scholarly journals Rapid Evaluation of the Pozzolanic Activity of Bayer Red Mud by a Polymerization Degree Method: Correlations with Alkali Dissolution of (Si+Al) and Strength

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5546
Author(s):  
Yaguang Wang ◽  
Xiaoming Liu ◽  
Zhiqing Xie ◽  
Huimin Wang ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Red Mud ◽  
Activity Index ◽  
Correlation Coefficients ◽  
Evaluation Methods ◽  
Pozzolanic Activity ◽  
Infrared Spectrometry ◽  
Polymerization Degree ◽  
Strength Index ◽  
Alumina Production ◽  
Bayer Red Mud

A large amount of Bayer process red mud is discharged in the process of alumina production, which has caused significant pollution in the environment. The pozzolanic activity of Bayer red mud as a supplementary cementitious material is a research hotspot. In this work, a new method for Fourier-transform infrared spectrometry is used to determine the polymerization degree of Bayer red mud in order to evaluate its pozzolanic activity. Based on the results of the dissolution concentration of (Si+Al), strength index and polymerization degree of Bayer red mud, the relationships between different evaluation methods were analyzed, and the relevant calculation formulas of pozzolanic activity were obtained. The results showed that different evaluation methods can reflect the variation law of pozzolanic activity in Bayer red mud. The polymerization degree of Bayer red mud had a good linear relationship with the pozzolanic activity index obtained by the strength index and dissolution concentration of (Si+Al), respectively. The polymerization degree was negatively correlated with pozzolanic activity index and dissolution concentration of (Si+Al), and the correlation coefficients were greater than 0.85. Therefore, this method was found to be effective and hence can be used as a rapid and simple test for pozzolanic activity evaluation of Bayer red mud.

scholarly journals Tailings after Iron Extraction in Bayer Red Mud by Biomass Reduction: Pozzolanic Activity and Hydration Characteristics

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3955
Author(s):  
Yaguang Wang ◽  
Xiaoming Liu ◽  
Yong Li ◽  
Dongsheng Li ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Red Mud ◽  
Activity Index ◽  
Cementitious Materials ◽  
Pozzolanic Activity ◽  
Hydration Reaction ◽  
Dense Matrix ◽  
Bayer Red Mud ◽  
Hydration Characteristics ◽  
Biomass Reduction ◽  
Active Substances

Bayer red mud (BRM) is a kind of solid waste with high hematite content, and its effective utilization is difficult due to the special physicochemical properties. In this work, Fe2O3 in BRM was reduced to Fe3O4 by biomass, and iron concentrate and high activity tailings were obtained after magnetic separation. The pozzolanic activity and hydration characteristics of the tailings were systematically studied. The results showed that the relatively stable polymerization structures of Si-O and Al-O in BRM are destroyed under the effect of biomass reduction at 650 °C, and some fracture bonds and activation points are formed in the structures. The aluminosilicate phases in the BRM were easy to transform into the active substances of Si and Al. The pozzolanic activity of tailings is greatly improved, and its pozzolanic activity index is 91%. High polymerization degree of gel and ettringite are formed since more active substances and alkali in the tailings promote the hydration reaction of cement-based cementitious materials, which made cementitious materials have dense matrix, good mechanical properties, and environmental performance. This work has realized the full quantitative utilization of BRM and provided a feasible way for the resource utilization of BRM.

scholarly journals Improving the flame retardancy of ethylene vinyl acetate composites by incorporating layered double hydroxides based on Bayer red mud

e-Polymers ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Yi Qian ◽  
Kangjia Jiang ◽  
Long Li
Keyword(s):  
Vinyl Acetate ◽  
Flame Retardancy ◽  
Layered Double Hydroxides ◽  
Red Mud ◽  
Ethylene Vinyl Acetate ◽  
Precipitation Method ◽  
Infrared Spectrometry ◽  
Cone Calorimeter Test ◽  
Bayer Red Mud ◽  
Double Hydroxides

AbstractNowadays, reducing the hazards of bayer red mud (BRM) is an important research direction in the fields of environmental and safety. In this article, Mg/Al/Fe ternary layered double hydroxides (Mg/Al/Fe-LDHs) were synthesized successfully by a co-precipitation method based on introducing Mg2+ into the BRM suspension. The thermogravimetric analysis (TGA) results showed that the decomposition rate of LDHs is higher than that of BRM, which indicates that LDHs can absorb more heat than BRM during the decomposition process. Subsequently, BRM and LDHs were added into the ethylene vinyl acetate (EVA) to investigate its effects on reducing flammability of the composites. The cone calorimeter test (CCT) results demonstrated that 50 wt% LDH-B can make the peak value of HRR (PHRR) decrease from 1694.8 kW/m2 (EVA) to 199.2 kW/m2 (ELDH2). The smoke density test (SDT) results showed that the luminous flux of ELDH2 is nearly 95% at the end of test with a pilot flame, which is much higher than that of EVA and EBRM. The thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) results confirmed that LDHs can improve the thermal stability of composites and reduce the production of some toxic gases. Compared with BRM, the improved flame retardancy of Mg/Al/Fe-LDHs is ascribed to the introduction of Mg2+, which offering an enhanced catalytic carbonization capability, as well as the physical barrier effect of char residue layer catalyzed by the lamellar LDHs

scholarly journals Effect of gas composition and temperature on reduction characteristic in red mud-coal composite pellets

2019 ◽  
Vol 23 (5 Part A) ◽  
pp. 2561-2568
Author(s):  
Yi Man ◽  
Jun-Xiao Feng ◽  
Zhan-Min Yang ◽  
Zeng-Lu Song ◽  
Chao Yang
Keyword(s):  
Red Mud ◽  
Reduction Process ◽  
Gas Composition ◽  
X Ray Diffraction ◽  
Alumina Production ◽  
X Ray ◽  
N2 Atmosphere ◽  
Composite Pellets ◽  
Optimum Reaction ◽  
Bayer Red Mud

The disposal of red mud, which is the by-product obtained from alumina production, has brought about environmental pollution because of its caustic nature as well its metal and alkaline contents. Red mud-coal composite pellets were directly reduced to deal with red mud. The influences of reduction temperature and gas composition on the reaction were studied. Experiment results indicated that the optimum reaction parameters were a temperature of 1100?C and an H2 atmosphere. Reduction degrees in H2 and CO atmospheres were significantly higher than those in N2 atmosphere. Reduction did not strictly follow the Fe2O3 ? Fe3O4 ? FeO ? Fe sequence in N2 atmosphere, and this phenomenondid not occur in H2 atmosphere. This gas?solid combination reduction process is appropriate for recovering Fe from Bayer red mud. Meanwhile, the microstructure and phase transformation of the reduction process were investigated via scanning electron microscopy and X-ray diffraction.

scholarly journals Patient-Reported Dysphagia in Adults with Eosinophilic Esophagitis: Translation and Validation of the Swedish Eosinophilic Esophagitis Activity Index

Dysphagia ◽  
2021 ◽  
Author(s):  
Sofie Albinsson ◽  
Lisa Tuomi ◽  
Christine Wennerås ◽  
Helen Larsson
Keyword(s):  
Eosinophilic Esophagitis ◽  
Activity Index ◽  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Control Group ◽  
Cronbach’S Alpha ◽  
Intraclass Correlation Coefficients ◽  
Cronbach's Alpha ◽  
Patient Reported ◽  
Eortc Qlq

AbstractThe lack of a Swedish patient-reported outcome instrument for eosinophilic esophagitis (EoE) has limited the assessment of the disease. The aims of the study were to translate and validate the Eosinophilic Esophagitis Activity Index (EEsAI) to Swedish and to assess the symptom severity of patients with EoE compared to a nondysphagia control group. The EEsAI was translated and adapted to a Swedish cultural context (S-EEsAI) based on international guidelines. The S-EEsAI was validated using adult Swedish patients with EoE (n = 97) and an age- and sex-matched nondysphagia control group (n = 97). All participants completed the S-EEsAI, the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Oesophageal Module 18 (EORTC QLQ-OES18), and supplementary questions regarding feasibility and demographics. Reliability and validity of the S-EEsAI were evaluated by Cronbach’s alpha and Spearman correlation coefficients between the domains of the S-EEsAI and the EORTC QLQ-OES18. A test–retest analysis of 29 patients was evaluated through intraclass correlation coefficients. The S-EEsAI had sufficient reliability with Cronbach’s alpha values of 0.83 and 0.85 for the “visual dysphagia question” and the “avoidance, modification and slow eating score” domains, respectively. The test–retest reliability was sufficient, with good to excellent intraclass correlation coefficients (0.60–0.89). The S-EEsAI domains showed moderate correlation to 6/10 EORTC QLQ-OES18 domains, indicating adequate validity. The patient S-EEsAI results differed significantly from those of the nondysphagia controls (p < 0.001). The S-EEsAI appears to be a valid and reliable instrument for monitoring adult patients with EoE in Sweden.

scholarly journals Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1571
Author(s):  
Pavel Grudinsky ◽  
Dmitry Zinoveev ◽  
Denis Pankratov ◽  
Artem Semenov ◽  
Maria Panova ◽  
...  
Keyword(s):  
Magnetic Separation ◽  
Grain Growth ◽  
Red Mud ◽  
Sodium Sulfate ◽  
Phase Distribution ◽  
Solid Phase ◽  
Alumina Production ◽  
Metallic Particles ◽  
Iron Phase ◽  
High Alkalinity

Red mud is an iron-containing waste of alumina production with high alkalinity. A promising approach for its recycling is solid-phase carbothermic roasting in the presence of special additives followed by magnetic separation. The crucial factor of the separation of the obtained iron metallic particles from gangue is sufficiently large iron grains. This study focuses on the influence of Na2SO4 addition on iron grain growth during carbothermic roasting of two red mud samples with different (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21, respectively. Iron phase distribution in the red mud and roasted samples were investigated in detail by Mössbauer spectroscopy method. Based on thermodynamic calculations and results of multifactorial experiments, the optimal conditions for the roasting of the red mud samples with (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21 were duration of 180 min with the addition of 13.65% Na2SO4 at 1150 °C and 1350 °C followed by magnetic separation that led to 97% and 83.91% of iron recovery, as well as 51.6% and 83.7% of iron grade, respectively. The mechanism of sodium sulfate effect on iron grain growth was proposed. The results pointed out that Na2SO4 addition is unfavorable for the red mud carbothermic roasting compared with other alkaline sulfur-free additives.

The Effect of Substituting Rdf on the Physical and Environmental Properties of Coal Fly Ash

1988 ◽  
Vol 136 ◽  
Author(s):  
Ashaari B. Mohamad ◽  
David L. Gress
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Physical Properties ◽  
Activity Index ◽  
Coal Fly Ash ◽  
Pozzolanic Activity ◽  
Portland Cement Concrete ◽  
Fly Ash Concrete ◽  
Refuse Derived Fuel ◽  
Cadmium And Lead

ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, respectively. Although the pozzolanic activity index of coal-RDF fly ash increases over normal coal fly ash, preliminary results show that the 28-day compressive strength of concrete with direct replacement of cement and sand decreases by up to 30%. Leaching tests on crushed concrete were conducted to evaluate the environmental effect of acid rain.

scholarly journals A Study of the Potential Use of Red Mud to Obtain Compositions Based on Portland Cement

2020 ◽  
Author(s):  
Ekaterina Gerasimova ◽  
Elizaveta Gumirova
Keyword(s):  
Portland Cement ◽  
Red Mud ◽  
Waste Product ◽  
Cement Stone ◽  
Mathematical Planning ◽  
Alumina Production ◽  
Mineral Additive ◽  
Composition Properties ◽  
Planning Of Experiments ◽  
Potential Use

The paper deals with the problem of utilization of red mud which is a waste product from alumina production using the Bayer method. The principal possible use for the red mud of JSC “Bogoslovsky aluminum plant” (Sverdlovsk region) for the compositions based on Portland cement is shown. It was found that the mud introduction accelerates beginning of the cement paste setting and thickens the paste reducing its mobility. It is concluded that the introduction of red mud up to 30 % is justified in terms of strength indicators. The work is carried out using mathematical planning of experiments. Keywords: red mud, Portland cement, active mineral additive, composition, properties, bauxite, chemical composition, cement stone strength, mathematical planning of experiments

Abstract 3426: Approximate Volume Using "XYZ/2" Is Equivalent to Planimetric Volume Mismatch Evaluation

Stroke ◽  
2012 ◽  
Vol 43 (suppl_1) ◽  
Author(s):  
Marie Luby ◽  
Jennifer Hong ◽  
José G Merino ◽  
John K Lynch ◽  
Amie W Hsia ◽  
...  
Keyword(s):  
Positive Predictive Value ◽  
Predictive Value ◽  
Gold Standard ◽  
Correlation Coefficients ◽  
High Sensitivity ◽  
Evaluation Methods ◽  
Slice Thickness ◽  
Linear Measurements ◽  
Visual Evaluation ◽  
Volume Measurements

Objectives: In the clinical setting, the extent of mismatch on MRI is frequently assessed with an approximate “XYZ/2” method but the agreement with the “gold standard” planimetric volume and the “visual evaluation” methods are not known. In a published study, we established that the visual evaluation and planimetric methods are equivalent as far as mismatch classification. The objectives of this study were to quantify the agreement of the approximate method with the “gold standard” and “visual evaluation” methods and to compare the mismatch classification results. Methods: Patients were selected from the Lesion Evolution of Stroke and Ischemia On Neuroimaging (LESION) database if they: had an acute ischemic stroke, were treated with intravenous rt-PA only, and had a pre-treatment MRI with evaluable maps including trace or isotropic b1000 DWI and MTT images. A trained rater viewed the images on the PACS, placed the two perpendicular linear measurements, “X” and “Y”, on the slices with the largest DWI and MTT lesion areas, and then used a “XYZ/2” formula where “Z” was the product of the slice thickness and the total number of slices containing the lesion. A separate expert rater measured the planimetric volumes on a slice-by-slice basis with a semiautomated segmentation tool followed by manual editing. Expert readers evaluated the MRI scans for the presence of qualitative mismatch. The expert readers were not the trained reader that performed the approximate volume measurements. Quantitative mismatch was considered present if MTT volume - DWI volume ≥50 ml. Mismatch classifications using the ≥ 50 ml definition were compared by constructing contingency tables. Results: A total of 194 patients met the study criteria and had median DWI and MTT planimetric volumes of 13.06 ml and 99.27 ml respectively. For both the DWI (n=170) and MTT (n=164), 94% of the measurements were within two standard deviations of the difference between the planimetric and approximate volume measurements. Comparing the planimetric and approximate volume measurements, the Spearman correlation coefficients were 0.855 and 0.886 for the DWI and MTT measurements respectively (p<0.01). Compared to the planimetric method, the approximate “XYZ/2” method had a high sensitivity (0.91), specificity (0.80), accuracy (0.86) and positive predictive value (0.85) to detect mismatch using the ≥ 50 ml definition. Compared to the qualitative method, the approximate “XYZ/2” method had a sensitivity (0.77), specificity (0.76), accuracy (0.77) and positive predictive value (0.87) to detect mismatch using the ≥ 50 ml definition. Conclusions: The approximate “XYZ/2” method is sufficient for classifying the presence of MRI determined mismatch in acute stroke patients and therefore is a potential tool when using MRI determined mismatch as an inclusion criteria for clinical trials.

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