Industrial Waste Slag Research Articles

Analysis on the Influence law and Mechanism of the Strength of Reclaimed Aggregate-Industrial Waste Slag Solidified Silt

To optimize the usage of construction waste resources, industrial waste slag and silt, this paper used Portland cement, mineral waste residue and phosphogypsum composite to make cementing material (CMPS) with construction waste reclaimed aggregate to solidify silt. The laboratory solidification test and microscopic analysis were conducted to assess the mechanical characteristics of solidified sludge. In order to clarify the mineral composition, microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt (SS), XRD, SEM and nitrogen adsorption pore analyzer were employed for further explore the regenerated aggregate and CMPS solidified silt effectively, and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively. The findings indicated that the strength of Portland cementmineral waste residue phosphogypsum terpolymer system curing agent increased by 107.34% than that of single Port-land cement SS at 56 d, and the strength of CMPS solidified silt increased by 25.68% under the action of reclaimed aggregate framework. The maintenance period and water composition of the silt have high correlation with the strength. Therefore, influence law of above two influencing factors on its mechanical properties were further explored and the strength prediction were made. The microscopic test results showed that, drawing from the hydration of Portland cement and pozzolans reaction of mineral waste residue, the solidified system has pre-pared CaSiO3 hydrate gel and ettringite crystals with gelatinous properties, which help to fill the pores and form a denser structure.

Evaluation on Preparation and Performance of a Low-Carbon Alkali-Activated Recycled Concrete under Different Cementitious Material Systems.

A green, low-carbon concrete is a top way to recycle waste in construction. This study uses industrial solid waste slag powder (S95) and fly ash (FA) as binders to completely replace cement. This study used recycled coarse aggregate (RCA) instead of natural coarse aggregate (NCA). This is to prepare alkali-activated recycled concrete (AARC) with different cementitious material systems. Alkali-activated concrete (AAC) mixtures are modified for strength and performance based on the mechanical qualities and durability of AARC. Also, the time-varying effects of the environment on AARC properties are explored. The results show that with the performance enhancement of RCA, the mechanical performance of AARC is significantly improved. As RCA's quality improves, so does AARC's compressive strength. At a cementitious material content of 550 kg/m3, AARC's 28d compressive strengths using I-, II-, and III-class RCA were reduced by 2.2%, 12.7%, and 21.8%, respectively. I-class AARC has characteristics similar to natural aggregate concrete (NAC) in terms of shrinkage, resistance to chloride penetration, carbonization, and frost resistance. AARC is a new type of green building material that uses industrial solid waste to prepare alkali-activated cementitious materials. It can effectively reduce the amount of cement and alleviate energy consumption. This is conducive to the reuse of resources, environmental protection, and sustainable development.

Fabrication of a cost-effective metal oxide-based adsorbent from industrial waste slag for efficient CO2 separation under flue gas conditions

Efficient and affordable adsorbents for CO2 capture are essential in implementing carbon capture technology to mitigate the negative impact of greenhouse gas emissions. This study focuses on synthesizing new nanoporous adsorbents from industrial waste slag using a simple and cost-effective coprecipitation method. In this method, raw slag was milled for 48 h and used as a benchmark for comparing two newly synthesized adsorbents. Selectivity and pure gas isotherm experiments were conducted for all adsorbents in the 25–65°C temperature range and under harsh industrial conditions of 65°C and 15 % CO2. This study utilized the response surface methodology (RSM) to optimize the CO2 adsorption parameters. Specifically, the optimized adsorption conditions were determined for the 15/85 % CO2/N2 condition, and the optimal values for pressure and temperature were found to be 5 bar and 45°C, resulting in CO2/N2 selectivity of 5.65. The NH3-slag adsorbent was identified as the superior choice based on its selectivity and maximum adsorption capacity. The maximum adsorption capacity and cyclic efficiency were determined to be 4.15 mmol/g and 98.1 %, respectively, at a temperature, pressure, and composition of 45°C, 5 bar, and 15 % CO2. Isotherm and thermodynamic models were employed to further investigate the adsorption process. The isotherm results indicated that the adsorption of CO2 by adsorbents occurred heterogeneously in patch-wise sites. Meanwhile, the thermodynamic parameters showed that the process was exothermic and spontaneous, with ΔH° falling below 20 (kJ/mol), showing physisorption phenomena.

Analysis of Steel Slag Sand – An Eco Friendly Fine Aggregate for Construction

Industrial waste slag is a major issue concerning the environmentalists today. The steel making industry produces a large amount of byproduct which is termed as Slag. Slag is produced during the steel-making operations that utilize Electric Arc Furnaces (EAF) and operate by smelting iron ore in the Basic Oxygen Furnace (BOF). Steel slag finds numerous uses in the construction industry e.g in the applications involving hot mixture asphalt, in Stone Matrix Asphalt (SMA), berms and embankments constructions, main ingredient in manufacturing of Portland cement, as fine and coarse aggregates, to name a few. But steel slag has a negative impact on the environment when disposed of. In that case a wide variety of use of steel slag becomes relevant. Steel Slag is a perfect candidate to replace the coarse and fine aggregates in the traditional concrete used in the construction industry. Most of the volume of concrete is aggregate. Steel Slag can be used as replacement to these aggregates in a more prominent way. In this research study, we will be making steel slag as substitution for raw fine aggregate. Fine aggregate would be replaced by these wastes in different proportions (20%, 40%, & 60 %) by weight of fine aggregate. The aim of this study is to investigate the compressive strength, split tensile strength and Material properties of concrete with partial replacement for fine aggregate. We will be performing pull off test on the applications of this modified concrete and checking the results for strength and durability.

Evaluation of active silica-alumina content and reactivity in bayer process red mud

Cement concrete plays a crucial role in modern construction, but its production process results in significant CO2 emissions, posing a substantial threat to the environment. To achieve green production, the use of industrial waste slag as a raw material for concrete has been widely accepted. This study focuses on the potential utilization of Bayer Process Red Mud (RM), a by-product of the alumina refining process, characterized by high alkalinity and low pozzolanic activity, limiting its application in cement concrete. The reactive activity of RM after calcination treatment was investigated to overcome this challenge and enhance the reactivity of RM. Fourier Transform Infrared Spectroscopy (FTIR) was employed to determine the degree of polymerization of RM at different calcination temperatures, and thus evaluate its pozzolanic activity. Integrating physical tests, chemical experiments, and microscopic analysis, this study thoroughly analyzes the relationships between different evaluation methods and finds a negative correlation between the degree of polymerization and the pozzolanic activity index, boasting a correlation coefficient of 0.904. The results indicate that RM exhibits the highest pozzolanic activity at a calcination temperature of 700 °C. Therefore, this method has been proven effective and can serve as a quick and convenient means of evaluating the pozzolanic activity of RM. The findings of this study are expected to promote the green development of the cement industry, better utilize waste slag resources, reduce CO2 emissions, and enhance the performance of building materials.

Molecular Dynamics Simulation and Viscosity Analysis of Red Mud-Steel Slag Glass-Ceramics.

The preparation of glass-ceramics with red mud and steel slag can not only solve the pollution problem caused by industrial waste slag but also produce economic benefits. It is difficult to analyze the high-temperature melt with the existing test methods, so the simulation experiment with molecular dynamics calculation becomes an important research method. The effects of steel slag content on the microstructure of red mud glass-ceramics were studied by molecular dynamics method. The results show that the binding ability of Si-O, Al-O, and Fe-O decreases with the increase in steel slag content. The number of Si-O-Si bridge oxygen increased gradually, while the number of Al-O-Al, Al-O-Fe, and Fe-O-Fe bridge oxygen decreased significantly. The number of tetrahedrons [SiO4] increased, the number of tetrahedrons [FeO4] and [AlO4] decreased, and the total number of three tetrahedrons decreased. The mean square displacement value of Si4+ and O2- increases first and then decreases, resulting in the viscosity of the system decreasing first and then increasing. The molecular dynamics method is used to analyze the structure of red mud-steel slag glass-ceramics on the microscopic scale, which can better understand the role of steel slag and has guiding significance for the experiment of this kind of glass-ceramics.

Compression and bending of alkali-activated slag cementitious materials at high temperature

Alkali-activated slag cementitious material (AASCM) with manufactured sand can effectively utilise industrial waste slag and reduce river sand consumption. Steel fibres can effectively improve the mechanical properties of AASCM. Therefore, in this study, the influence of steel fibres and aggregate type on the compression and bending properties of AASCM after high-temperature treatment was investigated. The results show that the mass loss rate, compressive strength and flexural strength loss rate of AASCM with manufactured sand were higher than those with natural river sand at different temperatures. Steel fibres can increase the mass loss rate of AASCM; however, the influence of the steel fibre content on the mass loss of AASCM was not apparent. When the temperature was lower than 600°C, the compressive and flexural strength of AASCM was effectively increased by steel fibres, while, for temperatures higher than 800°C, the mechanical properties of AASCM did not improve, owing to the oxidation failure of steel fibres. Microstructure analysis showed that the number of microcracks in the AASCM increased, owing to the high silicon content of the manufactured sand, and the bond property between the steel fibres and cementitious materials decreased with an increase in temperature.

Properties of Glass-Ceramics Prepared from Industrial Multi-Wastes

Because of their excellent properties, glass-ceramics have been widely developed and applied in many fields, and there are many potential application values to be disseminated. The preparation of glass-ceramics from industrial slag and metallurgical waste provides a new way for the comprehensive utilization of solid waste. Coal gangue is the largest of all kinds of industrial waste slag, while iron tailings and high-carbon ferrochrome slag also occupy a large proportion of China’s industrial solid waste. With cheap industrial solid waste as the main raw material, the production of high-value-added glass-ceramics can reduce pollution, protect the ecological environment, and have good economic and social benefits. Cordierite glass-ceramics were prepared using the sintering method with coal gangue, iron tailings, and high-carbon ferrochrome slag as the main raw materials. Meanwhile, an iron silicon alloy containing chromium was obtained. The heat treatment system of basic glass was determined by differential scanning calorimetry (DSC), and the sintered product was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). An orthogonal test was used to analyze the effects of the mass of basic glass powder, molding pressure, and holding time on the grain size and crystallinity of the samples. The hardness, acid and alkali resistance, density, and water absorption of the sintered products were determined. The results show that the main crystal phase of the prepared glass-ceramics is cordierite. The optimal combination for the green body is “basic glass powder mass 6 g, molding pressure 35 MPa, holding time 10 min”. The properties of glass-ceramics are good. At the crystallization temperature of 970 °C, the Vickers hardness is up to 866 HV, and the bulk density is up to 2.99 g/cm3. This study may provide a useful reference for the treatment of industrial solid waste.

Mineral evolution mechanism of Zinc-slag during high-temperature reactive process

The mineral transformation mechanism, microstructure evolution and chemical reactivity of Zinc-slag sintered at 1350–1550 °C for 10–60 min were systematically studied using Fe2O3, Al2O3, SiO2, CaO, MgO and ZnO as raw simulation materials. The molar ratio, sintering temperature and duration could affect the ions diffusion and migration in molten state attributing to the acid-base equilibrium and the energy of atomic thermal motion, and then influence the phase formation and transition process. Meanwhile, the FactSage software was used to calculate the equilibrium polyphase diagram for predicting the phase transformation mechanism of non-equilibrium system, while the Si4+ and Al3+ react with Ca2+ easily due to the tetrahedral structure. The phase composition of Zinc-slag contains Ca2Al2SiO7, Ca3(Si3O9), ZnFe2O4, Fe2O3, SiO2 and Fe when sintered at 1500 °C for 60 min, and it also has the optimal Zinc recovery efficiency of 91% with 1.2 mol/L H2SO4 and 0.04 mol/L H2S2O8 attributing to the large layer spacing and uniform distribution of ZnFe2O4. The lime sinter process with acid-leaching technology is beneficial to effectively improve the utilization rate of Zinc-slag, and it also could provide a strategy to solve the environmental pollution problem caused by industrial waste slag.

Synergistic and competitive adsorption of NOx and SO2 using a microwave-assisted approach with industrial waste materials fly ash and carbide slag as sorbents

A novel catalytic adsorption approach for microwave-assisted synergistic utilization of coal fly ash (FA) and carbide slag (CS) as adsorbents and Na2O/Na2O2 as a catalyst was proposed as an efficient and low-cost De-SO2 and De-NOx technology. The highest SO2 and NOx adsorption capabilities under these circumstances were 0.55 and 0.06 mg/g under 2% Na2O/FA-CS adsorbent at 150 °C respectively. The experimental results shows that the loaded Na2O2 as adsorbent in the Na2O2/FA-CS was strongly oxidized and decomposed into reactive oxygen (O∗), in which the conversion behavior of NOx (ads) and SOx (ads) contributed to the catalytic activation and adsorption performance. In the synergistic adsorption process, both NOx (ads) and SOx (ads) were present on the adsorption interface of the X% Na2O/FA-CS adsorbent, which also facilitated the production of unstable nitrogen and sulfur compounds. In the competitive adsorption process, NOx and SOx readily occupied the active adsorption spots of CaO used as an adsorbent in FA-CS while also contaminating the active catalytic spots of the coexisting Na2+/Na1+ ions, thus reducing the activity and efficiency of the adsorbent.Environmental implications: Coal fly ash is the main solid waste discharged from coal-fired power stations. The large amount of coal fly ash occupies land resources, while solid fine particles and heavy metals pollute the surrounding air. In addition, calcium carbide slag is a kind of industrial waste slag mainly comprising calcium hydroxide. Calcium carbide slag exhibits the characteristics of high humidity and alkalinity, leading to stockpiling and land pollution. To achieve resource utilization and high-value utilization, synergistic microwave-assisted utilization of industrial waste materials coal fly ash and carbide slag was assessed for high-efficiency desulfurization and denitrification.

Understanding the rheology and hydration behavior of cement paste with nickel slag

Nickel slag (NiS), an industrial waste slag produced by laterite nickel ore, is a potential mineral additive utilized in cement-based materials. This study compared the effects of NiS, fly ash (FA) and blast furnace slag (BFS) on the rheological properties and hydration behavior of cement paste, and further evaluated the rheological properties of ternary cementitious system. The results show that adding NiS is unfavorable to the rheological properties of cement paste. More specifically, the yield stress of the cement paste first increases and then almost keeps unchanged with increasing NiS content, while the plastic viscosity shows a continuous increase behavior. The cement pastes with BFS or FA exhibit improved rheological properties than the NiS containing cement pastes. Compared with the PC-NiS-FA ternary pastes, the PC-NiS-BFS ternary pastes have smaller shear thinning intensity, larger yield stress and higher plastic viscosity. The exothermic rate and hydration heat of NiS cement paste within 2 h, normalized to the amount of cement, are higher than those of cement pastes with BFS and FA.

Synthesis, Stability and Microstructure of a One-Step Mixed Geopolymer Backfill Paste Derived from Diverse Waste Slags

The advent of industrialization has produced an enormous amount of industrial waste slag, which drastically pollutes environmental resources. This study examines the production, stability, and microstructure of a novel backfill geopolymer paste derived from multiple industrial waste slags, including silica-alumina precursors (low-calcium composition) and waste slags (high-calcium composition), as well as two additives. The characteristics of self-hardening were discovered. The effects of low-calcium fly ash, granulated blast furnace slag, red mud, and lime powder on fluidity and compressive strength were then evaluated. To assess the stability, the resistances to drying shrinkage, permeability, and chemical attack by an optimized geopolymer backfill paste were investigated. Furthermore, SEM-EDS, XRD, FTIR, and TG-DSC tests were employed to reveal the microstructures, products, and thermal stability. The results show that the backfill paste hardens well and has no impact on alkalinity dissolution for adjacent soils and water. The optimum sample, P1, had a water-binder ratio of 0.70, resulting in 201 mm fluidity and 2.1 MPa 28-d compressive strength. In terms of drying shrinkage, permeability, and Na2SO4 and NaCl solution attack, sample P1 outperformed the conventional Ordinary Portland cement paste (OPC) for 90 days. The paste P1 containing about 46.0 wt% waste slags meets the fresh and hardened property requirements for goaf backfill, and the chemical binding of P1 is acquired from the mixture of (N,C)-A-S-H, C-S-H, and C-A-S-H gel products. These findings lay the groundwork for the scientific application of a wide range of waste slags in backfill engineering.

Effect of Ultrafine Fly Ash and Water Glass Content on the Performance of Phosphorus Slag-Based Geopolymer.

Phosphorus slag (PS), an industrial waste slag, has been used in geopolymers because it is rich in silicon and calcium. The poor performance of phosphorus slag-based geopolymer is due to its aluminum deficiency. In this work, low-calcium fly ash, treated by a wet-grinding process, named wet-grinding ultrafine fly ash (WUFA) was used as an Al supplement to replace some of the phosphorus slag, and the wet-grinding, ultrafine fly ash-phosphorus slag (WUFA-PS)-based geopolymer was prepared. The effects of the substitution amount of WUFA and the activator dosage on the hydration properties, mechanical properties, pore structure and SEM of the WUFA-PS geopolymer were discussed in detail. The results indicate that WUFA and more activators contribute to the Al and high alkalinity environment, which positively induces the production of more geopolymer gels, thus releasing more heat and optimizing the pore structure of the matrix. The compressive strength increased by up to 28.1%. The enhanced performance of the WUFA-PS-based geopolymer may also arise from the filling effect and activity improvement of WUFA. This study has proved the feasibility of preparing a geopolymer by blending wet-grinding ultrafine fly ash and phosphorus slag and has provided references for the ratio and performance evaluation of WUFA-PS-based geopolymer concrete.

Correction to: Heterogeneous Ti/PbO2-electro-Fenton degradation of aromatic methane dyes using industrial pyrite waste slag as catalyst

Correction to: Heterogeneous Ti/PbO2-electro-Fenton degradation of aromatic methane dyes using industrial pyrite waste slag as catalyst

Heterogeneous Ti/PbO2-electro-Fenton degradation of aromatic methane dyes using industrial pyrite waste slag as catalyst.

It is imperative to search the eco-friendly and cost-effective technologies for degrading contaminants. Coupling the effect of Ti/PbO2 at the anode with heterogeneous electro-Fenton was an efficient method. Industrial pyrite waste slag characterized by a variety of methods had catalytic performance and stable performance to activate hydrogen peroxide (H2O2) into hydroxyl radical (∙OH). Meanwhile, the processing conditions, the malachite green wastewater concentration, the current density, the pH range, and the dosage of industrial pyrite waste slag were emphatically optimized. Herein, the total organic carbon (TOC) removal efficiency reached 97.70%, the mineralization current efficiency (MCE) was 0.392%, and the energy consumption (EC) was 1.942 kWh/m3 after 240 min. Heterogeneous Ti/PbO2-electro-Fenton using industrial pyrite waste slag as catalyst was an environmentally friendly technology and provided a recycling method with traditional wastes. Finally, catalytic mechanisms and possible pathways were represented according to the results of quantum chemistry calculations and gas chromatography-mass spectrometry (GCMS).

Study on untreated and alkali treated rice straw reinforced geopolymer composites

In this study, plant fibre reinforced geopolymer composites were prepared using industrial waste slag and agricultural residue rice straw. The properties of the untreated and alkali treated rice straw reinforced geopolymer composites were investigated. The bending strength, water absorption thickness swelling rate and water absorption of the composite materials were evaluated. The results show that both the untreated and alkali treated rice straw can significantly improve the bending strength of the geopolymer; however, the alkali treated rice straw exhibited a higher enhancement effect. At a curing time of 28 days, the bending strength of the alkali treated rice straw reinforced geopolymer composites (ATRSRGC) with 10% fibre content reached 13.6 MPa, which exceeds the requirement specified by the China National Standard “Cement Bonded Particleboard” for superior product (≥10 MPa). The water absorption thickness swelling rate and water absorption of these two composite materials increased with the increase in the fibre content. However, with the increase in the water immersion time, their water absorption thickness swelling rate and water absorption showed different changes. We found that the ATRSRGC had a higher water absorption thickness swelling rate than the untreated rice straw reinforced geopolymer composites (UTRSRGC), indicating that high water absorption thickness swelling rate should be considered if the alkali treated rice straw is used for the production of particleboards. Infrared spectroscopy analysis shows that the rice straw and geopolymer were physically combined. Furthermore, scanning electron microscopy analysis results show that the geopolymer matrix bonded with the alkali treated rice straw better than the untreated rice straw.

Recovery of aluminum from waste aluminum alloy by low-temperature molten salt electrolysis

Large amounts of industrial waste discharge have serious implications for the environment. The production of coarse Al-Si alloy by carbothermal reduction is considered to be one potential method for making use of industrial aluminiferous waste slag. Here, we discuss the influence of different processing parameters on electrolytic refining of aluminum alloy and investigate the mechanism of extracting Al from coarse Al-Si alloy in a low-temperature molten salt system. Aluminum is obtained with the use of coarse Al-Si alloy as a soluble anode in the AlCl3-NaCl-KCl molten salt system. The current efficiency reached over 94% when the electrolysis temperature was 170 ℃, the current density was 30 mA/cm2 and electrolysis was performed for 1.5 h. In the electrolysis process, Al in the coarse Al-Si alloy was present in the form of Al2Cl7− and AlCl4−, which precipitated at the cathode. The purity of aluminum electrodeposited on the aluminum cathode was 99.3%.

Treatment of Methyl Blue Wastewater by Steel Slag Particle Three-Dimensional Electrode System

The particle electrode was prepared by using industrial waste slag as raw material, and the surface morphology of the particle electrode was characterized by scanning electron microscopy. The comparison experiments showed that under the same experimental conditions, the efficiency of removing the methyl blue from the three-dimensional electrode of the steel slag particles was 23.48% higher than that of the two-dimensional electrode, and the energy consumption was reduced by 36.2%. The results showed that the primary and secondary factors affecting the methyl blue wastewater of steel slag particles are electrolyte concentration, voltage, initial waste concentration and particle volume. Under the optimal combination of pH 3, voltage 12 V, initial methyl blue concentration of 15 mg/L and electrolyte concentration of 0.3 mol/L, the removal rate of methyl blue reached 91.41%.

Study on the Effect of Ash-Slag Ratio on Mechanical Properties of Magnesium Slag Cementitious Material

Magnesium slag is a kind of industrial waste slag with silicate mineral as the main component when smelting magnesium metal. Its main component is similar to Portland cement clinker and can be used as cementitious material. In this paper, the mechanical properties of magnesia slag cementitious materials under different ash-slag ratios are studied and analysed. Magnesium slag and fly ash are prepared by composite method. The flexural and compressive tests are carried out. The effects of different ash-slag ratios on the mechanical properties of magnesia slag cementitious materials are studied. The experimental data are analysed and theoretical studies are carried out, and the conclusion is drawn on: (1) When the ash-slag ratio is between 0.43 and 0.8, the forming effect of Mg-slag cementitious material specimen is better; (2) When the ash-slag ratio changes from large to small, the properties of Mg-slag cementitious material will change greatly, from curable to powdered after curing, unable to form, and the critical value of the ash-slag ratio is between 0.25 and 0.43; (3) When the ash-slag ratio is in the range of 0.43-1.2, the mechanical strength of magnesium slag cementitious material is higher, the maximum flexural strength can reach 10 MPa, and the maximum compressive strength can reach 50 MPa.

A Study on the Effect of Ceramic Polishing Powder on the Nucleation and Growth of Hydrates in Cement Paste

The production of cement leads to a large amount of CO2 emission. Using industrial waste slag, such as ceramic polishing powder (PP), to replace part of Portland cement can reduce the pollution caused by the cement industry and solid waste disposal. In order to use PP as a replacement for cement, its effects on the properties of cement paste need to be clarified. In this study, the effect of PP on the nucleation and growth of hydrates in cement paste at very early ages was investigated. Quartz was used as a reference. The interactions of their surface with various ions in cement paste solution, which has an important effect on the nucleation and growth of hydrates, were studied by using the zeta potential test. The morphology of the nucleus and crystal of hydrates was investigated by using SEM. The zeta potential measurements showed that the affinity of the surface of PP and quartz to ions in the pore solution of cement paste is similar. The image of SEM indicated that there is also not much difference in the crystallization of hydrates on the surfaces of PP and quartz. These evidences suggested that PP has similar surface charge properties as quartz, and its effects on the properties of cement paste are the same as that of quartz. From the viewpoint of the effect on very early hydration, PP can be used in cement paste, similar to quartz power.