Soil contamination is a growing concern for sustainable development worldwide. Conventional remediation approaches, such as using ordinary Portland cement (OPC) or lime are limited due to high CO2 ...emissions, energy consumption, and natural resource consumption. This paper proposes a sustainable method using CO2 and a waste from steel production (ladle slag, LS) for rapid remediation of Cr and Zn-contaminated soils. Contaminated soils spiked by Cr and Zn with various initial concentrations were treated with 10% LS and subjected to conventional and CO2 curing for different periods. The results demonstrated that LS with conventional curing could reduce leaching concentrations of Cr and Zn in contaminated soils. However, it necessitated 28 days to meet the criteria of inert waste and drinking water standards. In contrast, LS with CO2 curing required significantly less time (32 h for Cr and 8 h for Zn) to achieve lower leaching concentrations of Cr and Zn than those with 28-day conventional curing. After CO2 curing for 152 h for Cr- and 80–120 h for Zn-contaminated soils, leaching concentrations of Cr and Zn were 1.5–4 times and 6–72 times lower than those with 28-day conventional curing, respectively. Simultaneously, carbon capture was increased from 10.6% to 17.5% and 19.9%, respectively, with the initial Cr and Zn concentrations increased from 0 to 8000 mg/kg. The strength of Cr- and Zn-contaminated soils with CO2 curing also effectively enhanced up to around 3.3–3.6 times and 1.3–3.3 times higher than those with 28-day conventional curing, respectively.
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•Chromium (Cr) and zinc (Zn) are rapidly immobilized in soil by ladle slag and CO2.•CO2 is rapidly sequestered and chemically stored.•Strength of contaminated soils are enhanced.•Binder cost, LS landfilling, and use of nature resources and energy are reduced.
With the regulations pertaining to the environment and waste disposal becoming stringent day by day, the steelmaking industry is being compelled to adopt a zero-waste-policy for sustainability. As a ...consequence, 3R (reduce, reuse and recycle) technique of waste handling has become the most favoured option among the industries. This paper focuses on recycling of slag generated after secondary refining process. Trials were conducted in two stages, namely (a) prevention of dusting phenomenon of Al-killed steel ladle slag to generate lump slag by suitably selecting the ladle covering compound and chemically modifying the slag, and (b) utilisation of the lump slag as a 100% replacement of synthetic slag in Si-killed steel ladles, leading to a reduction in its specific consumption from 1.2 kg/TLS to zero. As a process requirement, specific power consumption, arcing time and degree of desulphurisation were considered as the major parameters for comparing the results using hypothesis test statistical tool.
•Ladle slag with higher SiO2 content and lower free lime showed stronger carbonation reactivity.•Heat treatment at 1100°C with silica addition is effective to produce more dicalcium silicate ...phases.•The total CaO content of slag should not be considered as the only factor for its CO2 reactivity.•The products based on carbonation activated slag have shown reduced natural material consumption.
The viability of converting steelmaking ladle slag into cementing binder through carbon dioxide activation was studied. Two typical ladle slag materials were examined: one with higher silica content and one with higher alumina content. It was found that ladle slag with higher silica content contained more calcium silicate compounds and less free lime, leading to higher carbonation reactivity in its as-received form. Ladle slag with higher alumina could not be activated directly by carbon dioxide to gain strength. Heat treatment with silica addition was thus developed to produce more calcium silicates and reduce free lime content. Findings reveal that carbonation reactivity is not solely based on chemical compositions of the material, rather, the constituting mineralogical phases. Calcium silicates of any polymorph played a critical role in the formation of the strength-contributing binder matrix activated by carbonation. Strength gain was the result of simultaneous formation of calcium silicate hydrates and calcium carbonates. To produce value-added ladle slag as cementing binder to replace Portland cement, silicon is recommended as deoxidation agent in steel refinery process. The building products based on carbonation activated ladle slag have shown much reduced embodied energy and much reduced natural material consumption.
•Building ceramics were prepared at 700–900 °C using industrial side streams.•Sodium hydroxide performed better that sodium carbonate as fluxing agent.•The materials achieved max compressive and ...flexural strength of 55 and 14 MPa.•The results are of interest for waste management and sustainable use of resources.
This paper deals with the valorization of quartz and felspar rich lithium mine tailings (QFS) in the development of construction materials. Ladle slag was used as green strength increasing agent. Sodium hydroxide and carbonate were used as fluxing agents to allow sintering at 700–900 °C. Of these, sodium hydroxide was found to be the more efficient. The sintered ceramics were characterized by X-ray diffraction, scanning electron microscopy, compressive test, water absorption, apparent density and dilatometry; the results were found to comply with ASTM C62-99 specifications for building brick, and interesting for a sustainable use of resources.
The effect of CaO/Al2O3 (=C/A) ratio of the ladle slag on the formation behavior of non-metallic inclusions in the Mn-V-alloyed steel was investigated using both the experimental method and ...refractory-slag-metal-inclusion (ReSMI) multiphase reactions simulation. The formation behavior of inclusion was strongly affected by the activity of MgO in the initial slag at the early stage of the reaction. However, since the MgO activity converged to unity due to MgO dissolution from refractory to slag during the reaction, the formation behavior of inclusion was affected by the activity of CaO and Al2O3 in the slag rather than that of MgO at the final stage of the reaction. From the experimental results and ReSMI multiphase reaction model, the formation behavior of inclusions could be divided into three cases according to the C/A ratio of the slag as follows; 1) C/A < 1.5; Alumina → Spinel → Spinel + Liquid oxide, 2) 1.5 < C/A < 2.5; Alumina → Spinel → Liquid oxide, 3) C/A > 3.0; Alumina → Spinel → Liquid oxide → Magnesia. Therefore, it was concluded that the C/A ratio of the ladle slag should be controlled from about 1.5 to 2.5 in order to suppress the harmful solid inclusions such as spinel during secondary refining processes.
•Metallurgical wastes can substitute of natural aggregates in the polymer concretes.•The chemical resistance depended on the target material used.•Metallurgical wastes showed a good resistance ...against the chemical substances.•Ladle slag showed the best mechanical strength and surface strength against impacts.•The surface resistance against scratching depended on the resin.
Varied target materials can be incorporated into polyester polymer concretes (PPC). This allows natural aggregates to be substituted for different waste products in non-structural polymeric construction and building materials. Many studies have explored the mechanical properties of waste-based PPC, but the durability and surface resistance of these materials is not fully known. In this study, we compared the suitability of two metallurgical wastes to that of two natural aggregates for manufacturing durable PPC products. Durability against environmental conditions, durability against chemical products, and surface strength against physical damage were tested. Durability against environmental conditions was characterised according to visual damage and mechanical strength losses after freezing-thawing; no PPC combinations exhibited surface damage following the ageing cycles. The ladle slag (LS) samples exhibited the best pre- and post-test flexural and compressive strength. The properties of the alumina filler (AF) combinations exhibited the highest flexural and compressive strength losses after freezing-thawing. The calcareous sand combinations were damaged most severely by acid, while LS and AF exhibited good resistance against chemical substances. The LS combinations exhibited the highest surface strength against impacts in the rebound number test, while the results obtained for the AF combinations were close to those of natural aggregates. The surface resistance against scratching depended on the resin, not on the target material.
Alkali activation is studied as a potential technology to produce a group of high performance building materials from industrial residues such as metallurgical slag. Namely, slags containing ...aluminate and silicate form a useful solid material when activated by an alkaline solution. The alkali-activated (AA) slag-based materials are promising alternative products for civil engineering sector and industrial purposes. In the present study the locally available electric arc furnace steel slag (Slag A) and the ladle furnace basic slag (Slag R) from different metallurgical industries in Slovenia were selected for alkali activation because of promising amorphous Al/Si rich content. Different mixtures of selected precursors were prepared in the Slag A/Slag R ratios 1/0, 3/1, 1/1, 1/3 and 0/1 and further activated with potassium silicate using an activator to slag ratio of 1:2 in order to select the optimal composition with respect to their mechanical properties. Bending strength of investigated samples ranged between 4 and 18 MPa, whereas compressive strength varied between 30 and 60 MPa. The optimal mixture (Slag A/Slag R = 1/1) was further used to study strength development under the influence of different curing temperatures at room temperature (R. T.), and in a heat-chamber at 50, 70 and 90 °C, and the effects of curing time for 1, 3, 7 and 28 days was furthermore studied. The influence of curing time at room temperature on the mechanical strength at an early age was found to be nearly linear. Further, it was shown that specimens cured at 70 °C for 3 days attained almost identical (bending/compressive) strength to those cured at room temperature for 28 days. Additionally, microstructure evaluation of input materials and samples cured under different conditions was performed by means of XRD, FTIR, SEM and mercury intrusion porosimetry (MIP).
Phosphorus in steel is detrimental element for mechanical properties and dephosphorization treatment of hot iron is necessary to produce high-grade steel products. However, it is difficult to perform ...dephosphorization treatment to attain lower phosphorus content using CaO–SiO2–FeO flux without fluorite of which use is limited owing to stringent environmental regulations. It is because increasing slag basicity is difficult without slagging promotion agent. In the present work, addition of ladle slag and lime powder top blowing method were applied in 2 t test converter to obtain the higher slag basicity. Obtained results are as follows: (1) phosphorus content of hot iron decreased to 0.001 mass% under the condition of (CaO)/(SiO2)=3. (2) Rate constant, K, of dephosphorization reaction below P=0.02 mass% increased with increasing bottom gas flow rate, but K decreased under the condition of too much bottom gas flow rate. (3) Phosphorus distribution in the final stage of blowing was much higher than predicted values on a basis of thermodynamic relation between top slag and hot iron. (4) It is suggested that the FeO–CaO melt formed at hot spot is capable of decreasing the phosphorus content of hot iron to the ultralow range even at high temperature at hot spot.
Geopolymers are representing the most promising green and eco-friendly alternative to ordinary Portland cement and cementitious materials, thanks to their proven durability, mechanical and thermal ...properties. However, despite these features, the poor tensile and bending strengths usually exhibited by geopolymers due to their brittle and ceramic-like nature, can easily lead to catastrophic failure and represent the main drawback limiting the use of those materials in several applications. Fiber reinforced geopolymer composites may be considered a solution to improve flexural strength and fracture toughness. Different types of dispersed short fibers are here investigated as a reinforcing fraction for a geopolymer matrix based on an alkali-activated ladle-slag. It has been demonstrated that both organic and inorganic fibers can lead to a significant flexural strength enhancement. Moreover, the investigated geopolymers exhibit an increase in toughness, thus determining a switch from a brittle failure mode to a more ductile one.
Recycling industrial waste to produce new materials is a driving path to promote a sustainable development. Alkali activation can be a very effective tool to reach this goal especially when the ...starting material can be carbon fly ash and blast furnace slag instead of calcined natural clays such as metakaolin. With the aim to further increase the type of waste to be used as precursor and to promote a new recycling route, alkali activated materials based on partial substitution of metakaolin with ladle slag, deriving from the refining process of steel produced by arc electric furnace technology, are reported. In particular, being ladle slag rich in Ca-containing crystalline phases, its effect on the consolidation process has been investigated by means of microstructure analysis carried out with XRD, SEM and MIP techniques. The results show that ladle slag are activated by alkaline solutions and participate in gels formation. Indeed, an optimization in terms of ladle slag content (60–80wt.%) and the coexistence of different types of gels (3D aluminosilicate, C-S-H and Ca-rich aluminosilicate) have been envisaged.
► Un-common slag used in alkali activation process. ► Detailed study of crystalline phase dissolution. ► Effect of Ca content on porosity, microstructure and mechanical properties of AAM. ► Highlighted green aspects of the investigated formulations.
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