Search Results (78)

The cement sheath is critical for ensuring the long-term safety and operational efficiency of oil and gas wells. However, complex geological conditions and operational stresses during production can induce cement sheath deterioration and cracking, leading to reduced zonal isolation, diminished hydrocarbon recovery, and elevated operational expenditures. This study investigates the development of a novel microbial self-healing well cement slurry system, employing fly ash as microbial carriers and sustained-release microcapsules encapsulating calcium sources and nutrients. Systematic evaluations were conducted, encompassing microbial viability, cement slurry rheology, fluid loss control, anti-channeling capability, and the mechanical strength, permeability, and microstructural characteristics of set cement stones. Results demonstrated that fly ash outperformed blast furnace slag and nano-silica as a carrier, exhibiting superior microbial loading capacity and viability. Optimal performance was observed with additions of 3% microorganisms and 3% microcapsules to the cement slurry. Microscopic analysis further revealed effective calcium carbonate precipitation within and around micro-pores, indicating a self-healing mechanism. These findings highlight the significant potential of the proposed system to enhance cement sheath integrity through localized self-healing, offering valuable insights for the development of advanced, durable well-cementing materials tailored for challenging downhole environments. Full article

In this study, a chemometrics-assisted calibration method was developed for the Z-903 SciAps handheld Laser-Induced Breakdown Spectroscopy (h-LIBS) device. For this purpose, seventeen silica-based standard samples with known chemical composition were collected, pelleted, and analyzed using h-LIBS. Spectral data were pre-processed using a Whittaker filter and normalized via Standard Normal Variate (SNV). The dataset was divided into calibration and validation sets using the Kennard–Stone algorithm. Partial Least Square (PLS) regression was employed for multivariate regression analysis, and a variable selection method (i.e., Variable Importance in Projection, VIP) was applied to reduce the number of predictors. Results from the PLS-VIP approach demonstrated that this device is suitable for the quantitative measurement of nineteen chemical elements, including major and minor elements, achieving significant R² values for major elements including Na (R² = 0.91), Mg (R² = 0.95), and Si (R² = 0.89). The limits of detection reached are satisfying, being, for example, 0.24%, 0.41%, 0.43%, 1.5%, and 1.7% for Na, Al, Ca, Si, and Fe, respectively, among major elements, and 189 ppm, 165 ppm, 203 ppm, and 1 ppm for Ba, Cu, Mn, and Rb, respectively, among minor elements. Uncertainties in prediction of the element concentrations were compared with data from the literature, and the effect of another baseline pretreatment algorithm, airPLS (adaptive iteratively reweighted PLS), was also tested. The method was then applied to nine silica-based artifacts of different typologies sampled from the Archaeological Park of Tindari (Italy), including bricks from the theatre, archaeological glasses, and volcanic rocks. Full article

Mesoporous silica nanoparticles (MSNs) functionalized with silane quaternary ammonium compounds (SiQACs) were synthesized and utilized as carriers for thymus essential oil (TO), a green bio-antifouling agent. The synthesis of MSNs functionalized with SiQACs was carried out in a single step, with clear advantages in terms of simplicity of the process, high yield (94%) and saving of reagents and solvents for the MSN purification. After loading with TO, this innovative dual-action antifouling system was able to integrate the intrinsic biocidal properties of SiQACs with the release of TO from MSN pores, resulting in an engineered material with prolonged efficacy. The antifouling compounds incorporated into the nanoparticles accounted for 42% of the total weight. The biocidal performance was evaluated by monitoring the growth inhibition of Chlorella sorokiniana, a microalga commonly associated with stone biodeterioration. Additionally, these nanoparticles were embedded in a commercial silane-based protective coating and applied to tuff stone samples to assess their ability to mitigate biofilm formation over extended periods. Results demonstrated the system’s high potential for durable protection against microbial colonization and biofilm growth on stone surfaces. Full article

The challenge of thermally upgrading traditional stone masonry buildings is addressed through the analysis of a representative example typical of regional rural architecture in central Poland, constructed using soft silica limestone and clay mortar. These buildings, which form an important part of the local cultural heritage, are increasingly becoming the subject of interdisciplinary research and conservation initiatives. This study presents a detailed characterization of the materials and architectural features specific to this building typology. Thermal transmittance calculations were performed and analyzed, with the use of THERM 7.6.1.0 software enabling precise modeling of the wall’s heterogeneous structure. The physical and thermal properties of natural materials—particularly soft silica limestone and clay—were taken into account. The analysis included evaluation of the heat transfer coefficient, temperature distribution, and heat flux density for a reference wall model, as well as for variants with both internal and external insulation layers. The study explores thermal comfort and energy performance within the broader context of preserving and reusing historic rural buildings. Furthermore, the findings are discussed in relation to current European energy efficiency regulations and heritage protection frameworks. The scientific value of this work lies in its context-specific, material-sensitive methodology and in providing practical insight into balancing energy retrofitting with architectural conservation. Full article

This study explored the effect of compounding artificial hydraulic lime and silica fume for use as a sandstone grotto patching material. Different proportions of silica fume were added to hydraulic lime in lab tests, and their effects on the mortar’s physical and mechanical properties were studied. The results show that adding silica fume significantly increased the flexural and compressive strengths of the mortar and the shrinkage rate. A comparative analysis revealed that the comprehensive performance of the mortar reached the optimal state when the silica fume content was 10%. This met the strength requirements of repair materials for sandstone grottoes, as well as the control requirements regarding the shrinkage rate. Additionally, it demonstrated excellent weather resistance. This study’s results provide a scientific basis for the restoration of sandstone grottoes and the screening of an appropriate ratio of repair materials, which holds significant practical application value for the protection and reinforcement of stone relics. Full article

This study introduces an innovative process for stabilizing BOF slag by blowing oxygen into molten slag, addressing challenges associated with conventional methods that require silica injection. Molten BOF slag from a steelmaking workshop at China Steel Corporation is directly modified at the slag modification station, where chemical compositions and crystalline phases are analyzed under varying oxygen injection amounts. In 70 industrial trials (20–25 tons per trial) with the basicity of the BOF slag ranging from 2.2 to 4.5, the reduction in the slag expansion rate increases proportionally with oxygen-blowing amounts. Oxygen blowing facilitates the oxidation of FeO to Fe₂O₃, which reacts with f-CaO to form volumetrically stable C₂AF (brownmillerite, Ca₂Al_xFe_2−xO₅), as confirmed by XRD and SEM-EDX analyses. The treated BOF slag exhibits excellent volumetric stability (expansion < 0.5%), lower pH (10.6–10.8) in comparison to original BOF slag, and compliance with Taiwan’s EPA-leaching regulations. This stabilized slag demonstrates potential for engineering applications, such as pavement bricks, concrete products, and high-value engineered stones. Additionally, the high brownmillerite content highlights its promise for low-carbon cement applications, offering a scalable and cost-effective solution for BOF slag utilization in the steel industry. Full article

The low injectability and strong permeation of micro-fractures in argillaceous rock masses significantly impair the impermeabilization and reinforcement performance of conventional cement-based grouting materials. This study first develops a highly injectable and high-strength nano-silica sol-based composite grout. Then, the characteristics of silica sol, cement grout, and composite grout in argillaceous fractured rock masses are analyzed and compared. The permeation mechanism of the composite-grout grouting in these rock masses is preliminarily elucidated, and the grouting process is described in detail, showing its application prospects. The research results indicate the following: (1) The electrical conductivity and stone-formation rate of granular pulp can reflect the characteristics of pulp filtration. Silica sol is a grouting material with nanometer particles, and the stone rate and gel strength are weakly affected by rock mass infiltration. (2) A large amount of water cannot be combined into the gel network and separated during the cement slurry percolation process, resulting in a significant reduction in the stone rate and compressive strength of deep rock mass. The minimum stone rate decreased to 45.19%, and the minimum compressive strength decreased to 2.29 MPa. This reduces the sealing and reinforcement effect of cement grouting on deep rock masses. (3) Rock permeation primarily affects the compressive strength of the formed stones, with minimal impact on the stability and stone-formation rate of the composite grout. As permeability decreases, the position of rock permeation shifts closer to the rock surface, while the sealing of deeper rock masses is less affected, enabling the composite grout to achieve dual functions of superficial reinforcement and deep sealing. This study provides theoretical support for the practical application of composite-grout grouting in reinforcing argillaceous rock masses. Full article

Wide varieties of igneous rocks are extensively utilized as stones for decoration purposes and as a potential source for building. With the use of petrological (mineralogical and chemical) and physico-mechanical analyses, the current work accurately mapped the Dokhan Volcanics (DV) and utilized them as decorative stones and their prospective in building materials using Frattini’s test. Field observations indicate that metavolcanics, DV, and monzogranites are the principal rock units exposed in the studied area. The DV rocks are characterized by a dense series of stratified, rhyolitic to andesitic lava interspersed with a few pyroclastics. Andesite, andesite porphyry, dacite, and rhyolite are the primary representatives of the selected DV. The lack of infrequent appearance of mafic units in the current volcanic eruptions indicates that the primary magma is not mantle-derived. This is supported by their Mg# (17.86–33.57). Additionally, the examined DV rocks have Y/Nb ratios above 1.2, suggesting a crustal source. The role of fractionation is interpreted by their variation from andesite passing through dacite to rhyolite, which is indicated by gradual negative distribution groups between silica and TiO₂, Fe₂O₃, CaO, MgO, Co, and Cu from andesite to rhyolitic lava. Additionally, a wide range of widely used DV rocks like Y/Nb, Rb/Zr, and Ba/Nb point to crustal contamination in the rhyolitic rocks. The partial melting of the lower crust can produce andesitic magma, which ascend to higher crustal levels and form lava of calc-alkaline. A portion of this lava may split, settle at shallow crustal depths, and undergo differentiation to create the DV rocks. Based on the results of physico-mechanical properties, the studied samples met the requirements for natural stone to be used as decorative stones, whether as interior or exterior installations. The pozzolanic assessment of the studied rocks revealed their usability as supplementary cementitious materials in the building sector. Full article

Passive evaporative cooling technology using the building envelope is a crucial measure to mitigate the urban heat island effect. This study aims to enhance the cooling efficiency of the surface of enclosure structures by utilizing volcanic ash, potassium–sodium stone powder, and silica-based mesoporous oxide (SMO) as primary materials. These components are incorporated into the ceramic brick production process to create innovative humidity-controlling ceramic bricks (HCCTs). This study extensively investigates the impact of SMO and the amount of applied glaze on the physical and mechanical characteristics of these HCCTs. Additionally, it examines the water absorption and evaporative cooling properties of the studied materials under optimal substitution conditions. Numerical calculations are used to determine the heat and moisture transfer properties of HCCTs. The results indicate that incorporating 2% SMO and applying 70 g/m² of glaze results in a moisture absorption capacity of 385 g/m² and a moisture discharge capacity of 370 g/m². These conditions also yield a notable flexural strength of 15.2 MPa. Importantly, the HCCTs exhibit significantly enhanced capillary water absorption and water retention capabilities. Increased water absorption reduces surface temperature by 2–3 °C, maintaining the evaporative cooling effect for 20 to 30 h. It is also found that the temperature of HCCTs decreases linearly with increasing water content and porosity, while the temperature difference gradually decreases with thickness. Water migration in HCCTs with greater thickness is notably influenced by gravity, with water moving from top to bottom. Therefore, it is recommended that brick thickness does not exceed 15 mm. Full article

The main goal of this study was to validate a circular production route utilizing the waste ash generated during stone wool production in cementitious binders. To achieve this goal, two types of waste ash with different compositions and particle sizes were used. The performance evaluation results showed that silica-based ashes exhibit pozzolanic behavior, reduce the amount of portlandite, and can improve the strength of the mortar even at early ages. The ashes increased the initial setting time regardless of their composition. The outcomes of this study create an economic value for large volumes of material of previously zero value. Full article

The preservation of cultural heritage, particularly historical stone structures, represents a very challenging matter due to several environmental and anthropogenic factors. Vicenza stone, a calcareous rock known for its historical significance and widespread use in architectural masterpieces, requires significant attention for conservation. In fact, as the demand for sustainable and effective preservation methods intensifies, the exploration of innovative consolidation strategies becomes essential. To this end, inorganic consolidants, based on alkaline silicate formulations and nano-silica, were explored for their promising performance in enhancing the surface properties and chemical stability of Vicenza stone. In particular, the durability of treated and untreated Vicenza stone samples was evaluated by means of accelerated weathering tests such as freeze–thaw cycles, salt crystallization and simulation of acid rain. The experimental results revealed that Vicenza stone is very resistant to the effects of freeze–thaw cycles and acid rain; both the accelerated weathering tests did not show significant differences between treated and untreated VS samples. A different behavior was detected for the test for resistance to salt crystallization, whose findings led us to deduce that, for this kind of degradation, it is possible to observe a more beneficial effect of the consolidation treatments on the stone durability. Full article

The purpose of this research was to study the influence of multifunctional anatase–silica photocatalytic materials (ASPMs) with various photocatalytic and pozzolanic activities on the properties of white portland cement and fine-grained concrete. ASPMs were synthesized by a sol–gel method, during which the levels of photocatalytic and pozzolanic activity were regulated by a certain amount of solvent. ASPMb, obtained with the use of a smaller amount of solvent, was characterized by increased pozzolanic activity due to the lower degree of coating of the surface of diatomite particles with titanium dioxide and the higher content of an opal–cristobalite–tridymite-phase and Bronsted acid sites. They promoted the reaction of diatomite with portlandite of cement stone and allowed significant decreases in the strength of cement–sand mortar to be avoided when replacing 15% of the cement with ASPMs. This allowed self-cleaning fine-grained concrete to be produced, which, after forced carbonization, simulating the natural aging of the product during operation, retained the ability of self-cleaning without changes. ASPMc, produced with the use of a larger amount of solvent with a more uniform distribution of titanium dioxide on the surface of diatomite, allowed fine-grained concrete with a high self-cleaning ability to be obtained, but with a lesser manifestation of the pozzolanic effect. 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

Silicosis caused by engineered stone (ES-silicosis) is an emerging worldwide issue characterized by inflammation and fibrosis in the lungs. To our knowledge, only a few reports have investigated leukocyte/lymphocyte subsets in ES-silicosis patients. The present study was designed to explore the proportions of the main lymphocyte subsets in ES-silicosis patients stratified into two groups, one with simple silicosis (SS) and the other with a more advanced state of the disease, defined as progressive massive fibrosis (PMF). The proportions of B (memory and plasmablasts) cells, T (helper, cytotoxic, regulatory) cells, and natural killer (NK) (regulatory and cytotoxic) cells were investigated by multiparameter flow cytometry in 91 ES-silicosis patients (53 SS patients and 38 PMF patients) and 22 healthy controls (HC). Although the total number of leukocytes did not differ between the groups studied, lymphopenia was observed in patients compared to healthy controls. Compared with those in healthy controls, the proportions of memory B cells, naïve helper T cells, and the CD4⁺/CD8⁺ T cells’ ratio in the peripheral blood of patients with silicosis were significantly decreased, while the percentages of plasma cells, memory helper T cells, and regulatory T cells were significantly increased. For the NK cell subsets, no significant differences were found between the groups studied. These results revealed altered cellular immune processes in the peripheral blood of patients with ES-silicosis and provided further insight into silicosis pathogenesis. 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