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The valorization of slag from the production of high-carbon ferrochrome is a challenge for ferrochrome producers. The recycling of high-carbon ferrochrome slag was explored through the smelting route to recover Fe–Si–Al–Cr alloys and reengineer the residual slag for alumina-enriched refractory material. In this research, the focus was to reduce the SiO2% and enrichment of Al2O3% in the final slag and recover the metallic value in the form of a complex alloy containing Fe, Si, Cr and Al. The manuscript consists of a thermochemical simulation of the smelting of FeCr slag followed by smelting experiments to optimize the process parameters such as temperature and the addition of coke, cast iron and alumina. An experimental investigation revealed that the maximum recovery of Si (57.4% recovery), Al in the alloy (20.56% recovery) and Al2O3 (85.78% recovery) in the slag was achieved at a charge mix consisting of 1000 g of FeCr slag, 300 g of alumina, 200 g of cast iron and 300 g of coke. The present study also demonstrated the usefulness of prior thermochemical calculations for smelting metallurgical wastes such as slag from high-carbon ferrochrome production for value creation and reutilization purposes. [ABSTRACT FROM AUTHOR]

Ferrochrome slag aggregate concrete (FCSAC) incorporated with fly ash offers multiple benefits over FCSAC alone and natural aggregate concrete (NAC) in terms of durability and environmental impacts, without sacrificing essential strength. However, structural behavior of fly ash-based FCSAC is poorly understood due to lack of investigations. This study examined shear performance of 16 full-scale reinforced concrete beams. FCSAC was prepared using 100% FCS coarse aggregate and fly ash as fractional cement replacement (0%, 20% and 30%). To completely comprehend the shear resistance mechanism of FCSAC, eight beams were built without shear reinforcement and eight with it. NAC and FCSAC (without fly ash) were considered as the reference beams. Existing design guidelines and fracture mechanics approaches were verified to predict shear capacity of FCSAC beams. The findings of the study revealed that fly ash incorporated FCSAC beam exhibited fewer cracks and higher shear capacity (about 7%) than NAC beam, but lower strength (about 8%) than FCSAC without fly ash beam. Shear provisions outlined in CSA provisions and fracture model by Gastebled and May could be adopted for FCSAC (with or without fly ash) beams without risk. This research demonstrates that fly ash-based FCSAC can be utilized safely for structural purposes. [ABSTRACT FROM AUTHOR]

Ferrochrome slag (FCS), a type of industrial solid waste, has promising properties that make it a viable alternative aggregate for concrete production. This can be a partial solution to reduce the pressure on natural aggregates. However, the usage of this solid waste in concrete or composite structures is not documented well. As a result, the purpose of this study is to evaluate experimentally the effect of employing FCS concrete in the concrete-filled steel tube (CFST) on strength and its fire-resistant capabilities. The influence of heating temperatures ranging from 200 to 800 °C and the level of FCS fine aggregate substitution on load–displacement behaviour, ultimate load, and failure mechanism was examined. The CFST stub columns were filled with three different concrete mixtures: one with 100% natural fine aggregate and the other two with 50% and 100% FCS fine aggregate. The findings demonstrate that the ultimate load and stiffness of the CFST stub columns increased as the amount of FCS fine aggregate in the concrete increased. Similar results were found for residual strength and stiffness after high-temperature exposure. The fine natural aggregate can be fully replaced by the FCS fine aggregate without compromising any strength properties of concrete, as well as CFST columns at room and high temperatures. The Eurocode 4 and ACI codes show a conservative estimation of ultimate strengths for the CFST stub columns at room and elevated temperatures compared to the experimental results for all three concrete mixes. However, Eurocode 4 provides a closer estimation for the ultimate load for all concrete mixes than the ACI recommendation. [ABSTRACT FROM AUTHOR]

Reactive powder concrete (RPC) is a new generation concrete with high strength, used in special structures, and its use is increasing day by day. In this study, instead of using high-strength aggregates typically used in RPC, wastes released in ferrochrome production were used. In addition, the possibility of using fibers obtained from end-of-life automobile tires (ELT), instead of the micro steel fibers typically used in RPC, was investigated. Thus, sustainable green reactive powder concrete (GRPC), the material which is obtained from waste materials except the binder and chemical additive, has been developed. As ferrochrome wastes, olivine, serpentine, rum, slag, and pure waste were used as powder and aggregate in GRPC. Firstly, in GRPC without fiber, the physical and mechanical properties of ferrochrome wastes were examined by using different ratios. Then, the optimum mixture was selected, and different ratios of industrial steel and ELT fiber were added to this mixture. As a result, the compressive strength of GRPC using olivine and pure waste (ferrochrome slag) is close to the reference RPC. However, it is 28% more economical. The flexural strength of the samples with a 4% addition of industrial or ELT fiber increased by 182% and 213%, respectively, compared to the reference sample without fiber. With the use of 4% ELT fiber (by volume) in GRPC, the flexural strength increased by 11% compared to the use of industrial steel fiber. In terms of cost, with the use of ferrochrome waste and ELT fiber, GRPC was 48% more economical. When examined in terms of the flexural and compressive unit strength cost, GRPC was approximately 41% more economical. As a result of this study, high-performance concrete with high mechanical properties that is economical, sustainable, and environmentally friendly has been produced by evaluating the use of waste materials. [ABSTRACT FROM AUTHOR]

Since the natural raw materials used in the manufacture of clay-based ceramic products vary greatly in the sintering stage, the resulting products are quite heterogeneous. In addition, different types of waste could be used to make ceramic tiles and bricks. Therefore, this study aimed to investigate the effects of pumice, bauxite, and ferrochrome slag on the vitrified ceramic body. In this context, firstly, binary slip mixtures were prepared by composing 40% clay with 60% pumice, bauxite, and ferrochrome slag one by one, which was reduced to 150 µm in particle size. Then, the mixtures were shaped by slip casting method and sintered at 1000°C, 1100°C, 1200°C, and 1250°C. The qualitative XRD analysis was performed in order to see the phase variation, and physical properties were determined with shrinkage and water adsorption measurements. Since pumice transformed into a glassy phase after sintering at 1100°C, an amorphous phase was observed in all samples produced with pumice. In addition, the mullite development occurred in clay-pumice body composition with the temperature increment. However, tridymite and cristobalite phases were analysed in clay bauxite and ferrochrome body compositions. The shrinkage and water adsorption values, which were high in the samples sintered at 1000°C, began to reduce from 1100°C to 1250°C significantly. In particular, water adsorption reached 0% in the clay-pumice system which was suitable for a fully vitrified-high density standard (ISO13006-10545/98). Besides, the brighter colour was reached in the clay-pumice system while brown and black colour was seen in clay-bauxite and clay-ferrochrome bodies, respectively. [ABSTRACT FROM AUTHOR]

There is limited data on studies that have focused on the kinetics, thermodynamics, and characterization of struvite crystallization from alternative magnesium sources. This study focused on thermal analysis of struvite (produced using ferrochrome slag as a magnesium source) and the results indicated that the residual quantities of struvite were lower than the theoretical mass loss of struvite of 51.42%. When using ferrochrome slag (FCS) as the magnesium source, 47.9%, 47.4%, and 46.9% losses in mass were observed for heating rates of 5°C/min; 10°C/min and 15°C/min respectively. The mean activation energies for struvite produced using FCS were deduced using isoconversional kinetic methods and ranged from 49.81to 56.20 kJ/mol which is very similar to the activation energies deduced using MgCl2. The study also focused on the surface morphology, and particle size of the final product at different pH and N:P ratios. The final particle size distribution of the product was significantly influenced by the solution pH. To improve the crystal growth kinetics for both MgCl2 and FCS, a high ratio of N:P molar ratios should be adopted. The product's highest median particle size was obtained using FCS as the magnesium source at a low pH. Median particle size increased with decrease in pH, at a pH of 7.5 the recorded median particle size was 96 µm whilst, the lowest was 31 µm at a pH of 9.5. The highest percent of fines (

The supplanting of fine aggregate was encapsulated in this study to reduce the usage of non-renewable materials in concrete. Initially, nano–micro cementitious material (NMCM) such as metakaolin (MK) and nano silica (NS) was incorporated with Portland cement to make referral concrete (RC). An alternate for virgin river sand is crushed gravel sand (Csand) which is mostly in use. The objective of this research is to effectively supplant Csand by means of ferrochrome slag (FS). Precisely, the optimum level of MK (10%) and NS (1%) was used in place of cement. In addition, the FS was incorporated in place of Csand by 10, 20, 30, 40, 50 and 100%. A significant rise in the compressive strength of about 3.18% was achieved by replacing FS4 at 28 days than RC. Ultrasonic pulse velocity (UPV) and water permeability (WP) results of FS4 were better than those of RC. F4 was 12.5% higher in the RCPT result than for the RC specimen. The SEM image of FS4 indicates the densest calcium silicate hydrate (CSH(H)) and rigidified interfacial transition zone (ITZ). TG/DTG predicts that the FS4 mix has a minimal Portlandite (CH-3.92%) compared to RC. The strength, durability, microstructure and TG results of the FS4 matrix imply that FS can be substituted for fine aggregate. [ABSTRACT FROM AUTHOR]

Ferrochrome slag (FS) contains a large number of glass phase, which cannot be effectively transformed into crystalline phases during the reutilization for fabricating ceramic materials. In this study, cordierite with a low expansion coefficient was successfully prepared from FS and quartz. The composition and structural characteristics of FS were analyzed. The phase evolution, microstructure, coefficient of thermal expansion (CTE), and material properties were studied. With 34 wt% quartz and maximum cordierite crystal content of 75.1 wt%, the glass phase decreased from 78.7 to 12.7 wt%. The melted quartz generated silica-rich microdomains with high viscosity during heating. Subsequently, the nuclear dynamic conditions were improved to promote the formation of cordierite crystals. Appropriate sintering temperature and holding time can boost the crystallization rate of the glass phase. Further, the diffusion of silica-rich microdomains was beneficial for the formation of cordierite crystals. Finally, the optimal cordierite ceramic material was obtained at 1300 °C for 2 h with a flexural strength of 38.3 MPa and CTE of 3.01 × 10−6/°C. These studies provide an effective way of re-utilizing large volumes of FS, and suggest a new method for preparing ceramic materials using high-temperature silicate waste residues. [ABSTRACT FROM AUTHOR]

The present research aims to analyze the comminution behavior of ferrochrome slag using high-pressure grinding rolls. The laboratory bench scale high-pressure grinding rolls were used to study the three significant variables on the grinding efficiency of ferrochrome slag. The Central Composite Design was used to study the process variables, such as roll gap, applied load, and roller speed. The grinding efficiency was evaluated based on the product size and the energy consumption. The results showed that the increased gap between the rolls and roller speed decreases the product size with increased energy consumption. The results also found that an increase in applied load decreases the product fineness with increased energy consumption. The models were developed for the responses of P80 (size of 80% mass finer) and Ecs (specific energy consumption). Both the responses show high regression coefficients, thus ensuring adequate models with the experimental data. The minimum values of the P80 size and specific energy were determined using quadratic programming. The optimum values of the roll gap applied load and roll speed were found to be 1.43 mm, 16 kN, and 800 Rpm, respectively. The minimum values of P80 and the specific energy consumption were found to be 1264 µm and 0.56 kWh/t, respectively. [ABSTRACT FROM AUTHOR]

Environmentally friendly porous asphalt mixtures have poor tensile strength performance and durability due to their porous structure. This results in their service life typically being less than ten years. Reinforcement with fibers can be a possible solution to structural weaknesses in porous asphalt road surfaces. Fibers have been proven to be an effective additive in improving the mechanical performance of asphalt mixes, but little attention has been paid to porous asphalt mixes. This study investigates the effect of four different fibers; (a) polypropylene fiber, (b) glass fiber, (c) basalt fiber, and (d) crumb rubber, on the functional and mechanical performance of porous asphalt mixtures. Fibers were used in four different percentages (0.2, 0.4, 0.6 and 0.8%) according to the mix aggregate weight. The experimental test plan includes the characterization of air voids for permeability, Cantabro particle loss, indirect tensile strength, and moisture sensitivity. Type-3 gradation (in Turkish Highways Technical Specification) was chosen as the mixture gradation. Mixture specimens were prepared using a Marshall compactor in 6.0 and 6.5% polymer-modified bitumen. Test results show that void and permeability generally decrease with increasing fiber content, except for polypropylene fiber. Cantabro particle loss was significantly reduced for all fibers at 6.5% bitumen compared to 6.0%. Minimum wear loss value was obtained in 0.2% basalt fiber. Indirect Tensile Strength (ITS) improved significantly for all fibers. The ITS of 0.2% basalt fiber was enhanced by 124% compared to the control specimens. The optimum fiber contents were determined as 0.2% for basalt fiber and 0.4% for glass fiber. [ABSTRACT FROM AUTHOR]

The circular economy initiative has driven the agriculture and agro-based industry to beneficiate from waste,thus closing the material loop towards enhancing economic and environmental performance. In this study, the aim was to recover phosphorus from anaerobic digestate of piggery wastewater (ADPW) using ferrochrome slag (FCSL) as the magnesium source to improve the environmental and economic sustainability of struvite precipitation. This was achieved by leaching 100 g L−1 of ferrochrome slag with 5 M HCl where 14.02 g L−1 of magnesium ions were extracted, and this acid-leachate of ferrochrome slag also contained 2650 mg L−1 of total iron. To simultaneously remove both high concentrations of organic matters in ADPW and iron in FCSL which are known to be detrimental to struvite precipitation, hydrogen peroxide (H2O2) at an H2O2/Fe molar ratio of 0.75 and pH 4.0 was added to the mixture of ADPW and FCSL. After the Fenton reaction, removal efficiencies of chemical oxygen demand (COD) and total iron reached 95.06% and 94.00%, respectively. Then COD and an iron-reduced mixture of ADPW and FCSL were added with a satisfying Mg:N:P molar ratio of 1.2:1:1.15 at pH 9.5 to produce struvite in 1 h. From 1 L of ADPW (2.6 g NH3–N), 0.5 L of FCSL (5.34 g Mg2+), and 6.62 g of PO43− P, were consumed to produce 45.57 g of struvite precipitate. Additionally, the economic feasibility of ferrochrome slag was assessed by estimating the chemical costs of FCSL against that of magnesium chloride which is commercially used. It was observed that using FCSL was cheaper as compared to using commercial MgCl2. Response surface methodology coupled with the central composite design was applied as a statistical tool to determine the effects of the key parameters (N:P; Mg:PO4; pH) on phosphorus recovery. Second-order polynomial equations were determined to correlate the parameters. ANOVA was applied and showed that p values for all the investigated parameters were less than 0.05 showing that they had a statistically significant effect on the phosphorus recovery. The study confirmed that it was possible to recover phosphorus as struvite from anaerobic digestate of pig manure with ferrochrome slag as a magnesium source.

In this study, high-carbon ferrochrome slag powder produced by grinding was used to replace different proportions of cement, and the effect of the amount of ferrochrome slag powder on the physical and mechanical properties of ferrochrome-slag-cement composites was analyzed. Water-cooled ferrochrome slag with a particle size of <5 mm was optimized to replace part of river sand as fine aggregate, and air-cooled ferrochrome slag with a particle size of >5 mm was used to completely replace coarse aggregate to prepare ferrochrome-slag-based concretes. The microstructure of ferrochrome-slag-cement composites was analyzed by X-ray diffraction, scanning electron microscopy, and thermogravimetry–differential scanning calorimetry analysis. The compressive strength, water absorption, and aggregate–slurry interface bonding properties of ferrochrome-slag-based concrete were studied. The results demonstrate that a ferrochrome slag powder amount of 15% leads to the highest performance of ferrochrome-slag-cement composite material, and the fluidity ratio of ferrochrome-slag-cement mortar is 103, higher than reference samples. Furthermore, the compressive strengths of ferrochrome slag concretes are 15.8% and 3.6% higher than conventional concrete, and the water absorption of ferrochrome slag low-carbon concrete is better than that of conventional concrete. The interface bonding structure between concrete aggregate and slurry was optimized. This research can provide a reference for studying the application of ferrochrome slag, both the feasibility of high-carbon ferrochrome slag powder as supplementary cementitious material and the application of ferrochrome slag as concrete aggregate, and it can help to achieve the purpose of saving energy and reducing carbon emissions. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for ferrochrome alloys has resulted in a substantial accumulation of ferrochrome slag by-products in many mining areas. On the other hand, the ferrochrome slag has been identified as one waste material that is rich in magnesium (Mg) and has not been effectively exploited. Beneficiating of ferrochrome slag (FCS) waste material is envisaged as a means of achieving sustainable recovery of Mg. Previous studies have used sulphuric acid as a lixiviant for leaching FCS at moderate temperatures to recover Mg. In this study, the recovery of Mg from ferrochrome slag was investigated using hydrochloric acid (HCl) as the lixiviant at low temperatures. Previous studies have shown that various metal oxides have been proven to be more amenable to leaching using HCl. This study examined the effects of acid content, leaching temperature, and reaction time on the recovery of Mg from FCS. Kinetic and thermodynamic analysis of the leaching process were also investigated as these are critical factors for maximum extraction of the Mg. The results showed that the highest recovery of Mg of 88.2% was obtained from FCS using 5 M HCl with a solid to liquid ratio of 1:10, mixing intensity of 250 rpm, reaction time and temperature of 150 min and 70 °C, respectively. The shrinking core model (SCM) was used in kinetic analysis to find the experimental data's best fit. A linear relationship was obtained with the coefficient of determination for the chemical reaction model (Kc) of >0.9 which indicates a good fit. The activation energy obtained for the diffusion and chemical reaction models were 95.44 and 41.45 kJ/mol, respectively, demonstrating that the rate-limiting phase is the one involving the chemical reaction.

The main intention of this research is to reuse the industrial by product ferrochrome slag and silica fume as a partial replacement of natural coarse aggregate and fly ash, respectively for the production of Geopolymer concrete with improved mechanical properties. Natural coarse aggregate was replaced by ferrochrome slag (FS) in varying percentages from 0 to 40% by weight. Fly ash was replaced by silica fume (SF) at different percentages 0 to 15% by weight. The combined effect of FS and SF was studied by developing Geopolymer concrete. Tests for compressive strength, splitting tensile strength and flexural strength of the GPC have been carried out at 7, 28 and 90 days of curing. The scanning electron microscope (SEM) was performed for the inspection of surface texture of the microstructure of the hardened samples. X-ray diffraction (XRD) was conducted to investigate the crystallinity of the mineral phases of the material as well as the activation product. Fourier transformed infrared spectroscopy (FTIR) was carried out to know the degree of polymerization of the samples. At 28 days, compressive strength, splitting tensile strength and flexural strength of GPC produced by replacing 30% FS and 10% SF increases by 38.9%, 47% and 20.4% respectively. Acronyms: CS Compressive strength; FS Ferrochrome slag; NCA Natural coarse aggregates; NFA Natural fine aggregates. [ABSTRACT FROM AUTHOR]

In this study, wet-mix shotcrete specimens were produced by substituting natural aggregate (NA) with ferrochrome slag aggregate (FS). Volumetrically, the amount of NA was reduced by 25%, 50%, 75% and 100% and a corresponding amount of FS aggregate was added. The physical, mechanical, durability and radiation shielding properties of the specimens were analysed. The gamma radiation performance was determined using energies 133Ba, 137Cs, 60Co and 22Na (ranging from 276.5 keV to 1332.5 keV) and a high-purity germanium HPGe detector system. The neutron radiation performance of the shotcrete specimens was obtained using FLUKA simulation. The WinXCOM interface was used for theoretical calculations, while the FLUKA Monte Carlo code was used for simulation calculations, and the data obtained were compared. It was observed that shotcrete mixtures having up to 50% ferrochrome slag aggregate showed a significant increase in mechanical properties. In radiation shielding performances, linear attenuation coefficient (μ), half-value layer (HVL), Tenth-value layer (TVL), mean free path (MFP) and radiation protection efficiency (RPE) parameters increased with increasing ferrochrome slag aggregate ratio, while mass attenuation coefficient (μ⁄ρ) values remained almost constant. It was experimentally determined that the 5 cm thickness shotcrete produced had RPE values of 75% and 50% at low (276.4 keV) and high (1332.5 keV) energies, respectively. It was concluded that the use of 50% ferrochrome slag aggregate has a positive effect on the mechanical properties of shotcrete mixtures. Additionally, ferrochrome slag-reinforced shotcrete is a good gamma and neutron radiation shielding material. • Wet mix shotcrete with ferrochrome slag admixture was produced. • Physical, mechanical and durability properties were analysed. • Experimental, theoretical and simulation methods were used. • Specimen FS50 has the best mechanical properties. • Sample FS100 has the best gamma radiation shielding properties. [ABSTRACT FROM AUTHOR]

Samples of concrete stone based on ferrochrome slags with addition of fly ash and Portland cement were obtained by mechanochemical activation. The samples were studied in terms of their chemical, phase, and particle size composition, specific surface area, as well as morphology and strength characteristics. [ABSTRACT FROM AUTHOR]

The present research aims to analyze the comminution behavior of ferrochrome slag using high-pressure grinding rolls. The laboratory bench scale high-pressure grinding rolls were used to study the three significant variables on the grinding efficiency of ferrochrome slag. The Central Composite Design was used to study the process variables, such as roll gap, applied load, and roller speed. The grinding efficiency was evaluated based on the product size and the energy consumption. The results showed that the increased gap between the rolls and roller speed decreases the product size with increased energy consumption. The results also found that an increase in applied load decreases the product fineness with increased energy consumption. The models were developed for the responses of P80 (size of 80% mass finer) and Ecs (specific energy consumption). Both the responses show high regression coefficients, thus ensuring adequate models with the experimental data. The minimum values of the P80 size and specific energy were determined using quadratic programming. The optimum values of the roll gap applied load and roll speed were found to be 1.43 mm, 16 kN, and 800 Rpm, respectively. The minimum values of P80 and the specific energy consumption were found to be 1264 µm and 0.56 kWh/t, respectively.

Near-net shape casting having complex geometry is manufactured through the sand casting process. However, day by day, the availability of natural or synthetic silica sand has been decreasing and increasing the production cost of sand casting components. Therefore, there is a need to look into low-cost and readily available alternative materials to substitute the commercial-grade silica sand for the sand mould casting process. The constituent of silica sand is primarily silica (SiO2), Al2O3, and Fe2O3. The major constituents of industrial wastes such as fly ash, blast furnace slag, ferrochrome slag, stone dust, and red mud have SiO2, Al2O3, and Fe2O3. Therefore, industrial wastes may be used individually or combined with silica sand at a different ratio to substitute the commercial-grade silica sand in green mould castings. Researchers and scientists have evaluated the suitability of industrial wastes and local riverbed sand as an alternative material for green sand mould castings. The present review summarizes the advantages and constraints of using industrial wastes and local riverbed sand as an alternative to green sand mould casting process. [ABSTRACT FROM AUTHOR]

Ferrochrome slag (FCS) possesses promising properties that promote its use as an alternative to natural aggregates in concrete production. Still, there is a concern about the effect of high-temperature exposure on the properties of concrete containing FCS aggregate. Therefore, due to durability and structural fire safety, it is necessary to evaluate the properties of FCS concrete after being exposed to elevated temperatures. The present study investigates the effect of FCS fine aggregate on the physical and mechanical properties of concrete at room and elevated temperatures (i.e., 200−1000 °C). Microstructural properties at high temperatures were also evaluated using SEM-EDS analysis. The results showed an improvement in the mechanical properties of concrete with FCS fine aggregate compared to conventional concrete. After being exposed to high temperatures, the concrete containing FCS fine aggregate showed less reduction in strength properties and mass than conventional concrete. Such improvements in mechanical and physical properties are achieved due to the chemical composition and surface texture of the FCS aggregate. Microstructural observation and ultrasonic pulse velocity confirmed that FCS concrete suffered less damage upon exposure to high temperatures. Furthermore, the effect of high temperatures on the strength properties of FCS concrete is consistent with the recommendations of the codes (Eurocode 2 and ACI 216.1).

In this study, high-carbon ferrochrome slag powder produced by grinding was used to replace different proportions of cement, and the effect of the amount of ferrochrome slag powder on the physical and mechanical properties of ferrochrome-slag-cement composites was analyzed. Water-cooled ferrochrome slag with a particle size of 5 mm was used to completely replace coarse aggregate to prepare ferrochrome-slag-based concretes. The microstructure of ferrochrome-slag-cement composites was analyzed by X-ray diffraction, scanning electron microscopy, and thermogravimetry–differential scanning calorimetry analysis. The compressive strength, water absorption, and aggregate–slurry interface bonding properties of ferrochrome-slag-based concrete were studied. The results demonstrate that a ferrochrome slag powder amount of 15% leads to the highest performance of ferrochrome-slag-cement composite material, and the fluidity ratio of ferrochrome-slag-cement mortar is 103, higher than reference samples. Furthermore, the compressive strengths of ferrochrome slag concretes are 15.8% and 3.6% higher than conventional concrete, and the water absorption of ferrochrome slag low-carbon concrete is better than that of conventional concrete. The interface bonding structure between concrete aggregate and slurry was optimized. This research can provide a reference for studying the application of ferrochrome slag, both the feasibility of high-carbon ferrochrome slag powder as supplementary cementitious material and the application of ferrochrome slag as concrete aggregate, and it can help to achieve the purpose of saving energy and reducing carbon emissions.

Lately, energy-saving attempts in the construction and building materials industry have become more popular due to the diminishing natural resources. With this motivation, we investigated the first foam glass consisting of ferrochrome slag (FS) and waste soda-lime glass (SLG) for potential use as a heat insulation material. For this, FS and SLG waste materials were valorized as main constituents, whereas a mixture of water glass (WG) & glycerol (G) and a sufficient amount of water (W) was used as a foaming agent and a moisturizer in the batch mixture, respectively. The studied series was prepared with the composition of 20FS-70SLG-xG-(8-x)WG-2W where x: 2, 4, and 6 wt%. After that, three different process temperatures (800, 825, and 850 °C), two distinct heating rates (5 and 10 °C/min), and two discrete dwell times (15 and 30 min) paved the way for the synthesis of 36 different foam glass samples. Eventually, the fabricated 36 different samples were subjected to physical, thermal, mechanical, and microstructural evaluations. According to the findings, one can say that samples synthesized with a lower G-to-WG ratio, higher process temperature, lower heating rate, and higher dwell time have the best features. From the physical property determinations, we found out that bulk density (ρ bulk) varied between 233 and 903 kg m−3 while the estimated porosity (P) ranged from 59.4 to 89.5%. Further, thermal conductivity (k) measurements demonstrated that the fabricated foam glass series provides lower values, namely from 0.038 to 0.130 W m−1 K−1. Besides, compressive strength (CS) values were found to be changing from 0.127 to 2.225 MPa. Microstructural evaluations via scanning electron microscopy (SEM) revealed the pore formations and the relevant alterations as a result of the different parameters. All in all, the authors concluded that a heat insulation material composed of nearly fully waste substances can effectively be produced. [ABSTRACT FROM AUTHOR]

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The utilization of ferrochrome slag as a solid waste resource holds significant potential for reducing environmental impact and promoting sustainable practices. This review summarizes the material characteristics and utilizations of ferrochrome slag based on existing research. The benefits such as enhanced mechanical strength from 100% to 120% are indicated compared with conventional concrete. Furthermore, advanced utilization methods and environmental impact analyses indicate promising high-value applications. For instance, the leaching value of hexavalent chromium is generally below 0.5 mg/L, and a notable 14.4% reduction in environmental disturbance indicators according to life cycle assessment (LCA) analyses is noted. However, limitations persist, including the performance variations of ferrochrome slag, its impact on the shrinkage and durability of concrete when used as aggregate, and the underutilization of its material characteristics and waste heat resources during production. Suggestions for future research directions and improvement measures are proposed to promote the utilization value and broaden its application. Finally, the adoption of construction materials and the promotion of sustainable waste management practices are expected for the future utilization of ferrochrome slag. • The material characteristics of ferrochrome slag were reviewed. • The primary utilization of ferrochrome slag as aggregate was analyzed. • The advanced applications and environmental impact were summarized. • The limitations during the existing research of ferrochrome slag were concluded. • The directions of future studies for ferrochrome slag were proposed accordingly. [ABSTRACT FROM AUTHOR]

Abstract Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 10 M KOH and an L/S of 0.26 yielded a geopolymer with a UCS 13.0 MPa after 28 d of ambient temperature curing. A 0.125 wt KS:KOH addition yielded a geopolymer with a UCS of 14.7 MPa whilst a 1.25 wt KA:KOH addition yielded a geopolymer with a UCS of 24.5 MPa. The increase in strength was due to the formation of Calcium Silicate (Aluminate) hydrate. The aluminate activated FeCr slag geopolymer was the most competent of all geopolymers synthesised as it resulted in over 97% immobilisation of Fe, Zn, Mn, Ni and Cr. The 360-d static leachability tests for the aluminate activated geopolymer yielded a metal release rate lower than 90 mg mm− 2 of the geopolymer. The aluminate activated geopolymer also was resistant to changes in wet and dry cycles as it had a UCS reduction of 42% after 10 cycles whereas the pure FeCr slag geopolymer and the silicate activated geopolymer had a UCS reduction of 91 and 72% respectively after 10 cycles. The aluminate activated geopolymer met the minimum requirements for use as a paving brick for low traffic pavements. The study provides opportunities for sustainable use of FeCr slag with minimal environmental impact.

Ferrochrome (FeCr) slag was milled and stabilised with either ascorbic acid or phosphoric acid. The stabilised FeCr was then geopolymerised with 1 M KOH in order to obtain a monolith with at least an unconfined compressive strength of 1 MPa. The leachability of metals of the stabilised geopolymerised monoliths were then compared with the unstabilised geopolymerised monolith. Ascorbic acid stabilisation was only effective in Cr leaching reduction by 99.45% but was not effective on immobilisation of Fe, Zn, Ni and Mn. Ascorbic acid stabilisation was thought to proceed via the reduction of Cr(VI) species to insoluble Cr (III) species. Phosphate stabilisation reduced the leachability of Cr, Ni, Zn, Mn, Fe by 99.5%, 67.1%, 71.1%, 96.8% and 85.4% respectively. Phosphate stabilisation was thought to proceed via the formation of phosphate compounds of the metal ions in question. The phosphate stabilised FeCr slag leachability was within the allowable Toxicity Characteristic Leaching Procedure (TCLP) limits and its use is not detrimental to the environment. [ABSTRACT FROM AUTHOR]

Ferrodirome slag (FeCr-GP) and gold mine tailings (GMT-GP) based geopolymers were synthesized and used as adsorbents of heavy metals in aqueous solutions. Batchwise adsorption experiments were used to determine the effect of solid loading (S/L), temperature and time on the adsorption of Cu, Ni and Mn. X-ray diffraction studies showed that GMT-GP was amorphous with calcium aluminium silicate hydrate as the geopolymerization product leading to an increased surface area while GMT-GP had a significant reduction in the intensity of crystalline peaks as compared to the precursor. FeCr-GP could adsorb above 99% of the metal ions (Cu2+, Ni2+ and Mn2+) in solution with an initial metal concentration of 400 ppm at 298, while GMT-GP could only adsorb at least 98% of the metal with an initial metal concentration of 200 ppm. The adsorption was accompanied by a pH rise from 2.3 to 4.5 and 4.8 for GMT-GP and FeCr-GP, respectively. The maximum adsorption capacity of FeCr-GP was double that of GMT-GP. FeCr-GP could be desorbed using HCl and reverse osmosis water and could be used for a further three cycles without significant loss in adsorbing ability, while desorption of GMT-GP resulted a reduction in adsorption capability. [ABSTRACT FROM AUTHOR]

This study introduces the possible utilization of water cooled ferrochrome slag, an industrial waste from ferrochrome industry in concrete production. Traditional sand was substituted with six percentages (0% for reference mix, 10%, 20%, 30%, 40% and 50%) of ferrochrome slag by weight in all concrete mixtures. Leaching, micro-structural and mechanical properties, these three aspects were explored for the qualification of ferrochrome slag concrete. Different tests for the physical and mechanical performance of the concrete were done and the outcome demonstrated that substitution of sand by ferrochrome slag reduced a little in the performance of the strength and water absorption increases along with the increase of rate of substitution. However, the concrete having 30% ferrochrome slag shows almost comparable results with the reference mix. Leachability characteristics were also observed by pH dependence leaching test method for the five concrete samples and one raw slag sample. Moreover, micro-structural study of reference mix and concrete mix with 10–50% ferrochrome slag was performed by utilizing SEM techniques. This experimental study concludes that that ferrochrome slag can be used in the production of concrete as a partial substitution of traditional sand with no unfavourable ecological, micro-structural and mechanical effects. Cr- Chromium; FeCr- Ferrochrome; GBFS- Granulated Blast Furnace Slag; ISF- Imperial Smelting Furnace; PSC- Portland Slag Cement; SAI- Slag Activity Index; SEM- Scanning Electron Microscope; TCLP- Toxicity Characteristic Leaching Procedure; USEPA- United States Environmental Protection Agency; WCFS- Water Cooled Ferrochrome Slag; XRD- X-Ray Diffraction [ABSTRACT FROM AUTHOR]

Ferrochrome slag (FS) and ground granulated blast furnace slag (GGBFS) were used as resource material in geopolymer concrete mixtures. A mixture of 10 M sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as the activator. After the two different slag‐based geopolymer concrete (SGC) mixtures were prepared and molded. They were kept at 80°C for 24 hr, and then the SGC samples were cured in 23 ± 1°C water for 27 days. Samples that completed the curing times were exposed to the 300 freeze–thaw (F–T) cycles. The compressive strength, ultrasonic pulse velocity, relative dynamic elasticity modulus values, weight changes, and appearances of the SGC samples were examined at the end of every 50 F–T cycles. Scanning electron microscopy analysis was performed to examine the microstructure changes of the samples after 300 F–T cycles. As the GGBFS proportion in the SGC mix increased, the mechanical properties of the samples against the F–T effect increased. Samples containing 100% FS and 75% FS fell apart at the end of 150 and 200 F–T cycles, respectively. The deterioration of the geopolymer gel structures of the samples exposed to F–T was decreased with increasing GGBFS ratio in the mix. [ABSTRACT FROM AUTHOR]

This study investigates the mechanical and thermal properties of cement mortars incorporating two types of waste slags: ferrochrome (FeCr) slag aggregate was used as a replacement for sand at ratios of 25, 50, 75 and 100 wt%, and ground granulated blast furnace slag (GGBS) was used as a partial replacement for cement at a ratio of 25 wt%. Compressive strength, volume of permeable voids (VPV), drying shrinkage, and thermal conductivity tests were conducted after 28 days of curing. The microstructure characteristics were examined by scanning electron microscopy. The experimental results revealed that FeCr waste aggregates could satisfactorily replace natural fine sand in cement mortars up to 25 wt% without a remarkable degradation of compressive strength. Furthermore, increasing the replacement ratios of FeCr aggregates by over 25 wt% resulted in a noticeable decrease in thermal conductivity and an increase in the permeable void content of cement mortars. The increased VPV of FeCr slag-blended mortars led to a significant increase in drying shrinkage. The integration of GGBS with FeCr aggregates led to enhanced compressive strength and reduced VPV and drying shrinkage, thus contributing to an improved microstructure. [ABSTRACT FROM AUTHOR]

This paper reports the characteristics of ferrochrome slag and its feasibility as aggregate in refractories aiming to substitute virgin refractory raw materials. Refractory castable specimens were formulated with ferrochrome slag as an aggregate and commercial calcium aluminate cement as a binder. Objective was to prepare refractory specimens with a maximum slag utilization but simultaneously to sustain good properties, comparable to those of virgin raw material refractory products. Mechanical and thermo-physical properties of the cured, dried and sintered specimens were characterized. Cold crushing strengths of best performing ferrochrome slag containing specimens were higher than 90 MPa and compressive strength values measured at 1200 °C were over 9 MPa. Thermal insulation properties were even better than those of commercial refractory reference, showing thermal conductivity values as low as λRT−1000 °C = 1.3 − 0.9 W/m K. The liquid phase formation above 1200 °C limits the ferrochrome slag use for refractory applications. Results suggest ferrochrome slag's feasibility as an aggregate raw material for refractory materials up to temperatures of 1200 °C in air and up to temperatures of 700 °C in acidic gaseous atmosphere. Possible applications for this kind of novel refractory materials are, e.g., insulating secondary layers or bottom zones in metallurgical processes to substitute virgin refractories. A direct contact to molten metal must be avoided, but they are applicable as, e.g. floorings when exposed only to occasional melt droplets. [ABSTRACT FROM AUTHOR]

Development and utilization of controlled low-strength material (CLSM), a flowable self-compacting material using industrial wastes is an effective way of sustainable infrastructure development. In the present study, an effort has been made to characterize ferrochrome slag, a less explored industrial waste as a construction material in general and FS as a base material with cement and fly ash for CLSM material, in particular. Different tests such as scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscope image, compaction, electrical conductivity, total dissolved solids (TDS), thermal conductivity are conducted to characterize ferrochrome slag as an alternate construction material. Then the properties of developed CLSM are discussed in terms of its flowability, fresh density, bleeding, unconfined compressive strength (UCS), settlement analysis and California bearing ratio (CBR) values. Based on the above results it was observed the FS can be used as a structural fill material with cement and fly ash for infrastructure development thereby conserving the natural resources, utilizing the industrial wastes and helping in sustainable development. [ABSTRACT FROM AUTHOR]

Solid waste, such as ferrochrome slag (FCS), has been extensively studied for its potential use as a construction material. This research focuses on utilizing FCS as the primary raw material to produce a high-strength ceramic aggregate, referred to as FCS-HSCA. The impact of calcination parameters on the performance of FCS-HSCA was investigated, while the underlying transformation mechanism was comprehensively explored. Subsequently, concrete with FCS-HSCA was prepared, and its influence on the performance of concrete was evaluated. The results reveal that the optimal performance of FCS-HSCA is achieved with a compressive strength of 310.3 MPa, a water absorption of 0.27%, and an apparent density of 2930 kg/m3. These characteristics are associated with specific parameters during the calcination stages, namely a preheating temperature of 1100 ℃, preheating time of 60 min, calcination temperature of 1500 ℃, and calcination time of 180 min. Moreover, the increased crystalline phases promote the solid dissolution of chromium into Mg(Al 1.5 Cr 0.5)O 4 , and the occurrence state of chromium is stable during the preparation of FCS-HSCA. This results in a decreased leaching value from 0.439 mg/L to 0.188 mg/L, reducing the impact on the environment and human health. Additionally, replacing FCS with FCS-HSCA in concrete enhances its compressive strength from 59.9 MPa to 66.1 MPa. This improvement is attributed to a notable reduction in the diameter of pores on the surface of FCS-HSCA, leading to a denser structure and improved bondability with cementitious composites. Finally, this novel approach maximizes the utilization of material characteristics while enhancing the stability of waste FCS. • A novel way to maximize the utilization of waste characteristics was proposed. • The optimal performance of FCS-HSCA was achieved through various analyses. • The surface roughness and performance variations were refined in preparing FCS-HSCA. • The improved bonding ability contributed to the increased performance of concrete. • The solidification of chromium was beneficial in reducing the environmental impact. [ABSTRACT FROM AUTHOR]