Phosphorus in steel is detrimental element for mechanical properties and dephosphorization treatment of hot iron is necessary to produce high-grade steel products. However, it is difficult to perform ...dephosphorization treatment to attain lower phosphorus content using CaO–SiO2–FeO flux without fluorite of which use is limited owing to stringent environmental regulations. In the present work, addition of ladle slag and lime powder top blowing method were applied in 2 t test converter to obtain the higher slag basicity. Obtained results are as follows:(1) By simultaneously adopting lime powder top blowing and ladle slag addition, phosphorus content of hot iron decreased to 0.01 mass% under the condition of (CaO)/(SiO2)=2.(2) By comparison of the results of the heats with and without ladle slag, the ratio of dephosphorization at hot spot by lime top blowing was estimated to be 35%.(3) (FeO) content of CaO–FeO melt at hot spot was estimated 37% on a basis of oxygen flow rate except to be consumed for decarburization and lime feeding rate. CaO–FeO phase diagram shows that the melt is liquid at hot spot but solid in hot iron. It is suggested that low ratio of dephosphorization at hot spot is attributed to this result.
This paper examines the durability of alkali activated ladle slag mortars. Ladle slag, currently an under-utilized crystalline metallurgical by-product, is a promising raw material for alkali ...activation. However, there is no information about the durability of this material. The aim of this study is to investigate the durability of the alkali activated ladle slag mortar and the effect of aggregate content on the properties. The mechanical strength tests were carried out at 7, 28, 56 and 90 days. In addition, the samples were subjected to drying shrinkage, freeze–thaw, and water absorption tests. Furthermore, the reaction products conversion related to the strength properties were also analysed through thermal analysis. Overall, significant strength and durability properties was attained and significantly influenced by the mix design.
Partial replacement and co-hydration of calcium aluminate cement (CAC) with ladle slag was investigated in this study as a pathway in valorizing the slag and reducing the economic cost of CAC. The ...impact of this replacement on the physical and microstructural properties were analysed using different techniques such as mechanical strength test, freeze-thaw, sulfate attack, XRD, SEM etc. Thermodynamic modelling was used to predict the phase assemblages of the blended cement using the hydration kinetics of the system. Experimental results showed the reference CAC mortar and the substituted mortar exhibited comparable strength gain at 7 and 28 days, and durability as measured by sulfate attack, abrasion, and freeze-thaw resistance. A low water-to-binder ratio (0.35) lessened the effect of conversion on the hydrates, as XRD showed metastable CAH10 and C2AH7.5 as the hydrates at 7, 28 and 60 days. This however can convert later to the thermodynamically stable phase C3AH6. Thermodynamic modelling suggests these two metastable phases as major binding phases, while Si-hydrogarnet and FeOOH appeared a minor trace in the binder.
*Cement chemistry notation used, where C = CaO, A = Al2O3 and H = H2O
•Proposed mix design of blended CAC using steelmaking slag, shows no effect on hydration mechanism.•Addition of slag to the cement improved microstructure and mortar durability.•Lower water-to-binder ratio lessened the conversion mechanism, and.•CAH10 and C2AH7.5 identified as metastable hydrates after co-hydration consistent with thermodynamic modelling.
The research was dealing use of ladle slag and its impact on the physical and mechanical parameters of hardened cement composites. The goal was to find a suitable percentage share of ladle slag used ...as an admixture. The results of compressive strength tests show the possibility of replacement of a significant amount of cements with a specific secondary product. A decrease in compressive strength of about 8% after 28 days has to be taken into account when using Portland cement CEM I 42.5R and a 10% replacement with ladle slag.
Ionizing radiation has become an integral component of modern scientific advancement. However, radiation can be harmful to human health if not shielded efficiently. Extensive research has been ...carried out to improve the shielding efficiencies of different construction materials, thereby leading to varying possible alternatives for future radiation-safe constructions. In contrast, the shielding capacities of existing structures and raw materials have received less attention, and no evaluation of the safety of the inhabitants in case of an emergency appears to have been conducted in Bangladesh. Therefore, this research aims to study the radiation shielding properties of ordinary mortar and concrete used in Bangladeshi dwellings. Three of the most used field concretes (1:1.25:2.5, 1:1.5:3, and 1:2:4) and mortar (1:3, 1:4, and 1:5) mixes are tailor-made for this purpose. Additional samples were prepared by partial replacement (15% and 30%) of cement in the media with ladle slag. The samples' transmission characteristics of 662 keV, 1173 keV, and 1332 keV gamma rays were measured using Co60 and Cs137 as radiation sources. A p-type, coaxial HPGe gamma-ray detector was used for this purpose, and each sample was tested for a consecutive period of 20000 s. Linear attenuation coefficient, mass attenuation coefficient, half value layer, tenth value layer, mean free path, and radiation protection efficiency are evaluated from the experimental results. Furthermore, the mechanical properties of concrete and mortar samples are determined. It is found that concrete with a field mix ratio of 1: 1.5: 3 offers better shielding at low energy, while 1: 1.25: 2.5 composition is more effective at higher energy. Similarly, 1:3 mortars are more effective for low energy, and 1:5 mortars provide better results for high energy radiation. However, the differences between the various concrete and mortar compositions are minimal. The ladle furnace slag slightly reduced the radiation shielding capacity of both mortar and concrete. The highest strength and lowest sorptivity were obtained for 1: 1.25: 2.5 concrete, whereas the opposite trend is observed for 1: 2: 4. On the other hand, 1: 3 and 1: 5 mortars show the highest and lowest compressive strength, respectively. No definite correlation between sample strength and shielding capacity can be established, although ultrasonic pulse velocity seems to be a good indicator in this case. Overall, conventional mortar and concrete used in infrastructure construction in Bangladesh show satisfactory results in shielding gamma rays in the energy range of 661–1332 keV.
•Radiation shielding performance of commonly used construction materials has been evaluated.•The field mix ratios of cement mortars and concretes frequently used in Bangladesh were used in this research.•No past work has conducted this exact evaluation.•Attenuation coefficients, HVL, TVL, MFP, and RPE are determined for three distinguished gamma-ray energies.•Ladle furnace slag was used to observe its influence on concrete and mortar performance.
Ambient weathering of steelmaking ladle slags Moliné, Marcos N.; Calvo, Walter A.; Martinez, Analía G. Tomba ...
Ceramics international,
10/2018, Letnik:
44, Številka:
15
Journal Article
Recenzirano
During cooling and permanence outside, the solidified slag involved in the refinement process taking place in the steelmaking ladles suffers attack by environmental components such as water vapor and ...gaseous CO2 (weathering). The reactions involved are hydration and carbonation, and as a consequence, the pulverization of the slag occurs. In the present paper, the results of a study of the degradation of a typical steelmaking ladle slag over a period of eighteen weeks (126 days) are reported. To monitor the slag evolution, several experimental techniques were used, some of them rarely employed in this context, after dividing the initial slag batch in four granulometric fractions between > 7.2 mm and < 1.4 mm: granulometry by sieving, X-ray fluorescence (XRF), X-ray diffraction (XRD), and thermogravimetric (TGA) and thermal differential (DTA) analyses. As was already known, the main elements responsible for the slag degradation are free lime, followed by calcium aluminates and magnesia. It was also found that anhydrous and hydrated calcium aluminates are concentrated in the finest granulometric fractions and contribute to the generation of fines mainly during the final stage of hydration. The high percentage of particles smaller than 1.4 mm, with cementitious properties provided mainly by the presence of anhydrous calcium aluminates, are promising characteristics for alternative reusing of the studied ladle slag. Furthermore, slag weathering mechanisms are critical for understanding other steelmaking processes in which the slag is deeply involved, such as the protective role of the remaining thin slag layer against decarburation of ladle or converter working lining refractory bricks.
Bu çalışma da demir
çelik üretiminde pota metalurjisinde (II. Metalurji) oluşan cürufun, kolemanit
kullanılarak ıslahı için endüstriyel çalışma anlatılmış ve sonuçları
paylaşılmıştır. Endüstriyel ...çalışmalar 1.300.000 ton/yıl düşük ve orta karbonlu
çelik üretim kapasitesine sahip Diler Demir Çelik İşletmesinin Gebze Dilovası
tesislerinde endüstriyel boyutta gerçekleştirilmiştir. Özgün olarak soğuma
esnasında gama-dikalsiyum silikat γ-Ca2(SiO4)
formunda oluşan pota cürufuna, farklı oranlarda kolemanit ilave edilerek soğuma
esnasında beta-dikalsiyum silikat β -Ca2(SiO4)
yapısına dönüşümü sağlanarak dünyada yıllık yaklaşık 30 milyon ton atığa
ulaşan, taşıma, stoklama problemi olan pota cürufunun soğuma esnasında
yoğunluğu artırılarak, taşınabilir, yan ürün olarak değerlendirilebilen çevre
problemleri ortadan kaldırılmış ürünler haline dönüştürülmüştür. Elde edilen
cürufların kimyasal analizleri ve yoğunluk ölçümleri yapılmış, XRD, SEM/EDS
incelemelerine bakılmıştır. Kompakt yapının oluştuğu % B2O3/Curuf
(kg/kg) oranının 1 olduğu çalışmada, elde edilen cürufların yığma yoğunluğu
1,36 dan 2,64 ton/m3 artırılmış yine aynı çalışmada çelik bünyesinde
maksimum 9 ppm B endüstriyel olarak ispat edilmiştir.
This research investigated the suitability of a locally available ladle furnace slag (LFS) as a supplementary cementitious material (SCM) to partially replace cement in concrete. The engineering ...properties of the LFS blended concrete were evaluated through an extensive experimental program. The SCM was used as (i) raw slag and (ii) sieved (finer than 75 µm) slag to use to produce different strength class concrete, viz., C35 and C40. Mechanical strengths and non-destructive tests were conducted for concrete with 5%, 10%, 15%, 20%, 25%, and 50% LFS replacement by weight of cement for various curing duration. Besides, indirect durability tests such as sorptivity and nitrogen gas permeability tests on LFS blended concretes were performed. Uniaxial compressive strength (UCS) for lower-grade concrete at 5% and 10% LFS levels are always higher relative to the control sample, regardless of the material type and curing period. The ultrasonic pulse velocity (UPV) test on concrete suggests that pulse velocity has a pattern similar to that of the UCS. Nitrogen gas permeability varies by LFS level, temperature, and material fineness. Capillary absorption indicates an evident general trend of increased water absorption with exposure/absorption time and LFS level. These properties for higher-grade concrete are reasonably similar to that of lower-grade concrete, however, the finer material shows better performance in this case.
•A unique steel processing slag was used as a substitution to cement.•Two different graded concrete were produced and tested.•Slag powder was categorized as raw and sieved.•UPV, UCS, gas permeability, and sorptivity of concrete were determined.•Unique correlation between UPV and UCS is established.
The reoxidation of molten steel by oxidising slag directly affects the molten steel cleanliness. There is a good relationship between molten steel cleanliness and the defect sources of cold rolled ...sheets. The results show that there is a direct relationship of the slag composition to steel cleanliness and the rate of surface defects on the final products. The thermodynamic calculations show that the activity of iron oxide decreases with the increase of w(CaO)/w(Al
2
O
3
) specifically when the content of T.Fe in slag remains at lower levels. In order to enhance the absorption ability of the slag to Al
2
O
3
inclusions, w(CaO)/w(Al
2
O
3
) should be controlled in the range of 1.0-1.4 in the liquid region of slag when T.Fe content in RH final slag is less than 6 mass%. By reasonable control of T.Fe content and w(CaO)/w(Al
2
O
3
) in the slag, the defect content of sheets significantly declines.
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•Chemical and mechanical properties were studied in cement composites with added ladle slag.•Leachability tests based on diffusion were performed in compact and ground ...composites.•Cr(VI) was immobilized in cement composites with the addition of ladle slag.•To prevent leaching of Mo and Ba, crushing of the composites should be omitted.•The investigated ladle slag can be implemented as supplementary cementitious material.
In the present work compact and ground cement composites in which 30% of cement by mass was replaced by ladle slag were investigated for their chemical and physico-mechanical properties. To evaluate long-term environmental impacts, leachability test based on diffusion, which combined both, diffusion and dissolution of contaminants, was performed in water and saline water. Total element concentrations and Cr(VI) were determined in leachates over a time period of 180days. At the end of the experiment, the mineralogical composition and the physico-mechanical stability of cement composites was also assessed. The results revealed that Cr(III) and Cr(VI) were immobilized by the hydration products formed in the cement composites with the addition of ladle slag. Cr(VI) content originating from the cement was also appreciably reduced by Fe(II) from minerals present in the added ladle slag, which thus had significant positive environmental effects. Among metals, only Mo and Ba were leached in elevated concentrations, but solely in ground cement composites with the addition of ladle slag. Lower V concentrations were observed in leachates of ground than compact composite. It was demonstrated that the presence of ladle slag in cement composites can even contribute to improved mortar resistance. The investigated ladle slag can be successfully implemented in cement composites as supplementary cementitious material.
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