Influence Of Red Mud Research Articles

Influence of Red Mud on Swelling-shrinkage and Mechanical Performance of Compacted Expansive Soil

Influence of Red Mud on Swelling-shrinkage and Mechanical Performance of Compacted Expansive Soil

Influence of red mud as a catalyst in the thermocatalytic reforming process

AbstractThis work studies red mud, a residue from the processing of bauxite, as a support catalyst in the thermocatalytic reforming (TCR) process, using wood, digestate, and straw as case studies. Thermocatalytic reforming is a thermochemical process for the conversion of biomass into biofuels, combining intermediate pyrolysis and catalytic reforming and resulting in high‐quality biofuels. The quantity and quality of the catalyst in the postreformer is vital as it influences the reactions taking place in it. Normally, nonreactive components of the char produced in the process act as the catalyst in the postreformer but adding a support catalyst may improve the products. In this work, red mud is introduced in the process by mixing it with the feedstock in a ratio of 1:3. The results, in comparison with normal TCR experiments on the same feedstock materials, show that the introduction of red mud into the process generally reduces the biochar yield and generally increases the biogas and product water yields, and the bio‐oil yield remains constant. Its introduction also increases the hydrogen fraction of the gas and tends to reduce the nitrogen and sulfur content of the products, thus improving their quality. These observations are consistent across feedstock materials and postreformer temperatures. The results therefore suggest that red mud is a good support catalyst for increasing the gas yield, increasing the hydrogen fraction of the gas, and improving the quality of the products from the TCR process.

Influence of red mud on the engineering and microstructural properties of sustainable ultra-high performance concrete

This paper introduces a new application of industrial solid waste red mud to use as a cementitious material in the development of ultra-high performance concrete (UHPC) performances. In addition, utilization of red mud can reduce the environmental impact of red mud landfill. For gaining this aims, UHPC specimens were prepared with different contents of red mud and analyzed the effects of different RM contents on the fluidity, setting time, mechanical properties, durability, drying shrinkage and microstructure of the red mud-based UHPC. The results indicated that fluidity was reduced to 310 mm at 20% red mud level, but it still belongs to enormous fluidity, which is convenient for construction. In addition, it is worth noting that using red mud instead of cement can significantly shorten the setting time, providing a new method for applying the UHPC rapid-repairing process. Red mud-based UHPC mortar prepared with appropriate red mud instead of cement exhibits higher mechanical properties, better durability and reduced drying shrinkage of UHPC during curing. After curing for 28d, the highest compressive strength of UHPC samples containing 20% red mud was 129.5 MPa, the compressive strength of the UHPC samples' sulfate resistance was 136.6 MPa, and the drying shrinkage value was around 414 µm. Moreover, observed information from scanning electron microscopy (SEM) noted that red mud can fill the micro-cracks between particles of cementitious materials, make the structure more compact and form new hydrates. Finally, the two characteristics of low cost and energy consumption further promote the sustainable application of red mud-based UHPC. Therefore, replacing OPC with 20% RM is meaningful to produce a sustainable UHPC mixture and field applications.

Improved corrosion resistance of reinforcing steel in mortars containing red mud after long-term exposure to aggressive environments

The influence of red mud (RM) on long-term corrosion resistance of reinforcing steel in mortars exposed to coupled actions of chloride attack and natural carbonation was evaluated in this study. Moreover, the pore structure and hydration products of RM mortar with 20 wt% red mud were compared with those of ordinary Portland cement (OPC) mortar. Compared with OPC mortar, the higher electrical resistivity of RM mortar during the long-term exposure to aggressive environments delayed the penetration of chloride ions and the diffusion of oxygen, therefore providing an effective protection for the embedded steel. In addition, owing to the possible filling effect of CaCO3, the natural carbonation of RM mortar was unexpectedly beneficial for improving the corrosion resistance of steel by facilitating the formation of a compact steel-mortar interface.

Influence of red mud on performance enhancement of fly ash-based geopolymer concrete

Influence of red mud on performance enhancement of fly ash-based geopolymer concrete

Role of red mud in natural passivation and chloride-induced depassivation of reinforcing steels in alkaline concrete pore solutions

The influence of red mud (RM) on electrochemical behaviour, chemical composition, surface morphology and thickness of passive films naturally formed on low-carbon steel and 2304 stainless steel in alkaline concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. Furthermore, chloride-induced pitting corrosion of passivated steels was characterized with and without RM. Results show that RM was detrimental to the passivity of steels by forming defective passive films with reduced thickness. Despite the formation of a less protective passive film on low-carbon steel, beneficial role of RM was highlighted in preventing chloride-induced depassivation and corrosion propagation.

Influence of red mud and waste glass on the microstructure, strength, and leaching behavior of bottom ash-based geopolymer composites

The influence of waste glass and red mud addition as alternative source of aluminosilicate precursors on the microstructural, mechanical, and leaching properties of bottom ash-based geopolymer was studied in this work through mineralogical, morphological, and spectroscopic analysis, as well as by conducting compressive strength and leaching tests. The bottom ash-based geopolymer composites were synthesized by adding a constant amount of waste glass (10% by weight) and increasing amounts of red mud (up to 30% by weight). The results derived from FTIR, 29Si and 27Al MAS NMR, and SEM–EDX revealed that adding up to 10% (by weight) red mud to the synthesis mixes leads to an increase in the degree of geopolymerization of the activated mixes. The compressive strength followed the same trend. An increase of more than 10% (by weight) red mud added to the synthesis mixes results in a significant decrease of compressive strength of the geopolymer composites. A low leachability of geopolymer composites in regard with their contaminants was revealed especially for those with good compressive strength.

Influence of red mud on mechanical and durability performance of self-compacting concrete.

Red mud is a hazardous waste material produced during alkaline leaching of bauxite in the Bayer process. This study proposed the use of red mud to replace fly ash in self-compacting concrete (SCC) and the influences of red mud on fresh and hardened properties, and durability performances of SCC were studied. The fresh concrete results show that red mud had a slight negative impact on the fresh properties of SCC. The hardened concrete results show that the mechanical strength of concrete increased with increasing of red mud content. The half-cell potential test results indicated that red mud had a significant effect on restraining the corrosion process in SCC. Compared to the control sample, the red mud samples suffered less corrosion. Cracks associated with corrosion of reinforcement were observed in RMC0 and RMC100 samples after 28 day accelerated corrosion test. The ICP-MS results showed that there's no significant difference in metal elements among the solutions regardless the red mud content in concrete.The relative corrosion rate test results suggested that red mud can suppress the corrosion current. The SCC samples consisting 75% red mud performed the best resistance to corrosion according to the results of half-cell potentials and mass loss of rebar.

COMBINED UTILIZATION OF RED MUD AND MECHANICALLY ACTIVATED FLY ASH IN GEOPOLYMERS

This paper focuses on the investigation of the co-utilization of two major industrial waste materials, power station fly ash and red mud. Experimental studies were carried out to establish the correlation between the physical properties of a geopolymer product and a mixture composition. The effect of mechanical activation and the red mud dosage on the geopolymerisation was investigated. Geopolymerisation of mechanically activated fly ash has been carried out with various proportions of red mud ranging between 0–30 % by weight. The compressive strength of fly ash based geopolymer increased until 15% of red mud addition. The optimal red mud addition in fly ash geopolymer was determined. The influence of red mud on phase composition and chemical bonds of the resulted geopolymer were determined by XRD analysis and FTIR studies. Due to the geopolymerisation reactions, new phases like hydroxy-cancrinite, faujasite and thenardite appeared in the product.

Influence of red mud on fresh and hardened properties of self-compacting concrete

Red mud is a waste product from the production of alumina, it currently has limited industrial use. This study proposed to use red mud to partially replace fly ash (12.5, 25 and 50% by weight) in self-compacting concrete (SCC) and the influence of red mud on the fresh and hardened properties and microstructural behaviour of SCC were studied. Slump-flow, T500 and J-ring tests were carried out on fresh SCC mixtures. The hardened properties of red mud SCCs including compressive strength, tensile strength and elastic modulus were studied. Moreover, the chemical composition and microstructural properties of red mud concrete samples were analysed using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS), respectively. The results show that the mechanical strength of concrete increased with increasing red mud content. SCC samples consisting 50% red mud performed the best for the compressive strength and elastic modulus. The results from microscopic studies indicated that there was a slight improvement in the interfacial transition zone (ITZ) between aggregate and cement paste for red mud concrete compared with control concrete. The XRD results indicated that the chemical composition of cement paste containing red mud showed higher sodium and iron contents. With increasing red mud content, some albite crystals appearing in triclinic shape were also identified by XRD.

Influence of red mud on soil microbial communities: Application and comprehensive evaluation of the Biolog EcoPlate approach as a tool in soil microbiological studies

Red mud can be applied as soil ameliorant to acidic, sandy and micronutrient deficient soils. There are still knowledge gaps regarding the effects of red mud on the soil microbial community. The Biolog EcoPlate technique is a promising tool for community level physiological profiling. This study presents a detailed evaluation of Biolog EcoPlate data from two case studies. In experiment “A” red mud from Ajka (Hungary) was mixed into acidic sandy soil in soil microcosms at 5–50 w/w%. In experiement “B” red mud soil mixture was mixed into low quality subsoil in a field experiment at 5–50 w/w%. According to average well color development, substrate average well color development and substrate richness 5–20% red mud increased the microbial activity of the acidic sandy soil over the short term, but the effect did not last for 10months. Shannon diversity index showed that red mud at up to 20% did not change microbial diversity over the short term, but the diversity decreased by the 10th month. 30–50% red mud had deteriorating effect on the soil microflora. 5–20% red mud soil mixture in the low quality subsoil had a long lasting enhancing effect on the microbial community based on all Biolog EcoPlate parameters. However, 50% red mud soil mixture caused a decrease in diversity and substrate richness. With the Biolog EcoPlate we were able to monitor the changes of the microbial community in red mud affected soils and to assess the amount of red mud and red mud soil mixture applicable for soil treatment in these cases.

Influence of redmud on the mechanical, damping and chemical resistance properties of banana/polyester hybrid composites

A novel hybrid composite was developed with the addition of redmud as secondary reinforcing filler with banana fiber reinforced polyester composites (BFRPCs). The effect of varying parameters such as particle size (4, 6 and 13μm) and weight percentage (2, 4, 6, 8 and 10wt%) of redmud were analyzed on static mechanical, free vibration and chemical resistance properties of hybrid composites. The addition of redmud shown enhanced performance compared to the virgin BFRPCs in all the above said properties. The maximum increase of 50% in mechanical strength was observed for the BFRPCs with the addition of redmud having 4μm particle size and 8wt% of filler content compared to pure BFRPCs. The increased value of fundamental natural frequencies with associated modal damping characteristics of redmud filled BFRPCs were found using half-power band width method. All the fabricated composites performed well against various chemicals and it indicates that the resistance to the weight loss is due to the uniformly distributed redmud. To study the effect of redmud on interfacial bonding between the banana fiber and polyester matrix the Scanning Electron Microscope (SEM) image analysis was performed.

Influence of red mud, zeolite and lime on heavy metal immobilization, culturable heterotrophic microbial populations and enzyme activities in a contaminated soil

In this study we compared the efficiency of different amendments, notably red mud (a bauxite residue), natural zeolite and lime, to immobilize the heavy metals present in a polluted acidic soil [Pb (3266 mg kg − 1 d.m.), Cd (35.4 mg kg − 1 d.m.) and Zn (1495 mg kg − 1 d.m.)] and to influence several microbiological properties. The addition of all the amendments decreased significantly ( P < 0.05) the solubility of Pb, Cd and Zn and the increase of soil pH was identified as a common mechanism of action for both red mud and lime. Despite reducing the heavy metal solubility, the addition of zeolite and lime did not affect the number of culturable fast-growing heterotrophic bacteria whereas the red mud caused a significant increase ( P < 0.05) of this soil microbial component. All the amendments reduced the number of heterotrophic fungi ( P < 0.05) while only the lime addition influenced negatively the number of free-living N 2-fixing bacteria. Furthermore, the addition of red mud and lime caused a significant change of the dominant culturable bacterial community. Partial sequencing of the 16S rDNA gene of randomly selected bacterial isolates revealed that dominant strains from the lime and red mud-soils were mostly belonging to β-Proteobacteria and Bacteroidetes/Chlorobi group whilst only Actinobacteria and Firmicutes were identified in control and zeolite soils. These latter were largely colonized by Arthrobacter and Bacillus while Ralstonia and Pedobacter prevailed in soils treated with lime and red mud. Moreover, the Biolog Ecoplate assay revealed that the number of substrates utilized (OD 590 > 0.15) by the different microbial communities (richness) was following the order: red mud-soil > lime-soil > zeolite-soil = control-soil. The same trend was observed for the urease activity but not for dehydrogenase and β-glucosidase. It is concluded that all the amendments considered influenced with a different extent the heavy metal mobility in soil as well as the structure and function of the resident culturable microbial communities. Red mud was the most effective at reducing the “mobile” form of the metals considered and at promoting bacterial abundance and soil enzyme activity. Nevertheless, red mud and lime addition caused a dramatic shift of the culturable bacterial population from Gram positive to Gram negative forms. The poor catabolic activity detected with the Biolog assay for zeolite and control-soil suggested the inability of Arthrobacter and Bacillus strains to oxidize the substrates in the Ecoplate rather than reflect the actual catabolic versatility of the microbial communities.