Search Results (89)

TiC-bearing slag is an intermediate product in the titanium extraction process following the “high-temperature carbonization and low-temperature chlorination” method. It exhibits complex grinding characteristics, and traditional grinding methods often yield issues such as broad particle size distribution (PSD) and overgrinding, adversely affecting process efficiency. In this study, TiC-bearing slag was investigated as the raw material. Through methods such as SEM-EDS, MLA, and scientific experiments, we established quantitative relationships between mechanical inputs and product granulometry. The results indicate that the coexistence of TiC and pyroxene-group minerals leads to poor grinding selectivity, causing TiC to resist fracturing while pyroxene minerals are prone to overgrinding. Furthermore, the experiments demonstrated that high circulating-load grinding combined with staged sieving is most effective for producing narrow PSD products. This research explores the methods and paths for achieving controlled narrow PSD of TiC-containing slag in the crushing process, and providing data support for the selection of industrial-scale grinding processes. Full article

This study aims to assess the by-products generated through the thermal and catalytic pyrolysis of the organic matter and paper fractions of municipal solid waste (MSW) in different socioeconomic regions, through the yields of reaction products (bio-oil, biochar, H₂O, and gas), acid value and chemical composition of bio-oils, and characterization of biochar, on a laboratory scale. The organic matter and paper segregated from the gravimetric composition of the total waste sample were subjected to drying, crushing, and sieving pre-treatment. The experiments were carried out at 450 °C and 1.0 atmosphere, and at 400 °C and 475 °C and 1.0 atmosphere, using a basic catalyst, Ca(OH)₂, at 10.0% by mass, in discontinuous mode. The bio-oil was characterized by acidity value and the chemical functions present in the bio-oil identified by FT-IR, NMR, and composition by GC-MS. The biochar was characterized by SEM/EDS and XRD. The bio-oil yield increased with the addition of the catalyst and the pyrolysis temperature. For catalytic pyrolysis, bio-char and gas yields increased slightly with the Ca(OH)₂ content, while bio-oil and H₂O phases remained constant. The GC-MS of the liquid reaction products identified the presence of hydrocarbons and oxygenates, as well as nitrogen-containing compounds, including amides and amines. The acidity of the bio-oil decreased with the addition of the basic catalyst in the process. The concentration of hydrocarbons in the bio-oil appeared with the addition of the catalyst in the catalytic pyrolysis process as the catalytic deoxygenation of fatty acid molecules occurred, through decarboxylation/decarbonylation, producing aliphatic and aromatic hydrocarbons, introducing the basic catalyst into the thermal process. Full article

This study investigates sustainable mortars using lightweight synthetic sand (LSS), made from dune sand and recycled PET bottles, to replace natural sand (0–100% by volume). This aligns with circular economy principles by valorizing plastic waste into a construction aggregate. LSS is produced via controlled thermal treatment (250 ± 5 °C, 50–60 rpm), crushing, and sieving (≤3.15 mm), leading to a significantly improved interfacial transition zone (ITZ) with the cement matrix. The evaluation included physico-mechanical tests (density, strength, UPV, dynamic modulus, ductility), thermal properties (conductivity, diffusivity, heat capacity), porosity, sorptivity, alkali–silica reaction (ASR), and SEM. The results show LSS incorporation reduces mortar density (4–23% for 25–100% LSS), lowering material and logistical costs. While compressive strength decreases (35–70%), these mortars remain suitable for low-stress applications. Specifically, at ≤25% LSS, composites retain 80% of their strength, making them ideal for structural uses. LSS also enhances ductility and reduces dynamic modulus (18–69%), providing beneficial flexibility. UPV decreases (8–39%), indicating improved acoustic insulation. Thermal performance improves (4–18% conductivity reduction), suggesting insulation applicability. A progressive decrease in sorptivity (up to 46%) enhances durability. Crucially, the lack of ASR susceptibility reinforces long-term durability. This research significantly contributes to the repurposing of plastic waste into sustainable cement-based materials, advancing sustainable material management in the construction sector. Full article

Previous research on geopolymers has not fully established their porosity and its influence on the matrix structure, as well as its relevance to mechanical and durability properties, supporting the potential of this material as a sustainable alternative to traditional construction materials. In this study, three geopolymer mortar (GM) mixtures were prepared: the first was obtained with fly ash (FA) without mechanical grinding (GM_FA), the second with FA that required crushing and sieving through a #200 sieve (GM_FA_200), and the third was a GM with FA that required crushing and sieving through a #325 sieve (GM_FA_325). The main objective was to evaluate the porosity of the geopolymeric paste and the interfacial transition zone (ITZ) between the aggregate and the geopolymerization products. Due to the susceptibility of this area to develop higher porosity, which leads to reduced mechanical properties and durability, it has become a significant focus of investigation in materials such as concrete and mortar. These analyses were carried out using physical adsorption of gases (PAG), and a methodology for image analysis of GM microporosity was implemented using micrographs obtained from a scanning electron microscope (SEM) and processed with the NI Vision Assistant 8.6 software (VA). The results from both image analysis and physical adsorption demonstrated that the GM_FA_325 matrix exhibited 19% less porosity compared to the GM_FA matrix. The results confirmed that GMs are predominantly mesoporous. It was observed that GM_FA_325 has the lowest total porosity, resulting in a denser and more compact microstructure, which is a key factor in its mechanical performance and potential applications as an eco-friendly construction material for coatings and precast elements such as blocks, panels, and similar products. In addition, image analysis using VA is highlighted as an efficient, cost-effective, and complementary technique to PAG, enabling robust results and resource optimization. Full article

There is a poor mechanization level among the existing chili seed extractors. The separation operation still relies on manual labor, with low efficiency and high costs. In this study, a fresh chili seed extractor for small-scale operations was designed, and the relevant parameters were optimized. The rotational speed of the drum, feeding speed, sieve diameter, threshing gap, number of peg teeth, and inclination angle of the frame were used as test factors, and the comprehensive score (loss rate, crushing rate, and impurity rate) of the effect of the chili seed extractor was set as an evaluation index. The initial parameters were selected via the Plackett–Burman test. The steepest climb test was carried out to determine the ranges of significance for the parameters. Moreover, a Box–Behnken test were conducted to obtain the optimal parameter combination: the drum rotation speed was 661 r/min, the sieve diameter was 8.5 mm, and the disengagement gap was 9.4 mm. The test results showed that the loss rate was 3.83%, the crushing rate was 2.01%, and the impurity rate was 11.31%, which met the actual production requirements for chili seeds. This study is expected to provide a necessary reference for the design of chili seed extractors. Full article

Tunnel Boring Machine (TBM) excavation materials were recycled by sieving and separating particles into sizes 5–10 mm (coarse aggregates) and below 5 mm (manufactured sand) to explore their potential as aggregates in shotcrete production, with the aim of reducing environmental harm from waste disposal. Mix proportion experiments were conducted to evaluate the mechanical properties—including failure patterns, compressive strength, flexural strength, and deflection—of the shotcrete specimens through cubic axial compression and four-point bending tests; furthermore, rebound tests were conducted on shotcrete mixed with the recycled TBM aggregates in foundation pit engineering. These tests assessed the effects of key parameters (water–binder ratio, sand ratio, fly ash content, synthetic fibers, and liquid alkali-free accelerator) on shotcrete composed of recycled TBM sand and gravel. The results indicated that crushing and grading flaky TBM-excavated rock fragments, and subsequently blending them with pre-screened fine aggregates in a 4:1 ratio, yielded manufactured sand with an optimized particle gradation and controlled stone powder content (18%). Adjusting the water–binder ratio (0.4–0.5), fly ash dosage (mixed with 0–20%), and sand ratio (0.5–0.6) are feasible steps in preparing shotcrete with a compressive strength of 29.1 MPa to 50.4 MPa and slump of 9 cm to 20 cm. Moreover, the rebound rate of the shotcrete reached 11.3% by applying polyoxymethylene (POM) fibers with a 0.15% volume fraction and a liquid-state alkali-free setting accelerator (8% dosage), demonstrating that the implemented approach enables a decrease in the rebound rate of shotcrete. Full article

Background: Compounding is performed to adjust dosages and support medication for children. In Japan, tablets are crushed, diluted with lactose, and stored in bottles or sachets until use, but the stability and impact on dissolution of the ingredients after crushing have not been evaluated. Methods: Using a database established by the National Center for Child Health and Development in collaboration with 11 medical facilities, the status of tablet crushing was investigated. Commonly compounded drugs were selected as the target drugs. The selected drugs were sieved through a 500 μm mesh after crushing and diluted with lactose hydrate. The stability at 25 ± 2 °C/60 ± 5% relative humidity and the dissolution of the ingredients were evaluated after storing them for up to 120 days under the following conditions: (I) stored in a closed polycarbonate bottle (closed), (II) bottle opened once a day (in-use), or (III) stored in a laminated cellophane and polyethylene sachet (laminated). The changes in the ingredient content and dissolution behavior were evaluated in accordance with the Japanese Pharmacopoeia. Results: Five cardiovascular drugs (amlodipine besylate, carvedilol, propranolol hydrochloride, hydrochlorothiazide, and tadalafil) were selected as target drugs. No more than 10% change in ingredient content was observed for all five formulations compared to day 0. In addition, no related substances (impurities) were detected at more than 0.01%. There was no change in the dissolution rate of the samples after 120 days of storage under each storage condition. Conclusions: The five cardiovascular drugs commonly compounded for children in Japan maintained their pharmaceutical quality after compounding, even after long-term storage. Full article

Advancing material efficiency in the steel and cement industry is essential for achieving climate goals. One approach to addressing this is to increase the provisioning of alternative reactive binder materials from residues, in this case, from the steel industry. Different mixtures of identified residues are evaluated for metal recovery and suitability as supplementary cementitious material. For this purpose, suitable combinations are modeled according to specified quality requirements from the cement industry. These mixtures are heated up to 1600 °C for a targeted reduction of predominantly transition metal oxides and a separation into a mineral fraction. Subsequently, controlled cooling of the molten material is implemented through water granulation. The produced granulate is crushed and sieved, and finally, the metallic and mineral fractions are magnetically separated. The chemical modification, reduction, and phase modification are tested to prevent landfilling and provide alternative secondary resources for the steel and cement industry. According to the results, it is possible to recover metals from metallurgical residues and simultaneously separate the modified mineral fraction as an alternative cement constituent. These findings will be further investigated through additional research to identify the variables that influence and impact/affect the reduction efficiency. Full article

In the construction industry, along with traditional approaches for the visual and instrumental assessment of building materials, methods based on intelligent algorithms are increasingly appearing; in particular, machine learning and neural network technologies. The utilization of modern technologies enables us to enhance building processes to a new quality level, decreasing the construction pace without precision losses compared to traditional methods. This research introduces a novel method for characterizing crushed stone grain morphology using the application of specially designed three-dimensional computer vision neural networks to point data clouds. Flakiness affects the strength, adhesion, and location of crushed stone grains. So, calculating this indicator by determining the planar dimensions of each particle in the crushed stone is necessary for the assessment of its suitability for various types of construction work. Architectures based on PointNet and PointCloudTransformer are chosen as the basis for the classification algorithms. The input data were 3D images of crushed stone grains, the shapes of which were divided into needle-shaped, plate-shaped, and cubic classes. The accuracy quality metric achieved during the training of both models was 0.86. Using intelligent algorithms, along with grain analysis methods via manual selection, sieve analysis, or using special equipment, will reduce manual labor and can also serve as an additional source for verifying the quality of building materials at various stages of construction. Full article

The integrated gasification combined cycle is a relatively new and eco-friendly power generation technology. However, this process produces coal gasification slag (CGS) as a by-product, which is usually landfilled or discarded. To enable efficient recycling of CGS, this study investigated the effects of using pretreated CGS as a fine aggregate on the quality and durability of concrete. A pretreatment system comprising sieve screening, size reduction, and wet flotation processes was devised. Experiments were conducted to evaluate the properties and durability of concrete prepared using mixtures of pretreated or non-pretreated CGS, ordinary Portland cement, crushed gravel, and crushed sand (CS). The results demonstrate that pretreated CGS (P_CGS) reduces the amounts of water-reducing and air-entraining agents required. In particular, it reduces the losses of air content induced when using CGS. P_CGS effectively increases the compressive strength of concrete; however, the strength decreases by 8–10% if the CGS content is >50%. P_CGS exhibits durability similar to that of commonly used CS, indicating its potential applicability as a valuable recycled construction material and safe aggregate for enhancing concrete durability. Full article

This study explored the impact of microwave pretreatment on the grinding efficiency of bastnaesite ore using a stirred mill. Bastnaesite ore was prepared using a staged crushing and sieving process, followed by microwave pretreatment in a specially designed microwave furnace system. Representative samples of the crushed ore underwent stirred mill grinding, with power draw measurements recorded and adjusted to reflect only the specific energy input required for grinding. Particle size distribution was analyzed periodically using laser particle size analysis. In addition, a Box–Behnken design was used to statistically assess the effects of various parameters on the results, ensuring a robust analysis of the factors influencing energy consumption and particle size reduction. The findings reveal that microwave pretreatment significantly influenced specific energy and product P₈₀, with SEM analyses showing increased microcracking and porosity and XRD analyses suggesting possible mineralogical alterations. This enhancement was also proved via statistical tools and analyses such as Design Expert software Ver. 13 and ANOVA. In summary, the research concludes with the following critical points: (1) Microwave pretreatment was found to reduce the energy consumption required for bastnaesite grinding by 27%. (2) Following pretreatment, bastnaesite achieved a 25% finer product size under identical grinding conditions. (3) Structural and compositional changes in bastnaesite after grinding were confirmed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. (4) Based on these analyses, potential mechanisms for the observed energy savings and product size reductions have been suggested. Additionally, we have enhanced the Abstract to better highlight the methods used in the study. This investigation not only advances our understanding of microwave-assisted comminution but also opens avenues for future research on optimizing and implementing this technique in large-scale mining operations. Full article

Aiming to address the problems of poor separation of peanuts and soil and severe damage of pods during peanut harvesting in saline soil, a peanut digging and harvesting machine was designed using extrusion shaking vibration and roller extrusion. Theoretical calculations determined the structural parameters of critical components. The law of motion of the seedling soil assemblage at the stage of separation and transportation was derived by analyzing the kinematic properties. The soil extrusion vibration crushing dispersion and sieving process was analyzed, and the factors affecting soil crushing and separation were determined by establishing the extrusion collision model. One-way and orthogonal tests used soil content, breakage, and loss rates as test indicators. The orthogonal test showed that the working parameters were as follows: working speed was 0.889 m/s, the inclination angle was 21.5°, the working line speed of the sieve surface was 2.00 m/s and the roller gap of the roller squeezing device was 37 mm, the peanut harvesting rate of soil content was 1.36%, the breakage rate was 0.78%, and the loss rate was 1.15%. The paper references developing a peanut harvester for clay-heavy soil with soil separation performance improvement. Full article

This study explores the influence of different concentrations of recycled concrete aggregate (RCA) on the fresh and hardened properties of self-consolidating concrete (SCC) in order to assess the structural suitability of the use of RCA in a precast concrete plant. The study particularly emphasizes the early strength of the produced concrete. The RCA was sourced from crushed concrete used in roadway applications and was sieved to replicate the characteristics of natural aggregate. Five different SCC mixes were produced, with RCA substituting 0%, 10%, 30%, 50%, and 70% of the natural coarse aggregate (NCA) by weight. For each different mix design, the hardened properties tested were the compressive strength and tensile strength. The fresh properties investigated were the passing and filling ability. Additionally, aggregate properties including grain size distribution and absorption of coarse aggregate were studied. The selected mix design follows a typical well-graded self-consolidating concrete mix with 28-day strength of 8000 psi (55.16 MPa). It was found that replacing up to 50% of the NCA with RCA improves the early strength of concrete without a significant impact on the fresh and hardened concrete properties. Full article

In this study, the analysis of metals in the solubilized extract of the organic fraction of Urban Solid Waste (MSW) from the municipality of Belém do Pará was carried out. The waste used in this research was collected in residential areas, through door-to-door collection, with the points and neighborhoods served in the municipality of Belém determined by the sectorization of these locations, with family income as the main parameter. The MSW was collected and transported to the segregation area. Gravimetric analysis of MSW was carried out and the selected organic and paper fractions were subjected to drying, crushing and sieving pre-treatment. Next, the solubilized extract of the organic fraction of MSW was obtained following the method set out in NBR nº 10.006/2004 of the Brazilian Association of Technical Standards. The values obtained were compared with CONAMA Resolutions n° 357/2005, 396/2008 and 430/2011, in addition to being compared with results of bibliographical research. The results indicated that these wastes do not comply with environmental and health regulations. Although a highly significant association was found between chromium and boron through Pearson’s correlation, the remaining strong correlations between other elements did not reach statistical significance. Furthermore, a similarity was observed in the solubilization conditions of these wastes with those found in landfill leachate. Full article

Asphalt mixtures can include various recycled materials, which often replace some of the coarse and fine aggregate components. In some cases, a percentage of material called mineral filler, made up of particles that pass through a No. 200-sieve, is also admitted in the preparation of the mixture. With the increasing amount of packaging used as containers for various products, many of which need to be disposed of properly and become an environmental burden in warehouses without proper reuse, there is potential for including these elements in the sustainable modification of asphalt mixtures. This research suggests reusing plastic and aluminum coffee capsules, which are difficult to recycle. While most studies crush recycled materials to sizes smaller than 0.075 mm for use in mixes, this research focuses on assembling the waste capsules into a network of cells inside specimens subjected to bending to observe the mechanical behavior of the asphalt mixture. The findings indicate that incorporating capsule networks can lead to a significant enhancement in the flexural strength of the examined beams, with an increase of up to 200%. Moreover, the deformation is reduced by an average of 66% upon the emergence of the initial crack in the specimen. Full article