace volume. From the literature reviewed it was found that very few published investigations covered melt compositions and oxygen partial pressures similar to those encountered in the platinum industry. Relevant studies were found to deal with significantly lower bulk chromium oxide and iron oxide contents. It became clear that a need exists for information on the behaviour of chromium oxide and its effects on phase chemistry and stability in melter slags. It was decided to study the phase equilibria through drop-quench experiments using six synthetic slags with bulk FeOx/MgO ratios between 0.6 and 1.9 and bulk chromium oxide contents between 1.2 and 7 wt%. Temperatures investigated were 1400, 1500 and 1600°C. The oxygen partial pressure was varied between 6.8x10-10 atm at 1400°C to8.3x10-5 atm at 1600°C. Experiments were conducted in a sealed vertical tube furnace and the required oxygen partial pressure in the furnace tube was maintained by controlling the flow rates of purified CO and CO2 gas mixtures through the tube. Reaction products were quenched after a reaction time of between 20 and 24 hours, depending on temperature, and the phase compositions were analysed by microprobe. The experimental study revealed that chromium oxide partitions very strongly into the spinel phase relative to the liquid phase, especially at lower temperatures, and higher oxygen partial pressures and bulk chromium oxide contents. The solubility of chromium oxide in the liquid phase was found to increase with increasing temperature and decreasing oxygen partial pressure. An increase in bulk chromium oxide contents of 1 wt%, under otherwise constant conditions, resulted in an increase in slag liquidus temperature of approximately 100°C over the range of temperatures investigated. At 1500°C and bulk chromium oxide contents of 3.7 and 6.4 wt% a reduction in oxygen partial pressure from 1.1x10-5 to 1.1x10-7 atm resulted in increases in soluble chromium oxide of 0.9 and 2.0 wt%, respectively. A further decrease in oxygen partial pressure to 6.7x10-9 atm resulted in increases in soluble chromium oxide of 2.8 and 4.7 wt%, respectively. Experimental results were compared to values predicted by the multi-phase equilibrium (MPE) model developed by CSIRO, and found to agree well. Slag basicity was not varied experimentally and therefore the model was used to predict its effect on the solubility of chromium oxide in the liquid phase and the stability of crystalline phases. At constant temperature, an increase in basicity resulted in a decrease in the solubility of chromium oxide in the liquid phase as well as stabilisation of the spinel phase. It was concluded that practicable combinations of one or more of four main factors, namely increased operating temperature and decreased bulk chromium oxide content, slag basicity and oxygen partial pressure, should be applied and evaluated in a plantenvironment to optimise furnace operation. The MPE model would be a valuable tool in predicting the outcomes of such investigations.
AFRIKAANSE OPSOMMING: Hierdie tesis detaileer die resultate wat verkry is uit ‘n eksperimentele studie uitgevoer om die effek van bedryfstemperatuur, die parsiële druk van suurstof, die algehele chroomoksied inhoud en die algehele FeOx/MgO verhouding op die gedrag van chroomoksied in smelter slakke in die platinum industrie te bestudeer. Twee PGM-bevattende ertslae in die Bosveldkompleks in Suid Afrika, die Merensky en UG2 riwwe, word huidiglik gemyn vir die ekstraksie van basismetale en platinumgroep metale (PGM). Die Merensky rif is ‘n piroksenitiese laag terwyl die UG2 rif ‘n platinumbevattende chromitiet laag is. As gevolg van ‘n geleidelike afname in reserwes van Merensky erts beweeg platinumprodusente al meer na die verwerking van groter hoeveelhede UG2 erts. Die tegniese probleme wat gepaard gaan met die smelting van konsentrate met hoë chroomoksied inhoud kan ‘n rede tot kommer wees. Die vorming van chromiet spinelle in die slak- en matfases verhoog likuidus temperature en viskositeite en bemoeilik die tap van hierdie fases uit oonde. Die opbou van soliede fases verlaag ook die effektiewe oondvolume. Uit die literatuurstudie is gevind dat gepubliseerde studies waarin slak samestellings en parsiële suurstofdrukke wat betrekking het op die platinumindustrie bespreek is, baie beperk is. Dit is gevind dat relevante navorsing gedoen is met aansienlik laer algehele chroom- en ysteroksied konsentrasies. Gevolglik het dit duidelik geword dat ‘n behoefte bestaan vir inligting oor die gedrag van chroomoksied in oonde en die effekte daarvan op fasechemie en –stabiliteit in smelter slakke. Daar is besluit om eksperimente uit te voer deur die gebruik van ses sintetiese slakke met algehele FeOx/MgO verhoudings tussen 0.6 en 1.9 en algehele chroomoksied konsentrasies tussen 1.2 en 7.0 % (op ‘n massabasis). Temperature van 1400, 1500 en 1600°C en suurstof parsiële drukke tussen 6.8x10-10 atm by 1400°C en 8.3x10-5 atm by 1600°C is ondersoek. Eksperimente is uitgevoer in ‘n geseëlde vertikale buisoond en dievereiste suurstofdruk in die oond is gehandhaaf deur beheer van die vloeitempos van gesuiwerde CO en CO2 gas deur die oond. Reaksieprodukte is in water geblus na ‘n reaksietyd van tussen 20 en 24 ure, afhangende van die reaksietemperatuur. Fasesamestellings is bepaal deur mikrosonde analises. Die eksperimentele studie het bewys dat chroomoksied baie sterk in die spinelfase konsentreer relatief tot die vloeistoffase, veral by laer temperature, suurstofdrukke en algehele chroomoksied konsentrasies. Dit is gevind dat die oplosbaarheid van chroomoksied in die vloeistoffase toeneem met toenemende temperatuur en afnemende suurstofdruk. ‘n Toename in die algehele chroomoksied konsentrasie van 1 massa%, onder andersins onveranderde toestande, het ‘n toename van ongeveer 100°C in likuidus temperature veroorsaak tussen 1400 en 1600°C. By 1500°C en algehele chroomoksied konsentrasies van 3.7 en 6.4 massa%, het ‘n verlaging in suurstofdruk vanaf 1.1x10-5 tot 1.1x10-7 atm respektiewelike toenames in die chroomoksied oplosbaarheid van 0.9 en 2.0 massa% veroorsaak. ‘n Verdere verlaging in suurstofdruk tot 6.7x10-9 atm het respektiewelike toenames in chroomoksied oplosbaarheid van 2.8 en 4.7 massa% veroorsaak. Eksperimentele resultate is vergelyk met waardes wat voorspel is deur die multifase ewewigsmodel (MPE), ontwikkel deur CSIRO, en goeie ooreenstemming is gevind. Verskillende slak basisiteite is nie eksperimenteel ondersoek nie en daarom is die model gebruik om die effek daarvan op die oplosbaarheid van chroomoksied in die vloeistoffase asook die stabiliteit van kristallyne fases te bepaal. By konstante temperatuur het ‘n toename in slak basisiteit ‘n afname in chroomoksied oplosbaarheid veroorsaak en die spinelfase gestabiliseer. Die aanbeveling is gemaak dat ‘n kombinasie van een of meer van vier hooffaktore, naamlik hoër bedryfstemperature en laer algehele chroomoksied konsentrasies, slak basisiteit en suurstofdruk, in die praktyk toegepas en geëvalueer moet word om sodoendeoptimum bedryfkondisies te bepaal. Die multifase ewewigsmodel is ‘n nuttige instrument wat gebruik kan word om die resultate van sulke ondersoeke te voorspel.
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Boukendakdji, Mustapha. "Mechanical properties and long-term deformation of slag cement concrete." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236998.
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Coetzee, Colette. "Solidification behaviour of titania slags." Diss., Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-02282007-152308.
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Tanaka, Shigenori. "Modelling inclusion behaviour and slag entrainment in liquid steel processing vessels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1986. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ44661.pdf.
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Kountouriotis, Zacharias. "Modelling of the liquid slag behaviour in the continuous casting mould." Thesis, University of Greenwich, 2011. http://gala.gre.ac.uk/7658/.
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This work presents a fluid dynamics model of a continuous caster mould region, including the transient behaviour of the steel/slag interface. The research was carried out in collaboration with ArcelorMittal Research (AMR), based in Maizieres-les-Metz in France. The industrial objective of the thesis was to understand the factors affecting the transient behaviour of the liquid slag layer covering the steel and its interaction with the Submerged Entry Nozzle (SEN) jet supplying the steel from the tundish to the Continuous Casting (CC) mould. The study includes the very complex phenomenon of argon bubble transport which also affects the behaviour of the slag layer and SEN jet. The model developed in this study is based on the finite volume method with the liquid regions (steel, slag) solved in an Eulerian scheme on a fixed unstructured mesh. The interface behaviour is modelled using a number of VOF type schemes, including the time-efficient Counter Diffusion Method (CDM). A coupled Lagrangian particle tracking scheme is used to represent the presence of argon bubbles and their influence on the flowfield (mainly due to buoyancy) in conjunction with the fluctuating surface dynamics. The bulk of the research concerns comparisons against flowfield and interface data obtained from an experimental water/oil study of the process. However, the model is extended to include predictions of heat transfer and phase change in the steel and flux powder regions in an industrial CC unit and validation against available data. The three-phase model is developed making use of the unstructured mesh multi-physics finite volume code PHYSICA [1]. As stated, the main goal of this particular work has to do with the study of the dynamic behaviour of the steel/slag interface, including the effects of casting speed and injected gas. Because of the great difficulty in physical experiments with a real caster, the research is supported with water model experiments and mathematical simulation. Comparisons of observed interface profiles, measured and predicted mean and fluctuating velocities, gave an insight to the degree of coupling between interface behaviour and the fluid dynamics within the mould region. In particular, a spectral analysis of the dominant fluctuation frequencies in the water/oil experiment suggests a strong link between the upper and lower recirculation loops generated by the SEN jet as it splits after contact with the narrow face for the mould. The presence of gas bubbles alters the spectral picture, since the buoyancy induced in the flow affects the behaviour of the jet, leading to the one/two loop behaviour known from experiments. Good qualitative and quantitative agreement was achieved between the numerical results and water-model experimental data. The main observations drawn from the water model simulation and experiment are as follows: - An increase in casting speed, which is equivalent to an increase in SEN velocity leads to an increase in the amplitude of interfacial fluctuations. - At the highest SEN velocities, the oil layer is pushed away from the narrow ends of the mould, exposing the water surface to air. - When there is no oil on top of the water surface, the surface remains for all practical purpose flat. - Air entering through the SEN influences the flowfield in the mould and also disturbs the oil/water interface when it passes through it. - The ratio of water to air flow rate seems to be the most important parameter, with high air/water flow ratios leading to a change in flowfield at the top of the mould as the gas buoyancy lifts the SEN jet towards the surface. To achieve a good correlation between the experiments and the simulations a number of factors in the numerics were found to be important. These are: - The quality of the mesh used, especially in the complex transition from the SEN geometry – essentially a cylinder with two outlets set at a specific angle of 20o to the vertical, to the thin rectangular geometry of the mould which is designed to cast flat products. - The turbulence model, which was initially found to suppress interface oscillations whenever an oil layer was introduced. Various approaches were followed to overcome this problem, (a)removing the turbulence model from the oil layer, (b) using a low frequency filter to remove resolved turbulence kinetic energy from the k-ε model, (c)opting for the high order SMART numerical scheme in preference to the default Hybrid. - The interface tracking algorithm used as a default in the code PHYSICA is essentially a VOF technique with options for a Van-Leer (TVD) scheme [2] or alternative the popular Donor Acceptor scheme [3,4], both options work well but they are explicit and therefore extremely expensive computationally. Due to the size of the mesh and the CFL limit for stability, timesteps as small as 10-3s become necessary, meaning a 600s simulation could take up to 8 weeks! To overcome this, the implicit CDM scheme [5] was used, which allows the interface to spread by diffusion but then pushed back against the gradient to re-sharpen at the end of each timestep. With this scheme, timesteps up to 2 orders of magnitude larger become possible, the limit then governed by the frequency range to be resolved. A non-standard approach to the Lagrangian particle tracking scheme was adopted in the simulation with the following characteristics: - The amount of gas entering was divided into packets of equal bubble diameter and then each packet was further divided into individual tracks. The transport of 1000 and more particles tracks was used to ensure a realistic dispersion. - Tracks were updated at regular time intervals (but not necessarily at each Eulerian timestep) and then followed until they exited the calculation domain. - The residence time of particles in each cell provided information for the gas content of the cell and therefore its density. With this approach, the Navier-Stokes equations then solve for mixture (gas and liquid) and lighter cells are influenced by buoyancy. - The bubble tracks are affected by the mean velocity of the surrounding fluid and also by a stochastic component derived from the turbulence model. However, there is no direct feedback to fluid turbulence from the bubbles. To extend simulations to a real caster, heat transfer and phase change were introduced in the model, in addition to the property changes (water to steel, oil to slag, air to argon). Of importance here was the development of a solidified skin of steel on the water-cooled mould walls and also the melting of flux powder into a liquid layer on the top surface. This last component of the research was introduced to enable comparisons against plant data obtained by AMR. Of particular interest in this study was the transition from a double to a single roll recirculation in the top section of the mould, as a function of the relative quality of argon entering the SEN. The model was able to reproduce this behaviour for the cases studied. Although much has been done in developing this model of the continuous casting process it is evident that much more research is needed, especially in the case of a real caster. For example, the thermophysical property variations in the slag due to temperature, composition and mass transfer were ignored. A very simple approach was used for the phase change in steel and flux powder, although since the PHYSICA framework is modular, more sophisticated alternatives can be easily introduced. The boundary conditions for heat transfer remain uncertain and the values used in this study were obtained from the industrial partner from earlier experiments. In spite the aforementioned limitations, the model is very useful, especially in understanding the dynamic interactions between the SEN jets, and the slag/steel interface and in this respect in advance of other models used by industry.
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Zheng, Yong Chu. "Shrinkage behaviour of geopolymers /." Connect to thesis, 2010. http://repository.unimelb.edu.au/10187/7157.
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Luganova-Chnyrenkova, Tatiana. "Factors affecting behaviour of minor elements in dore metal-soda slag partitioning." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26404.
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A series of experiments determined the influence of oxygen partial pressure and SiO$ sb2$ content in soda slag on the distribution of metals between soda slag and dore metal. Oxygen partial pressure ranged from 10$ sp{-8}$ to one atmosphere and the SiO$ sb2$ content from 0 to 10 wt%.Minor elements, including the precious metals, partition between the dore metal and the soda slag. The main purpose of this research was to determine the process parameters which influence this distribution, and the nature and forms of the precious metals in the metal and in the slag phases.
From the results of the experiments it was found that: (a) Increasing oxygen partial pressure from 10$ sp{-8}$ to 1 atm does not influence gold, palladium and platinum removal from dore metal, but leads to the practically complete removal of Te (down to 4.8 ppm), Rh (down to 2.7 ppm), Pb (down to 6.0 ppm) and quite good removal of Se (down to 0.0112 wt%) and Cu (down to 0.42 wt%) from the dore metal. (b) Silica content of the soda slag does not influence gold, palladium and platinum chemical losses with soda slag. However it was found that increasing silica in slag leads to an increase of mechanical loss of precious metals because of the increase in slag viscosity. (c) Increase in silica content of slag increased lead and copper removal from dore metal, and decreased the removal of rhodium, selenium and tellurium, especially at low oxygen potential. (d) It was concluded that most of precious metals leave dore metal in the form of mechanical losses, but silver and rhodium were found in slags as intermetallic phases with the other components. Rhodium is also lost in the form of the volatile oxide RhO$ sb2$. (Abstract shortened by UMI.)
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Wikström, Jenny. "A Mathematical and Experimental Study of Inclusion Behaviour at a Steel-Slag Interface." Doctoral thesis, KTH, Materialvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4574.
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The aim of this thesis work is to increase the knowledge of inclusion behavior at the steel-slag interface by mathematical modeling and in-situ Confocal Scanning Laser Microscope experiments. Mathematical models based on the equation of motion predicting liquid and solid inclusion behavior was first investigated. Four main forces, the buoyancy force, the added mass force, the rebound force and the drag force, act on the inclusion as it crosses the interface. There are three types of behavior an inclusion at the steel-slag interface can adopt. These are a) pass, which means that the inclusion is separated to the slag, b) remain, where the inclusion stays at the interface without being fully transferred to the slag or c) oscillate, and the inclusion rises and descends at the interface until the motion is dampened out by the interfacial forces. The studies showed the importance of accurate experimental physical property data. Application of the models to industrial conditions illustrated that useful plots could be made showing the industry how to optimize their interfacial properties in the ladle and tundish to obtain maximum inclusion separation. In-situ Confocal Scanning Laser Microscope (CSLM) experiments were carried out in order to study agglomeration of liquid and semi liquid inclusions at the steel-gas and steel-slag interfaces and in the slag. Liquid-liquid inclusion agglomeration at steel-gas and steel-slag interfaces was seen to not occur without using force. However, when already transferred to the slag the inclusions agglomerated freely due to a higher free energy force. Comparison of experimental and theoretical agglomeration force showed good agreement between experiments and theory. The main conclusion of this work is that inclusion separation is a complex field of study and there exist no model that takes everything into account. Here the tendency for inclusion transfer and how to manipulate the physical properties for inclusion separation together with agglomeration experiments have been studied. For the future maybe coupling of models for computational fluid dynamics, agglomeration, inclusion separation, dissolution and slag entrainment in addition with experimental physical property data can provide a better overview and understanding.QC 20100823
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Diener, Silvia. "Ageing behaviour of steel slags in landfill liners." Licentiate thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26542.
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Steel slags are by-products of the steelmaking process. To avoid unnecessary disposal, e.g. into landfill, their chemical and physical properties should be exploited to support alternative uses. Steel slags can be recycled within the steel plant or used as construction material in roads, hydraulic engineering and different types of barriers, including landfill covers. A landfill cover consists of several layers, including a liner with low water and gas permeability in order to reduce methane and leachate emissions. Several studies have demonstrated that steel slags have good potential to fulfil such an application. However, there are questions regarding the stability of the slag minerals over long periods of time. A landfill cover must function well for many decades and centuries. In order to predict the long-term stability of steel slags as a landfill liner, laboratory experiments have been performed to study the effects of accelerated ageing of steel slag under controlled conditions. The factors investigated in the storage atmosphere were carbon dioxide content, relative humidity and temperature. The influence of leachate contact and ageing time were also assessed.This thesis reports the study of electric arc furnace slags and ladle slag from the production of high-alloyed tool steel after accelerated ageing for periods of three months and ten months. Mineralogy and leaching were studied using two different leaching tests, thermal analysis, acid-neutralization capacity assays and X-ray diffraction. For the ageing periods considered, the exposure of the slags to an atmosphere enriched with carbon dioxide had the greatest impact on leaching. In general, calcium, aluminium, sulphur and sodium leached from the slag matrix to the greatest extent while other metals such as chromium, nickel, lead and zinc were found at very low levels in the leachate. The leaching of calcium and aluminium reduced with increasing carbon dioxide level. Thermal analysis revealed the decomposition of carbonates. Weight and enthalpy changes were evaluated between 100 and 1000 °C. The buffer capacity of the steel slags, represented by the acid neutralization capacity (ANC 4.5) was not reduced after 10 months of ageing. However, the division of the titration into two steps revealed a shift of buffering zones for more highly aged samples, probably due to the formation of carbonates. The mineralogy of the investigated steel slags was complex with a large variety of mineral phases, principally calcium silicates, monticellite, periclase and a spinel phase. Other possible phases were gehlenite, merwinite, akermanite and iron. The existence of different solid solution is likely among the slag phases and can cause shifting of peaks in the X-ray diffractogram. Also, calcite was identified. Short-term carbonation has not shown significant impact on mineralogy despite of calcite formation. The results of the study contribute to a better understanding of the chemical and mineral stability of electric arc furnace slag and ladle slag in the environment of a landfill liner. The consequences of slag ageing include reduced leaching rates for certain elements. To predict the long-term behaviour of aged slag, the results of this study should be combined with data from two other sources - an ongoing ageing experiment that includes mechanical tests and a full scale field test at the Hagfors landfill. Additional analytical methods that can better characterise the mineralogy, for example scanning electron microscopy (SEM) and energydispersive X-ray spectroscopy (EDX), should also be applied to better quantify the mineralogical phases and to determine which trace elements are most abundant in specific minerals.Stålslagg är en restprodukt som kommer från ståltillverkningen. Den har kemiska och fysikaliska egenskaper som bör utnyttjas och som gör den lämplig för återanvändning, samtidigt som onödig deponering kan undvikas. Stålslagg kan återanvändas inom ståltillverkningen eller så kan den användas som konstruktionsmaterial i väg- och vattenbyggnadskonstruktioner eller i olika typer av barriärkonstruktioner som till exempel deponisluttäckningar. En deponisluttäckning består av flera skikt där tätskiktet ska ha en låg vatten- och gaspermeabilitet för att minska metan- och lakvattenutsläpp. Flera studier visar att stålslagg uppfyller dessa egenskaper och har potential att kunna användas i deponitäckning. Men det finns fortfarande oklarheter angående slaggmineralernas stabilitet över en längre tid. En deponitäcknings funktion förväntas vara stabil i många tiotals eller hundratals år. För att kunna förutsäga det långsiktiga beteendet för stålslagg i ett tätskikt genomfördes ett laboratorieexperiment vars syfte var att studera effekterna av accelererad åldring under kontrollerade förhållanden. De faktorer som studerades var koldioxidhalten, relativa luftfuktigheten, temperaturen, kontakten med lakvatten samt åldringstiden. I denna avhandling presenteras undersökningen av ljusbågsugnsslagg och skänkslagg, från framställning av höglegerat verktygsstål, efter tre respektive tio månaders accelererad åldring. Mineralogin och lakningsegenskaperna studerades genom två typer av laktester, termiska analyser, analys av syraneutraliserande kapacitet samt röntgendiffraktion. För de studerade åldringstiderna var det exponeringen av stålslaggen för en koldioxidrik atmosfär som hade den största inverkan på lakningsegenskaperna. Kalcium, aluminium, svavel och natrium var de ämnen som uppvisade den högsta utlakningen från slaggen medan metaller som krom, nickel, bly och zink endast fanns i väldigt låga koncentrationer i lakvattnet. Utlakningen av kalcium och aluminium minskade med en ökande halt av koldioxid. Termiska analyser visade på en nedbrytning av karbonater. Vikt- och entalpiförändringar mellan 100 och 1000°C utvärderades. Stålslaggens buffertkapacitet, representerad av den syraneutraliserande kapaciteten (ANC pH 4,5), reducerades inte efter tio månaders åldrande. Däremot visade uppdelningen av titreringen i två steg på en förskjutning av buffertområdena för de prover som åldrats tio månader, förmodligen på grund av karbonatbildning. Mineralogin för de undersökta stålslaggerna var komplex med en stor variation av mineralfaser, främst kalciumsilikater, monticellit, periklas och en spinellfas. Andra möjliga mineralfaser var gehlenit, merwinit, åkermanit och järn. Förekomsten av olika fastfaslösningar i stålslaggsmineralerna är sannolik vilket kan orsaka förskjutningar av topparna i diffraktogrammen. Kalcit identifierades också. Karbonatisering under en kort tid visade sig inte ha någon signifikant inverkan på mineralogin, förutom en viss kalcitbildning. Resultaten från studien bidrar till en bättre förståelse av stabiliteten för ljusbågsugns- och skänkslagg i den miljö som finns i ett tätskikt. Åldringen av slaggen resulterade i en reducerad utlakning av vissa element. För att kunna förutsäga det långsiktiga beteendet för åldrad slagg bör resultaten från den här studien kombineras med data från ett pågående åldringsförsök som inkluderar mekaniska tester samt ett fullskaligt fältförsök på Hagfors deponi. Analysmetoder som mer detaljerat kan karaktärisera mineralogin, till exempel svepelektronmikroskopi (SEM) och energidispersiv röntgenspektroskopi (EDX), bör också användas för att bättre kunna kvantifiera mineralfaserna och bestämma vilka spårelement som är vanligast i specifika mineraler.
Godkänd; 2009; 20090320 (sildie); LICENTIATSEMINARIUM Ämnesområde: Avfallsteknik Examinator: Professor Anders Lagerkvist, Luleå tekniska universitet Tid: Fredag den 24 april 2009 kl 14.15 Plats: F 664f, Luleå tekniska universitet
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Cho, Soon Ho. "Slab behaviour in composite beams at web openings." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74647.
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An explanation is provided for the slab behaviour in composite beams at web holes where the concrete slab carries heavy vertical shear. This is based on the truss concept, and requires consideration of shear studs in the hole region as vertical tension members. According to this, a structural action between the concrete slab and shear connectors for carrying or transferring vertical shear to the steel beam was clearly identified.On the basis of the slab behaviour identified, truss idealizations capable of determining the slab shear carrying capacity in a rational manner were developed. Then, the ultimate strength for composite beams at web holes was formulated including the truss idealizations. Another ultimate strength analysis accounting for the slab shear carrying capacity in a simple manner, which was also developed during this research project, is given. This provided the fundamental solution procedure for the plastic analysis used.
A series of nine tests was carried out with particular attention being directed to the verification of the proposed truss analogy. The major test parameters included the configurations of the studs in the hole region, the width of the concrete slab and stud detailing near the high moment end of the hole. The ultimate strength predictions were made by the two methods developed, and compared with previous and present test results.
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Mai, Paolo. "Effect of iron redox state on crystallization behaviour of Fayalite slags." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286327.
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In the copper smelting processes, the viscosity of the matte and the slag is an important factor for establishing efficiency. Impurities in the concentrates affect the viscosity not only by changing the melt structure but also by promoting precipitation of solid phase which sharply rises it. In this master thesis, a comprehensive methodology was established to study the MgO effects on the properties of a copper smelting slag. Thus, glassy samples were obtained and after confirmation of the composition and the glassy structure with EDS, SEM, and XRD analysis, they were examined through Ramanspectroscopy to study their glassy structure. Moreover, Mössbauer spectroscopy was used to determine the amount of Fe3+ in the samples. Models from the literature were compared to the experimental data. Coherence with the literature was found with the effect of MgO as a network modifier of the oxide melt structure and a promoter of high coordinated structures. Estimations through models were performed to study the iron redox equilibria of the melt and were compared with experimental data, but it was not possible to find the limit of Fe3+ at which precipitation of solid phase initiates.I kopparsmältningsprocesserna är mattans och slaggens viskositet en viktig faktor för att uppnå effektivitet. Föroreningar i koncentraten påverkar viskositeten inte bara genom att ändra smältstrukturen utan också genom att främja utfällning av fast fas som kraftigt höjer den. I denna magisteruppsats fastställdes en omfattande metod för att studera MgO-effekterna på egenskaperna hos en kopparsmältningsslagg. Således erhölls glasiga prover och efter bekräftelse av kompositionen och den glasiga strukturen med EDS-, SEM- och XRD-analys undersöktes de genom Ramanspektroskopi för att studera deras glasstruktur. Dessutom användes Mössbauerspektroskopi för att bestämma mängden Fe3+ i proverna. Modeller från litteraturen jämfördes med experimentella data. Överensstämmelse med litteraturen hittades med effekten av MgO som ett nätverksmodifierare av oxidsmältstrukturen och en promotor för högkoordinerade strukturer. Uppskattningar genom modeller utfördes för att studera smältans järnredoxjämvikter och dessa jämfördes med experimentella data, men det var inte möjligt att hitta gränsen för Fe3+ vid vilken utfällning av fast fas initierades.
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Baah, Prince. "Cracking Behavior of Structural Slab Bridge Decks." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1417539467.
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Wikström, Jenny. "A mathematical and experimental study of inclusion behavior at a steel-slag interface /." Stockholm : Royal Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4574.
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Lin, Zuohua Joseph. "The modelling of emulsification, slag foaming and alloy addition behaviour in intensively stirred metallurgical reactors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30324.pdf.
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Manatakos, Kyriakos. "Behaviour and design of reinforced concrete core-slab-frame structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ30330.pdf.
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Manatakos, Kyriakos 1960. "Behaviour and design of reinforced concrete core-slab-frame structures." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42088.
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This dissertation examines the response and design of reinforced concrete core-slab-frame structures subjected to monotonically increasing earthquake and gravity loads throughout the entire load range until failure, presenting findings from three separate studies by Manatakos and Mirza (1995) continuing the M. Eng. thesis research by Manatakos (1989). A typical building is selected consisting of a central core substructure composed of elevator, staircase and infilled slab cores, with coupling and lintel beams, and surrounding slabs joining to a frame substructure composed of slab-band girders, slabs and columns.Stage 1 concentrates on the elastic response and Stage 3 examines the nonlinear response of the core-slab-frame structure considering the effects of cracking and crushing of concrete, strain-hardening of the reinforcement, and tension-stiffening. Analyses involve three-dimensional elastic and nonlinear finite element modeling techniques of the structure to investigate the contribution and influence of the various structural components. The structural response is examined for the deformations, the concentrated reinforcement strains and concrete stresses in the cores, the force and stress distributions in the structural members, and the failure mode.
Stage 2 focuses on the design and detailing of the core-slab-frame structure following seismic provisions of building code requirements for reinforced concrete structures where applicable as given in the CSA Standard CAN3-A23.3-MS4 (1984), the ACI Standard ACI 318M-83 (1983) and the New Zealand Standard NZS3101 (1982). Assumptions made in the conventional design procedures and any shortcomings encountered are examined. Suitable design procedures and reinforcement details are suggested where no provisions exist in the codes.
Findings demonstrate complex three-dimensional interaction among the cores, beams, slabs and frames in resisting the lateral and gravity loads, and show considerable strength, ductility and energy absorption capability of the structure. Critical areas for design include the joints and junctions near the vicinity of core wall-slab-beams ends and corners. Plastic hinging extends over the lower 2.5% to 33% height of the structure with the majority of inelastic action and damage concentrated in the bottom 10% to 15% height, predicting an ultimate load of 3.4 to 5.9 times the design earthquake load with top drifts of the structure between 750 mm to 1375 mm.
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Garraway, Richard. "The action of semiochemicals on olfactory nerve activity and behaviour of Deroceras reticulatum (Mull)." Thesis, University of Portsmouth, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303955.
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Tabor, A. M. "The effects of conspecific mucus on the behaviour of some gastropod molluscs." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377724.
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Howling, Gavin G. "The foraging and feeding behaviour of pest slugs with reference to control in the field." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335864.
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Engström, Fredrik. "Mineralogical influence on leaching behaviour of steelmaking slags : a laboratory investigation." Doctoral thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26653.
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The Swedish steelmaking industry produces large amounts of by-products. In 2008, the total amount of slag produced reached approximately 1,300,000 metric tons, of which 20% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction, since it has similar or better qualities than ordinary ballast stone, which makes it a competitive construction material. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties:Volume expansion Disintegration Leaching of metalsBy controlling and modifying process parameters during slag handling in liquid state, the physical and chemical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major goal of this work has been to investigate how different treatment methods including hot stage processing, cooling rates, ageing time and chemical composition influence the final properties of the slag. Analysis techniques used in this investigation include: thermodynamic calculations using FactsageTM, X-ray diffraction analyses (XRD), scanning electron microscopy (SEM), leaching tests (EN12457-2/3) and thermo-gravimetric analyses (TG).The results from this study show that it is possible to control/change the properties of the final product by additions to the liquid slag, thereby changing the chemical composition, as well as by varying the rate and method of cooling. The mineralogical composition, the size of the crystals and the composition of some solid solutions are affected by the cooling rate. The solubility of elements such as chromium and molybdenum varies, probably due to their presence in different minerals. The reactivity of the investigated slag samples increases as the cooling rate increases.When steel slags are aged, the leaching properties of the materials are changed. The total leachability and the pH decrease for all the investigated samples. All elements except magnesium decrease in leachability. As the slags are aged CaCO3 is formed on the slag surfaces. The degree of carbonation differs between different slags, due to the presence of different calcium-rich minerals in the slag. In order to form CaCO3, the calcium-containing mineral must be dissolved. This means that the solubility of the calcium-containing mineral will affect the outcome of the carbonation. The rate of dissolution for six typical slag minerals was investigated in order to distinguish the difference in solubility between the different minerals. Acidic to alkaline pHs (4, 7 and 10) were selected to investigate the solubility of the minerals under conditions comparable to those prevailing in newly produced slags and the potential future pH values obtained under acid conditions. It can be concluded that all six minerals behave differently when dissolving and that the rate of dissolution is generally slower at higher pH. At pH 10, the solubility of merwinite, akermanite and gehlenite is considered slow. The dissolution of γ-Ca2SiO4 is not affected in the same way as the other minerals when the pH is changed.Godkänd; 2010; 20101213 (fren); DISPUTATION Ämnesområde: Processmetallurgi/Process Metallurgy Opponent: Professor Pekka Taskinen, Dept. of Materials Science and Engineering, Aalto University, Finland Ordförande: Professor Bo Björkman, Institutionen för TKG, Avd för mineralteknik och metallurgi, Luleå tekniska universitet Tid: Fredag den 4 februari 2011, kl 10.00 Plats: F341, Luleå tekniska universitet
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Eder, Martin A. "Inelastic behaviour of hybrid steel/concrete column-to-flat slab assemblages." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7017.
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The use of tubular columns in conjunction with reinforced concrete flat slabs provides structurally efficient solutions which avoid undesirable failure modes such as those associated with shear. This thesis is concerned with the development of a tubular column-to- flat slab connection system that enables reliable performance under seismic loading conditions. During this research a novel detail which features a gap around the column is proposed and developed; hence only the structural steel shearhead establishes the connection. The exposed parts of the shear arms (fuses) are designed to yield prior to punching shear failure, in a way that utilises the favourable features of steel in terms of the response to seismically induced loads. The proposed connection could serve as a primary lateral resisting system within all building configurations in regions of low to moderate seismicity or as a secondary system in areas of signi cant seismicity. In order to provide validation for the proposed details as well as associated numerical and design procedures, a purpose-built rig which is suitable for large scale testing of structural sub assemblages under combined gravity and uniaxial lateral loading, has been designed and constructed, and subsequently employed for a number of tests. Test results and numerical analyses are presented with respect to a conventional con guration, as well as for the proposed, partially embedded connection. The latter is shown to offer enhanced ductility compared with traditional forms. The results are used to demonstrate the favourable inelastic performance of the proposed detail in terms of ductility, low degradation effects and increased energy dissipation capabilities. Complementary small scale slab panel tests are also used to further optimise the composite behaviour of the proposed detail. Additionally, a closed form solution based on plastic limit analysis which can serve as a basis for a simplified design approach is proposed. Finally, the main findings from the experimental and analytical investigations are highlighted, and recommendations for future research are outlined.
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Trygstad, Steinar. "Structural Behaviour of Post Tensioned Concrete Structures : Flat Slab. Slabs on Ground." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-114.
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In this investigation strength and structural behaviour of prestressed concrete is studied with one full scale test of one flat slab, 16000 mm x 19000 mm, and three slabs on ground each 4000 mm x 4000 mm with thickness 150 mm. The flat slab was constructed and tested in Aalesund. This slab has nine circular columns as support, each with diameter 450 mm. Thickness of this test slab was 230 mm and there were two spans in each direction, 2 x 9000 mm in x-direction and 2 x 7500 mm in y-direction from centre to centre column. The slab was reinforced with twenty tendons in the middle column strip in y-direction and eight tendons in both outer column strips. In x-direction tendons were distributed with 340 mm distance. There were also ordinary reinforcement bars in the slab. Strain gauges were welded to this reinforcement, which together with the deflection measurements gives a good indication of deformation and strains in the structure.
At a live load of 6.5 kN/m2 shear failure around the central column occurred: The shear capacity calculated after NS 3473 and EuroCode2 was passed with 58 and 69 %, respectively. Time dependent and non-linear FE analyses were performed with the program system DIANA. Although calculated and measured results partly agree well, the test show that this type of structure is complicated to analyse by non-linear FEM.
Prestressed slabs on ground have no tradition in Norway. In this test one reinforced and two prestressed slabs on ground were tested and compared to give a basis for a better solution for slabs on ground. This test was done in the laboratory at Norwegian University of Science and Technology in Trondheim. The first slab is reinforced with 8 mm bars in both directions distributed at a distance of 150 mm in top and bottom. Slab two and three are prestressed with 100 mm2 tendons located in the middle of slab thickness, and distributed at a distance of 630 mm in slab two and 930 mm in slab three. Strain gauges were glued to the reinforcement in slab one and at top and bottom surface of all three slabs. In slab two and three there were four load cells on the tendons.
Each slab were loaded with three different load cases, in the centre of slab, at the edge and finally in the corner. This test shows that stiffness of sub-base is one of the most important parameters when calculating slabs on ground. Deflection and crack load level depends of this parameter. Since the finish of slabs on ground is important, it can be more interesting to find the load level when cracks start, than deflection for the slab. It is shown in this test that crack load level was higher in prestressed slabs than in reinforced slab. There was no crack in the top surface with load in the centre, but strain gauges in the bottom surface indicate that crack starts at a load of 28 kN in the reinforced slab, and 45 kN in the prestressed slabs. Load at the edge give a crack load of 30 kN in reinforced slab, 45 kN and 60 kN in prestressed slabs. The last load case gives crack load of 30 kN in reinforced slab, 107 kN and 75 kN in prestressed slabs. As for the flat slab, FE analyses were performed for all of the three slabs on ground, and analyses shows that a good understanding of parameters like stiffness of sub-base and tension softening model, is needed for correct result of the analyses.
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Engström, Fredrik. "Mineralogical influence of different cooling conditions on leaching behaviour of steelmaking slags." Licentiate thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26246.
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The Swedish steelmaking industry produces large amounts of by-products. In 2006, the total amount of slag produced reached approximately 1 375 000 metric tons, of which 30% was deposited. Due to its strength, durability and chemistry, steel slag is of interest in the field of construction due to it's similarities with ordinary ballast stone. However, some steel slags face an array of quality concerns that might hinder their use. These concerns generally involve the following physical and chemical properties: Volume expansion, Disintegration, Leaching of metals By controlling and modifying process parameters during slag handling in liquid state, the physical properties of steel slags can be adequately modified to obtain a high-quality product for external application. The present work was undertaken as a research project within the Minerals and Metals Recycling Research Centre, MiMeR. The major objectives of this work have been to investigate how different cooling methods and cooling rates influence the properties of slag products. Four types of steel slags, Ladle slag, BOF (Basic Oxygen Furnace) slag and two different EAF (Electric Arc Furnace) slags, were characterized and modified by semi-rapid cooling in crucibles and rapid cooling by water granulation. Experiments were conducted in laboratory scale using an induction furnace. Analysis techniques used in this investigation include: thermodynamic calculations using FactSageTM, X-ray diffraction analyses (XRD), scanning electron microscope (SEM) and a standard leaching test (prEN 12457-2/3). The experimental results show that disintegrating ladle slag is volume stabilized by water granulation resulting in a product consisting of 98% glass. However EAF slag 1, EAF slag 2 and the BOF slag formed only 17%, 1% and 1% glass, respectively. The leaching tests showed that water granulation did not prevent leaching of minor elements from the modified slags. The solubility of chromium, molybdenum and vanadium varied in the different modifications, probably due to their presence in different minerals. Variations in crystal size as well as phase composition and distribution were observed in the different materials as a result of different cooling methods. The magnesium content of the wustite-type solid solution (Fe,Mg,Mn)O in BOF slag increased when rapid cooling was used. The reactivity factor, á, was calculated for the BOF and EAF slag 1. A majority of the elements of interests in the slags became more reactive when cooled rapidly. The reactivity for silica in BOF and EAF slag 1 was increased by ~4700% and ~1200%, respectively, and for chromium by ~5300% and ~1500%.Godkänd; 2007; 20071121 (ysko)
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AlHarras, Omar. "Seismic behaviour and nonlinear modeling of reinforced concrete flat slab-column connections." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54469.
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The contemporary structural design practice of tall buildings typically incorporates a lateral force resisting system, along with a gravity system that often includes reinforced concrete flat slabs. A major challenge with the design of this system is ensuring adequate strength and deformation capacities of the flat slab-column connections, especially when the structure is prone to strong seismic excitations. When a flat slab-column connection is subjected to a combination of gravity and lateral loads, failure may occur in multiple modes. Comprehensive literature reviews of the experimental studies and the analytical models related to reinforced concrete flat slabs, and flat slab-column connections are presented in Chapters 2 and 3, respectively.
The existing nonlinear models that are currently available in literature were developed as assessment tools for old flat-plate structures. Thus, they are not capable of capturing the hysteretic behaviour of ductile flat slab-column connections with shear reinforcement. In Chapter 4, a new nonlinear model for flat slab-column connections is proposed. Utilizing the proposed model allows detecting potential failures due to all the possible modes of failure. The model was verified and calibrated using data from actual experimental studies.
Chapter 5 investigates the effects of flat slabs on the global seismic response of typical high-rise concrete shear wall buildings. Two analytical case studies were conducted using a prototype building designed in Vancouver, Canada. The results from nonlinear dynamic analyses confirmed that including flat slabs in the analysis models of tall buildings is important to obtain accurate estimates of the structural responses and seismic demands. A concise summary of the research outcomes is presented in Chapter 6.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Howlett, Sally Ann. "The biology, behaviour and control of the field slug, Deroceras reticulatum (Müller)." Thesis, University of Newcastle Upon Tyne, 2005. http://hdl.handle.net/10443/1640.
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Deroceras reticulatum (Müller) is the most destructive slug pest of arable crops in Britain. Control on a field scale relies heavily on molluscicide pellets. These are often only partially effective; considerable economic loss and collateral damage still occur. More effective targeting of pellets will depend on accurate predictions of damage severity through a better understanding of population dynamics, reliable estimates of surface activity and behavioural studies to evaluate current control strategies. Lifecycle parameters of D. reticulatum were studied. There was considerable variation in growth even under identical conditions and growth rate was inversely related to survival. For field collected slugs, the association between growth rate and temperature was low but negative for spring hatching individuals; however, this was relatively trivial compared to the high and positive association exhibited by those hatching in autumn. For self-fertilised slugs, egg development took longer and the hatching rate was lower than for slugs laid by field collected adults, but the growth rate was faster. It is suggested that field populations may be composed of fast and slow growers, and that this might be determined by whether eggs are fertilised with auto- or allosperm. An equation was derived to predict female-phase maturity from body weight. Refuge traps sampled approximately one third of the surface active population over a 24 hour period. The timing and number of trap entries and exits did not differ between small and large D. reticulatum. Behavioural studies of D. reticulatum demonstrated that the time elapsed and distance travelled before feeding on bait pellets was shorter when they were broadcast compared to drilled. Soil splash did not reduce pellet efficacy. Trails were more sinuous on fine than coarse seedbeds and were reduced by pellets. The practical implications of these results for assessing and controlling D. reticulatum in arable crops are discussed.
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Haynes, Sarah. "Reproductive behaviour and mating patterns of the field slug Deroceras recticulatum (Muller)." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307935.
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Ma, Charlie. "Aspects of Ash Transformations in Pressurised Entrained-Flow Gasification of Woody Biomass : Pilot-scale studies." Doctoral thesis, Luleå tekniska universitet, Energivetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62914.
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Pressurised entrained-flow gasification (PEFG) of woody biomass has the potential to produce high purity syngas for the production of vital chemicals, e.g., biofuels. However, ash-related issues such as reactor blockages and refractory corrosion need to be addressed before this potential can be realised from a technical perspective. These undesirable consequences can be brought about by slag formation involving inorganic ash-forming elements and the chemical transformations that they undergo during fuel conversion. The objective of this study was to elucidate the ash transformations of the major ash-forming elements and the slag formation process. A pilot-scale PEFG reactor was used as the basis of the study, gasifying different woody biomass-based fuels including wood, bark, and a bark/peat mixture. Different ash fractions were collected and chemically analysed. Reactor slags had elemental distributions differing from that of the fuel ash, indicating the occurrence of fractionation of ash material during fuel conversion. Fly ash particles from a bark campaign were also heterogeneous with particles exhibiting differing compositions and physical properties; e.g., molten and crystalline formations. Si was consistently enriched in the reactor slags compared to other major ash-forming elements, while analyses of other ash fractions indicated that K was likely volatilised to a significant extent. In terms of slag behaviour, near-wall temperatures of approximately 1050-1200 °C inside the reactor were insufficient to form flowing ash slag for continuous extraction of ash material during firing the woody biomass fuels alone. However, fuel blending of a bark fuel with a silica-rich peat changed the chemical composition of the reactor slags and bulk slag flow behaviour was evident. Thermochemical equilibrium calculations supported the importance of Si in melt formation and in lowering solidus and liquidus temperatures of Ca-rich slag compositions that are typical from clean wood and bark. Viscosity estimations also showed the impact that solids have upon slag flow behaviour and corresponded qualitatively to the experimental observations. Corrosion of reactor refractory was observed. The mullite-based refractory of the reactor formed a slag with the fuel ash slag, which caused the former to flux away. Reactor blockages were also resultant because of the high viscosity of this slag near the outlet. A preliminary study into the corrosion of different refractories was also carried out, based on firing a bark/peat mixture. Alumina-rich refractories consisting of corundum, hibonite, mullite, and andalusite tended to form anorthite and exhibited varying degrees of degradation. Infiltration of slag was evident for all the samples and was a severe mode of degradation for some refractories. For fused-cast periclase and spinel-based refractories, slag infiltration was limited to voids and no extensive signs of refractory dissolution were found. This is also supported by a thermochemical equilibrium calculations mimicking slag infiltration that incorporated viscosity estimations. The findings from this thesis contribute towards the development of woody biomass PEFG by highlighting issues concerning ash fractionation, slag behaviours and ash\slash refractory interaction that should be investigated further.
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Keskinkilic, Ender. "Examination Of Desulfurization Behaviour Of Ladle Furnace Slags Of A Low-sulfur Steel." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608978/index.pdf.
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The aim of this research was mainly to investigate desulfurization behaviour of ladle furnace slags of a low-sulfur steel. First, the change of the amount of unstable oxides (FetO and MnO) in slags was studied from the converter till the end of ladle furnace treatment for different steel quality groups. It was found that the change in the amount of unstable oxides could be examined best with low-C steel qualities. Then, the change of activity of iron oxide was investigated for a member of low-C steel quality group, namely 4937K, a low-S steel. The relation between the degree of desulfurization at the ladle furnace, % DeS (measured), and the change in activity of iron oxide, % Decrease in aFetO, was examined first using an empirical expression obtained from literature. Then, this relationship was studied using steel oxygen activity measurements conducted at the ladle furnace. With this method, a regression formula was proposed for 4937K slags relating activity coefficient of iron oxide, gama(FetO), with the major slag components. The results obtained from steel oxygen activities were found to be representative for 4937K steel-slag system showing similar behaviour with the ones from the empirical expression obtained
from literature. Similar results were found using Temkin equation and the polymeric anion model. In relation to formation of less harmful inclusions to suppress adverse effects of sulfur, morphological studies of some steels produced in ERDEMiR plant were performed. D-type globular inclusions with severity values of 1-2 were observed.
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Yan, Ping Yu. "Behaviour of shearhead system between flat reinforced concrete slab and steel tubular column." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/behaviour-of-shearhead-system-between-flat-reinforced-concrete-slab-and-steel-tubular-column(7a3b5496-ca58-4a85-8028-3f64ad0eeddd).html.
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This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate punching shear resistance for a new shearhead system between tubular steel column and reinforced concrete flat slab. This shearhead system enables two of the most popular structural systems, i.e. reinforced concrete flat slab floor and steel tubular column, to be used to produce efficient structures of low cost and short construction time. This research investigates slabs without and with a service hole adjacent to the column. The new shearhead system should not only possess sufficient punching shear resistance, but should also be efficient for construction. The main methodology for this project was based on numerical finite element simulations verified by two full scale tests. These two tests were carried out in the University of Manchester's Structural Testing Laboratory. The two specimens had the same slab size, thickness and reinforcement ratio, but differed in the column shape (rectangular or circular), central reinforcement arrangement (continuous or discontinuous), shearhead position in the slab thickness and shearhead fabrication arrangement. Recorded load-deflection and load-strain relationships, crack development and critical perimeter were used for detailed validation of using the commercial finite element software ABAQUS. The validated ABAQUS model was used to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of varied column size, shearhead arm length, shearhead arm cross section, shearhead arm angle, amount of flexural reinforcement, slab thickness, shearhead positions and hole positions. The main conclusion from the parametric study was that the shearhead system could be treated as an enlarged column in normal flat slab structure. The parametric study enabled pressure distribution below the shearhead arms to be approximated for checking whether the shearhead arms would be sufficient for the enlarged column assumption to be valid. The parametric study results were also used to determine the effective depth of the flat slab and critical punching shear perimeter of the slab with and without a service hole.Using the enlarged column assumption, the punching shear resistance of all structures used in the parametric study were re-calculated using Eurocode 2 (EC2), British stand 8110 (BS8110) and American Concrete Institute code 318 (ACI 318). Comparison of calculation results using these three design methods indicates that both EC2 and BS8110 predicted very close value which reached very good agreement with the ABAQUS simulation (normally within 10%). Among these three design methods, ACI 318 was the only code that explicitly considered shearhead system. ACI 318 was not able to predict the slab critical perimeter length with good accuracy, however, its prediction of slab punching shear resistance achieved reasonably good agreement with numerical analysis results and were on the safe side. Based on these studies, a design method for calculating punching resistance of the proposed shearhead system between reinforced concrete flat slab and steel tubular column has been developed in this thesis.
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Gowacki, William Alan. "Taxonomy, Ecology, and Behavior of the Kleptoplastic Sea Slug Elysia papillosa." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6848.
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Sacoglossan sea slugs are one of the best known examples of specialist herbivores in the marine environment and can be found strongly associated with their algal hosts and food sources. Perhaps the most intriguing characteristic of many sacoglossans is their ability to sequester functional chloroplasts from their algal food sources in a process called kleptoplasty. Despite this, there continues to be issues regarding taxonomic identification of species. In turn, the ecological characteristics of many of these slugs, such as algal host and food source preference, as well as their behavioral aspects, have received little attention. A prime example of these issues arises in one such kleptoplastic sacoglossan found at Sunset Beach, Tarpon Springs, USA. The slug had previously been identified as Elysia patina based on a recent description, but later evidence suggested this was incorrect. Furthermore, despite the evidence found for the slug’s photosynthetic capabilities, little was known of its ecological relationships and behavior. The purposes of this study were to: 1) correct the uncertain taxonomy of the Tarpon Springs slug previously identified as Elysia patina, and 2) explore the ecological and behavioral characteristics of the slug.
First, a comparative study was performed between the Tarpon Springs slug and its original description, as well as descriptions for the superficially-similar congener slug, Elysia papillosa. The gross anatomy, dorsal surface vascular morphology, radular morphology, egg mass morphology, and developmental timeline of the Tarpon Springs slug were used as means of comparison with the previous descriptions. The results of the comparison show that the Tarpon Springs slug was in fact E. papillosa rather than E. patina, and that the most recent description used to identify the slug as E. patina was incorrect and should not be used. Second, a descriptive study of the ecological and behavioral aspects of E. papillosa at the Sunset Beach site were performed. From October 2014 to September 2015, bi-weekly algal collections were made to determine the seasonal abundance of the slug and a possible relationship between slug abundance and algal abundance. Next, a second collection study was performed bi-monthly from April to July 2016 to identify the preferred algal host of E. papillosa between the three most abundant rhizophytic algae at the site, Penicillus capitatus, Penicillus lamourouxii, and Halimeda incrassata, all of which have been previously reported as being hosts of E. papillosa.
The results of these studies showed no relationship between slug abundance and algal abundance, however E. papillosa was found to have a seasonal population fluctuation, with the fewest slugs found in winter and summer months and the most slugs found in the spring and fall months, especially in April and May. Elysia papillosa was also found in significantly higher numbers on the alga P. capitatus compared to the other two algal species, although some slugs were found on P. lamourouxii. Only one slug was found on H. incrassata, indicating it is not being used as a host despite previous reports. Further exploration into the genetics of sequestered chloroplasts would provide critical details into E. papillosa’s feeding behavior in situ. Lastly, because of E. papillosa’s photosynthetic abilities, an experiment was performed to determine if E. papillosa exhibited phototactic behavior. Fully-fed slugs were found to have no preference for either light or dark conditions, indicating their behavior was not being influenced by their photosynthetic abilities. This information provides a means of comparison with future studies of the phototactic behavior of kleptoplastic slugs, and could provide insight into how the longevity of functional chloroplasts in each species of slug could influence their behavior.
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Park, Hae-geun. "MECHANICAL BEHAVIOR OF REINFORCED CONCRETE SLAB RETROFITTED WITH CARBON FIBER SHEET." Kyoto University, 2000. http://hdl.handle.net/2433/157080.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第8355号
工博第1920号
新制||工||1170(附属図書館)
UT51-2000-F259
京都大学大学院工学研究科土木システム工学専攻
(主査)教授 小野 紘一, 教授 田村 武, 教授 宮川 豊章
学位規則第4条第1項該当
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Huang, Da. "Structural behaviour of two-way fibre reinforced composite slabs." University of Southern Queensland, Faculty of Engineering and Surveying, 2004. http://eprints.usq.edu.au/archive/00001450/.
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Innovative new flooring systems utilising lightweight fibre reinforced polymer composite materials may have the significant potential to offer both economic and performance benefits for infrastructure asset owners compared to conventional concrete and steel systems. Over recent years, a range of prototype floor systems using fibre reinforced polymer composites have been developed by researchers at the University of Southern Queensland. However before such structural systems can be widely adopted by industries, fundamental understanding of their behaviour must be improved. Such work will allow for the development of new design and analysis procedures which will enable engineers to efficiently and accurately design and analyse such structures. This dissertation presents an investigation into a new two-way fibre reinforced composite floor slab system. The proposed new two-way slab system is, in essence, a sandwich structure with an innovative hollow core made from a castable particulate filled resin system. The key focus of this dissertation is the development of a new analysis tool to analyse the two-way fibre reinforced composite slab and facilitate subsequent parametric studies into slab configurations for concept refinement. The detailed 3D finite element analyses and experimental investigations are performed to verify the new analysis tool, and provide more detailed insight into the structural behaviour of this new two-way fibre reinforced composite slab. Comparisons with detailed 3D FEA and experiments illustrate that the simplified analysis tool is capable of providing sufficient accuracy for the preliminary analysis of a slab structure. Moreover, the 3D finite element analyses agree well with the experiments, and it is concluded that the behavioural responses of the proposed new slab structure can be reliably predicted. The experimental results show that this new slab concept exhibits quite a robust static behaviour and is likely to have a robust fatigue performance.
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De, Vittorio Stefano. "Time-dependent behaviour of reinforced concrete slabs." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3247/.
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In this thesis is studied the long-term behaviour of steel reinforced slabs paying particular attention to the effects due to shrinkage and creep. Despite the universal popularity of using this kind of slabs for simply construction floors, the major world codes focus their attention in a design based on the ultimate limit state, restraining the exercise limit state to a simply verification after the design. For Australia, on the contrary, this is not true. In fact, since this country is not subjected to seismic effects, the main concern is related to the long-term behaviour of the structure.
Even if there are a lot of studies about long-term effects of shrinkage and creep, up to date, there are not so many studies concerning the behaviour of slabs with a cracked cross section and how shrinkage and creep influence it. For this reason, a series of ten full scale reinforced slabs was prepared and monitored under laboratory conditions to investigate this behaviour. A wide range of situations is studied in order to cover as many cases as possible, as for example the use of a fog room able to reproduce an environment of 100% humidity.
The results show how there is a huge difference in terms of deflections between the case of slabs which are subjected to both shrinkage and creep effects soon after the partial cracking of the cross section, and the case of slabs which have already experienced shrinkage effects for several weeks, when the section has not still cracked, and creep effects only after the cracking.
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Ho, S. L. "An investigation into the behaviour of hollow ribbed (waffle) rectangular reinforced concrete slabs at ultimate limit state." Thesis, University of Abertay Dundee, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234752.
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ElGendy, Mohammed. "Punching shear behaviour of slab-column edge connections reinforced with fibre-reinforced polymer (FRP) composite bars." Canadian Society of Civil Engineering, 2014. http://hdl.handle.net/1993/24092.
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The use of fibre reinforced polymer (FRP) composites as an alternate to steel has proved to be an effective solution to the corrosion problem. However, FRP bars have low axial and transverse stiffness compared to steel bars which results in a lower shear capacity of FRP reinforced concrete (RC) elements compared to steel-RC elements.
Flat plate systems are commonly used to take advantages of the absence of beams. They, however, are susceptible to punching shear failure where the column suddenly punches through the slab.
An experimental program was conducted to investigate the punching shear behaviour of slab-column edge connections. Nine isolated full-scale slab-column edge connections were constructed and tested to failure. One connection was reinforced with steel flexural reinforcement, six with GFRP flexural reinforcement and two with GFRP flexural and shear reinforcement. The parameters investigated were the flexural reinforcement type and ratio, the moment-to-shear ratio and the shear reinforcement spacing.
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Hogan, J. M. "The behaviour of the grey field slug, Deroceras reticulatum (Muller), with particular reference to control in winter wheat." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356806.
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Dodds, Catherine Jane. "The action of naturally-occuring semiochemicals on feeding behaviour and neurophysiology of the field slug Deroceras reticulatum (Mueller)." Thesis, University of Portsmouth, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310443.
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BELTRAO, ALLYSON JOSE DO NASCIMENTO. "STRUCTURAL BEHAVIOUR OF COMPOSITE SLAB WITH CORRUGATIONS IN THE COLD FORMED SECTION PROFILES WEB." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4370@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta um estudo de um sistema de laje mista com o uso de perfis metálicos de chapa dobrada com corrugações na alma e chapa de vedação lateral com mossas seqüencialmente dispostos lado a lado e preenchidos com concreto armado. A principal motivação para este estudo foi o desenvolvimento de um eficiente sistema de laje de rápida construção. O sistema de laje desenvolvido maximiza o espaço livre útil da construção, eliminando a necessidade de formas e escoras tendo assim como conseqüência direta a minimização das perdas construtivas. Este trabalho é iniciado com uma avaliação da forma ideal dos perfis de chapa dobrada de acordo com as suas características estáticas e dinâmicas. Variáveis como peso, altura, espessura, tensão de escoamento, vão máximo, e carga suportada foram estudadas. Além disso foi feito um estudo para confecção das ferramentas de fabricação das corrugações e mossas na alma do perfil e na chapa de vedação lateral de forma eficiente e econômica. Após definição e otimização da seção do perfil metálico, foi efetuado um estudo experimental composto de uma série de três testes em escala real. O objetivo principal dos testes experimentais foi de comprovação dos resultados teóricos de resistência ultima da laje mista com perfis corrugados na alma e efetuar uma comparação com o sistema de laje previamente proposto por Takey. Os testes demostraram a real aderência entre concreto e perfil metálico e sua influência nos estados limites últimos de flexão, cisalhamento e deslizamento. Ensaios tipo push-out também foram executados para estabelecer a carga ultima de deslizamento na interface aço/concreto. A fase final compreendeu a comparação dos resultados experimentais com as normas de projeto de laje mista e com o trabalho desenvolvido por Takey para validação e comparação de resultados do sistema de laje mista.
This work presents an investigation of a composite slab system made of cold formed section profiles with web corrugations and corrugated steel deck plates spanning between suck profiles, both acting compositely with concrete slab cast in place. The main motivation for this work was the development of an efficient slab system associated with easy and fast erection procedures. The proposed slab system also maximises the construction usable space, eliminating the use of temporary propping and, consequently reducing the final construction cost. This work initiates with an evaluation of the ideal cold- formed steel profile geometry according to its static and dynamical characteristics. Variables like weight, height, thickness, yield stress, and collapse load were considered. Additionally, a study of the more suitable fabrication tools to be used in the process of incorporating the corrugations to the profile webs and deck supporting plates was executed. With the optimum steel profile in hand, an experimental investigation of three full scale composite slabs, spanning three meters, was conducted. The main objective of these tests was to access the ultimate limit states associated with the proposed composite slab system and compared it to a previously proposed solution, developed by Takey. The tests made possible the evaluation of the concrete versus steel slippage resistance when compare to the other ultimate limit states associated with flexion and shear. The adopted solution, despite the natural chemical bond present in the steel/concrete interface, enhances its performance due to the action of the web profile corrugations. Push-out tests were also executed to enable the determination of the ultimate slippage load in the steel/concrete interface due to the presence of the proposed corrugations. The final stage of this investigation concerned the comparison of the experimental data to the current composite design standards, and to the previous system, developed by Takey, in order to validate its use.
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Armsworth, Clare Gillian. "Influence of a carabid beetle predator on the behaviour and dispersal of slug pests." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55967/.
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It is becoming increasingly recognised that natural enemies in arable land, particularly polyphagous predators such as carabid beetles, may help to suppress populations of pests, and that appropriate management of such predators may lead to a satisfactory level of pest control. Previous work has shown that a polyphagous carabid predator, Pterostichus melanarius, is capable of affecting the spatial and temporal dynamics of slug pest populations. This project is an examination of how P. melanarius affects the survival, behaviour and dispersion of two important slug pests, Deroceras reticulatum and Arion intermedins, and how this information applies to spatial and temporal data previously obtained from the field. Deroceras reticulatum, but not Arion intermedius, elicited a variety of anti-predator behaviour in the presence of substrates previously exposed to the predator. The movements of slugs in arenas, incorporating a zone containing paper upon which the predatory beetles had previously been maintained and a control zone, were recorded at intervals. Significantly more slugs of all the size classes tested accumulated on the control half of arenas after 24 hours, with small slugs being quickest to respond. Slugs avoided paper exposed to both male and female beetles. Slugs also avoided paper exposed to another predatory carabid, Pterostichus madidus, but not to Harpalus affinis, a phytophagous carabid. Slugs did not respond to paper that had been exposed to beetles and then stored for five days prior to the test. Changes in parameters of movement of slugs when in the presence of P. melanarius chemicals were detected using a video-tracking system. These changes are consistent with a kinesis that would enable slugs to rapidly escape from areas where beetles were recently present. Despite this no changes in the rate of dispersion of D. reticulatum juveniles was detected in mini-plots previously exposed to P. melanarius. However, adult D. reticulatum reduced feeding and egg-laying and increased refuge on soil previously exposed to P. melanarius. Chemicals on the exterior of P. melanarius were isolated and two compounds were found to reduce feeding by D. reticulatum on leaf discs compared to control discs. One of these chemicals is currently being analysed using mass spectroscopy and NMR to determine it's structure and identity. It was concluded that D. reticulatum have evolved behavioural responses to chemical cues from either this generalist carabid predator in particular, or carabid beetles generally, many species of which include molluscs in their diets. During a video-tracking study of beetle movements, some evidence was found for the detection and response of beetles to slug mucus, and amputation work suggested that the palps may be important in slug detection. Previous feeding experience was found not to influence prey choice in P. melanarius during a food choice experiment, with beetles always selecting a mixed diet when offered. Analysis of spatial data showed that slug size, but not beetle sex, was important in the spatial relationship between the predator and the prey, and this agrees with results from the laboratory experiments of slug behaviour. This work has added to the evidence provided by other studies that some generalist predators can have significant effects on the dynamics of pest populations and therefore may become useful biocontrol agents for pests if effectively managed. The implications of this work in the field of predator-prey ecology and for the efficacy of P. melanarius as a biological control agent of slugs are discussed.
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Engström, Fredrik. "Mineralogical influence of different cooling conditions on leaching behaviour of steelmaking slags : a laboratory investigation /." Luleå : Luleå University of Technology, 2007. http://epubl.ltu.se/1402-1757/2007/58/.
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VIEIRA, JANINE DOMINGOS. "THEORETICAL-EXPERIMENTAL BEHAVIOR STUDY OF COMPOSITE DECK-SLAB WITH INCORPORATE FORMED STEEL SHAPE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3717@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEsta dissertação apresenta um novo tipo de laje mista com uso de perfil de chapa dobrada incorporada. O perfil substitui as barras de aço, a fôrma e as escoras. O sistema estrutural construído consistiu em uma laje mista com perfil C enrijecido preenchido com concreto estrutural. Foram realizados dez testes experimentais em que foram analisados os momentos positivos, os momentos negativos e a influência de séptos. Através da análise teórico-experimental, foi possível perceber a grande influência dos séptos na resistência das lajes mistas testadas.
This work presents a new type of composite deck-slab using incorporate formed steel profiles. The steel profile replaces the reinforcement bars, the form and charry system. The structural system is built by one composite deck-slab with C stiffness steel profile, filed with reinforced concrete. It was performed ten tested and it was analyzed the positive moments, the negative moments and the influence of the diaphragm. Analizing the results it was possible to realize the great influence of the diaphragm over the resistence of composite deck slab tested.
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Ismail, Eman. "Distribution of stresses and displacements in skewed concrete slabs." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66839.
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A 3D nonlinear finite element analysis was developed for simulating the behavior of skewed concrete slabs and to identify the response of the slab with different angles and element sizes. The purpose of this research is helping the engineering and construction industry to utilize the FEM study and results more in different structural applications.Simulations performed in ABAQUS for skewed slabs are also compared to straight and skewed slabs according to the analytical formulation by Timoshenko.The result showed that when the distance increases, the load capacity measured by reaction forces decreases for all different skew angles except angle 0° and 15° which show a stable reaction force along the entire path. .The study reveals that depending on the skew angle and the element size, the stress distribution and vertical displacements in the slab vary significantly from those in a straight slab. It is shown that the displacement decreases with the increase of the skew angle while the stresses increase with the decrease of the skew angle.There are small differences in the vertical displacements and stress distribution between the results obtained by this study and the results obtained by Timoshenko regarding the plates with skews of 0°, 30° and 45°.
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Pawlowicz, Jakub. "Evaluation of air entraining behaviour in concrete using computer aided methods on hardened samples." Thesis, KTH, Betongbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264752.
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Increasing awareness of sustainability in the concrete industry forces structural design and executionto focus on avoiding costly and unpredictable maintenance action, instead paying higher attention todamage prevention by direct actions on early stages of production. One of such approaches, whichdeals with the problem of freezing and thawing deterioration, is intentional air bubble introductionto the concrete mix. However, the mechanism of air entrainment in concrete can be negativelyaffected on different stages of production by many factors including cement type, admixture dosage,casting conditions or mixing procedure. Therefore, reliable tools for the end-product evaluationought to be considered. The experimental study, presented in this work, focuses on understandingthe blast furnace slag (BFS) influence as well as admixtures’ dosage effect on pore structure ofhardened concrete. Three types of cement were evaluated, including ordinary portland cement(OPC) and two types of CEM III cements with different BFS percentage. The optimal amountsof air entraining agent (AEA) and super plasticizer (SP) were chosen and later reduced in orderto evaluate their impact on total air content, spacing factor and specific surface of the air voids.The main method chosen for this evaluation was the use of an office flat-bed scanner to acquireimages and application of BubbleCounter software for the analysis of the air void structure. Thisapproach is based on linear traverse method and requires special surface treatment for contrastenhancement. Specimens for the analysis were cut from hardened concrete cubes and polishedto achieve a flat surface. The samples were later treated with black ink and zinc oxide paste toachieve a clear contrast between white voids and black paste/aggregate area. In order to estimatethe accuracy of this method, more conventional tools such as pressurised gauge method and air voidanalyser were applied for comparison. Resulted mixtures showed significant differences in air voidproperties between OPC and BFS containing concrete, with the latter being less affected by AEAdosage reduction. Changes in spacing factor and specific surface were also registered; however,their deterioration did not follow the same pattern as that of total air content. No significantdeviation between the two cements containing BFS was observed. An interesting effect of the usedpolycarboxylate ether SP on the AEA reactivity was registered, showing deterioration of air voidproperties with the decrease of plasticizer amount. Comparison of the results from different air voidanalysis methods, suggested an overall agreement on the measured air void system changes due tochanging the AEA content. However, the BubbleCounter software tended to slightly overestimatethe material’s resistance to freeze and thaw phenomenon, giving the most optimistic values inspacing factor and specific surface of air voids.Betongindustrins ökande medvetenhet om hållbarhet leder till att man inom dimensionering ochutförande fokuserar mot att undvika kostnadskrävande och oförutsedda underhållsåtgärder ochistället lägga större vikt på att förebygga skador i produktionens tidiga skeden. En av dessaåtgärder, som hanterar problemet frostnedbrytning, är en medveten inblandning av luftbubblor ibetongen. Mekanismen för att skapa luftporssystemet kan emellertid bli negativt påverkad underolika skeden av produktionen av många faktorer såsom cementtyp, tillsatsmedelsdos, gjutvillkoroch blandningsordning. Därför behöver man reflektera över pålitliga verktyg för utvärderingenav slutprodukten. Den experimentella studien, som presenteras i detta arbete, fokuserar motförståelse hur slagg och tillsatsmedelsdos påverkar den hårdnade betongens luftporssystem. Tretyper av cement utvärderades, dels ett normalt portlandcement, dels två typer av CEM III-cementmed olika andelar av slagg. Optimala mängder av luftporbildare och flyttillsatsmedel valdesmen reducerades senare för att undersöka deras inverkan på totalt luftinnehåll samt luftporernasavståndsfaktor och specifika yta. Den huvudsakliga metoden som valdes för denna utvärderingvar en flatbäddsscanner (kontorsmodell) för att ta bilder och användningen av en programvaravid namn BubbleCounter för att analysera luftporssystemet. Detta tillvägagångssätt baseras påanalys av tvärgående linjer och kräver en speciell behandling av ytan för att åstadkomma kontraster.Provkroppar för analysen sågades ut ur hårdnade betongkuber och polerades för att erhålla en jämnyta. Provkropparna var senare behandlade med svart bläck och zinkoxidpasta för att åstadkomma entydlig kontrast mellan de vita porerna och den svarta ytan av cementpasta och ballast. För att studeranoggrannheten hos denna metod användes som jämförelse även mer konventionella metoder sommätningar med trycksatta givare och luftporsanalys. De framtagna blandningarna visade signifikantaskillnader i luftporernas egenskaper mellan betong med normalt portlandcement och betong medslaggcement, där den senare påverkades i mindre grad av reduktioner i dosen luftporbildare.Förändringar I avståndsfaktor och specifik yta noterades också men försämringen följde inte sammamönster som den för totala luftinnehållet. Ingen signifikant skillnad mellan de två cementeninnehållande slagg kunde observeras. En intressant inverkan av det använda polykarboxylateterbaseradeflyttillsatsmedlet på luftporbildarens reaktivitet noterades. Den visade en försämringav luftporernas egenskaper vid en reduktion av mängden flyttillsatsmedel. En jämförelse avresultaten från de olika metoderna för luftporsanalys indikerade en övergripande överensstämmelsegällande de uppmätta luftporssystemens förändring p.g.a. förändringar i mängden luftporbildare.Programvaran BubbleCounter tenderade emellertid att något överskatta materialets motstånd motfrostnedbrytning med de mest optimistiska värdena för luftporernas avståndsfaktor och specifikayta.
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Assis, Andre N. "The Phosphorus Reaction in Oxygen Steelmaking: Thermodynamic Equilibrium and Metal Droplet Behavior." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/464.
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Low phosphorus content steels are essential for steel applications where high ductility is required, such as thin sheets, deep drawn, pipelines and automobile exteriors. In the past, phosphorus control was not considered a big challenge in steel production in the US because iron ores with low phosphorus contents were readily available and considered cheap. However, in the last decade, the iron ore price has risen by roughly 400% and lower cost iron sources generally have higher phosphorus content. In integrated steel plants, phosphorus removal usually takes place during the oxygen steelmaking process (OSM) but in Japan a intermediate step for hot metal dephosphorization is commonly used. There are various types of OSM furnaces but the most widely used remains the top-blown Basic Oxygen Furnace (BOF). The BOF slag can be recycled to a sinter plant or directly to the blast furnace, ultimately increasing the phosphorus input in the process. In order to meet new demands for phosphorus control, it is necessary to improve our understanding on the thermodynamics and kinetics of the phosphorus partitioning reaction between slag and metal melts during steelmaking. Therefore, the present work has been divided in three strongly correlated sections: phosphorus equilibrium between metal and slag; analysis of plant data; and observations of the reaction kinetics. Phosphorus equilibrium between liquid metal and slag has been extensively studied since the 1940's. It is well known that CaO and FeO are the main slag constituents that help promote dephosphorization. On the other hand, dephosphorization decreases with temperature due to the endothermic nature of the reaction. Many correlations have been developed to predict the phosphorus partition ratio as a function of metal and slag composition as well as temperature. Nevertheless, there are still disagreements in the laboratory data and the equilibrium phosphorus partition can be predicted with an uncertainty of a factor of up to 5. The first part of the present work focuses on generating more reliable equilibrium data for BOF-type slags by approaching equilibrium from both sides of the reaction. The experimental results were combined with two other sets of data from different authors to produce a new correlation that includes the effect of SiO2 on the phosphorus partition coefficient, LP . Although the quantification of phosphorus equilibrium is extremely important, most industrial furnaces do not operate at equilibrium, usually due to liquid slag formation, kinetics and time constraints. Thus, it is important to know how close to equilibrium different furnaces operate in order to suggest optimal slag compositions to promote dephosphorization. The present work analyzed four large sets of data containing the chemical compositions of both slag and metal phase as well as the tapping temperature of each heat. Each set of data corresponded to different furnaces: one AOD (Argon Oxygen Decarburization), two top-blown BOFs and one Q-BOP or OBM. It was found that the bulk slag composition can greatly \mask" the data due to solid phases coexisting with the liquid slag. The author used the software package FactSage to estimate the amount of solids in the slag and liquid slag composition. It was found that the AOD is the reactor closest to equilibrium, followed by the Q-BOP (OBM) and the two top-blown BOFs. It was noted that the stirring conditions and slag composition are two key variables to enable optimum phosphorus removal. Also, over saturating the slag with CaO and MgO does not seem to benefit the process to any extent. Lastly, interesting observations on the behavior of small metal droplets reacting with slag are presented and discussed. It was found that dynamic interfacial phenomena at the metal-slag interface is likely to play a significant role in the kinetic behavior of the system, due to the exchange of surface active elements, such as oxygen, which dramatically lowers the interfacial tension and cause spontaneous emulsification. Although this phenomenon has been studied, actual quantification of changes in interfacial area remain a challenge. The author developed an experimental method to enable better quantification of spontaneous emulsification and two sets of experiments were carried. One with an Fe containing 0.2 wt.% P and another in a P-free system where pure iron was oxidized. It was found that phosphorus did not play a role in spontaneous emulsification and it was rapidly removed before the onset of dynamic interfacial phenomena. Emulsificaion was maybe caused by de-oxidation of the metal after phosphorus removal took place and the metal became super saturated with oxygen by an unknown reason. The estimated surface area rapidly increases by over an order of magnitude during the beginning and intermediate periods of the reaction. The metal drop breaks into hundreds of small droplets, effectively emulsifying the metal into the slag. With time, the surface area decreases and the metal droplets coalesce. Similar results were observed for an Fe droplet being oxidized. Spontaneous emulsification takes place regardless of the direction of oxygen transfer and the changes in surface area are similar for both cases. The last chapter describes the industrial relevance of the present work, summarizes the findings, revisits the hypotheses and presents potential future work where further research is encouraged.
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Pieraccini, Luca. "Shear behaviour of reinforced cconcrete slab under concentrated load: an investigation through non-linear and sequentially linear analysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5902/.
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The assessment of safety in existing bridges and viaducts led the Ministry of Public Works of the Netherlands to finance a specific campaing aimed at the study of the response of the elements of these infrastructures. Therefore, this activity is focused on the investigation of the behaviour of reinforced concrete slabs under concentrated loads, adopting finite element modeling and comparison with experimental results.
These elements are characterized by shear behaviour and crisi, whose modeling is, from a computational point of view, a hard challeng, due to the brittle behavior combined with three-dimensional effects.
The numerical modeling of the failure is studied through Sequentially Linear Analysis (SLA), an alternative Finite Element method, with respect to traditional incremental and iterative approaches. The comparison between the two different numerical techniques represents one of the first works and comparisons in a three-dimensional environment. It's carried out adopting one of the experimental test executed on reinforced concrete slabs as well.
The advantage of the SLA is to avoid the well known problems of convergence of typical non-linear analysis, by directly specifying a damage increment, in terms of reduction of stiffness and resistance in particular finite element, instead of load or displacement increasing on the whole structure
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For the first time, particular attention has been paid to specific aspects of the slabs, like an accurate constraints modeling and sensitivity of the solution with respect to the mesh density. This detailed analysis with respect to the main parameters proofed a strong influence of the tensile fracture energy, mesh density and chosen model on the solution in terms of force-displacement diagram, distribution of the crack patterns and shear failure mode.
The SLA showed a great potential, but it requires a further developments for what regards two aspects of modeling: load conditions (constant and proportional loads) and softening behaviour of brittle materials (like concrete) in the three-dimensional field, in order to widen its horizons in these new contexts of study.
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Khan, Akram. "Composite Behaviour of Normalweight and Lightweight Concrete Panels With Partially Embedded Light-Gauge Steel Channels." Thesis, University of New Brunswick, 2010. http://hdl.handle.net/1882/1092.
Full textAbstract:
This research investigates prefabricated light-gauge steel and concrete panels using
reliable and commercially viable shear connectors. An analytical and experimental
investigation was undertaken to study the flexural behaviour of light-gauge steel and
concrete composite panels under uniform pressure. Normalweight and lightweight
concrete panels were fabricated by embedding 16-gauge 41 mm x 203 mm steel channel
sections (running parallel to each other) to a depth of 38 mm into a 64 mm thick
concrete slab. Push-out tests were also conducted to evaluate the efficiency of three
types of shear connection mechanism; natural surface bonding, predrilled holes, and
punched holes. Only two types of shear connectors (predrilled holes and punched holes)
were used in the full-scale panel specimens.
Results show that the predrilled holes and punched holes provide full shear transfer
between the steel and concrete. The ultimate load carrying capacity of the lightweight
concrete panels exhibited similar behaviour to the normalweight concrete panels. All the
panels exhibited good load carrying capacity and ductility, and satisfied the
serviceability limit state of deflection. Thus, the proposed panels present a potential for
a commercially viable composite floor system for building construction utilizing a
maximum span of 2330 mm.
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Benichou, Noureddine. "Behavior of composite slab-on-girder and box girder bridges at inelastic and ultimate limit states." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5290.
Full text
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Middlebrooks, Michael Louis. "Consequences of Kleptoplasty on the Distribution, Ecology, and Behavior of the Sacoglossan Sea Slug, Elysia clarki." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4162.
Full textAbstract:
The sacoglossan sea slug Elysia clarki is able to photosynthesize for three to four months using chloroplasts sequestered from its algal food sources. Furthermore, the slug is able to store multiple chloroplasts from different algal species within the same cell. This research, consisting of several related studies, explores the role that provision of organic nutrients via photosynthesis plays in the biology of the slug. The first chapter demonstrates that, under conditions of starvation, photosynthetic activity in E. clarki remains fully functional for one month after which it then declines. During the first month of starvation the slug exhibits similar feeding behavior as slugs provided a continuous supply of food, suggesting that photosynthesis delays the onset of starvation-induced behavioral changes. The second chapter explores E. clarki's spatial relationships with algae known to be food sources in the field. In areas with high slug density, edible algal populations were very low. DNA barcoding was employed to demonstrate that the algae found near slugs were poor predictors of which foods were actually consumed by slugs. Generally, there was a mismatch between algae available in the field and slug diets. The third chapter explores how E. clarki is able to maintain photosynthesis. After labeling with a C14 ALA incubation process, then chlorophyll was extracted from slugs and purified using HPLC. Results indicate that recently collected E. clarki are able to synthesize chlorophyll, whereas slugs starved for 3 months were not. Photosynthesis plays a very important role for E. clarki and its relationships with food algae.
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Chang, Ming-Fung, and 張明峰. "A Study of the Mechanical Behaviors of Blast Furnace Slag and De-Sulphurized Slag." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/09744532746748695688.
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Zheng, Yong Chu. "Shrinkage behaviour of geopolymer." 2009. http://repository.unimelb.edu.au/10187/7157.
Full textAbstract:
Geopolymer cements offer an alternative to, and potential replacement for, ordinary Portland cement (OPC). Geopolymer technology also has the potential to reduce global greenhouse emissions caused by OPC production. There is already a considerable amount of work and research conducted on geopolymers in the past decades, and it is now possible to implement this technology commercially. However, to ensure that geopolymer becomes commercially available and able to be used in the world, further understanding of its ability to provide durable and long lasting materials is required. One main property which is still relatively unexplored compared to other properties is its shrinkage properties. The objective of this thesis is therefore to examine the shrinkage of geopolymers and factors which might influence it.The factors which influence geopolymer strength were investigated as being the factors which may influence shrinkage. The selection of the activating solution is an important factor in forming the final product of a geopolymer. Activating solution SiO2/Na2O ratio is determined to be an important influence on the shrinkage of geopolymer. SEM images of the samples enable observation of the sample topology and microstructure. An important observation was the existence of a ‘knee point’ which also occurs in OPC shrinkage. The ‘knee point’ is the point where the shrinkage goes from rapid shrinkage to slow shrinkage. From SEMs it is noted that the samples past the knee point are shown to have a smoother topology which means it is more reacted.
Autogenous shrinkage is an important issue for OPC containing a high amount of silica, and is also a key factor in geopolymer shrinkage. Autogenous shrinkage is tested by keeping samples in a sealed environment where water lost to drying is kept to a minimum. It is noted that sealing and bagging the samples reduces the shrinkage considerably. The water to cement ratio, which is an important factor in OPC shrinkage, is also explored for the case of geopolymers. Water content plays an important role in determining early stage shrinkage, and has little to no effect on the later stage shrinkage. The water loss from the samples during drying on exposure to environment is noted and compared. The addition of more water did not necessary means that more water was lost.
Addition of slag is known to be beneficial to geopolymers by giving early structural strength and faster setting time. Commercial geopolymer concrete will also include the use of slag. However, the addition of slag up to a certain extent gives a deleterious affect on shrinkage.
A different type of Class F fly ash source with different composition data was used to see its effect on shrinkage, with only a slight influence observed between the two ashes tested. Fly ash was also ground for different lengths of time before use in geopolymerization, with grinding for less than 12 hours giving higher shrinkage than an unground sample, but shrinkage the decreasing with grinding for 18 or 24 hours. This initial higher shrinkage has been attributed to the mechanism of grinding which resulted in unevenly shaped fly ash particles taking up a larger initial volume resulting in higher shrinkage. The sample grinded for 24 hours showed higher shrinkage due to the particle size to be so fine that agglomerates may have form during mixing which would result in a lower reaction rate which increases the shrinkage. Elevated curing temperatures also reduce geopolymer shrinkage.
Thus, it is clear that the shrinkage of geopolymers is influenced by a wide range of variables, and more notably by a few important variables: activating solution ratio, addition of water, grinding and bagging. The shrinkage of geopolymers can be correlated to the strength to a certain extent. However, the understanding of the shrinkage of geopolymers is still at a very initial phase, and further research is required.