Search Results (62)

Quality requirements for mineral aggregate for concrete used to construct pavement for busy highways are high because of the fatigue traffic loads and environmental exposure. The use of local aggregate for infrastructure projects could result in important sustainability improvements, provided that the concrete’s durability is assured. The objective of this study was to identify the potential alkaline reactivity of local greywacke aggregate and select appropriate mitigation measures against the alkali–silica reaction. Experimental tests on concrete specimens were performed using the miniature concrete prism test at 60 °C. Mixtures of coarse greywacke aggregate up to 12.5 mm with natural fine aggregate of different potential reactivity were evaluated in respect to the expansion, compressive strength, and elastic modulus of the concrete. Two preventive measures were studied—the use of metakaolin and slag-blended cement. A moderate reactivity potential of the greywacke aggregate was found, and the influence of reactive quartz sand on the expansion and instability of the mechanical properties of concrete was evaluated. Both crystalline and amorphous alkali–silica reaction products were detected in the cracks of the greywacke aggregate. Efficient expansion mitigation was obtained for the replacement of 15% of Portland cement by metakaolin or the use of CEM III/A cement with the slag content of 52%, even if greywacke aggregate was blended with moderately reactive quartz sand. It resulted in a relative reduction in expansion by 85–96%. The elastic modulus deterioration was less than 10%, confirming an increased stability of the elastic properties of concrete. Full article

Background/Objectives: This study investigates the impact of high humidity (25 °C, 75% relative humidity) on gelatin and hydroxypropyl methylcellulose (HPMC) capsules used in dry powder inhalers (DPIs), focusing on moisture dynamics, structural responses, and mechanical performance, with an emphasis on understanding how different capsule types respond to prolonged exposure to humid conditions. Methods: Capsules were exposed to controlled humidity conditions, and moisture uptake was measured via thermal analysis. Visual observations of silica bead color changes were performed to assess moisture absorption, while surface wettability was measured using the sessile drop method. Hardness testing, mechanical deformation, and puncture tests were performed to evaluate structural and mechanical changes. Positron annihilation lifetime spectroscopy (PALS) was used to analyze free volume expansion. Results: HPMC capsules exhibited rapid moisture uptake, attributed to their lower equilibrium moisture content and ability to rearrange dynamically, preventing brittleness. In contrast, gelatin capsules showed slower moisture absorption but reached higher equilibrium levels, resulting in plasticization and softening. Mechanical testing showed that HPMC capsules retained structural integrity with minimal deformation, while gelatin capsules became softer and exhibited reduced puncture resistance. Structural analysis revealed greater free volume expansion in HPMC capsules, consistent with their amorphous nature, compared with gelatin’s semi-crystalline matrix. Conclusions: HPMC capsules demonstrated superior humidity resilience, making them more suitable for protecting moisture-sensitive active pharmaceutical ingredients (APIs) in DPI formulations. These findings underline the importance of appropriate storage conditions, as outlined in the Summary of Product Characteristics, to ensure optimal capsule performance throughout patient use. Full article

This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and transmission electron microscopy (HRTEM), we trace the crystallographic pathways of quartz, moganite, tridymite, and cristobalite under controlled thermal and mechanical stress regimes. The experimental results demonstrated that phase behavior is highly dependent on intrinsic properties such as initial phase composition, impurity presence, and crystallinity. Heating at 1400 °C induced irreversible conversion of quartz, moganite, and tridymite into cristobalite. Samples enriched in cristobalite and tridymite exhibited notable increases in crystallinity, whereas quartz-dominant samples showed either stability or a decline in structural order. Rietveld analyses underscored the critical influence of microstrain and crystallite size on thermal resilience and phase persistence. Thermal profiles revealed by DSC and TGA expose overlapping processes including polymorphic transitions, minor phase dehydration, and redox-driven changes, likely associated with trace components. Mechanochemical processing resulted in partial amorphization and the emergence of phases such as opal and feldspar minerals (microcline, albite, anorthite), interpreted as the product of lattice collapse and subsequent reprecipitation. Heat treatment of chert leads to a progressive rearrangement and recrystallization of its silica phases: quartz collapses around 1000 °C before recovering, tridymite emerges as an intermediate phase, and cristobalite shows the greatest crystallite size growth and least deformation at 1400 °C. These phase changes serve as markers of high-temperature exposure, guiding the identification of heat-altered lithic artefacts, reconstructing geological and diagenetic histories, and allowing engineers to adjust the thermal expansion of ceramic materials. Mechanochemical results provide new insights into the physicochemical evolution of metastable silica systems and offer valuable implications for the design and thermal conditioning of silica-based functional materials used in high-temperature ceramics, glasses, and refractory applications. From a geoarchaeological standpoint, the mechanochemically treated material could simulate natural weathering of prehistoric chert tools, providing insights into diagenetic pathways and lithic degradation processes. Full article

Background: Lithium is an essential commodity; however, its mining and processing can expose miners to airborne contaminants such as inhalable dust, respirable dust and respirable crystalline silica. These exposures may adversely affect respiratory health. To protect the health of miners, exposure assessment and control activities are required, followed by respiratory health monitoring to assess the effect of exposure on respiratory health. This study aimed to investigate the relationship between workgroup exposure to airborne contaminants and respiratory health. To determine group exposure levels, exposure data was collected at the group level, which limits individual-level inference, followed by health monitoring. Methods: Industry health monitoring data were collected from miners in three surface lithium mines in Western Australia for the period between October 2023 and October 2024. Miners from Management Administration & Technical, Crusher/Dry/Wet Plant, and Laboratory Operations participated in a pulmonary function test, completed a health and exposure questionnaire and underwent a low dose high-resolution computed tomography. Multivariable linear and logistic regression models were fitted to identify factors associated with lung function and respiratory symptoms. Results: Older age, smoking and pre-existing respiratory conditions were correlated with poor respiratory airflow. The odds of having a respiratory obstruction or restriction were significantly higher by 3.942 and 2.165 times respectively, for miners who were 40 years old or above, and those who had existing diagnosed respiratory medical conditions. The risk of coughing among current smokers was more than four times higher compared to non-smokers. In addition, working in Crushing and Processing was significantly associated with the risk of experiencing respiratory symptoms compared to working in Management Administration & Technical and Laboratory Operations. Conclusions: The study demonstrated that respiratory health was influenced by non-work-related risk factors. Based on these results, it is recommended that health promotion programs be developed and implemented to empower miners to cease smoking and to manage non-work-related respiratory conditions. Full article

Rising greenhouse gas concentrations are causing climatic change that threatens ecosystem sustainability. This study investigated the impact of silica incorporation into alumina-supported nickel catalysts for the partial oxidation of methane (POM), a crucial process for syngas production. The investigation also focuses on the impact of using different calcination temperatures. The catalysts were synthesized using the impregnation method and structurally characterized with BET, TPR, FTIR, UV, XRD, TGA, Raman, and TEM analysis techniques. These characterization techniques revealed that increasing the silica content reduced the surface area and weakened the interaction between nickel and the support. The calcination temperature significantly influenced catalyst properties, affecting pore structure, nickel reducibility, and the formation of nickel aluminates and silicates. Activity tests of synthesized catalysts were performed in a packed-bed reactor at 600 °C with a 24 mL/min gas flow rate. The catalyst composition of 5Ni/10Si + 90Al demonstrated the highest activity, achieving optimal performance at lower calcination temperatures. This catalyst generates a greater concentration of active sites, primarily due to nickel oxide (NiO), which creates these sites through both mild and strong interactions. The degree of graphitization is notably lowest for the 5Ni/10Si + 90Al composition. This catalyst achieved an impressive hydrogen yield of approximately 54%, with an H₂/CO ratio of 3.4 over a streaming period of up to 240 min. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the Partial Oxidation of Methane (POM) reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher weight percentages of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the POM reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher wt.% of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. These findings highlight the complex interplay between silica content, calcination temperature, and catalyst properties, significantly influencing catalytic performance in POM. Full article

Occupational exposure to carcinogenic respirable crystalline silica and noise requires a deeper understanding and an assessment of the possible health risks caused by their combined action. Data on individual exposure to respirable crystalline silica (RCS) and occupational noise (ON) was collected among 44 open-pit miners. The study group was divided into two groups according to the job tasks performed. The individual exposure, exceeding of maximum admissible concentration/intensity, and predicted hearing thresholds (HTs) (according to ISO 1999:2013) were compared between the groups directly participating in the technological process (group 1; N = 23) and performing auxiliary, supervising, or laboratory activities (group 2; N = 21). All the analysed indices were significantly higher for group 1; therefore, the job category may predict ON and RCS exposure among open-pit miners. A statistically significant relationship (r_s = 0.66, p < 0.05) was found between the time-weighted average (TWA) 8 h RCS and individual daily noise exposure levels. Exposure to noise in the course of employment causes the risk of hearing impairment (mean HTs for 2, 3, and 4 kHz > 25 dB) up to 74% and 4.4% (in the case of groups 1 and 2, respectively). Further studies are needed before conclusions concerning the effects of co-exposure to ON and RCS on open-pit miners can be made. Full article

Silicon dioxide (SiO₂), commonly known as silica, is a naturally occurring mineral extracted from the Earth’s crust. It is widely used in commercial products such as food, medicine, and dental ceramics. There are few studies on the health effects of pyrogenic and colloidal silica after ingestion. No research has compared the impact of microscale morphologies on mitochondrial activity in colon cells after acute exposure. The results show that crystalline and amorphous silica had a concentration-independent effect on cells, with an initial increase in mitochondrial activity followed by a decrease. Vitreous silica did not affect cells. Diatomaceous earth and pyrogenic silica had a concentration-dependent response, causing a reduction in mitochondrial activity as concentration increased. Diatomaceous earth triggered the highest cellular response, with mitochondrial activity ranging from 78.84% ± 12.34 at the highest concentration (1000 ppm) to 62.54% ± 17.43 at the lowest concentration (0.01 ppm) and an average H₂O₂ concentration of 1.48 ± 0.15 RLUs. This research advances our understanding of silica’s impact on human gastrointestinal cells, highlighting the need for ongoing exploration. These findings can improve risk mitigation strategies in silica-exposed environments. Full article

Exposure to respirable crystalline silica dust is one of the most common and severe risks due to the associated health outcomes among workers and results in many occupational-related lung diseases, such as silicosis and lung cancer. The study aimed to determine knowledge, attitudes, and practices on occupation health and safety among mine workers exposed to crystalline silica dust in Lesotho. A descriptive retrospective cross-sectional study design was used in the study. A record review guide was used to retrieve secondary data from the Southern Africa Tuberculosis and Health Systems Support (SATBHSS) project, which were thereafter entered into STATA software, version 17 for descriptive and inferential analysis. The study participants were purposively selected. Most participants were between the ages of 31 to 40 years of age and there was a significant difference between the genders with 35 (9%) females and 350 (91%) males. The majority of the participants had a high school level of education (305, 79%). The knowledge was generally positive in the study with a knowledge score mean of 13.43 (standard deviation: 2.99). The miners agreed with most attitude statements except for A1 (25%), A2 (35%), A3 (18%), and A4 (31%). The practice of exposed mine workers in the study was influenced by working in a dolerite mine (p = 0.003), knowledge score (p ˂ 0.001), and having an attitude about health and safety rules at the mine (p ˂ 0.001; 95% CI: 0.92 to 0.79), while age was a protective factor in the study. The findings of this study highlighted positive knowledge, attitudes, and practices toward occupational health and safety among mine workers. However, more educational programs can be implemented to ensure all mine workers understand the importance of good knowledge, positive attitude, and appropriate practices towards occupational health and safety in their environment. Full article

Engineered stone (ES) is a popular building product, due to its architectural versatility and generally lower cost. However, the fabrication of organic resin-based ES kitchen benchtops from slabs has been associated with alarming rates of silicosis among workers. In 2024, fifteen years after the first reported ES-related cases in the world, Australia became the first country to ban the use and importation of ES. A range of interacting factors are relevant for ES-associated silicosis, including ES material composition, characteristics of dust exposure and lung cell-particle response. In turn, these are influenced by consumer demand, work practices, particle size and chemistry, dust control measures, industry regulation and worker-related characteristics. This literature review provides an evidence synthesis using a narrative approach, with the themes of product, exposure and host. Exposure pathways and pathogenesis are explored. Apart from crystalline silica content, consideration is given to non-siliceous ES components such as resins and metals that may modify chemical interactions and disease risk. Preventive effort can be aligned with each theme and associated evidence. Full article

The lifetime risk of silicosis associated with low-level occupational exposure to respirable crystalline silica remains unclear because most previous radiographic studies included workers with varying exposure concentrations and durations. This study assessed the prevalence of silicosis after lengthy exposure to respirable crystalline silica at levels ≤ 0.10 mg/m³. Vermont granite workers employed any time during 1979–1987 were traced and chest radiographs were obtained for 356 who were alive in 2017 and residing in Vermont. Work history, smoking habits and respiratory symptoms were obtained by interview, and exposure was estimated using a previously developed job-exposure matrix. Associations between radiographic findings, exposure, and respiratory symptoms were assessed by ANOVA, chi-square tests and binary regression. Fourteen workers (3.9%) had radiographic evidence of silicosis, and all had been employed ≥30 years. They were more likely to have been stone cutters or carvers and their average exposure concentrations and cumulative exposures to respirable crystalline silica were significantly higher than workers with similar durations of employment and no classifiable parenchymal abnormalities. This provides direct evidence that workers with long-term exposure to low-level respirable crystalline silica (≤0.10 mg/m³) are at risk of developing silicosis. Full article

Occupational exposure to airborne dust is responsible for numerous respiratory and cardiovascular diseases. Because of these hazards, air samples are regularly collected on filters and sent for laboratory analysis to ensure compliance with regulations. Unfortunately, this approach often takes weeks to provide a result, which makes it impossible to identify dust sources or protect workers in real time. To address these challenges, we developed a system that characterizes airborne dust by its spectro-chemical profile. In this device, a micro-cyclone concentrates particles from the air and introduces them into a hollow waveguide where an infrared signature is obtained. An algorithm is then used to quantitate the composition of respirable particles by incorporating the infrared features of the most relevant chemical groups and compensating for Mie scattering. With this approach, the system can successfully differentiate mixtures of inorganic materials associated with construction sites in near-real time. The use of a free-space optic assembly improves the light throughput significantly, which enables detection limits of approximately 10 µg/m³ with a 10 minute sampling time. While respirable crystalline silica was the focus of this work, it is hoped that the flexibility of the platform will enable different aerosols to be detected in other occupational settings. Full article

When possible, choosing materials with a low quartz content is the most effective and cost-efficient way to prevent the respirable quartz exposure of workers and other end users of powdery products. Therefore, methods are needed to analyze low amounts of quartz from powdery products, such as sand, gravel, plaster, cement, and concrete. To this end, we present a method to analyze respirable dust and quartz from powdered materials, such as construction products. The method includes separation of the respirable dust fraction by liquid sedimentation, followed by gravimetric analysis and determination of the crystalline silica content by X-ray diffractometry. While also aiding in the development of less harmful products, analysis of the quartz concentration of powdery products is statutory in Eu countries, excluding natural products not chemically modified. According to EU Regulation No. 1272/2008, products must be classified if they contain harmful substances in concentrations above 0.1 wt.%, and clauses pertaining to cancerous properties and harmfulness to lungs should be included. Also, mineral producers in the EU recommend that products containing respirable quartz should be labelled based on their quartz concentration, provided the concentration exceeds 1 wt.%. The present method meets these needs. The analysis can be performed in parallel from 50 to 1000 mg (dry weight) of powdery materials. The quantitative limit of determination was 10 µg per sample, corresponding to 0.01 wt.%, and the linear range 0.02–10 wt.% (10–5000 µg quartz per sample, Pearson correlation coefficient 0.99). The accuracy of the method was 82% and the repeatability 11%. Full article

High-temperature (HT) geothermal wells can provide green power 24 hours a day, 7 days a week. Under harsh environmental and operational conditions, the long-term durability requirements of such wells require special cementitious composites for well construction. This paper reports a comprehensive assessment of geothermal cement composites in cyclic pressure function laboratory tests and field exposures in an HT geothermal well (300–350 °C), as well as a numerical model to complement the experimental results. Performances of calcium–aluminate cement (CAC)-based composites and calcium-free cement were compared against the reference ordinary Portland cement (OPC)/silica blend. The stability and degradation of the tested materials were characterized by crystalline composition, thermo-gravimetric and elemental analyses, morphological studies, water-fillable porosity, and mechanical property measurements. All CAC-based formulations outperformed the reference blend both in the function and exposure tests. The reference OPC/silica lost its mechanical properties during the 9-month well exposure through extensive HT carbonation, while the properties of the CAC-based blends improved over that period. The Modified Cam-Clay (MCC) plasticity parameters of several HT cement formulations were extracted from triaxial and Brazilian tests and verified against the experimental results of function cyclic tests. These parameters can be used in well integrity models to predict the field-scale behavior of the cement sheath under geothermal well conditions. Full article

This paper presents the results of laboratory tests for new materials made of a carbon fibre-reinforced polymer (CFRP) composite with a single-sided protective coating. The protective coatings were made of five different powders—Al₂O₃, aluminium, quartz sand, crystalline silica and copper—laminated in a single process during curing of the prepreg substrate with an epoxy matrix. The specimens were subjected to flame exposure and solid particle erosion tests, followed by uniaxial tensile tests. A digital image correlation (DIC) system was used to observe the damage location and deformation of the specimens. All coatings subjected to solid particle erosion allowed an increase in tensile failure force ranging from 5% to 31% compared to reference specimens made of purely CFRP. When exposed to flame, only three of the five materials tested, Al₂O₃, aluminium, quartz sand, could be used to protect the surface, which allowed an increase in tensile failure force of 5.6%. Full article

The use of manufactured silica nanoparticles (SiNPs) has become widespread in everyday life, household products, and various industrial applications. While the harmful effects of crystalline silica on the lungs, known as silicosis or chronic pulmonary diseases, are well understood, the impact of SiNPs on the airway is not fully explored. This study aimed to investigate the potential effects of SiNPs on human tracheal smooth muscle cells (HTSMCs). Our findings revealed that SiNPs induced the expression of cyclooxygenase-2 (COX-2) mRNA/protein and the production of prostaglandin E₂ (PGE₂) without causing cytotoxicity. This induction was transcription-dependent, as confirmed by cell viability assays and COX-2 luciferase reporter assays. Further analysis, including Western blot with pharmacological inhibitors and siRNA interference, showed the involvement of receptor tyrosine kinase (RTK) EGF receptor (EGFR), non-RTK Pyk2, protein kinase Cα (PKCα), and p42/p44 MAPK in the induction process. Notably, EGFR activation initiated cellular signaling that led to NF-κB p65 phosphorylation and translocation into the cell nucleus, where it bound and stimulated COX-2 gene transcription. The resulting COX-2 protein triggered PGE₂ production and secretion into the extracellular space. Our study demonstrated that SiNPs mediate COX-2 up-regulation and PGE₂ secretion in HTSMCs through the sequential activation of the EGFR/Pyk2/PKCα/p42/p44MAPKs-dependent NF-κB signaling pathway. Since PGE₂ can have both physiological bronchodilatory and anti-inflammatory effects, as well as pathological pro-inflammatory effects, the increased PGE₂ production in the airway might act as a protective compensatory mechanism and/or a contributing factor during airway exposure to SiNPs. Full article