Papers by Keyword: Steel Slag

Abstract: Taking fluidity and compressive strength of mortar as index, steel slag slag composite admixture replaces cement by 50%. The influence of the fineness and content of steel slag powder on the properties of composite admixture was studied by uniform experimental design. The fitting regression equation between the parameters of steel slag fineness and dosage and the performance indexes is established, and the contour map is drawn. The results show that the predicted value is in good agreement with the measured value, and the correlation coefficient is more than 0.99. Through regression analysis and contour map analysis, it is shown that increasing the fineness of slag powder and reducing the content of slag are beneficial to improving the cementitious activity of slag composite.

Abstract: This article presents the results of research on the use of unstable steel slag with a fraction of 0/8 mm as a 100% substitute for natural aggregate in concrete production. Two types of cements were used for the production of concrete: Portland cement CEM I 42.5N and hybrid cement H-CEMENT. Both of these cements were produced by the company Považská cementárna, a.s., Ladce. The main objective of this study was to assess the suitable type of binder to be combined with unstable steel slag in the production of concrete composite. The prepared concrete was used to test the properties of a fresh concrete mix, i.e. its consistency and bulk density. Hardened concrete was used to test the strength and deformation properties, including cube strength after 3, 7, 14, 21, 28 and 90 days, as well as prism strength after 28 days. The static modulus of elasticity was determined using prisms after 28 days of age of the test specimens. Our attention was also focused on determining the class of leachability of the concretes based on steel slag with CEM I 42.5N and H-CEMENT. The durability of concrete prepared on the basis of steel slag was tested in an environment with increased temperature and pressure. The results of the strength characteristics tests show a difference between the 28-day average cube strength of concrete using CEM I 42.5N and H-CEMENT (34.6 MPa and 29.1 MPa), while after 90 days, the average cube strength value stabilized at about 38 MPa. The average values ​​of the static modulus of elasticity when using CEM I 42.5N and H-CEMENT are almost identical, achieving values ​​of 32.5 GPa and 32.8 GPa, respectively. Concrete based on steel slag with CEM I 42.5N and H-CEMENT can be included in leachability class IIb. The results of the durability test of concrete based on steel slag in an environment with increased temperature and pressure confirmed the use of H-CEMENT hybrid cement from the company Považská cementáren, a.s., Ladce, as a suitable binder. .

Abstract: The accelerated carbonation with different pressure steaming conditions was used to process the steel slag, so the slag could turn into a primary cementitious product with carbonation activity. XRD, FTIR, TG, N₂ absorption BET surface area analyzer and SEM were used to characterize the mineral and chemical compositions and microstructure of each sample before and after the carbonation. The results show that: the carbonation products with different morphologies are formed under different temperature conditions. The optimum temperature for the accelerated carbonation for processing the steel slag is selected to be 90 °C, which results in the compressive strength of 32.8 MPa. The BET specific surface area of the steel slag reduces after carbonation, the sample density increased after carbonation.

Abstract: An experimental program was carried out to investigate how to improve the characteristics of steel slag. Mainly the pretreatment methods of cooking and autoclave were used to detect such as free CaO content in the steel slag. The physical and chemical characteristics of steel slag were measured by X-ray diffraction (XRD) and fluorescence (XRF) analysis. The aim of improving the slag utilization is an important way to resolve large production problem, and then the research progress of steel slag utilization at home and abroad are recycled as raw material to be applied. By means of those ways to manage steel slag we have received the following conclusions: With the increase of cooking temperature the content of free CaO is gradually reduced. When temperature higher than 90oC the means could greatly reduce the free CaO content from about 7% wt. to less than 2.5% wt. in 3 h. By means of autoclave pressure upto 1.5MPa could greatly reduce the free CaO content from about 7% wt. to less than 3.2% wt. in 3 h. Through the study of the relevant of steel slag after pretreatment can effectively reduce the free CaO content in the steel slag, improving the stability of the steel slag is advantageous to the seven used in the construction field.

Abstract: Through the XRD and XRF analysis of the converter steel slag, we can identify the chemical components and the mineral phase and ensure the extraction method of RO phase from steel slag. The possibility of the extraction of silicate phase from steel slag with Salicylic acid ethanol (SAE) solution was studied firstly. Then, the effect of dissolution temperature of steel slag, dissolution time of the samples, concentration of salicylic acid and specific surface area of steel slag on the extraction mass of silicate phase were analyzed by orthogonal experiment, and the optimum experiment conditions of the extraction of silicate phase from steel slag with SAE solution were concluded. Finally, the RO phase was obtained by the extraction and separation of the intermediate phase from steel slag using potassium hydroxide-sucrose (KOSH) solution. The effect of extraction was determined by detecting the chemical and mineral composition of the extracted residue with XRD and XRF. The results show that the SAE solution can be used to extract the silicate phase from steel slag and the best extraction conditions were 40 degrees of dissolution temperature, 3 h of solution time, salicylic acid concentration 0.2 g/ml and the specific surface area of steel slag 600 m²/kg. Then the intermediate phases (mainly C₂F) from steel slag were extracted by KOSH solution, which can get a relatively pure RO phase. The experiment provides a basis for further exploring the cause of the difference in activity of RO phase and improving the utilization ratio of steel slag.

Abstract: A steel slag has been treated by air granulation, in order to enhance cementitious properties of the slag. Two samples with sizes ranged 1.68-2.38mm and 212-297μm and coded as Slag A and Slag B, respectively, were chosen from the granulated slag for investigations. A sample of the original steel slag was also studied. XRD analyses indicated the formations of α-C₂S, β-C₂S, C₂F, C₂MS₂, f-MgO and α-C₂S, C₂F, f-MgO in Slag A and Slag B, respectively. The phases in the two slag samples were quite different from the phases found in steel slag. The SEM results show a reduction of C₂S sizes from 10-20μm for the steel slag to nano-scales by air quenching for Slag B. This treatment of air quenching has increased the cumulative heat of hydration to 105.35J/g measured for Slag B, almost two times greater than that of the steel slag. The study results demonstrate a high potential for utilizations of the steel slag in cement and concrete applications after the slag treatment by air quenching. The treatment may thus lead to an environmental friendly and cost-effective recycling for the steel slag. This can also contribute to the sustainable developments in the steel and cement/concrete industries.

Abstract: In order to establish a rapid evaluation method of steel slag cementitious activity, extraction test of steel slag in EDTA-NaOH solution have been investigated and the relationship between extraction characteristics and cementitious activity expressed as mortar strength has been analyzed. Results show that the linear relationship between the quantity extracted from steel slag and the mortar compressive strength is significant. According to the analysis results of mineral composition and microscopic morphologies, EDTA-NaOH solution can selectively extract the silicate and aluminate minerals of steel slag, which could be used as a rapid evaluation method of steel slag cementitious activity.

Abstract: Powder characteristics and granule morphology of steel slag cooled by water-quenching and air splashing were observed with SEM and their rest angle, compressed density and mechanical characteristics were measured. The result shows that particle sphericity of air splashing steel slag is lower than that of water-quenching steel slag. A compressive stress has a more effective on the deaggregation of water-quenching steel slag powder. Both of the two steel slag powders are typical Coulomb powder. Compared with the water-quenching steel slag powder, air splashing steel slag powder has a higher internal friction angle and cohesiveness. The cementitious activity of BOFS Powder can only meets the standard of the second grade powder according to the Chinese National Standards.

Abstract: This article presents the results of an experimental research dealing with the measurement of the thermal characteristics of concretes based on natural and artificial aggregates (steel slag). The samples of concrete composites were prepared on the basis of natural aggregate fractions 0/4, 4/8 and 8/16 mm and on the basis of steel slag fr. 4/8 mm. The volume ratio of the individual aggregate fractions in all experimental mixtures used for the production of concrete composites was 40:30:30 (fr. 0/4: 4/8: 8/16). The prepared samples of concrete composites based on natural aggregate and natural aggregate combined with steel slag were subjected to the tests of strength characteristics, water-tightness, thermal characteristics using a commercial device ISOMET 2104 (measurement of the coefficient of thermal conductivity λ, specific heat capacity c, and the coefficient of thermal diffusivity a), and heating in a prototype calorimetric computer-controlled chamber. The main attention was focused on the testing of the value changes of the coefficients of thermal conductivity λ depending on the changes of temperatures within the range of -5 °C to + 40 °C. The measurements of these thermal characteristics have very high informative value, especially because these material parameters are not tabulated for the newly designed building materials, and that is why they are not examined at extreme temperatures. This is a reason why they cannot be used as important data during the thermal calculations of a non-insulated concrete structure (e.g. using polystyrene and / or glass wool).

Abstract: In this paper, the performance of steel slag composite cementitious material and the performance of steel slag concrete were studied, which provides reference for the comprehensive utilization of steel slag. The test shows that the activity of steel slag composite cementitious material with the specific surface area is greater than or equal to 400m²/kg to meet the use requirements; When the maximum content of coarse aggregate of steel slag was 25%, the volume stability of steel slag concrete was best. But when the content of steel slag powder was controlled within 30%, the concrete had good resistance to carbonation.