Papers by Keyword: Slag

Abstract: Carbonatation represents one of the potential degradation processes whose can negatively affect the service life of constructions based on the inorganic binders. The carbonatation depth of the constructions when exposed to various environments is significantly dependent on the existing conditions. The most crucial parameters are the partial pressure of carbon dioxide and humidity. There were selected four environments for the deposition of samples made of the alkali-activated blast furnace slag mortars (exterior, interior, water and CO₂ chamber) in this study. These types of environments guarantee the variation of desired parameters influencing the carbonatation rate. The progress of carbonatation was evaluated with a selected technique in time intervals of 28; 56 and 84 days of the sample's exposition to the selected environments. The characterization was done using the destructive techniques (compressive and flexural strength, phenolphthalein method) as well as the non-destructive one like the Impact-Echo or the Ultrasound time passage measurement. The combination of these techniques allows to determine and evaluate the progress of carbonation without the destructive testing of the samples which is necessary for the real applications of these materials.

Abstract: The use of fluorspar in modern metallurgical slags, incl. slags of the argon-oxygen decarburization (AOD) process, as a fluxing agent, is associated with many disadvantages. Those disadvantages can be solved by using boron oxide as an alternative, which also provides conditions for direct microalloying of steel with boron. The paper presents the results of thermodynamic modeling of the effect of basicity and boron oxide content in slags of the CaO–SiO₂–B₂O₃–Cr₂O₃–Al₂O₃–MgO system on the equilibrium interphase distribution of sulfur and boron, and their equilibrium content in the metal. Modeling was carried out using the HSC 8.03 Chemistry software package (Outokumpu). Slag from the desulfurization period of the AOD-process was used as the oxide phase. As a result, it was shown that, in the range of basicities 2.0-2.5 and a content of 2-4% B₂O₃, it is possible to carry out desulfurization of the metal, providing a sulfur content of 0.001-0.007%, and simultaneous microalloying of steel with boron in an amount of up to 0.0103%.

Abstract: The equilibrium interfacial distribution of sulfur and boron was estimated using the HSC 6.1 Chemistry software package (Outokumpu) and the simplex-lattice planning method. Adequate mathematical models have been constructed in the form of III degree polynomial, which describe the effect of the composition of the studied oxide system on the equilibrium distribution of sulfur and boron between the slag and the metal. Generalization of the results of experimental studies and thermodynamic modeling made it possible to obtain new data on the influence of the basicity and content of B₂O₃ in the slag of the CaO-SiO₂-B₂O₃-MgO-Al₂O₃ system on the interphase distribution of sulfur and boron. It was found that in the range of boron oxide concentration of 1.0-10%, an increase in slag basicity from 2 to 5 at 1600°C leads to an increase in the sulfur distribution coefficient from 1 to 20 and, as a consequence, a decrease in the sulfur content in the metal from 0.02 to 0.0014 %, i.e. an increase in slag basicity favorably affects the development of the metal desulfurization process. An increase in the B₂O₃ content from 2.0 to 10.0% in slags formed in the region of moderate basicity, not exceeding 2-3, is accompanied at 1600°C by a decrease in the boron interphase distribution coefficient from 450 to 150 and an increase in the boron concentration in the metal from 0.006 to 0.021 %, which indicates the progress of boron reduction from slag to metal. The shift of the formed slags to the area of ​​increased basicity up to 5.0 shows a high degree of boron reduction from slag to metal. The results of the laboratory experiment confirmed the results of thermodynamic modeling.

Abstract: The article presents a study of the physical and technical properties of ash and slag waste Coal Power Plant. The main problem when using ash-slag mixtures is the variability of the particle size distribution of the material. Determining the characteristics of slag stored in the dumps of thermal power plants will help to choose the separation methods of this material, to address the disposal and accumulation of industrial waste, to expand the scope of their application. The obtained research results of physical and technical properties of waste of the Coal TPP testify to wide potential in the further use in many branches of the industry. Possible applications include fillers for concrete, materials for sandblasting (abrasive material), raw materials for the metallurgical industry, additives for the manufacture of binders, etc.

Abstract: Slag is widely used as mineral admixtures in cement-based materials by its potential hydration activity. It has the advantage of saving resources and energy, reducing carbon emission, improving the performance of concrete, and plays an increasingly important role in the building materials industry. But the early strength of slag is low, and the industrialization of useful hydration products also need to be activated, so the utilization rate of slag in high grade cement is restricted. The hydration activity of slag depends not only on the content of vitreous in slag, but also on the structure of vitreous slag. To explore slag glass micro composition and structure of its active role, The slag micro-structure was analyzed from the structure levels, and then the factors affecting the activity of slag was evaluated. The potential advantages and disadvantages of some different methods to active slag were discussed such as physical ways, chemical activation method and compound activation way. The existing problems and development direction of improving the activity of slag were summarized , which could provide a valuable reference for the efficient use of slag.

Abstract: The present study considers various technological approaches to the processes of complex utilization of nickel slags with preliminary additional extraction of non-ferrous metals, iron, and ways of utilization of the obtained gangue. The valuable components are often produced from waste using the mineral acids or mixtures; the metals are extracted from acid solutions in a free form or in the form of compounds using electrochemical or chemical methods. Slag dumps have a heterogeneous structure and mineralization; the zone distribution of slag is clearly defined due to different cooling and solidification rates. The slag composition is mostly represented by dense low-porous varieties consisting of dark brown glass. The porous slag fragments are secondary. The third texture diversity in the composition of slag is represented by nodular and kidney-shaped particles. The diversity and size of the ore minerals is directly connected with the distribution of pores in slag. The major ways for utilization of nickel industrial waste are pyro-metallurgical and hydrometallurgical methods. In addition, each of the methods is usually preceded by the stage of mechanical preparation of the raw materials, where the techno-genic waste is crushed.

Abstract: Production of Portland cement is relatively environmentally demanding (high CO₂ emissions, extraction of raw materials for its production). Alkali-activated materials are an alternative to conventional Portland cement in the production of concrete. For alkali-activated binder concretes, their ability to withstand corrosive environments and their ability to protect steel reinforcement must be assessed. It is also necessary to know the suitability of non-destructive methods for monitoring the degradation process of these concretes. The paper deals with the carbonation monitoring of concrete with alkali-activated binder (slag) by the impact-echo method. Slag activated by sodium hydroxide (NaOH) was used as a binder. The specimens were tested by the non-destructive method (Impact-echo, ultrasound velocity). We focused on the shift of the dominant frequency obtained by the Impact-echo method.

Abstract: In this study investigates utilizing of slag as an additional material to improve engineering properties of contaminated soil by crude oil to changing the engineering characteristics to be satisfying and compatible, this is due to its pozzolanic reactivity. The aim of this study the impact of slag material in geotechnical engineering and to stabilize properties of contaminated soils. Two percentages of slag were utilized in this study, which is 0% and 6%. Compaction and direct shear strength tests had been conducted on the artificial contaminated prepared soil samples. In the results, showed that the increasing of slag leads to a decrease in the optimum water contents while the maximum dry density values increase. Furthermore, the shear strength is improved by utilizing slag so that slag can be considered as a stabilizing material to improve the properties of contamination soil.

Abstract: The mechanical properties of slag solidified bodies tend to be degraded when the temperature of slag solidified bodies is high. It is easy to crack under the action of perforated fracturing to lose the effect of sealing and interlayer sealing, and affect the cementing quality. Therefore, the mechanical properties of the solidified slag at several bottom-hole cyclic temperatures (30 °C, 50 °C, 70 °C, 90 °C) were studied in the present investigation. The results showed that the early strength of the slag solidified body cured at 90 °C was stronger than the early strength of the slag solidified body at 30 °C and 50 °C but lower than 70 °C. However, when the curing time reaches 28 days, the compressive strength of the slag solidified body at 90 °C droped sharply lower than the strength of the slag solidified body at 30°C. SEM and XRD indicated that the hydration products of slag at 90 °C were primarily network-like C-S-H gels. Compared with low temperature conditions, slag solidified bodies at high temperatures (>90 °C) were prone to micro-cracks and the structure easily damaged.

Abstract: Analysis of forming chromium-bearing ferroalloys production waste in Russian Federation was performed. Chemical, phase, fractional compositions and physico-chemical, technological properties of high-carbon ferrochromium slag were defined. Physico-chemical, thermo-mechanical and thermo-physical properties of fire-resistant materials, obtained from ferrochromium production slag and dust, were researched. It was shown that researched waste may be utilized as raw for fire-resistant materials production. Because of their chemical and phase composition, researched materials may be utilized for production of forsterite-spinel-based and forsterite-spinel-periclase-based fire-resistant materials. Technological properties of researched materials allow obtaining dense strength fire-resistant materials. Such fire-resistant materials are promising in the field of ferrous metallurgy (lining up furnaces, ladles and overflow launders in ferroalloys production).