Search Results (62)

The current study investigated the effects of geopolymer composites formulated from pumice dust partially replaced by ground granulated blast furnace slag (GGBFS) and fly ash (FA) at levels of 10%, 20%, 30%, and 40% by weight. The mixtures were evaluated for flowability, compressive strength (7, 28, and 56 days), density, and water absorption (28 and 56 days) at ambient temperatures. Moreover, compressive strength, mass loss, density, and water absorption were evaluated after exposure of the mixtures to elevated temperatures (250 °C, 500 °C, and 750 °C) at 28 days. All specimens were initially cured at 60 °C for 24 h, followed by storage under ambient laboratory conditions until testing. The inclusion of GGBFS into the mixtures decreased flowability, and the inclusion of FA resulted in its improvement. At ambient temperature, GGBFS-based mixtures, which were high in calcium content, exhibited substantially superior compressive strength and reduced absorption relative to FA-based mixtures due to the development of dense C-A-S-H gel networks. However, the compressive strength of FA-based mixtures considerably increased when exposed to a temperature of 250 °C. Moreover, at 750 °C, the FA-based mixtures showed superior residual strength (up to 18.1 MPa), lower mass loss, and reduced absorption, indicating enhanced thermal stability due to the dominance of thermally resistant N-A-S-H gels. X-ray diffraction results further supported these trends by showing the rapid deterioration of calcium-rich phases under heat and the comparative stability of aluminosilicate structures in FA-based systems. Overall, the inclusion of up to 40% GGBFS is beneficial for early strength and densification, whereas the incorporation of up to 40% FA improves durability and mechanical retention under high-temperature conditions. Full article

Blast furnace tuyeres are the primary dust emission source in ironmaking facilities (accounting for over 30% of total pollutants). High-temperature dust plumes with intense thermal energy are prone to dispersion, while China’s steel industry ultra-low emission standards (particulate matter ≤ 10 mg/m³) impose strict requirements on capture efficiency. Existing technologies often neglect crosswind interference and lack coordinated design between air volume regulation and hood structure, leading to excessive fugitive emissions and non-compliance. This study established a localized numerical model for high-temperature dust capture at blast furnace tuyeres, investigating air volume’s impact on velocity fields and capture efficiency, revealing crosswind interference mechanisms, and proposing optimization strategies (adding hood baffles, adjusting dimensions, installing ejector fans). Results show crosswind significantly reduces efficiency—only 78% at 1.5 m/s crosswind and 400,000 m³/h flow rate. The optimal configuration (2.5 m side flaps plus1.4 m baffles) achieves 99% efficiency, maintaining high performance at lower flow rates: 350,000 m³/h (1.5 m/s crosswind) and 250,000 m³/h (0.9 m/s crosswind). This study provides technical support for blast furnace tuyere dust control and facilitates ultra-low emission compliance in the steel industry. This study supports blast furnace tuyere dust control and aids the steel industry in meeting ultra-low emission standards. Notably, the proposed optimization scheme boasts simple structural adjustments, low retrofitting costs, and good compatibility with existing production lines, enabling direct industrial promotion and notable environmental and economic gains. Full article

Intensive calcination, selection and metallurgical joint comprehensive utilization of solid waste blast furnace gas ash generated by a Chinese iron and steel plant. The main valuable elements in the gas ash are Fe, Pb, Zn, and C, with contents of 22.46%, 3.22%, 10.57%, and 27.02%, respectively. The iron minerals are mainly magnetite and hematite/limonite. Lead exists primarily in the form of lead vanadate and basic lead chloride. Zinc is associated with oxygen, sulfur, and iron in the form of zinc ferrite crystals. The effects of calcination temperature, calcination time, and reducing agent dosage on gasification and reduction indices were investigated. Results showed that using a gasification and reduction calcination–magnetic separation process with weak magnetism, at a calcination temperature of 1150 °C, with 20% anthracite as the reducing agent and a calcination time of 2 h, the volatilization rates of lead and zinc reached 96.70% and 98.26%, respectively. When the roasted ore was ground to a particle size of D₉₀ = 0.085 mm, high-quality iron concentrate with 65.61% iron grade and low lead and zinc contents of 0.08% and 0.17% was obtained, meeting the quality requirements for iron concentrate. The tailings from iron selection can be used as additives in cement and other construction materials. This integrated process combining pyrometallurgy and mineral processing enables the efficient and comprehensive utilization of blast furnace gas dust. Full article

The development of sustainable self-compacting concrete (SCC) requires alternative binders that minimise ordinary Portland cement (OPC) consumption while ensuring long-term performance. This study investigates sulfate-activated SCC (SA SCC) incorporating high volumes of industrial by-products, whereby 72% ground granulated blast furnace slag (GGBS) and 18% fly ash (FA) were activated with varying proportions of OPC and gypsum. Quarry dust was used as a fine aggregate, while granite and electric arc furnace (EAF) slag served as coarse aggregates. Among all formulations, the binder containing 72% GGBS, 18% FA, 4% OPC, and 6% gypsum was identified as the optimum composition, providing superior mechanical performance across all curing durations. This mix achieved slump flow within the EFNARC SF2 class (700–725 mm), compressive strength exceeding 50 MPa at 270 days, and flexural strength up to 20% higher than OPC SCC. Drying shrinkage values remained below Eurocode 2 and ASTM C157 limits, while EAF slag increased density, but slightly worsened shrinkage compared to granite mixes. Microstructural analysis (SEM-EDX) confirmed that strength development was governed by discrete C-S-H and C-A-S-H gels surrounding unreacted binder particles, forming a dense interlocked matrix. The results demonstrate that sulfate activation with a 4% OPC + 6% gypsum blend enables the production of high-performance SCC with 94–98% industrial by-products, reducing OPC dependency and environmental impact. This work offers a practical pathway for low-carbon SCC. Full article

Today, several conventional wastes (fly ash, ground granulated blast furnace slags, etc.) are used as valid precursors for geopolymer synthesis. However, there are several new wastes that can be studied to replace geopolymer precursors. This study investigates the behavior of four industrial wastes—suction dust (SW1), red mud (SW2), electro-filter dust (SW3), and extraction sludge (SW4)—as 20 wt.% substitutes for metakaolin in geopolymer synthesis. The objective is to assess how their incorporation before alkali activation affects the structural, thermal, mechanical, chemical, and antimicrobial properties of the resulting geopolymers, namely GPSW1–4. FT-IR analysis confirmed successful geopolymerization in all samples (the main Si-O-T band underwent redshift, confirming Al incorporation in geopolymer structures after alkaline activation), and stability tests revealed that none of the GPSW1–4 samples disintegrated under thermal or water stress. However, GPSW3 showed an increase in efflorescence phenomena after these tests. Moreover, compressive strength was reduced across all waste-containing geopolymers (from 22.0 MPa for GP to 12.6 MPa for GPSW4 and values lower than 8.1 MPa for GPSW1–3), while leaching tests showed that GPSW1 and GPSW4 released antimony (127.5 and 0.128 ppm, respectively) above the legal limits for landfill disposal (0.07 ppm). Thermal analysis indicated that waste composition influenced dehydration and decomposition behavior. The antimicrobial activity of waste-based geopolymers was observed against E. coli, while E. faecalis showed stronger resistance. Overall, considering leaching properties, SW2 and SW3 were properly entrapped in the GP structure, but showed lower mechanical properties. However, their antimicrobial activity could be useful for surface coating applications. Regarding GPSW1 and GPSW4, the former needs some treatment before incorporation, since Sb is not stable, while the latter, showing a good compressive strength, higher thermal stability, and leaching Sb value not far from the legal limit, could be used for the inner reinforcement of building materials. Full article

This study explores the potential of using sustainable materials in brick manufacturing by designing a novel brick mix in the laboratory, incorporating sand, lime kiln dust (LKD) waste, tyre rubber, and ground granulated blast furnace slag (GGBFS) waste. These cementless bricks blended LKD–GGBFS wastes as the binder agent and fine crumb rubber from waste tyres as a partial replacement for sand in measured increments of 0%, 5%, and 10% by volume of sand. Ordinary Portland cement (OPC) and fired clay bricks were sourced from the industry, and their properties were compared to those of the laboratory bricks. Tests performed on the industry and laboratory bricks included compressive strength (CS), freeze-thaw (F-T), and water absorption (WA) tests for comparison purposes. Additionally, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed on the bricks to assess the morphological and mineralogical changes responsible for the observed strengths and durability. The CS and WA values of the engineered bricks were 12, 6, and 4 MPa, and 7, 12, and 15%, respectively, for 0, 5, and 10% crumb rubber replacements. The industry bricks’ average CS and WA values were 13 MPa and 8%, respectively. From the results obtained, the green laboratory bricks passed the minimum strength requirements for load-bearing and non-load-bearing bricks, which can be used to construct small houses. Lastly, the engineered bricks demonstrated strength and durability properties comparable to those of the industry-standard bricks, indicating their potential as a sustainable alternative to help divert waste from landfills, reduce the pressure on natural fine sand extraction, and support eco-conscious brick production for a sustainable environment. Full article

The iron and steel industry generates large quantities of iron-bearing dust (IBD), contributing to resource inefficiency and environmental concerns. This study investigates heating methods and the use of organic solid waste, specifically waste tire carbon (WTC), as a reductant for the recovery of Fe from sintering machine tail dust (SMTD) and steelmaking gravity dust. The results indicate that the optimal reduction conditions occurred at 1000 °C, with a 2:1 ratio of SMTD to WTC, and 0% O₂ holding for 45 min. WTC is the best material, and heating methods affect it limitedly. The leaching behavior of seven metals was measured, showing an increase in the leaching of Ca and Al compared to the raw materials. The study shows that WTC provides a promising alternative reductant for IBD reduction, offering an energy-saving and low-carbon alternative to conventional fossil fuel injections in blast furnaces. The risk of Cr leaching should be paid attention to while enhancing Fe recovery. Full article

The wet electrostatic precipitator (WESP) is crucial for the ultra-purification of blast furnace gas in gas-fired generator units. To address issues like high water consumption, poor atomization leading to spark discharge, and uneven water mist distribution, a water mist testing system using a laser particle-size analyzer was established. Eight spray nozzles were tested to identify the optimal atomization performance and operating parameters. The effect of chemical agglomeration agents on nozzle atomization and particle capture efficiency was also examined. The results show that the atomization effect was the best when the operating water pressure was 0.5 MPa. The D₅₀ of the blast furnace dust increased from 8.529 μm to 20.30 μm after electrostatic precipitation when the 1/8 rotating core nozzles were installed in the WESP, and the proportion of dust particles whose diameter is ≤5 μm decreased by 20.09% compared with the dust emitted from the inlet. The total dust removal efficiency reached 83.41%. With chemical agglomeration, the D₅₀ reached 24.88 μm, and removal efficiency rose to 96.98%. Among the tested nozzles, the 1/8 rotating core nozzle was the most effective, combining superior atomization, maximum dust removal efficiency, and minimal water consumption, making it ideal for blast furnace gas purification. Full article

Using solid waste-based materials, such as recycled building aggregate (RCA), preparing 3D-printed materials can reduce costs but increase the water–cement ratio of the printed material, which reduces its mechanical performance. In order to solve the problem of mechanical properties decline caused by an increase in the w/c ratio, this experiment found that adding calcined salt mud (CSM) to the printing materials and changing the water-to-cement ratio from 0.37 to 0.4 CSM can ensure that the compressive strength of the printing materials remains basically unchanged. Moreover, through TG, SEM, and other microscopic data, it can be seen that calcium hydroxide in CSM can not only participate in the synergistic reaction of ethylene/vinyl acetate copolymer (EVA) and dust ash (DA), produce more NaOH, and promote the hydration of granulated blast furnace slag (GBFS) but also promote the formation of ettringite together with SO₄²⁻ in solution, optimizing pore size distribution. Full article

Steel metallurgical dust, characterized by a substantial output, minute particle size, and intricate composition, poses a considerable risk of environmental contamination while simultaneously embodying an exceptionally high potential for recycling. To achieve its resource utilization, chemical analysis, particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy, and water leaching methods were employed to investigate the chemical compositions, particle size distributions, phase compositions, and microscopic morphologies of blast furnace bag dust, sintering dust, converter fine dust, and electric arc furnace dust from steel plants. The results indicate that the four types of dust have extremely fine particle sizes, with the main distribution range of particle size being less than 100 μm. The main constituent element is Fe (19–56%), and it also contains Zn (1.4–33.5%), Pb, K, C, and other valuable elements. Alkali metals in blast furnace bag dust and sintering machine head dust existed mainly in the form of chloride. The zinc phases in sintering machine head dust and converter fine dust were ZnFe₂O₄, and the zinc phases in blast furnace bag dust were ZnCl₂ and ZnFe₂O₄. Zinc in electric furnace dust was composed of ZnO and ZnFe₂O₄, accounting for 70.31% and 23.12%, respectively. There are significant differences in the types and contents of valuable elements among various dusts, making it difficult to achieve full-scale recovery through a single process. In view of this, a process of “in-plant recycling of harmless dusts—collaborative treatment of harmful dusts” has been proposed. Based on the characteristics of metallurgical dusts, multiple processes are used for collaborative treatment (using hydrometallurgical and pyrometallurgical methods), which can not only directly recover iron resources from dusts within the plant, but also avoid the waste of valuable elements such as Zn, Pb, K, Na, etc. It is hoped that the above work can provide a reference for steel enterprises to achieve full-scale and high value-added treatment of metallurgical dusts. Full article

A technology was developed for managing Zn-bearing dust, facilitating the recycling of hazardous solid waste and the production of porous carbon materials. In the one-step process, Zn-bearing dusts were employed not only as raw materials to prepare reduced Zn-bearing dust pellets but also as activators to prepare K, Na-embedded activated carbon. In the process, the Fe, C, Zn, K, and Na in the dusts were rationally utilized. Under optimal conditions, the reduced pellets and porous carbon materials were simultaneously produced and characterized using XRD, SEM/EDS, FTIR, and adsorption of nitrogen techniques. The results indicated that the reduced pellets, with low levels of harmful elements and high iron grade and strength, could be directly used as burden for enhancing blast furnace operation without additional agglomeration. Meanwhile, the K and Na-embedded porous carbon material demonstrated superior SO₂ and NO adsorption capacities compared to the commercial activated carbon, making it suitable for purifying SO₂ and NO-bearing flue gas. The hazardous solid wastes were effectively used to treat flue gases through this technology. The mechanism in the synergistic reduction and activation process was elucidated. The coupling effect between the reduction reactions of Fe₂O₃, Fe₃O₄, FeO, MgFe₂O₄, CaFe₂O₄, ZnFe₂O₄, KFeO₂, and NaFeO₂ in the dusts and activation reaction of C in the coal promoted the synchronous reduction and activation process. Full article

This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO₂ during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis. Full article

This study aimed to investigate the behavior of accelerated carbonation-cured laboratory specimens using the ultrasonic non-destructive testing (UNDT) method and compare the results with the destructive testing (DT) method. The materials used in the study included a blend of lime kiln dust and ground granulated blast furnace slag (LKD-GBFS) wastes, natural fine aggregate (sand), and alternative fine aggregates from waste tires. The chemical analysis of the LKD and GBFS samples highlighted them as suitable alternatives to OPC, hence their utilization in the study. A 60:40 (LKD-GBFS) blending ratio and a 1:2 mix design (one part LKD-GBFS blend and two part sand) was considered. The natural fine aggregate was partially replaced with fine waste tire rubber crumbs (TRCs) in stepped increments of 0, 5, and 10% by the volume of the sand. The samples produced were cured using three curing regimens: humid curing (HC), accelerated carbonation curing (ACC) with no water curing (NWC) afterwards, and water curing after carbonation (WC). From the results, an exponential model was developed, which showed a direct correlation between the UNDT and DT results. The developed model is a useful tool that can predict the CS of carbonated samples when cast samples are unavailable. Lastly, a total CO₂ uptake of 15,912 g (15.9 kg) was recorded, which underscores ACC as a promising curing technique that can be utilized in the construction industry. This technique will bring about savings in terms of the time required to produce masonry units while promoting a change in the basic assumptions of a safer and cleaner environment. Full article

The steel industry accounts, according to the International Energy Agency, for ~6.7% of global CO₂ emissions, and the major portion of its contribution is from steelmaking via the blast furnace (BF) route. In the short term, a significant reduction in fossil CO₂ emissions can be achieved through the introduction of bio-coal into the BF as part of cold bonded briquettes, by injection, or as part of coke. The use of bio-coal-containing residue briquettes was previously demonstrated in industrial trials in Sweden, whereas bio-coal injection was only tested on a pilot scale or in one-tuyere tests. Therefore, industrial trials replacing part of the pulverized coal (PC) were conducted. It was concluded that the grinding, conveying, and injection of up to 10% of charcoal (CC) with PC can be safely achieved without negative impacts on PC injection plant or BF operational conditions and without losses of CC with the dust. From a process point of view, higher addition is possible, but it must be verified that grinding and conveying is feasible. Through an experimentally validated computational fluid flow model, it was shown that a high moisture content and the presence of oversized particles delay devolatilization and ignition, lowering the combustion efficiency. By using CC with similar heating value to PC, compositional variations in the injected blend are not critical. Full article

The main purpose of this research is to develop a solid waste-based cementitious material (SWC) instead of cement for solidifying a large amount of marine soft soil with high water content and low bearing capacity in coastal areas. This aims to solve the problems encountered in the practical application of cement soil, such as slow strength growth and poor durability. The SWC includes ground granulated blast furnace slag (GGBS), dust ash (DA), and activated cinder powder (ACP), with admixtures of naphthalene sulfonate formaldehyde condensate (NS) and compound salt early strength agent (SA). Both the 7 d and 28 d compressive strength values of the SWC formulations G4 and G7 are about twice as strong as those of cement soil (GC), even when mixed with seawater. Immersion tests revealed that stabilized soil had superior resistance to seawater corrosion compared to cement soil. X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis explained that the main hydration products in cement soil are C-S-H and CH, while in stabilized soil, SWC generates a large amount of C-A-S-H with gelling properties and AFt with filling properties. These hydration products have better effects on strength and seawater erosion resistance. Full article