Search

In recent times, with rapid development in the construction sector, the use of enormous amounts of materials is required for the production of concrete. Fire penetrates concrete, leading to chemical contamination, small cracks, and lightening. These effects can significantly change the properties of concrete's structure, reduce its strength and durability, and also change the behavior of the structure and lead to effects on the environment. An attempt was made to study the effects of elevated temperature on the mechanical characteristics of self-compacting concrete (SCC) with by-products including fly ash as a partial replacement for cement and waste copper slag as a partial replacement for fine aggregate at 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The SCC specimens were subjected to elevated temperatures ranging from 200, 400, 600, and 800 °C, respectively, for a steady-state of two hours in a digital muffle furnace. The residual compressive strength, mass loss, ultrasonic pulse velocity, and residual density along with a visual inspection of cracks and color changes were observed. In this study, with over 400 °C temperatures, surface fractures appeared. The residual compressive strength (R-CMS) of all the individual temperatures of the SCC-WCS% mixes exhibited a gain in strength range from 31 to 34 MPa at 400 °C, 26 to 35 MPa at 600 °C, and 22.5 MPa to 33.5 MPa at 800 °C, respectively. Microstructural analysis of SCC-WCS% mixtures subjected to elevated ambient temperatures is carried out with a scanning electron microscope (SEM) and X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

In this work, a novel carbon-free smelting reduction process is proposed to recover valuable metals from molten copper slag, in which secondary aluminum dross is used as the reductant via co-modification with CaO and Na 2 O additions. The influence of Na 2 O addition on the metal recovery and slag properties under different CaO/SiO 2 ratios was investigated at 1550 °C. The results show that the modifier Na 2 O not only reduces the melting temperature of the slag, but also inhibits the precipitation of spinel and prevents the polymerization of aluminosilicate units to a certain extent by providing more O2-, which results in a relatively lower slag viscosity. These effects are more significant at the CaO/SiO 2 of 0.9. The multiple strengthening mechanisms improve the kinetic conditions for smelting reduction, resulting in optimal results when the Na 2 O addition reaches 4 wt% at the CaO/SiO 2 of 0.9, at which 99.1% of iron and 98.5% of copper in the slag can be recovered as the high-purity alloy. The leaching toxicity of the tailings is 2–3 orders of magnitude lower than the original slag, suggesting that they are clean sources for ceramic production. Furthermore, the assessment of the proposed process indicates that it is technically feasible even without an external energy supply, which indicates that the process is green, efficient, and cost-effective. [Display omitted] [ABSTRACT FROM AUTHOR]

In recent times, with rapid development in the construction sector, the use of enormous amounts of materials is required for the production of concrete. Fire penetrates concrete, leading to chemical contamination, small cracks, and lightening. These effects can significantly change the properties of concrete’s structure, reduce its strength and durability, and also change the behavior of the structure and lead to effects on the environment. An attempt was made to study the effects of elevated temperature on the mechanical characteristics of self-compacting concrete (SCC) with by-products including fly ash as a partial replacement for cement and waste copper slag as a partial replacement for fine aggregate at 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The SCC specimens were subjected to elevated temperatures ranging from 200, 400, 600, and 800 °C, respectively, for a steady-state of two hours in a digital muffle furnace. The residual compressive strength, mass loss, ultrasonic pulse velocity, and residual density along with a visual inspection of cracks and color changes were observed. In this study, with over 400 °C temperatures, surface fractures appeared. The residual compressive strength (R-CMS) of all the individual temperatures of the SCC-WCS% mixes exhibited a gain in strength range from 31 to 34 MPa at 400 °C, 26 to 35 MPa at 600 °C, and 22.5 MPa to 33.5 MPa at 800 °C, respectively. Microstructural analysis of SCC-WCS% mixtures subjected to elevated ambient temperatures is carried out with a scanning electron microscope (SEM) and X-ray diffraction (XRD).

The article presents the results of investigation of mechanical and thermal properties of lightweight concrete with waste copper slag as fine aggregate. The obtained results were compared with the results of concrete of the same composition in which natural fine aggregate (river sand) was used. The thermal properties tests carried out with the ISOMET 2114 device included determination of the following values: thermal conductivity coefficient, thermal volume capacity and thermal diffusivity. After determining the material density, the specific heat values were also calculated. The thermal parameters were determined in two states of water saturation: on fully saturated material and dried to constant mass at 65°C. Compressive strength, open porosity and bulk density are given as supplementary values. The results of the conducted research indicate that replacing sand with waste copper slag allows to obtain concrete of higher ecological values, with similar mechanical parameters and allowing to obtain significant energy savings in functioning of cubature structures made of it, due to a significantly lower value of thermal conductivity coefficient.

Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment. Although numerous studies on waste copper slag concrete can be found in the published literature, no research has focused on the structural application of this type of concrete. In particular, the variability in the strength properties of waste copper slag concrete, which is required for various structural applications, such as limit state design formulation, reliability-based structural analysis, etc., has so far not attracted the attention of researchers. This paper quantifies the uncertainty associated with the compressive-, flexural- and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate. Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments. In addition, the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building, considering the proposed distribution model. The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand. [ABSTRACT FROM AUTHOR]

One of the important issues of the modern world is the ecological problems, which raise the issues of rational and efficient use of natural resources and the reduction of industrial waste. Materials synthesized from industrial waste are an example of producing new useful materials for various applications as well as efficient utilization of waste. The present study aims to synthesize amorphous aluminosilicates from metallurgical waste - waste copper slag, aluminum dross as well as from agricultural waste (rice husks). A synthesis method was applied by which the necessary silica and alumina were extracted from the waste products by chemical treatment in an alkaline environment. Two types of aluminosilicate materials were obtained depending on the experimental procedure. In the first case during the synthesis, there was a stage of polymerization and gel formation and in the second - of co-precipitation. Accordingly, the materials designated as geopolymer and amorphous aluminosilicate were characterized experimentally. They were found to be X-ray amorphous by XRD. FTIR spectroscopy proved that their structure was characterized by a three-dimensional aluminosilicate network with a high degree of connectivity of silicon and aluminum tetrahedra. The microstructure of the materials was established by SEM-EDS and their homogeneity was confirmed. However, due to the difference in synthesis, some differences in the chemical composition and structure of the geopolymer and the amorphous aluminosilicate were experimentally established. Their composition, the structural and textural features of the obtained geopolymer and amorphous aluminosilicate show that such materials can find application as catalyst carriers. [ABSTRACT FROM AUTHOR]

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application.

Abstract Walnut shell is a common agricultural by-products for the production of biochar. In this study, the walnut shell was investigated by thermoanalytical methods to evaluate its thermal behavior; and the biochar was prepared from the pyrolysis at 600 °C. Biochar characterization was studied in detail, and proximate analysis result indicates that the biochar obtained from walnut shell has a high fixed carbon content, lower ash content. The biochar was used as a reductant to reduce the waste copper slag for recovering iron. The reduction process of copper slag by biochar was analyzed theoretically, and the iron in the slag was recovered efficiently by reduction and magnetic separation method. The phase transformation of the reduced slag and the kinetics of reduction process were analyzed during the reduction process with biochar. The research results suggest that biochar derived from walnut shell can be used as a green reductant to reduce iron phase in the waste copper slag and realize the clean utilization of hazardous waste. Highlights • Biochar with high fixed carbon content was obtained from walnut shell. • Walnut shell char was used as a reductant for reducing waste copper slag. • Reduction kinetics of waste slag by biochar was investigated in detail. • Iron elements in the waste copper slag was enriched efficiently via reduction method by using walnut shell biochar. [ABSTRACT FROM AUTHOR]

This research proposed an efficient, innovative and environmentally friendly technology named smelting reduction-sulfurizing process, which uses one waste (waste ferric-oxide desulfurizer) to treat another (waste copper slag). In the new process, the waste ferric-oxide desulfurizer was employed not only as a sulfurizing agent to sulfurize and collect the copper lost in copper slag, but also as a reductant to reduce the magnetite to “FeO” and thus improve slag fluidity. It was revealed that 90.81% Cu was recovered and enriched in copper matte under the smelting conditions. The matte contained 15.87% copper, 20.25% S and 49.56% Fe, which can be returned to the copper smelting process as a feeding. Meanwhile, the removal rate of hazardous elements, such as Ni, Pb, Zn, As, Sb, Bi and Hg, from the initial copper slag by the new process was also determined, and the elimination rate of those elements was all over 90%.The leaching toxicity was used to further evaluate the environmental impact of the cleaned slag, indicating that the concentrations of toxic element ions in the leachate are all much lower than the thresholds, which confirmed that the cleaned slag with trace toxic elements is safe and harmless. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel anorthite-based ceramics are prepared from reduced copper slag. • The effect of slag addition on the sintering and microstructure is clarified. • Slag-derived ceramics vitrify earlier and show much higher MOR than the traditional ones. • Leaching toxicity of the ceramics is 2 ∼ 3 orders of magnitude lower than the initial slag. • A high degree of whiteness (∼90) is also achieved for the slag-derived ceramics. Waste slags are promising sources of ceramic materials, but slag-derived ceramics also show inferior whiteness and quite different constituents compared to commercial products due to the introduction of impurity elements. To solve this issue, in this work, reduced copper slag after iron and copper extraction was used as a new raw material to prepare novel anorthite-based ceramics. The role of slag addition in the sintering, microstructure, physical and mechanical properties, leaching behavior, and color quality was investigated by using different characterization techniques such as DSC-TG, XRD, SEM, spectrophotometer, Archimedes method, 3-point bending method, and acetic acid buffer solution method. The results show that the ceramics are more effective in liquid generation with the slag addition, significantly enhancing the sintering and reducing the porosity. The slag also favors the development of anorthite grains as it is an Al 2 O 3 -SiO 2 -CaO-based system. As a result, a dense and well-bonded structure with few impurity phases and fine rounded pores is produced with 40 wt% of slag addition. These effects contribute to a remarkable improvement in flexural strength (87.6 MPa) and good maintenance of whiteness (∼90). Moreover, its leaching toxicity is ∼ 3 orders of magnitude lower than the thresholds. The high strength, appearance quality and cleanliness are the competitive advantages of the designed ceramics compared to other slag-derived ceramics. However, limited densification and severe blisters and bloating appear after introducing more than 50 wt% of slag, leading to a much inferior mechanical and color performance. [ABSTRACT FROM AUTHOR]

Abstract: A large amount of waste copper slag containing about 35–45wt.% iron is generated every year from pyrometallurgical processes for producing copper from copper concentrate. Recovery of iron from the waste copper slag is of great interest for comprehensive use of mineral resource and reduction of environmental problems. In this study, a method for upgrading iron from the waste copper slag discharged as an industrial waste has been developed. The process first crushes the waste copper slag between 150 and 203μm, followed by reduction reaction at 1250°C for 1.5h. And then, the resulting material is again crushed to 75–104μm, followed by dry magnetic separation. Using the developed process, a magnetic product containing more than 65wt.% iron was obtained from magnetic separation under a magnetic field strength of 0.03T for the waste copper slag treated by reduction reaction. At the same conditions, the percentage recovery of iron was over 85%. It was also found that iron in the magnetic product mainly exists in iron metal, iron carbide, and iron oxides. [Copyright &y& Elsevier]

Waste copper slag is a typical hazardous solid waste containing a variety of valuable elements and has not been effectively disposed of so far. In this paper, a stepwise extraction process was proposed to recover valuable elements (copper, iron, lead and zinc) from waste copper slag. The specific procedures are as follows: (1) A flotation process was adopted to enrich copper, and when the copper grade in the flotation concentrate was 21.50%, the copper recovery rate was 77.78%. (2) The flotation tailings were pelletized with limestone, then the green pellets were reduced, and the magnetic separation process was carried out. When the iron and copper grades in the magnetic concentrate were 90.21% Fe and 0.4% Cu, 91.34% iron and 83.41% copper were recovered, respectively. (3) Non-magnetic tailings were mixed with clinker and standard sand to produce common Portland cement. Several products were obtained from the waste copper slag through the proposed process: flotation concentrate, measured 21.50% Cu; magnetic concentrate, containing 90.21% TFe and 0.4% Cu; direct reduction dust, including 65.17% ZnO and 2.66% PbO; common Portland cement for building construction. The comprehensive utilization method for waste copper slag achieved zero tailing and has great potential for practical application. [ABSTRACT FROM AUTHOR]

The copper production process causes waste and by-products called waste copper slag (WCS). A considerable amount of WCS is produced globally. This research aims to utilise WCS as an alternative to natural coarse aggregate in self-compacting concrete (SCC). To achieve this goal, WCS was utilised in different percentages (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) as a natural coarse aggregate replacement in SCC production. Following this, the fresh, mechanical, and durability characteristics of SCCs incorporating WCS as a partial replacement of coarse aggregates were investigated in-depth. Incorporating 100% WCS as coarse aggregates in SCCs showed 27%, 29%, and 26% growth in compressive, split, and flexural strengths in 28 days, respectively. The reduction of free drying shrinkage of the mixture containing 100% WCS compared to the control mixture was approximately 36%, and the water absorption of all the specimens was less than 6%. Further, the increase in weight for the mixture containing 100% WCS as coarse aggregates was less than 15% compared to the control mixture. A cost analysis of the SCCs showed that incorporating WCS for all coarse aggregates reduced production costs by 19%. Investigating the economic index of concrete containing WCS as a coarse aggregate showed that utilising the WCS in green SCC was feasible. • This study investigated the fresh and mechanical properties of SCC with and without WCS. • WCS has been used in different percentages of 0–100 as coarse aggregate to produce SCC. • The addition of WCS into SCCs led to an increase in the workability. • By reducing the W/C ratio, the increasing WCS percentage is more effective for mechanical properties. • Cost analysis shows a 19% reduction in the cost of production of SCC with 100% WCS. [ABSTRACT FROM AUTHOR]

The aim of the research is a comprehensive evaluation of concrete using the EIPI method. In the evaluation the compressive strength of concrete and its durability properties represented by sorptivity and air permeability are taken into account. Since waste copper slag with increased natural radioactivity is used in the assessed concrete, additional evaluation is carried out taking into account the influence of natural radioactivity within the performance index. Additionally, the reference concrete, which is made without the use of waste copper slag, is evaluated for comparative purposes. In order to make the evaluation as comprehensive as possible, the concrete made with the use of three types of cement is subjected to CEM I, CEM II and CEM III assessments. If natural radioactivity is not taken into account in the evaluation, the best result of the most favourable value of Gross Ecological and Performance Indicator (GEPI) is obtained by the concrete made with waste copper slag, and if radioactivity is considered, the most favourable value of GEPI is obtained with concrete without addition of the waste. The results show that in both approaches the best result is achieved by concrete with CEM III cement. It follows from the above that although natural radioactivity has a significant impact on the EIPI evaluation result, the decisive factor is still the type of cement. [ABSTRACT FROM AUTHOR]