Search Results (31)

The growing demand for lightweight aggregates (LWAs) in the construction industry is driving the development of sustainable alternatives based on the reuse of solid industrial waste. The aim of this study was to assess the technical feasibility of using red ceramic waste (RCW) as a partial or total substitute for red clay (RC) to produce lightweight expandable aggregates. Six formulations were made with different proportions of RCW and RC and sintered at four temperatures (1100, 1150, 1200 and 1250 °C). They were characterised using physical, thermal, morphological, chemical and mechanical analyses, according to standard protocols. The results showed that almost all the formulations sintered at 1200 and 1250 °C had a positive bloating index (BI > 0), particle density of less than 2.0 g/cm³, low water absorption of less than 2% and mechanical strength of more than 5.4 MPa, revealing strong potential for use in lightweight structural and non-structural concrete. The main conclusion is that RCW, even used in isolation, has physicochemical and mineralogical properties suitable for the production of lightweight aggregates under optimised thermal conditions, contributing to the development of sustainable materials with a competitive technical performance compared to commercial LWAs. Full article

Copper slag and red mud with high iron contents were discharged with an annual global amount of 37.7 and 175 million tons but had low utilization rates due to wide reuse difficulties. Studies on their large-scale utilization have become urgent. Thermal storage ceramic is a kind of energy storage material with high-added value and a potentially large market. In this study, a method to convert copper slag and red mud into thermal storage ceramics through a ceramic fabrication process was proposed. Four samples were prepared and characterized by XRD and SEM-EDS, as well as physical and thermal property tests. The relationships among phase composition, microstructure, and properties were further discussed. The results showed the thermal storage ceramic from copper slag had the best properties with a flexural strength of 68.02 MPa and a thermal storage density of 1238.25 J/g, both equal and nearly twice those of traditional heat storage materials like Magnesia Fire Bricks and corundum. The grain sizes of mineral phases in the prepared thermal storage ceramics have significant impacts on the performance of the material. Increasing the proportion of copper slag in thermal storage ceramics from red mud could enhance their performance. This study provides a new perspective on the low-cost preparation of thermal storage ceramics and large-scale utilization of iron-containing solid waste. Full article

In this study, in order to solve the problems of resource utilization of electrolytic manganese residue and the destruction of natural resources by the over-exploitation of raw materials of traditional ceramics, electrolytic manganese residue (EMR), red mud (RM), and waste soil (WS) were used to prepare self-foaming expanded ceramsite (SEC), and different firing temperatures and four groups with different mixing ratios of these three raw materials were considered. Water absorption, porosity, heavy metal ion leaching, and compressive strength in the cylinder of SEC were evaluated. The chemical composition and microscopic morphology of SEC were investigated by XRD and SEM. The mechanism behind the reaction among EMR, RM, and WS and self-foaming was discussed. The results showed that both the temperature and mixing ratio significantly influenced the basic performance of SEC. With the temperature lower than 1200 °C, sphere appearance could be maintained in all of these four groups; however, the density, porosity, and compressive strength in the cylinder seemed unacceptable. When the temperature rose up to 1220 °C, sphere appearance could be only found in the group whose mixing ratio of EMR, RM, and WS was 2:2.5:0.5. Under this condition, the excellent performance of SEC was observed, with a porosity of 46.7%, bulk density of 0.61 g/cm³, and 3 d compressive strength in a cylinder of 26.82 MPa. The mechanism behind the reaction among EMR, RM, and WS could be described: when the temperature is up to 1180 °C, an obvious chemical reaction took place, followed by the liquid phase being produced and the gas released by the decomposition of Fe₂O₃ in RM and gypsum in EMR. When the temperature is up to 1200 °C, the viscosity of the liquid phase and the rate of gas generation achieved the balance, and the liquid phase encapsulated the gas and anorthite (CaAl₂Si₂O₈) began to grow slowly. As time passed, self-foaming expanded ceramsite was prepared. The results of this study are of great significance in the field of artificial lightweight aggregate and industrial solid waste resource utilization. Full article

This study explores the different techniques used to manufacture porous clay-based ceramics, examining their properties such as porosity, strength, permeability and filtration efficiency. Different techniques are discussed in this review, with additive manufacturing being one of the most innovative techniques for manufacturing porous ceramics. Porous ceramics have their applications in numerous domains. Such ceramic filters have the advantages of retaining heavy materials, suspended particles, bacteria, viruses and, water turbidity. Thus, the choice of the technique and propriety is a crucial step in obtaining a porous ceramic with the best performance. Barry et al. prepared porous phyllosilicate-based ceramics by freeze-tape casting on four samples and obtained porosity values in the range of 67–79% and diametrical compressive strength in the range of 3–7 MPa. Manni et al. prepared porous red ceramics from Moroccan clay and coffee waste (10, 20 and 30 wt.%) via uniaxial pressing and sintering at 1150 °C. They obtained porosities ranging from 30.2 to 63.8% and flexural strength values from 1.8 to 19.5 MPa. Medri et al. prepared ZrB2-based porous bodies with the use of sponges and polyurethane foams as templates via the replica method and obtained high porosity over 80% and compressive strength up to 4.8 MPa. The use of clay and peanut shell mixtures was used in preparing porous silicate ceramics after unidirectional pressing and sintering at 1100 °C. These samples included 25 mass% of peanut shells, and exhibited porosity in the range of 40 to 60% and diametrical compressive strength in the range of 1–6 MPa. Such properties are suitable for domestic use of these types of clay-based ceramic filters. Moreover, the permeability values and removal of some pollutants, like arsenic, have been satisfactory for the first set of samples. Full article

This work evaluated the effects of incorporating chicken eggshell waste in a low-water-absorption bi-layered red ceramic tile composition, focusing on its porosity. Red ceramic tile formulations were prepared with incorporations of 0, 5, 10, 15, 20 and 25 wt.% of chicken eggshell waste. The bi-layered red floor tile processing method consisted of dry powder granulation, double uniaxial pressing and firing at 1220 °C using a fast-firing cycle. The physical properties and microstructural development of the tile specimens were investigated. It was found that chicken eggshell waste exhibited good chemical compatibility for use in red ceramic tile formulations, enabling its recycling. The novel bi-layered red ceramic tiles presented water absorption between 0.34 and 0.97% and apparent density between 2.09 and 2.14 g/cm³. The results demonstrated that chicken eggshell waste, when incorporated up to 15 wt.%, can be used as an efficient pore-forming carbonate source to manufacture low-water-absorption bi-layered red ceramic tiles (BIa and BIb groups—ISO 13006), which allows use in ventilated façades. It was concluded that the proposed approach is suitable for recycling chicken eggshell waste into red ceramic tile formulations, with relevant repercussions for the circular economy. Full article

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. Full article

This paper designed cement-stabilized permeable road subgrade materials. Construction demolition waste with recycled aggregate replaced natural aggregate in cement-stabilized materials to utilize recycled resources for construction solid waste. This paper tests the compressive strength, water permeability, bending strength, and compressive resilience modulus of cement-stabilized permeable recycled aggregate materials under different cementitious additive ratios. The results show that at a recycled aggregate proportion of 30% in cement-stabilized permeable recycled aggregate material, the 7-d unconfined compressive strength exceeds 3.5 MPa, and the permeability coefficient surpasses 3.5 mm/s, which can meet the roadbed requirements in China. The incorporation of recycled aggregates significantly reduces the mechanical properties and water permeability of cement-stabilized permeable recycled aggregate materials, while cementitious additives improve the mechanical properties. Specifically, red brick, old concrete, and ceramics in recycled aggregates weaken the mechanical properties of the skeleton structure of cement-stabilized permeable recycled aggregate materials, and the compressive strength, bending strength, and compressive resilience modulus decrease with the recycled aggregate content. Cementitious additives can fill the micro-pores of the interface transition zone of cement-stabilized permeable recycled aggregate materials to improve the cementation strength between aggregates. Full article

Untreated and pH-reduced red mud is used as a potential raw material in ceramic technology. During the alkalinity reduction process, CO₂ is bubbled through the untreated red mud, which is particularly important as it can reduce the CO₂ content of the atmosphere, and the pH of the red mud. Therefore, this method serves as a CO₂ capture technique that utilizes waste as a raw material with low costs. Besides, reducing CO₂ emission, it allows the production of material suitable for brick manufacturing from waste. In this study, treated and reduced alkalinity red mud was mixed with clay in the range of 5–30 wt%, and the physical, chemical, mechanical, and technologically important properties of the dried and sintered bricks were examined. The application of reduced alkalinity red mud as an additive offers advantages, as the resulting bricks require less water for processing, are less sensitive to drying, and their strength values exceed those of the commercially available bricks. Therefore, the technique presented in the study enables the production of bricks and roof tiles with advantageous properties using waste materials. Full article

In this paper, ground granulated blast furnace slag, steel slag, red mud, waste ceramic powder, and desulfurization gypsum were used as raw materials to develop a kind of multi-source solid-waste-based soft soil solidification material. Three ratios and the strength activity index were used to determine the fractions of different solid wastes. The mineralogical and microstructural characterization was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), and thermogravimetric analysis–differential scanning calorimetry (TG&DSC) tests. The results showed that the unconfined compressive strength of the three types of soft soil increases with an increase in the content of the solidifying agent. The failure strain of the stabilized soil decreases from 1.0–1.3% to 0.75–1.0%, and the failure mode gradually changes from plastic failure to brittle failure. The optimum content of the solidifying agent was determined to be 17% (the lime saturation factor (KH), silica modulus (SM), and alumina modulus (IM) of the solidifying agent were set to 0.68, 1.74, and 1.70, respectively), and the unconfined compressive strength (28 d) of the solidified soil (sandy soil, silty clay, and organic clay) was 3.16 MPa, 2.05 MPa, 1.04 MPa, respectively. Both measurements can satisfy the technical requirements for a cement–soil mixing pile, suggesting the possibility of using various types of solid waste as a substitute for cement. Full article

This article evaluates the synthesis, characterization and 3D printing of hybrid cements based on high (70%) contents of powders from concrete waste (CoW), ceramic waste (CeW) and red clay brick waste (RCBW) from construction and demolition waste. For the synthesis of the hybrid cements, 30% (by weight) of ordinary Portland cement (OPC) was added. Sodium sulphate (Na₂SO₄) (4%) was used as a chemical activator. The effect of the liquid/solid ratio on the properties in the fresh state of the mixes was studied by means of minislump, flowability index, and buildability tests. The compressive strength was evaluated at 3, 7, 28 and 90 days of curing at room temperature (≈25 °C), obtaining strengths of up to 30.7 MPa (CoW), 37.0 MPa (CeW) and 33.2 MPa (RCBW) with an L/S ratio of 0.30. The results obtained allowed selecting the CoW 0.30, CeW 0.33 and RCBW 0.38 mixes as optimal for carrying out 3D printing tests on a laboratory scale, successfully printing elements with good print quality, adequate buildability, and compressive strength (CoW 0.30 = 18.2 MPa, CeW 0.33 = 27.7 MPa and RCBW 0.38 = 21.7 MPa) higher than the structural limit (≥17.5 MPa) established for concrete by Colombian Regulations for Earthquake Resistant Construction (NSR-10). Full article

The ornamental stone industry is growing and has a large production in Brazil, mainly in Espírito Santo, where the largest production in the country is concentrated. Brazil is part of the group of countries that produce the most ornamental stones in the world; however, the generation of waste in this sector is very large. These ornamental stone wastes when used for the manufacture of new materials, such as red ceramics, contribute to the reduction in the raw material clay and to the reduction in the environmental impact. The objective of this work was to incorporate fine wastes from the processing of ornamental stones called FIBRO in red ceramics and later, to contribute to the standardization of the use of these wastes in the ceramic industry, contributing to the manufacture of more economical and sustainable products. Wastes were incorporated in the proportion of 0 to 50% by mass that were prepared by extrusion and fired at 900 °C, 950 °C, and 1000 °C. After firing, the physical and mechanical properties of the ceramic material were evaluated. Specific mass apparent, water absorption, porosity, and flexural strength by three points tests were carried out. The results showed that from 30% at the lowest temperature, tile is already fabricated within the values stipulated by the standards, thus saving energy. The analyzed waste is a material with excellent chemical characteristics to be used in the ceramic mass, in addition to having improved the technological properties of the material, such as less water absorption and greater flexural strength. Full article

Given the current huge generation of solid waste worldwide, alternative and innovative methodologies for incorporating these materials should be encouraged elsewhere. In this context, the objective of this research is to evaluate the use of glass waste as a substitute for sand as raw material in ceramics. Formulations containing from 0% to 20% of glass waste were produced, thus replacing natural sand. Extruded and calcined specimens were produced at temperatures of 800, 900 and 1000 °C. The characterization results demonstrated the compatibility and their potential for the glass waste for improving the properties of ceramics. Results of density, water absorption and flexural strength improved when 20% of glass waste was added due to the porosity reduction, provided by the formation of a liquid phase and then by a sintering, promoted by the glass waste. This resulted in coherent properties with ceramic applications in the form of tiles and blocks, at a calcining temperature of 800 °C. On the contrary, results without glass did not reach the necessary parameters even at 1000 °C. In conclusion, the feasibility of using glass waste has been proven, which, in addition to improving the material’s properties, provides economy benefits for the ceramic industry, with the calcination process at milder temperatures. Full article

Brazil is one of the largest producers of ornamental stones in the world. The state of Espírito Santo has considerable social and economic relevance in the production of ornamental stones, particularly in exportation and the jobs that are directly related to this industry. The objectives of this work were to evaluate the effect of the incorporation of ornamental stone waste on the physical and mechanical properties of red ceramic manufactured using clays and waste from the state of Espírito Santo, and to collaborate to regulate the use of this ornamental stone waste in the ceramic industry when manufacturing products. Ornamental stone wastes were incorporated into the ceramic mass in the following proportions: 0, 10, 20, 30, 40 and 50% by weight. In the elaborated compositions, specimens were prepared by extrusion and were fired at 1050 °C and 1100 °C. After firing, the physical and mechanical properties of the material were analyzed using density, water absorption, porosity, linear shrinkage and mechanical strength. The results indicated an improvement in the properties of the ceramics with the addition of the waste by mass for the two temperatures. Therefore, the lower temperature (1050 °C) can be used to sinter the materials produced whilst obtaining satisfactory results and saving electrical energy. Ornamental stone waste has very promising applications in the ceramic industry. Full article

In the search for better constructive efficiency and a reduction of the waste of construction materials, several researches have been performed in the last years around the world. Red ceramic blocks are artifacts widely used in civil construction around the world, and they result in a great consumption of raw materials and energy. The great innovation of this research was the development of ceramic blocks through an innovative method of pressing and dosing materials, replacing the traditional stage of extrusion in the manufacture of ceramics. In such a sense, a new manufacturing technology for ceramic blocks was proposed through the pressing process, adapting the soil-cement brick press machine, thus attaining more even pieces with greater compliance to the dimensions and preset geometry. In this work, the physical and mechanical features of the pressed and burned blocks (PBB) are produced in a partnership with Arte Cerâmica Sardinha, a traditional ceramic industry in the region of Campos dos Goytacazes, RJ, Brazil. It was sought to set the quality parameters for the blocks, to set their mechanical compressive strength, deformation modules and the Poisson coefficient. The blocks were tested in use by means of three layers of prism and small wall samples, and it was checked the fragile-type failure of the PBB. Results indicate that the blocks can be employed in small-sized construction works, as the characteristic compressive strength to block measured was 3.62 N/mm² for average water absorption of 20.84%. Full article

Co-treatment for two kinds of hazardous solid waste is an effective method to reduce cost and increase recycle efficiency of value resource. This work developed an integrated process based on capture of red mud (RM) and a one-step heat-treatment process to efficiently recover PGMs from spent auto-catalysts (SAC) and reuse RM simultaneously. Firstly, the iron oxide in RM was reduced to metallic iron to capture PGMs by the reduction process, without the addition of an extra reducing agent, since SAC contained abundant organic volatiles. Then, the mixed waste of SAC and RM was melted under high temperature with additives of CaO and H₃BO₃. More than 99% of PGMs can be extracted under the optimal conditions of 40–50 wt% of RM addition, 14 wt% of H₃BO₃ addition, 0.7–0.8 of basicity, 1500 °C of temperature, and 40 min of holding time. In addition, PGM content in obtained glassy slag was less than 1 g/t. The mechanism of iron trapping PGMs was also discussed in detailed, which mainly contained two stages: migration of PGMs and separation of PGM-bearing alloy and slag phases. Besides, the obtained glassy slag was further prepared into glass-ceramic by a one-step heat-treatment process. It was found that the prepared glass-ceramic has good thermostability and an excellent stabilizing effect on heavy metals. Overall, the results indicated that the developed integrated smelting–collection process is an efficient and promising method for the reutilization of SAC and RM. Full article