Stabilization of free CaO in molten BOF slag by addition of silica at high temperature

2018 ◽  
Vol 115 (4) ◽  
pp. 414 ◽  
Author(s):  
Xiao Yin ◽  
Chongmin Zhang ◽  
Guocheng Wang ◽  
Yonghong Cai ◽  
Changming Zhao
Keyword(s):  
High Temperature ◽  
Reaction Temperature ◽  
Construction Material ◽  
Steel Slag ◽  
Elimination Rate ◽  
Influential Factors ◽  
National Standard ◽  
Stabilization Time ◽  
Bof Slag ◽  
Free Cao

The unstable free CaO (f-CaO) has always been the bottleneck that limits the application of basic oxygen furnace (BOF) slag as a construction material. In this work, silica was regarded as the stabilization addition to make the f-CaO in molten BOF slag stabilized at high temperature. The influences of experimental conditions on the f-CaO stabilization were studied. The results show that the main influential factors on elimination rate of f-CaO are the ratio CaO/SiO2, reaction temperature and stabilization time. In this work setting conditions, with the ratio CaO/SiO2 less than 2.7, the reaction temperature under 1525 °C and the stabilization time over 10 min, the f-CaO content in the stabilized slag falls to the level of less than 3.00%, which can fully meet the Chinese national standard of steel slag powder used for cement and concrete. Additionally, the XRD results indicate that f-CaO is stabilized by silica in forming akermanite phase at high temperature. Moreover, the observation obtained from FESEM indicates that the undissolved lime and precipitated CaO changed into clustered CaO in the stabilized slag with its size ranging from 0.6 µm to 2.5 µm.

Preparation and performance analysis of gas-quenched steel slag beads

2020 ◽  
Vol 117 (1) ◽  
pp. 105
Author(s):  
Hui Wang ◽  
Wei Zhang ◽  
Chao Liu ◽  
Hongwei Xing ◽  
Chen Guo ◽  
...  
Keyword(s):  
Formation Rate ◽  
Steel Slag ◽  
Elimination Rate ◽  
Fine Aggregate ◽  
Quenching Rate ◽  
Bead Formation ◽  
Bof Slag ◽  
Gas Quenching ◽  
Quenched Steel ◽  
Bf Slag

The low utilization rate of steel slag in China has exposed serious environmental and social problems. In the present work, the basic oxygen furnace (BOF) slag was modified by blast furnace (BF) slag and then beaded by the means of gas quenching. The gas-quenching rate, bead formation rate, physical properties, microscopic characteristics and free lime (f-CaO) of gas-quenched slag beads were analyzed to broaden the utilization of BOF slag. The results show that the more BF slag is added, the higher the gas-quenching rate is, and the lower the bead formation rate becomes. When no BF slag is added, the beads are mainly composed of magnetite, limonite and melilite. After BF slag is added, a large amount of glass phase and a little amount of Ca2SiO4 and MgO are found in beads. The content of f-CaO beads decreases after the modified slag is gas quenched at high temperature. Moreover, the more BF slag is added, the higher the elimination rate of f-CaO becomes. Considering the industry standard of steel slag sand in China as well as the gas-quenching rate, physical and chemical properties, the gas-quenched steel slag beads with 5 and 15% BF slag better meet the medium sand standard, which can be used as fine aggregate.

Comparison of Hydration Mechanism between Cements from Two Different Residual Muds

2016 ◽  
Vol 680 ◽  
pp. 466-471
Author(s):  
Zhi Wei Liu ◽  
Yu Li ◽  
Da Qiang Cang ◽  
Hao Ran Wang
Keyword(s):  
Steel Slag ◽  
National Standard ◽  
Arc Furnace ◽  
Dry Process ◽  
Composition Effects ◽  
Hydration Mechanism ◽  
Steel Making ◽  
Bof Slag ◽  
Eaf Slag ◽  
Lower Basicity

Steel slags are byproduct of steel making process in blast oxidizing furnace (BOF) and electric arc furnace (EAF), including BOF slag, EAF slag. Residual slag mud is discharged after recover of iron from steel slag by magnetic separation after a wet grinding process. The wet disposal process has higher efficiency than dry process but would deteriorate cementitious reactivity of wet residual mud. For residual EAF slag mud and residual BOF slag mud have different composition, effects of wet disposal process on their reactivity and hydration mechanism of related cements were researched in the paper. Analyses of microstructure and testes of mechanical properties for cements from the two different mud showed that the cements composed of 25 % of different mud respectively can reach the national standard of 42.5 grade cements. But residual EAF slag mud has better reactivity. Cement composed of residual EAF slag mud had a higher increase of compressive strength during 28 days of hydrations, and fluffy C-S-H gel and needlelike AFt crystal would increase obviously. Reactivity of BOF slag would degraded more in wet disposal process for its quicker hydration than EAF slag which resulted in more Ca(OH)2 and C-S-H gel formed in the discharged mud,. EAF had lower basicity, content of less f-CaOand C3S, more P2O5 and C2S, which would contribute to its stability in the wet disposal process. EAF slag is more suitable for wet-disposal process.

scholarly journals Greener Solution to Waste Corn Stalks and Shortage of Asphalt Resource: Hydrochar Produced by Hydrothermal Carbonization as a Novel Performance Enhancer for Asphalt Binder

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1427
Author(s):  
Xiaoming Wu ◽  
Chichun Hu
Keyword(s):  
High Temperature ◽  
Reaction Temperature ◽  
Storage Stability ◽  
Asphalt Binder ◽  
Aging Effect ◽  
Experimental Tests ◽  
Hydrothermal Carbonization ◽  
Modified Asphalt ◽  
Direct Combustion ◽  
Aging Property

Utilization of waste corn stalks (CS) has seized extensive attention due to high annual output and hazardous impact of piling aside or direct combustion on environment. However, previously there has been a lot of emphasis on improvement of its energy efficiency as solid fuel while limited investigations are available which explore the possibility of applying corn stalks as performance enhancer in asphalt binder. The purpose of this study is to examine the potential of employing hydrochar as modifiers in asphalt binder by a series of experimental tests. In this study, two hydrochar were produced from corn stalks by a novel process called hydrothermal carbonization at a different reaction temperature. The two hydrochar and their responding hydrochar-modified asphalt (HCMA) were tested by chemical and rheological tests. Chemical analysis detected the interaction between hydrochar and binder factions, resulting in poor compatibility but satisfying anti-aging property. Even though hydrochar increased the viscosity of bitumen, implying worse workability, and caused poor storage stability, ameliorated performance of asphalt binder at high temperature by incorporating hydrochar was verified by various criteria such as higher performance grade (PG) failure temperature and lower non-recoverable creep compliance (Jnr). Moreover, higher reaction temperature makes hydrochar’s particles smaller and more homogeneous, which results in slightly lower enhanced high temperature performance, more satisfying workability, better storage stability, and greater anti-aging effect of hydrochar-modified asphalt. Eventually, this study provided a promising win-win solution to environment problems concerning corn stalk treatment and shortage of asphalt binder. Further exploration of methods to improve HCMA’s storage stability, real-scale corroboration on trial section and life cycle assessment of asphalt pavement containing hydrochar modifiers will be followed in the future.

scholarly journals Effect of Fly Ash on the Properties of Ceramics Prepared from Steel Slag

2018 ◽  
Vol 8 (7) ◽  
pp. 1187 ◽  
Author(s):  
Yanbing Zong ◽  
Xuedong Zhang ◽  
Emile Mukiza ◽  
Xiaoxiong Xu ◽  
Fei Li
Keyword(s):  
Fly Ash ◽  
Flexural Strength ◽  
Water Absorption ◽  
Sintering Temperature ◽  
Steel Slag ◽  
Diffraction Peak ◽  
National Standard ◽  
Sintered Ceramic ◽  
Base Steel ◽  
Sintering Shrinkage

In this study, SiO2–Al2O3–CaO–MgO steel slag ceramics containing 5 wt % MgO were used for the preparation of ceramic bodies, with the replacement of 5–20 wt % quartz and feldspar by fly ash. The effect of the addition of fly ash on the sintering shrinkage, water absorption, sintering range, and flexural strength of the steel slag ceramic was studied. Furthermore, the crystalline phase transitions and microstructures of the sintered samples were investigated by XRD, Fourier transform infrared (FTIR), and SEM. The results showed that the addition of fly ash affected the crystalline phases of the sintered ceramic samples. The main crystal phases of the base steel slag ceramic sample without fly ash were quartz, diopside, and augite. With increasing fly ash content, the quartz diffraction peak decreased gradually, while the diffraction peak intensity of anorthite became stronger. The mechanical properties of the samples decreased with the increasing amount of fly ash. The addition of fly ash (0–20 wt %) affected the optimum sintering temperature (1130–1160 °C) and widened the sintering range. The maximum addition amount of fly ash should be 15 wt %, for which the optimum sintering temperature was 1145 °C, water absorption was 0.03%, and flexural strength was 43.37 MPa higher than the Chinese national standard GBT 4100-2015 requirements.

scholarly journals Assessing the long term effects on climate change of metallurgical slags valorization as construction material: a comparison between static and dynamic global warming impacts

2021 ◽  
Vol 1 (1) ◽  
pp. 88-111
Author(s):  
Andrea Di Maria ◽  
◽  
Annie Levasseur ◽  
Karel Van Acker ◽  
◽  
...  
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Carbon Footprint ◽  
Building Materials ◽  
Construction Material ◽  
Steel Slag ◽  
Construction Materials ◽  
Long Term Effects ◽  
Stainless Steel Slag ◽  
Environmental Evaluation

<abstract> <p>The interest in circular economy for the construction sector is constantly increasing, and Global Warming Potential (GWP) is often used to assess the carbon footprint of buildings and building materials. However, GWP presents some methodological challenges when assessing the environmental impacts of construction materials. Due to the long life of construction materials, GWP calculation should take into consideration also time-related aspects. However, in the current GWP, any temporal information is lost, making traditional static GWP better suited for retrospective assessment rather than forecasting purposes. Building on this need, this study uses a time-dependent GWP to assess the carbon footprint of two newly developed construction materials, produced through the recycling of industrial residues (stainless steel slag and industrial goethite). The results for both materials are further compared with the results of traditional ordinary Portland cement (OPC) based concrete, presenting similar characteristics. The results of the dynamic GWP (D_GWP) are also compared to the results of traditional static GWP (S_GWP), to see how the methodological development of D_GWP may influence the final environmental evaluation for construction materials. The results show the criticality of the recycling processes, especially in the case of goethite valorization. The analysis shows also that, although the D_GWP did not result in a shift in the ranking between the three materials compared with S_GWP, it provides a clearer picture of emission flows and their effect on climate change over time.</p> </abstract>

Study of Modification of High Temperature Melting Compound Steel Slag-Fly Ash

2011 ◽  
Vol 291-294 ◽  
pp. 1851-1855
Author(s):  
Yue Long ◽  
Yan Shi ◽  
Yun Bo Lei ◽  
Hong Wei Xing ◽  
Jie Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Steel Slag ◽  
Tricalcium Silicate ◽  
Dicalcium Silicate ◽  
Experimental Result ◽  
Aggregation State ◽  
Melting Compound ◽  
Cementitious Activity ◽  
Temperature Melting

Reconstruction of high temperature melting compound steel slag-fly ash can be effectively digest f-CaO in steel slag. The experimental result shows that the f-CaO contents in modified slag is greatly affected by fly ash addition(respectively 5%, 7%, 14%) when the temperature is 1580°C and constant temperature is 30min, the digestion rates are respectively 56.99%,63.69%,68.55%. Modified mineral content of the steel slag changes greatly, mainly reflects at enormous increase in magnetite, dicalcium silicate, tricalcium silicate, wustite and vitreous. By micro-structure analysis of several kinds of modified slag mineral, tricalcium silicate mainly shape for branch of tree, dicalcium silicate is in the form of a circular, wustite and vitreous mainly distribute in aggregation state. The above minerals can increase cementitious activity for modified slag becoming cement.

The High-Temperature Tensile Test of Quartz Fiber Fabric- Reinforced Resin Composites

2021 ◽  
Vol 904 ◽  
pp. 188-195
Author(s):  
Hua Qiong Wang ◽  
Li Li Zhang ◽  
Da Cheng Jiao ◽  
Yan Ru Wang ◽  
Zeng Hua Gao
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Tensile Test ◽  
Tensile Properties ◽  
Tensile Modulus ◽  
National Standard ◽  
Resin Composites ◽  
Quartz Fiber ◽  
High Temperature Tensile ◽  
Fiber Fabric

The tensile properties of quartz fiber fabric-reinforced resin composites at high temperature were studied. The effects of specimen type and dimension, temperature loading procedure, holding time and loading rate on the tensile properties of the composites at high temperatures were analyzed through series of comparative experiments, the tensile test parameters were determined. Chinese national standard for high-temperature tensile property testing of the composites was compiled based on the data collected. According to the established standard, the tensile testing at 500°C was carried out. Compared with the tensile properties at room temperature, the tensile strength and tensile modulus of the composite at high temperature decreases significantly, with the tensile strength decreasing by about 42.32% and the tensile modulus decreasing by about 24.18%. This is mainly due to the high temperature which causes part of the resin matrix to pyrolyze and detach from around the fiber, thus losing the integrity of the material. In addition, this national standard for high-temperature tensile properties has some general applicability to different types of fiber-reinforced resin composites.

Feasibility Studies on Selective Laser Melting of Copper Powders for the Development of High-temperature Circuit Carriers

2016 ◽  
Vol 2016 (1) ◽  
pp. 000517-000522
Author(s):  
Aarief Syed-Khaja ◽  
Christopher Kaestle ◽  
Joerg Franke
Keyword(s):  
High Temperature ◽  
Selective Laser Melting ◽  
Pure Copper ◽  
Feasibility Studies ◽  
Influential Factors ◽  
Powder Materials ◽  
Laser Melting ◽  
Bronze Alloy ◽  
Ceramic Surfaces ◽  
Copper Powders

Abstract Additive manufacturing (AM) has the potential to lead significant changes in the present state-of-the-art production processes. This provides tool-free and direct manufacturing of complex geometries simultaneously integrating various functions into components. Though AM techniques are widely used in various sectors, the application into electronics production has been not yet explored. In electronics production, substrate development has high relevance due to their multi-functionality in giving the mechanical support and electrically connecting electronic components. This contribution introduces an innovative approach in the development of high-temperature substrates through additive layered manufacturing. The technique used in the investigations was selective laser melting (SLM) of copper based powder materials mainly bronze alloy and pure copper, for the generation of conductive patterns on ceramic surfaces. The process parameters for the SLM technique and the influential factors in the generation of conductive structures are discussed in detail.

scholarly journals Growth, Stratification, and Liberation of Phosphorus-Rich C2S in Modified BOF Steel Slag

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 203 ◽  
Author(s):  
Lei Rao ◽  
Yuanchi Dong ◽  
Mancheng Gui ◽  
Yaohui Zhang ◽  
Xingmei Shen ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phosphorus Content ◽  
Steel Slag ◽  
Basic Oxygen Furnace ◽  
Holding Time ◽  
Basic Oxygen ◽  
Free Particles ◽  
Bof Slag ◽  
Grinding Time

Basic oxygen furnace (BOF) slag was modified by adding 3.5% SiO2 and holding at 1673 K for 0, 5, 40, 90, 240, or 360 min. Kilo-scale modification was also carried out. The growth, stratification, and liberation of P-rich C2S in the modified slag were investigated. The optimum holding time was 240 min, and 90% of C2S grains were above 30 μm in size. The phosphorus content increased with holding time, and after modification, the phosphorus content in C2S was nearly three times higher than that in the original slag (2.23%). Obvious stratification of C2S was observed in the kilo-scale modification. Upper C2S particles with a relatively larger size of 20–110 μm was independent of RO (FeO-MgO-MnO solid solution) and spinel, which is favorable for liberation. Lower C2S was less than 3 μm and was embedded in spinel, which is not conducive to liberation. The content of phosphorus in upper C2S (6.60%) was about twice that of the lower (3.80%). After grinding, most of the upper C2S existed as free particles and as locked particles in the lower. The liberation degree of C2S in the upper increased with grinding time, from 86.02% to 95.92% in the range of 30–300 s, and the optimum grinding time was 180 s. For the lower slag grinding for 300 s, the liberation degree of C2S was 40.07%.

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