In well cementing, the cement slurry is exposed to the conditions far different than those of ordinary Portland cement (PC) used in construction. After placement, hardened cement paste should preserve integrity and provide zonal isolation through the life of the well. American Petroleum Institute (API) Class G cement is the most common cement type used in various well conditions. Class G cement has a high degree of sulfate resistance which makes it more stable than PC when subjected to the compulsive well conditions. Ground granulated blast furnace slag (GGBFS) blended cement has a long history of use in the construction industry, but is not extensively used in well cementing applications. This study presents an experimental program to investigate the applicability of CEM I and GGBFS blended cement pastes in the well cementing industry. Class G cement and blends of CEM I and GGBFS with the proportions (80:20), (60:40), (40:60) and (20:80) are prepared with same water/cement ratio (0.44) as restricted for Class G cement in API Specification 10A to be tested. The cement pastes are cured for ages of 1 day, 7 days and 28 days at 80

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

Slurry walls have been widely used for more than 25 years to control the migration of contaminants in the subsurface. In the USA, vertical barriers are mostly constructed of soil-bentonite using the slurry trench method of construction. In this method, sodium bentonite is mixed with water to form a viscous slurry that is pumped into a trench during excavation to maintain the trench stability. The stable trench is then backfilled with a mixture of soil and slurry having a consistency of high slump concrete. These barriers have been designed primarily for low permeability, generally less than 10&minus / 9 m/s. Some investigations have pointed toward improved performance using admixtures that would provide low permeability. In this study, Soma thermal power plant fly ash, granulated blast furnace slag, lime, and steel slag are used as admixture to improve the performance of slurry walls. Permeability, compressive strength, slump, compressibility properties of the mixtures were found and checked for the minimum requirements. According to the findings of this study, granulated blast furnace slag (GGBS), fly ash and steel slag can be used at certain percentages and curing periods as additive in cement-bentonite barrier wall construction. Permeability of specimens having fly ash decreases by increasing fly ash content. Mixtures having 50 % of GGBS type I with 5 % of lime and 9% bentonite content gave acceptable results in 28 days of curing time. Specimens including 50 % of GGBS type II with 5 % of lime and 9% bentonite content gave the higher permeability value in 28 days of curing time with respect to GGBS type I. In addition, most of the mixtures prepared by steel slag gave the acceptable permeability values in 28 days of curing period. Unconfined compressive strength of all mixtures increase by increasing curing time. Cc, Cr, Cv, kcon values were found from consolidation test results. Permeability values found from consolidation tests are 10 times to 100 times higher than flexible wall k results for the same effective stress of 150 kPa. Generally, mv values are decreasing with increasing curing time. As mv decreases, D increases.

<p>The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle</p><p>treatment.</p><p>The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment.</p><p>Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al₂O₃-CaO-MgO-SiO₂and showed a continuous composition change throughout the ladle refining process, from high Al₂O_3, via MgO-spinel to finally complex types rich in CaO and Al₂O_3. The final composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition.</p><p>Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.</p>

This thesis deals with the study and design of composite materials based on silica matrix suitable for extreme conditions, eg. for the repair of concrete structures with anticipated increased risk of fire. The theoretical part summarizes basic knowledge concerning the fire resistance of structures and the behavior of the composite system during extreme conditions. Theoretically oriented section also contains information on alkali-activated materials and their use in high temperature environments. Based on the evaluation of the theoretical part of the experiment were designed and tested different types of composite materials with increased content of raw materials from alternative sources. Laboratory research has been based on testing of basic physico-mechanical parameters including phase composition and microstructure of the proposed formulations before and after thermal exposure of 1200 ° C. Also considered was the effect of different cooling conditions.

In the steel industry, slag foaming plays a crucial role in many steel processes, given its positive impact on the thermal efficiency of the furnace and its life span. However, excessive foaming causes an overflow in the converter known as “slopping”. Slopping hinders the effectiveness of the processes, especially with the complex and unpredictable foaming rate. This problem occurs mainly in the BOS-processes and after melt tapping to the ladle furnace. The goal of this study is to test and relate a new foaming control system, by blowing a gas (nitrogen or argon) on the surface of the melt to suppress the foam. Firstly, the foaming index of the provided industrial heats for a general LD converter (21 heats) and Outokumpu’s ladle furnace (31 heats) were calculated to find which heat is most likely to slop. Then, a series of experiments were performed to investigate the new foam controlling system’s reliability using a cold model. The results demonstrated that blowing argon instead of nitrogen from the top nozzle suppresses the foam more effectively, which can be attributed to its higher density. Additionally, the optimal argon flow rate required to suppress the foam in worst-case slopping scenarios in the LD converter and the ladle furnace were 874 and 221 m3/min respectively. The provided data further supports the efficacy of this slopping prevention technique, in theoretical and practical aspects. / I stålindustrin spelar slaggskumning en avgörande roll i många stålprocesser, med tanke på dess positiva inverkan på ugnens termiska effektivitet och dess livslängd. Överdriven skumning orsakar emellertid ett överflöde i konvertern som kallas "utkok". Utkok hindrar processernas effektivitet, särskilt med den komplexa och oförutsägbara skumningshastigheten. Detta problem uppstår främst i BOS-processerna och efter tappning till skänkugnen. Målet med denna studie är att testa ett nytt kontrollsystem genom att blåsa en gas (kväve eller argon) på smältytan för att slå sönder skummet. Först beräknades skumindexet för de tillhandahållna industriella chargerna för en allmän LD (21 charger) och Avestas skänk (31 charger) för att hitta vilken charge som har störst risk för utkok. Därefter utfördes en serie experiment för att undersöka det nya skumstyrsystemets tillförlitlighet med hjälp av en kall modell. Resultaten visade att blåsning av argon istället för kväve från det övre munstycket undertrycker skummet mer effektivt, vilket kan hänföras till dess högre densitet. Dessutom var den optimala argonflödeshastigheten som krävdes för att undertrycka skummet i värsta fallet i LD och skänkanläggningen 871 respektive 221 m3/min. De tillhandahållna uppgifterna stöder ytterligare effekten av denna förebyggande teknik, i teoretiska och praktiska aspekter.

The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle treatment. The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment. Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al2O3-CaO-MgO-SiO2 and showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3. The final composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition. Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion. / QC 20101109

The high temperature microstructure of the solid phases within the electric arc furnace (EAF) slag has a large effect on the process features such as foamability of the slag, chromium recovery, consumption of the ferroalloys and the wear rate of the refractory. The knowledge of the microstructural and compositional evolution of the slag phases during the EAF process stages is necessary for a good slag praxis. In supplement 1, an investigation of the typical characteristics of EAF slags in the production of the AISI 304L stainless steel was carried out. In addition, compositional and microstructural evolution of the slag during the different EAF process stages was also investigated. Computational thermodynamics was also used as a tool to predict the equilibrium phases in the top slag as well as the amount of these phases at the process temperatures. Furthermore, the influence of different parameters (MgO wt%, Cr2O3 wt%, temperature and the top slag basicity) on the amount of the spinel phase in the slag was studied. In supplement 2, a novel study to characterize the electric arc furnace (EAF) slags in the production of duplex stainless steel at the process temperatures was performed. The investigation was focused on determining the microstructural and compositional evolution of the EAF slag during and at the end of the refining period. Slag samples were collected from 14 heats of AISI 304L steel (2 slag samples per heat) and 7 heats of duplex steel (3 slags sample per heat). Simultaneously with each slag sampling, the temperature of the slag was measured. The selected slag samples were studied both using SEM-EDS and LOM. In some cases (supplement 2), X-ray diffraction (XRD) analyses were also performed on fine-powdered samples to confirm the existence of the observed phases. It was observed that at the process temperature and at all process stages, the stainless steel EAF slag consists mainly of liquid oxides, magnesiochromite spinel particles and metallic droplets. Under normal operation and at the final stages of the EAF, 304L steelmaking slag contains 2-6 wt% magnesiochromite spinel crystals. It was also found that, within the compositional range of the slag samples, the only critical parameter affecting the amount of solid spinel particles in the slag is the chromium oxide content. Petrographical investigation of the EAF duplex stainless steelmaking showed that, before FeSi-addition, the slag samples contain large amounts of undissolved particles and the apparent viscosity of the slag is higher, relative to the subsequent stages. In this stage, the slag also includes solid stoichiometric calcium chromite. It was also found that, after FeSi-injection into the EAF and during the refining period, the composition and the basicity of the slag in the EAF duplex steelmaking and EAF stainless steelmaking are fairly similar. This indicates that, during the refining period, the basic condition for the utilization of an EAF foaming-slag praxis, in both austenitic and duplex stainless steel cases, is the same. Depending on the slag basicity, the slag may contain perovskite and/or dicalcium silicate too. More specifically, the duplex stainless steel slag samples with a higher basicity than 1.55 found to contain perovskite crystals. / QC 20110413

Understanding the effects of the process parameters on the distribution behaviour of antimony between metal and slag in the iron blast furnace is critical to develop a universal method of controlling temper embrittlement in commercially pure low alloy steels.

Résumé : L’auto-cicatrisation des fissures des matériaux cimentaires présente un intérêt important pour améliorer leur durabilité (propriétés de transfert par exemple). L’impact du laitier de haut-fourneau sur ce phénomène a été peu étudié bien qu’il ait été observé sur des ouvrages du Génie Civil. Dans cette étude, la cinétique et l’amplitude de l’auto-cicatrisation ont été suivies par des essais non destructifs : la tomographie aux rayons X et la perméabilité à l’air, pour une fissuration créée à 7 jours et à 28 jours. Les résultats montrent que le laitier de haut-fourneau possède un potentiel d’auto-cicatrisation intéressant pouvant dépasser les résultats obtenus pour les formulations de référence sans laitier. Ce bon potentiel dépend des caractéristiques physico-chimiques des matériaux brutes et du potentiel d’hydratation de la formulation au cours du temps. De plus pour suivre l’auto-cicatrisation, un nouvel essai a été mis en place afin de fissurer les éprouvettes de mortier par retrait gêné et d’étudier l’auto-cicatrisation d’une fissure naturelle. Cet essai s’est avéré efficace sur la formulation de référence. Une caractérisation des produits de cicatrisation par MEB-EDS témoigne de la formation de nouveaux produits dans les fissures et de l’impact important des conditions de stockage sur le type de produits formés: des C-S-H pour un stockage sous eau et des carbonates de calcium pour un stockage en chambre humide (CO2 + eau). Les résultats de migration aux chlorures de nano-indentation montrent que ces produits de cicatrisation possèdent de bonnes propriétés de durabilité et des propriétés mécaniques à l’échelle microscopique intéressantes (pour le carbonate de calcium). Enfin, une modélisation du phénomène d’auto-cicatrisation est proposée au moyen du code de calcul de géochimie PHREEQC. L’étude a révélé le potentiel intéressant de PHREEQC pour modéliser l’auto-cicatrisation et en faire un outil de prédiction du phénomène. / Abstract : Self-healing of cementitious materials presents great interest to improve the durability of concrete structure (transfer properties for example). The impact of blast-furnace slag on this phenomenon is not yet clear even if the self-healing of concrete with blast-furnace slag was observed in building sites. To understand the blast-furnace slag influence, non-destructive methods were used to follow self-healing: X-ray tomography and gas permeability test. All specimens were cracked at 7 days and 28 days. The results show that the blast furnace slag has an interesting self-healing potential that can exceed the reference formulation results. This good potential depends on the physico-chemical characteristics of the raw materials and the hydration potential of the formulation over time. In addition to follow the self-healing, a new trial was set up to crack mortar specimens by restrained shrinkage and study the self-healing of a natural crack. In addition to follow the self-healing, a new trial was set up to crack mortar specimens by restrained shrinkage and study the self-healing of a natural crack. This test has proven effective over the reference formulation.The SEM with EDS analysis showed the formation of new products in the crack and the impact of storage conditions on these products : C-S-H for specimens stored in water and calcium carbonate for specimens stored in a damp chamber (CO2 + water). Migration chlorures and nano-indentation tests results showed that self-healing products had interesting durability properties and micro-mechanical properties (for calcium carbonate). Finally, self-healing modelling is proposed by means of geochemistry PHREEQC calculation code. The study revealed interesting potential PHREEQC to model self- healing phenomenon and make it a of predictive tool.