Properties Of Slag Research Articles

Effect of pre-wetting treatment for waste waterglass foundry sand on the properties of alkali-activated slag

Waste waterglass foundry sand (WwFS) is a solid waste generated by the foundry industries that is commonly discarded in landfills and has urgent needs for disposal and recycling. Accordingly, this study suggests using WwFS as aggregates source for the preparation of alkali-activated slag mortars (AASM). Two different pre-wetting methods (24 h pre-wetting at 20°C and 1~6 h pre-wetting at 70°C) were used to treat WwFS and compared their performances with adding quartz sand and dried WwFS mortars. Compared to WwFS mortars without pre-wetting treatment, the compressive strengths of WwFS mortars containing WwFS pre-wetting in water at 70°C at 28d were increased by 1.3~10.0%, and the C-(A)-S-H average elastic modulus was increased by 16%. This study confirmed the feasibility of using hot water pre-wetted WwFS as the single aggregate source for AASM, which is important for the large-scale utilization of WwFS.

Improving properties of Portland cement-blast furnace slag blended paste through sodium bicarbonate-induced carbonation

Improving properties of Portland cement-blast furnace slag blended paste through sodium bicarbonate-induced carbonation

Presidential Address: Metallurgical slags: A drive to circularity and search for new research agenda

Poor phase separation and fine dissemination of the desired components within congruous slag phases are key challenges limiting the recoverability of values from slags by conventional beneficiation methods. Slag microstructure conditioning is a pragmatic approach to increasing the value-in-use of discard slags, especially when integrated with the broader smelter infrastructure. Although not yet tested on oxide slag systems, this paper explores the potential application of magnetohydrodynamic principles to the crystallization behaviour of bulk slags. Integrating the slag microstructure conditioning infrastructure to the existing smelter infrastructure is key to unlocking the economic value of slags because it is most economic to condition the properties of molten slag directly after tapping. A new business model that integrates smelting units to transversal economic activities, such as cement production and suppliers of construction aggregates, can significantly increase the circularity of metallurgical slags.

Study of Li2O reduction in mould slag for continuous casting of low-carbon steel slab

The addition of Li2O increases production costs for continuous casting, despite its enhancement of the melting and flow properties of mould slag. Initially, laboratory research focused on assessing the individual impacts of Li2O, F, Na2O and Al2O3 on the viscosity and melting temperature of the slag, using a basicity of 0.95. Subsequently, four stages of industrial testing were conducted to optimise the slag, evaluating parameters such as temperature and friction force curves of the mould copper plate thermocouple, steel slag consumption per ton and strand surface quality. The optimised slag achieved a basicity of 0.98, a viscosity of 0.29 Pa·s and a melting temperature of 1115 °C, meeting all performance requirements for low-carbon steel mould slag. Compared to the original flux, the mass percentage of Li2O decreased significantly from 1.54 to 0 wt-%, while Na2O increased from 2.36 to 7.35 wt-%, and Al2O3 decreased from 7.28 to 3.49 wt-%. The operation of the optimised flux remained stable, with smooth fluctuations observed in the mould copper plate thermocouple temperature and friction force curves. These research findings hold significant reference and practical value for further development and application.

Enhancing mechanical properties of carbonated steel slag through surfactant-assisted CaCO3 crystallization

This study investigates the enhancement of mechanical properties in carbonated steel slag through surfactant-assisted CaCO3 crystallization. Sodium dodecyl benzene sulfonate (SDBS) was employed at various concentrations (0.1–0.4 mol/L) and temperatures (20–60 °C) to modulate the carbonation process. Optimal performance was achieved with 0.2 mol/L SDBS at 40 °C, resulting in a maximum CO2 uptake of 8.51 % and a compressive strength of 62.89 MPa, 81.66 % higher than unmodified steel slag. Characterization techniques confirmed the formation of crystalline calcite, vaterite, and aragonite, contributing to improved microstructure and strength. SDBS micelles act as templates for CaCO3 nucleation and growth, with low concentrations facilitating carbonation and high concentrations inhibiting it. This research offers new insights into surfactant-assisted crystallization for enhancing carbonated steel slag properties, paving the way for high-performance, eco-friendly building materials from industrial waste.

Experimental Investigation on the Properties of Concrete Containing Waste HDPE Plastic and Copper Slag as Coarse and Fine Aggregates Replacement

Resource concerns have become apparent globally, particularly in the construction sector due to the exploitation of resources for developing globalized infrastructures. This has led to challenges, especially in sourcing construction materials. Consequently, numerous studies have focused on waste management strategies with eco-efficient parameters, particularly in the realm of construction aggregates. While previous research has explored alternatives for these aggregates, there remains ample opportunity for further investigation on the effectiveness and potential of alternative materials in construction projects to promote sustainable resource management. The research aims to fill this gap by examining the impact of using alternatives for both fine and coarse aggregates, specifically copper slag and waste HDPE. This study investigates the effects of partially incorporating waste HDPE plastic and Copper slag on the strength and sustainability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials in the construction sector. Three percentages of High-Density Polyethylene (HDPE) Plastic (10%, 20%, and 30%) and Two Percentages (30% and 40 %) of copper slag were incorporated with the weight of Coarse aggregate and Fine aggregate respectively. Comparisons of conventional concrete with concrete incorporating HDPE waste & copper slag as coarse aggregate and fine aggregates were conducted. From investigation it was found that concrete incorporating 10% of HDPE and 40% of copper slag cured for 7 and 28 days had 10% increase in compressive strength compared to the nominal mix and flexural strength 25% and 40% more than nominal mix. The concrete incorporating 10% of HDPE and 30% of copper slag had 18% reduction in split tensile strength for cylinders cured for 7 days and 55% increase in split tensile strength for cylinders cured for 28 days.

FEATURES AND EXPERIENCE OF CONVERTING GAS-OIL BOILERS OF INDUSTRIAL CHP PLANTS TO BURNING BIOMASS AND SUB-BITUMINOUS COAL

The paper examines the features of biomass as a fuel and substantiates that for agrobiomass waste with a high content of alkali metal oxides and slag properties of ash, it is more appropriate to burn it in a dense bed in the form of pellets, which ensures a temperature at the exit from the furnace of no more than 900 °C, a low part of fly ash and low content of unburned carbon in it, and so eliminates the risk of smoldering deposits with their melting and slagging. Technical solutions are given and the experience is presented of gas and oil boilers of CHP plants of sugar factories reconstruction with their transfer to the burning of biomass and/or coal in a dense bed on a direct-flow grate with the replacement of the air heater with air-water heater, with the addition of stages of the boiling economizer to compensate for the decrease in the heat perception of the furnace screens, maintaining the overall height of the boiler and the plane of the boiler cell. The reconstruction of boilers according to the developed technical solutions is possible to perform in the interval between production seasons, its implementation on boilers BKZ-75 GMA of Radekhiv and Chortkiv sugar factories allowed to achieve acceptable technical, economic and environmental indicators and ensured payback due to the difference in commercial prices of gas and of agrobiomass pellets. It is proposed to replicate the positive experience in the creation of decentralized regulating thermal generation capacities of the country. Bibl. 30, Fig. 3, Tab. 4.

Fluidity and hydration evolution of cement-LS binder in the function of Mg/Al-LDH-PCE

In order to improve the early properties of lithium slag (LS) blended binder, Mg/Al-LDH/polycarboxylate (PCE) nanocomposites as chemical admixture were adopted. In this research, effects of Mg/Al-LDH/PCE nanocomposites on the hydration behavior of Portland cement including LS powder (20 wt%) were evaluated. The rheological properties and compressive strengths were studied. And the micro-analysis, such as hydration heat, hydration products and micro-morphology were also analyzed to reveal the potential hydration mechanism of LS-cement binder in the function of LDH-PCE. Results showed that LDH-PCE was beneficial for improving the rheological and mechanical performances of the fresh binder. Adding 1 wt% LDH-PCE contributed to the highest compressive strength, leading to 14.66 %, 32.62 %, and 24.88 % enhancement at 3 d, 7 d, and 28 d, respectively. LDH-PCE acted as nucleation sites and promoted the hydration process of LS blended binder. With the addition of LDH-PCE, the second exothermic peak of hydration heat evolution and cumulative hydration heat elevated obviously. The amount of CH enhanced at the early stage (3 d) due to the enhanced hydration of cement clinker and decreased at a later time (28 d) because of enhanced pozzolanic reaction. Enhanced cement hydration and pozzolanic reaction of LS generated more hydration products in the matrix, resulting in denser microstructure as well as enhanced mechanical strength. The addition of LDH-PCE significantly improved the rheological properties of the LS blended binder, shortened the setting time, increased the compressive strength of the mortar, and promoted the hydration process.

Composition and structural properties of coal gasification fine slag and its classified products – a case study

ABSTRACT Coal gasification fine slag (CGFS) is a large solid waste in the field of coal chemical industry, and its land occupation and environmental pollution caused by stockpiling and landfill make its comprehensive utilization imminent. The composition and structure of CGFS is the basis of its resource utilization, particle size classification and density classification is the important means to achieve the separation and enrichment of components in CGFS, while there are significant differences in the properties of CGFS in different particle size and different density fractions. Therefore, a CGFS sample from Shaanxi, China was used as an example in this paper, and X-ray diffraction analyzer (XRD), X-ray fluorescence spectrometry (XRF), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and low-temperature N2 adsorption tester were applied to comprehensively analyze the compositional and structural properties of the raw as well as the graded (both size-graded and density-graded) samples. The results show that the proximate composition, mineral composition, elemental composition, surface functional groups, apparent morphology, and pore structure show a good regularity with the particle size and density of the samples. Meanwhile, these properties and their variations with particle size and density were analyzed for their implication in the separation of components and resource utilizations of CGFS. The findings of this study provide ideas and data support for large-scale dissipation and high value-added disposal of CGFS.

Promising areas of slag processing in ferrous metallurgy

The characteristics of promising areas of slag processing in ferrous metallurgy are given. An increase in requirements for environmental protection was noted. Modern slag processing includes primary and secondary processing, which differ in the physical state of the slag. The technological foundations of mass processing of slag have been formed at the Ural Institute of Metals. An assessment of the state of slag processing shows that the capacity of crushing and screening plants, mainly due to complexes purchased abroad, exceeds the yield of slag of current production and leads to a decrease in dumps. Modern areas of economics and environmental protection require the creation and implementation of new technologies and equipment for the processing of slag in liquid and solid form, improving the quality of products at all stages of processing. Processing of slag in liquid form at furnace (or located near melting furnaces) plants will make it possible to organize the technological process in highly economical environmentally friendly small-sized units, to adjust the composition and properties of slag, to expand the range and quality of the resulting products, to create conditions for the utilization of melt heat and the recycling of slag processing products. These processes reduce the environmental burden on the environment, reduce material, energy and operational costs, and expand the range and quality of the products obtained

Effect of Carbonation Degree on Mineral Composition, Microstructure, and Cementitious Properties of BOF Slag

Effect of Carbonation Degree on Mineral Composition, Microstructure, and Cementitious Properties of BOF Slag

Enhancing effect of β-cyclodextrin on carbonation properties of steel slag

In order to improve the carbonation properties of steel slag, the carbonation reaction process of steel slag and the formation of carbonation products were regulated by the interaction between multiple hydroxyl groups within β-cyclodextrin (β-CD) molecule and calcium ions leached from steel slag. Through a meticulous experimental design, varying contents of β-CD, from 0.0 % to 5.0 %, were mixed with steel slag to investigate their impact on carbonation kinetics, mechanical strength, and microstructural evolution. The results indicate that β-CD significantly accelerates the carbonation process of steel slag, with a particular boost to the carbonation of β-dicalcium silicate (β-C2S), a key mineral contributing to the carbonation activity. At an optimal β-CD concentration of 2.5 %, the compressive strength of the treated slag reached a peak of 138.5 MPa, marking a 13.4 % improvement over the control sample. Similarly, the CO2 uptake was optimized at 17.9 %, increasing by 21.8 %. Mechanism analysis reveals that β-CD not only facilitates carbonation but also refines the resulting carbonation products, leading to a denser microstructure and enhanced mechanical properties. However, at a β-CD content of 5.0 %, the carbonation process was hindered by excessive viscosity. These pivotal findings propose an innovative strategy to augment the efficiency of carbonation and the inherent material properties of steel slag, thereby fostering a more sustainable approach to the utilization of industrial byproducts.

Physicochemical Properties of Air-Quenched Electric Arc Furnace Slag as Free-State Sandblasting Abrasives and Application Potential Analysis

Physicochemical Properties of Air-Quenched Electric Arc Furnace Slag as Free-State Sandblasting Abrasives and Application Potential Analysis

Utilization of Tunnel Waste Slag for Cement-Stabilized Base Layers in Highway Engineering.

The rapid expansion of highway infrastructure in the mountainous regions of China has led to a significant increase in tunnel construction, generating substantial amounts of tunnel waste slag. Concurrently, the development of transportation infrastructure has created a critical shortage of natural aggregates, necessitating the exploration of alternative sustainable sources. This study aimed to conduct a comprehensive evaluation of the physical and mechanical properties of tunnel waste slag and explore its potential for utilization in cement-stabilized base courses for highway engineering applications. The uniaxial compressive strength of the parent rock (tunnel waste slag) ranged from 81 MPa to 89 MPa in the desiccated state, indicating its suitability for use as a construction material. This study also determined the maximum dry density (2.432 g/cm3) and optimal moisture content (5.4%) of cement-stabilized mixtures incorporating recycled aggregates derived from tunnel waste slag. The splitting tensile strength of these mixtures at 28 days varied from 0.48 MPa to 0.73 MPa, demonstrating robust mechanical performance. Moreover, the unconfined compressive strength of these mixtures escalated from 7.0 MPa at 7 days to 11.0 MPa at 90 days, signifying a substantial enhancement in strength over time. These results validate the viability of utilizing tunnel waste slag in highway engineering and furnish valuable insights for designers, concrete manufacturers, and construction firms engaged in the development of cement-stabilized aggregate base courses.

Alkali-Activated Binders as Sustainable Alternatives to Portland Cement and Their Resistance to Saline Water.

Alkali-activated binders have emerged as promising alternatives to Ordinary Portland Cement (OPC) due to their sustainability features and potential advantages. This study evaluates the durability properties of heat-cured fly ash (FA) and ground granulated blast-furnace slag (GGBFS) geopolymer mortars activated with sodium hydroxide, which were subjected to wet-dry cycling in saline environments. Three series of FA, a FA/GGBFS blend, and GGBFS mortars previously optimized on a compressive strength basis were investigated and compared against two control OPC mixes. Performance indicators such as the water absorption, porosity, flexural strength, and compressive strength were analyzed. The results demonstrate that geopolymer mortars have significantly reduced water absorption and porosity with increasing wet-dry cycles. The compressive strength of the FA/GGBFS mortars also increased from 66.5 MPa (untreated) to 87.9 MPa over 45 cycles. The flexural strength remained stable or improved slightly across all geopolymer mortars. The control OPC specimens experienced significant deterioration, with compressive strength in CEM I 42.5R dropping from 51.8 to 17.1 MPa. These findings highlight the superior durability of geopolymer mortars under harsh saline conditions, demonstrating their potential as a resilient alternative for coastal and marine structures.

Nano-micro pore structure characteristics of carbon black and recycled carbon fiber reinforced alkali-activated materials

Microscopic scrutiny aids in alkali-activated materials’ (AAM) application in construction industry. This study delves into the pore structure and properties of one-part alkali-activated slag (AAS) mortar modified by carbon black (CB) and recycled carbon fiber (rCF). The additives enhanced flexural strength by 51.82% (12.16 MPa) with lower water absorption (10.24%). Refinement of pore size and reduction of connectivity are key factors in improving properties. The densification effect of CB and the strong interface between rCF and gel were observed. Furthermore, AAS mortars exhibited multifractal characteristics within the range of micropores and capillary pores. Despite altering fractal regions, the additives did not affect its size dependence. The backbone fractal dimension increases with the addition of CB and rCF, exhibiting strong correlations with various macro properties, thus serving as a comprehensive parameter to characterize pore shape and distribution. This study deepens understanding of AAM composites, facilitating their adoption of low-carbon building materials.

The influence of the composition and origin of ash and slag waste from coal generation on the response of organisms used in biotesting

Introduction. Different conditions of origin of ash and slag wastes has a significant impact on their final properties. Material and methods. The work is devoted to the search and establishment of dependencies of the influence of the origin of ash and slag waste on their chemical and biological parameters by a comprehensive assessment of the results of the impact of ash and slag waste on the vital signs of hydrobionts. Results. The values of the responses of hydrobionts for ash and slag wastes formed from coals of various origins were investigated. The component composition of aqueous extracts from the studied ash slag samples was evaluated. The dependences of the influence of the conditions of origin of ash and slag wastes on their final chemical and biological properties were established. Limitations. An assessment of the biological and chemical properties of ash and slag waste generated during the combustion of coal from six different deposits was carried out. The total volume was 95 samples. Conclusion. Ash and slag wastes formed from the burning of brown coals have the most pronounced toxic effect on hydrobionts, unlike ash and slag from coal.

Microstructural and wear properties of iron slag reinforced aluminum alloy (LM30) based composite prepared through a stir casting method

Aluminum alloys are widely used in various industries due to their as low density, high strength-to-weight ratio, and good corrosion resistance. However, their wear resistance is often inadequate for certain applications. Utilization of industrial waste materials, such as iron slag, as reinforcement in aluminum alloy matrix composites offers a sustainable approach to material development and waste management. The utilization of industrial waste materials for aluminum alloy matrix composite fabrication offers a waste utilization to material development. The loading of this reinforcement varied from 0 to 15 wt.% and different particle size range (220-140, 140-70, and 70-0 µm). A microscopic analysis indicated that the iron slag particles are spread uniformly inside the metallic matrix. There is also a reduction in the size of primary silicon, as well as morphological changes (acicular to globular shape). The wear behavior was calculated using a pin-on-disk wear set up in accordance with ASTM G99 standard. The composites were employed to dry sliding wear test under various operating conditions such as applied pressure (0.2–1.4 MPa), and sliding distance (0–3000 m). The 15F composite outperformed all other composite samples in terms of wear rate under all working conditions. When compared to the base alloy, it demonstrated a remarkable 67% drop in steady state wear rate. The enhancements in wear performance for the 15F composite were attributed to the effects of Fe slag reinforcement. The inclusion of iron slag particles induced strong interfacial bonding between matrix and reinforcement particles improving the durability of the mechanical mixed layer developed during relative motion. Importantly, the wear rate parameters of the 15F composite were similar to those of the brake drum material used in commercial applications. This emphasizes the composite suitability for usage in a variety of automobile components.

Effect of metakaolin on the chloride diffusion properties of alkali-activated slag in an acidic environment

Alkali-activated materials (AAMs) have good resistance to chemical corrosion compared to silicate cements, but the effect of the pH of chloride-containing solutions on the resistance of AAMs to chloride diffusion is not clear. In this paper, the resistance of alkali-activated slag (AAS) with different metakaolin replacement rate to chloride diffusion in HCl/NaCl solution was investigated in terms of mechanical properties, hydration product composition and pore structure. The experimental results show that acidic solutions lead to alkali leaching, and dissolution of gel and hydrotalcite. The capillary pores that appeared in the AAS after the replacement rate of 10% metakaolin resulted in a decrease in the average pore size of the AAS and low depth of chloride diffusion. 30% metakaolin replacement led to a decrease in the diffusion resistance. In HCl solution, the high [AlO4]5− retention corroded layer was observed in the AAS with 30% metakaolin replacement and this layer slowed down the migration rate of [Cl−]. This study shows the promising application of alkali-activated slag/metakaolin in complex chloride solution environments.

Effects of different activators on autogenous shrinkage of alkali-activated slag cement

Despite the exceptional early strength of sodium silicate or sodium hydroxide-activated slags, much emphasis has always been drawn to the volume instability brought on by their autogenous shrinkage. In this study, a ternary composite activation system was developed by introducing sodium sulfate (Na2SO4), and the effect of Na2SO4-Na2O·1.5SiO2-NaOH ternary composite activators system on the autogenous shrinkage, setting time, and mechanical properties of alkali-activated slag (AAS) was investigated. The effect mechanism of different activator compositions on the autogenous shrinkage of AAS was discussed through the internal relative humidity (IRH), surface tension of pore solution, and microstructure analysis. According to experimental results, the surface tension of pore solution can be reduced and IRH increased by increasing Na2SO4 content in AAS. Additionally, the formation of crystals (anhydrite, ettringite, and thenardite) with specific expansion properties can effectively mitigate autogenous shrinkage in AAS with Na2SO4. The proportions of Na2O·1.5SiO2 and NaOH determine the extent to which Na2SO4 impact the autogenous shrinkage of AAS. An optimal composite activator composition for AAS was determined using a model analysis: When the content of Na2O·1.5SiO2 ranged from 5 % to 17 %, Na2SO4 content ranged from 40 % to 55 %, and NaOH content ranged from 33 % to 56 %, the AAS mortar exhibited a compressive strength exceeding 42.5 MPa at 28 days. Furthermore, the autogenous shrinkage strain of AAS paste remained below 1500 microstrain within 7 days, with an initial setting time surpassing 45 min and a final setting time under 390 min.