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6 pages, 184 KB  
Brief Report
Assessing Clinical Outcomes of Metronidazole for Intra-Abdominal Infections When Dosed Every 12 h Versus Every 8 h in a Multi-Center Health System
by Sarah Galante, Ramya Castillo, Todd Price, MaiCuc Tran and Stefanie Stramel-Stafford
Antibiotics 2025, 14(7), 688; https://doi.org/10.3390/antibiotics14070688 - 8 Jul 2025
Viewed by 957
Abstract
Background: Metronidazole is the preferred anaerobic agent for empiric treatment of intra-abdominal infections (IAI). Although dosed every 8 h (q8hr), blood concentrations exceed the in vitro minimum inhibitory concentration (MIC) for anaerobic organisms at 12 h (q12hr). A drug shortage of intravenous [...] Read more.
Background: Metronidazole is the preferred anaerobic agent for empiric treatment of intra-abdominal infections (IAI). Although dosed every 8 h (q8hr), blood concentrations exceed the in vitro minimum inhibitory concentration (MIC) for anaerobic organisms at 12 h (q12hr). A drug shortage of intravenous (IV) metronidazole prompted the conversion to every 12 h dosing in qualifying patients treated for IAI. Objective: To determine efficacy outcomes of metronidazole dosed every 12 h versus every 8 h in patients treated for IAI. Methods: This was a multi-center, retrospective, cohort study of 201 patients from January to July 2021 (q8hr) and January to November 2023 (q12hr) at five hospitals through the greater Houston area. Included patients were adults with a diagnosis of IAI confirmed by radiographic evidence and a white blood count (WBC) > 12,000 cells/µL and/or temperature > 100.4 °F at the time of diagnosis. The primary outcome was clinical cure of IAI, defined as resolution of signs/symptoms of IAI and normalization of WBC or temperature. Results: A total of 201 patients were included, 103 patients in the q8hr group and 98 patients in the q12hr group. Clinical cure of IAI occurred in 72 patients (69.9%) in the q8hr group and 62 patients (63.2%) in the q12hr group (p = 0.318). The median duration of therapy days was similar for both groups (4.0 [4.0–6.0] vs. 4.0 [3.0–6.0] (p = 0.509)). The frequency of clinical failure was higher in the q12hr group (8.7% vs. 21.4%; p = 0.01). Seven patients in the q8hr group and fourteen patients in the q12hr group required escalation of antibiotics due to the need for broader-spectrum antimicrobial therapy by clinical failure definition. Conclusions: There was no difference in clinical cure of IAI with an extended dosing interval. Clinical failure and escalation in antibiotics was higher in the q12h group due to the need for broader-spectrum gram-negative coverage and not related to the need for anaerobic coverage. Findings suggest that every 12 h dosing has similar outcomes. Full article
(This article belongs to the Section Antibiotic Therapy in Infectious Diseases)
26 pages, 10116 KB  
Article
Intelligent Automated Monitoring and Curing System for Cracks in Concrete Elements Using Integrated Sensors and Embedded Controllers
by Papa Pio Ascona García, Guido Elar Ordoñez Carpio, Wilmer Moisés Zelada Zamora, Marco Antonio Aguirre Camacho, Wilmer Rojas Pintado, Emerson Julio Cuadros Rojas, Hipatia Merlita Mundaca Ramos and Nilthon Arce Fernández
Technologies 2025, 13(7), 284; https://doi.org/10.3390/technologies13070284 - 3 Jul 2025
Viewed by 657
Abstract
This study addresses the formation, detection, and repair of cracks in concrete elements exposed to temperatures above 25 °C, where accelerated evaporation compromises their structural strength. An automated intelligent curing system with embedded sensors (DS18B20, HD-38) and Arduino controllers was developed and applied [...] Read more.
This study addresses the formation, detection, and repair of cracks in concrete elements exposed to temperatures above 25 °C, where accelerated evaporation compromises their structural strength. An automated intelligent curing system with embedded sensors (DS18B20, HD-38) and Arduino controllers was developed and applied to solid slabs, columns, and concrete test specimens (1:2:3.5 mix ratio). The electronic design was simulated in Proteus and validated experimentally under tropical conditions. Data with normal distribution (p > 0.05) showed a significant correlation between internal and ambient temperature (r = 0.587; p = 0.001) and a low correlation in humidity (r = 0.143; p = 0.468), indicating hygrometric independence. The system healed cracks of 0.01 mm observed two hours after pouring the mixture, associated with an evaporation rate of 1.097 mL/s in 4 m2. For 28 days, automated irrigation cycles were applied every 30 to 60 min, with a total of 1680 L, achieving a 20% reduction in water consumption compared to traditional methods. The system maintained stable thermal conditions in the concrete despite ambient temperatures of up to 33.85 °C. A critical evaporation range was identified between 11:00 and 16:00 (UTC-5). The results demonstrate the effectiveness of the embedded system in optimizing curing, water efficiency, and concrete durability. Full article
(This article belongs to the Section Construction Technologies)
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27 pages, 1571 KB  
Article
Gaussian Versus Mean-Field Models: Contradictory Predictions for the Casimir Force Under Dirichlet–Neumann Boundary Conditions
by Daniel Dantchev, Vassil Vassilev and Joseph Rudnick
Entropy 2025, 27(5), 468; https://doi.org/10.3390/e27050468 - 25 Apr 2025
Viewed by 475
Abstract
The mean-field model (MFM) is the workhorse of statistical mechanics: one normally accepts that it yields results which, despite differing numerically from correct ones, are not “very wrong”, in that they resemble the actual behavior of the system as eventually obtained by more [...] Read more.
The mean-field model (MFM) is the workhorse of statistical mechanics: one normally accepts that it yields results which, despite differing numerically from correct ones, are not “very wrong”, in that they resemble the actual behavior of the system as eventually obtained by more advanced treatments. This, for example, turns out to be the case for the Casimir force under, say, Dirichlet–Dirichlet, (+,+) and (+,) boundary conditions (BC) for which, according to the general expectations, the MFM is attractive for similar BC or repulsive for dissimilar BC force, with the principally correct position of the maximum strength of the force below or above the critical point Tc. It turns out, however, that this is not the case with Dirichlet–Neumann (DN) BC. In this case, the mean-field approach leads to an attractive Casimir force. This contradiction with the “boundary condition rule” is cured in the case of the Gaussian model under DN BC. Our results, which are mathematically exact, demonstrate that the Casimir force within the MFM is attractive as a function of temperature T and external magnetic field h, while for the Gaussian model, it is repulsive for h=0 and can be, surprisingly, both repulsive and attractive for h0. The treatment of the MFM is based on the exact solution of one non-homogeneous, nonlinear differential equation of second order. The Gaussian model is analyzed in terms of both its continuum and lattice realization. The obtained outcome teaches us that the mean-field results should be accepted with caution in the case of fluctuation-induced forces and ought to be checked against the more precise treatment of fluctuations within the envisaged system. Full article
(This article belongs to the Section Statistical Physics)
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24 pages, 6600 KB  
Article
Preparation and Optimization of Thermochromic Microcapsules as a Ternary System of Crystal Violet Lactone: Bisphenol A: Decanol Encapsulated with Urea Formaldehyde Resin in a UV-Curable Primer
by Yuming Zou and Xiaoxing Yan
Polymers 2025, 17(7), 851; https://doi.org/10.3390/polym17070851 - 22 Mar 2025
Cited by 2 | Viewed by 644
Abstract
Coatings can achieve the property of changing color with temperature variations by adding thermochromic microcapsules, which can bring a variable surface to the substrate. Ultraviolet ray (UV)-cured primers have the advantages of a fast curing rate, low-temperature curing, and low pollution. Thermochromic microcapsules [...] Read more.
Coatings can achieve the property of changing color with temperature variations by adding thermochromic microcapsules, which can bring a variable surface to the substrate. Ultraviolet ray (UV)-cured primers have the advantages of a fast curing rate, low-temperature curing, and low pollution. Thermochromic microcapsules can expand the application range of UV primers. Thermochromic microcapsules were synthesized through an orthogonal test, using crystal violet lactone, bisphenol A, and decanol as the core materials in a 1:4:50 mass ratio, with urea formaldehyde resin as the wall material. The effects of the addition of batches of the urea, the mass ratio of the formaldehyde solution to the urea, the hydrophilic–lipophilic balance (HLB) value of the emulsifier, and core-to-wall mass ratio on microcapsules yields, encapsulation rates, thermochromic color differences (ΔE), and formaldehyde releases during synthesis were investigated. The results were normalized, with the thermochromic ΔE as the primary reference for analysis. The results indicate that the HLB value of the emulsifier was the key factor that affected the microcapsule performance. In a single-factor test, the HLB value was adjusted within the range of 6.00 to 10.00. It was found that when the HLB value was 10.00, the microcapsules exhibited the best comprehensive performance, with a yield of 43.29%, an encapsulation rate of 45%, a thermochromic ΔE of 4.60, and a formaldehyde concentration released of 1.310 mg/L. The 11# microcapsules with the optimal morphology and better comprehensive performance were compared with the best 14# microcapsules. Different amounts of these microcapsules were added to the UV primer to investigate the effects of the 11# and 14# microcapsules on the mechanical and optical properties of the UV primer. The main component of the UV primer was polyurethane acrylic resin, propylene glycol diacrylate, and hexanediol diacrylate. When 14# microcapsules were added to the UV primer at a concentration of 10%, the primer exhibited the best comprehensive performance, with a fracture elongation of 17.44%, a roughness of 0.15 μm, and a visible light transmittance of 83%. Microcapsule technology was used to modify UV primers, endowing them with thermochromic properties and expanding the application range of thermochromic microcapsules. Full article
(This article belongs to the Section Polymer Applications)
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23 pages, 4356 KB  
Article
Effects of High Temperature and Water Re-Curing on the Flexural Behavior and Mechanical Properties of Steel–Basalt Hybrid Fiber-Reinforced Concrete
by Zinnur Çelik and Yunus Urtekin
Appl. Sci. 2025, 15(3), 1587; https://doi.org/10.3390/app15031587 - 4 Feb 2025
Cited by 2 | Viewed by 1015
Abstract
Fiber-reinforced concrete (FRC) has become increasingly important in recent decades due to its superior mechanical properties, especially flexural strength and toughness, compared to normal concrete. FRC has also received significant attention because of its superior fire resistance performance compared to non-fiber concrete. In [...] Read more.
Fiber-reinforced concrete (FRC) has become increasingly important in recent decades due to its superior mechanical properties, especially flexural strength and toughness, compared to normal concrete. FRC has also received significant attention because of its superior fire resistance performance compared to non-fiber concrete. In recent years, studies on the mechanical performance, fire design, and post-fire repair of thermally damaged fibrous and non-fibrous concrete have gained importance. In particular, there are very few studies in the literature on the mechanical performance and flexural behavior of steel and basalt hybrid fiber concretes after high temperature and water re-curing. This study aims to determine the mechanical properties and toughness of concrete containing steel fiber (SF) and basalt fiber (BF) after ambient and high temperature (400 °C, 600 °C, and 800 °C). Additionally, this study aimed to examine the changes in fire-damaged FRCs as a result of water re-curing. In this context, high temperature and water re-curing were carried out on non-fibrous concrete (control) and four different fiber compositions: in the first mixture, only steel fibers were used, and in the other two mixtures, basalt fibers were substituted at 25% and 50% rates instead of steel fibers. Furthermore, in the fifth mixture, basalt fibers were replaced by polypropylene fibers (PPFs) to make a comparison with the steel and basalt hybrid fiber-reinforced mixture. This study examined the effects of different fiber compositions on the ultrasonic pulse velocity (UPV) and compressive and flexural strength of the specimens at ambient temperature and after exposure to elevated temperatures and water re-curing. Additionally, the load–deflection curves and toughness of the mixtures were determined. The study results showed that different fiber compositions varied in their healing effect at different stages. The hybrid use of SF and BF can improve the flexural strength before elevated temperature and particularly after 600 °C. However, it caused a decrease in the recovery rates, especially after re-curing with water in terms of toughness. Water re-curing provided remarkable improvement in terms of mechanical and toughness properties. This improvement was more evident in steel–polypropylene fiber-reinforced concretes. Full article
(This article belongs to the Section Civil Engineering)
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20 pages, 16954 KB  
Article
Study on the Properties of High Fly Ash Content Alkali-Activated Fly Ash Slag Pastes and Fiber-Reinforced Mortar Under Normal Temperature Curing
by Zhu Yuan, Yanmin Jia, Jinyu Sun, Xiaobo Zhang, Yaojie Hu and Xuhua Han
Materials 2024, 17(22), 5668; https://doi.org/10.3390/ma17225668 - 20 Nov 2024
Cited by 3 | Viewed by 1136
Abstract
In order to efficiently utilize industrial solid waste while minimizing the preparation cost of engineering materials and the technical difficulty of construction, this paper prepared a high fly ash content alkali-activated fly ash slag composite system at normal temperatures and conducted an in-depth [...] Read more.
In order to efficiently utilize industrial solid waste while minimizing the preparation cost of engineering materials and the technical difficulty of construction, this paper prepared a high fly ash content alkali-activated fly ash slag composite system at normal temperatures and conducted an in-depth investigation on it. A systematic study was conducted on the workability, mechanical properties, and microstructures of the alkali-activated fly ash slag pastes, including setting times, strength, phase, and molecular structures. We then designed and prepared fiber-reinforced alkali-activated fly ash slag mortar and studied the effects of the alkali activator modulus, glass fiber (GF), and polypropylene fiber (PPF) on the workability, mechanical properties, and frost resistance of the mortar. The following main conclusions were drawn: By adjusting the modulus of alkali activator for alkali-activated fly ash slag pastes, characteristics that meet engineering requirements could be obtained. The compressive strength of the pastes decreased with increasing proportions of fly ash, and it first increased and then decreased with increases in the activator modulus. The flexural strength decreased to varying degrees as the modulus of the activator increased. Through SEM, fly ash particles with different reaction degrees could be observed, indicating that the reaction was still ongoing. The addition of GF and PPF reduced the fluidity of mortar and significantly improved its strength and frost resistance. Fiber had the most significant effect on improving the strength of the mortar, as an activator modulus of 1.0. 0.45% PPF increased the flexural and compressive strength of the mortar by 14.33% and 29.1%, respectively, while 0.90% GF increased the flexural and compressive strength of the mortar by 3.12% and 19.21%, respectively. The frost resistance of the mortar with an activator modulus of 1.0 was significantly better than that of the mortar with an activator modulus of 1.4. 0.45% PPF and reduced the quality loss rate of the mortar by 49.30%, effectively delaying the deterioration of its freeze-thaw performance. Full article
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16 pages, 10782 KB  
Article
Fluorescence-Enhanced Assessments for Human Breast Cancer Cell Characterizations
by Mahsa Ghezelbash, Batool Sajad and Shadi Hojatizadeh
Photonics 2024, 11(8), 746; https://doi.org/10.3390/photonics11080746 - 9 Aug 2024
Viewed by 1555
Abstract
Even with 100% certainty of a complete cure for breast cancer (BC), there is still a long way to go toward more efficient treatment because it requires sensitive and timely detection and accurate pre/post-clinical characterizations. Despite the availability of advanced diagnostic tools, many [...] Read more.
Even with 100% certainty of a complete cure for breast cancer (BC), there is still a long way to go toward more efficient treatment because it requires sensitive and timely detection and accurate pre/post-clinical characterizations. Despite the availability of advanced diagnostic tools, many cancer patients lack access to efficient diagnostics that are both highly reliable and affordable. The fluorescence-based optical technique aims to make another significant leap forward in improving patient safety. It offers a convenient operation that reduces healthcare costs compared to visual examination tools (VETs). The primary and metastatic stages of BC consider different cancerous cell lines (MDAs), meaning the highest number of cells in this research (up to 300,000) represents the metastatic stages of BC, and 50,000 represents the primary level of BC. Developments have been studied based on fluorescence-enhanced photodynamic characterizations. The ability to characterize the fluorescence caused by MDA with 50,000 cells compared to the dominant radiation of MDA with 300,000 cells is emphatic proof of the high potential of fluorescence technique in timely BC detections, specifically before it spreads to the axillary lymph nodes. The specific cell numbers of 50,000 and 300,000 were chosen arbitrarily based on the cultivation of common biological limitations. Comparing the outcomes between 50,000 and 300,000 cells allows for evaluating the fluorescence technique’s diagnostic capability across various stages of breast cancer. This assessment provides valuable insights into the effectiveness of the fluorescence-based characterizing approach in detecting cancerous cells at different stages of the disease. Here, we have assessed fluorescence’s spectral shift and intensity difference as a diagnostic approach to distinguish between cancerous and normal breast cells. This study also presents a two-way structure of the 5-aminolevulinic acid (5-ALA) prodrug and Fluorescein Sodium (FS) effect in BC cell characterization from the perspective of photodynamical procedures and the detection side. 5-ALA induces an accumulation of protoporphyrin IX (PpIX) photosensitizer through a biosynthetic pathway, leading to red radiation of fluorescence measurements depending on different factors, such as temperature, incubation time, added glucose of the culturing medium, as well as photosynthesis processes. The presence and progression of breast cancer can be indicated by elevated levels of Reactive Oxygen Species (ROS), associated with the production of PpIX in cells following the administration of 5-ALA. In addition, nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) fluorophores are recognized as the main factors for fluorescence emissions at around 420–580 nm emission intervals. Considering the MDA’s high metastatic potential, the impact of 5-ALA on MDA’s cellular morphology and viability has been investigated. The molecular fluorophores are the primary probes to MDA’s cellular photodynamic considerations, allowing this widespread pre/post-clinical approach. The fluorescence signal reduction due to decreased cell viability and increased MDA’s cellular death rate after 24 h of the 5-ALA-induced staining corresponds to the changes in lipid metabolism enzymes of MDAs cultured at different doses, which could be known as a cell death inducer function. Furthermore, statistical concerns have been studied using PCA multivariate component analysis to differentiate MDA cell lines administrated by 5-ALA. Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
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24 pages, 5984 KB  
Article
High-Strength Controllable Resin Plugging Agent and Its Performance Evaluation for Fractured Formation
by Xiongwei Liu, Biao Qi, Xiuping Chen, Ziyao Shen and Jingbin Yang
Gels 2024, 10(8), 511; https://doi.org/10.3390/gels10080511 - 2 Aug 2024
Cited by 5 | Viewed by 1427
Abstract
Lost circulation is a common and complicated situation in drilling engineering. Serious lost circulation may lead to pressure drop in the well, affect normal drilling operations, and even cause wellbore instability, formation fluid flooding into the wellbore, and blowout. Therefore, appropriate preventive and [...] Read more.
Lost circulation is a common and complicated situation in drilling engineering. Serious lost circulation may lead to pressure drop in the well, affect normal drilling operations, and even cause wellbore instability, formation fluid flooding into the wellbore, and blowout. Therefore, appropriate preventive and treatment measures need to be taken to ensure the safe and smooth operation of drilling operations. So, it is necessary to conduct in-depth research on the development and performance of the plugging materials. In this study, urea formaldehyde resin with high temperature resistance and strength was used as the main raw material, and the curing conditions were optimized and adjusted by adding a variety of additives. The curing time, compressive strength, temperature resistance, and other key performance indexes of the resin plugging agent were studied, and a resin plugging agent system with excellent plugging performance was prepared. The formula is as follows: 25% urea formaldehyde resin +1% betaine +1% silane coupling agent KH-570 + 3% ammonium chloride +1% hexamethylenetetramine +1% sodium carboxymethyl cellulose. The optimal curing temperature is between 60 and 80 °C, with a controllable curing time of 1–3 h. Experimental studies examined the rheological and curing properties of the resin plugging agent system. The results showed that the viscosity of the high-strength curable resin system before curing remained stable with increasing shear rates. Additionally, the storage modulus and loss modulus of the resin solutions increased with shear stress, with the loss modulus being greater than the storage modulus, indicating a viscous fluid. The study also investigated the effect of different salt ion concentrations on the curing effect of the resin plugging system. The results showed that formation water containing Na+ at concentrations between 500 mg/L and 10,000 mg/L increased the resin’s curing strength and reduced curing time. However, excessively high concentrations at lower temperatures reduced the curing strength. Formation water containing Ca2+ increased the curing time of the resin plugging system and significantly impacted the curing strength, reducing it to some extent. Moreover, the high-strength curable resin plugging agent system can effectively stay in various fracture types (parallel, wedge-shaped) and different fracture sizes, forming a high-strength consolidation under certain temperature conditions for effective plugging. In wedge-shaped fractures with a width of 10 mm, the breakthrough pressure of the high-strength curable resin plugging agent system reached 8.1 MPa. As the fracture width decreases, the breakthrough pressure increases, reaching 9.98 MPa in wedge-shaped fractures with an outlet fracture width of 3 mm, forming a high-strength plugging layer. This research provides new ideas and methods for solving drilling fluid loss in fractured loss zones and has certain application and promotion value. Full article
(This article belongs to the Special Issue Chemical and Gels for Oil Drilling and Enhanced Recovery)
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21 pages, 1783 KB  
Article
Alpha-1-Acid Glycoprotein Quantification via Spatial Proximity Analyte Reagent Capture Luminescence Assay: Application as Diagnostic and Prognostic Marker in Serum and Effusions of Cats with Feline Infectious Peritonitis Undergoing GS-441524 Therapy
by A. Katrin Helfer-Hungerbuehler, Andrea M. Spiri, Theres Meili, Barbara Riond, Daniela Krentz, Katharina Zwicklbauer, Katharina Buchta, Anna-Maria Zuzzi-Krebitz, Katrin Hartmann, Regina Hofmann-Lehmann and Marina L. Meli
Viruses 2024, 16(5), 791; https://doi.org/10.3390/v16050791 - 16 May 2024
Cited by 3 | Viewed by 3289
Abstract
Until recently, the diagnosis of feline infectious peritonitis (FIP) in cats usually led to euthanasia, but recent research has revealed that antiviral drugs, including the nucleoside analog GS-441524, have the potential to effectively cure FIP. Alpha-1-acid glycoprotein (AGP) has been suggested as a [...] Read more.
Until recently, the diagnosis of feline infectious peritonitis (FIP) in cats usually led to euthanasia, but recent research has revealed that antiviral drugs, including the nucleoside analog GS-441524, have the potential to effectively cure FIP. Alpha-1-acid glycoprotein (AGP) has been suggested as a diagnostic marker for FIP. However, AGP quantification methods are not easily accessible. This study aimed to establish a Spatial Proximity Analyte Reagent Capture Luminescence (SPARCLTM) assay on the VetBio-1 analyzer to determine the AGP concentrations in feline serum and effusion samples. Linearity was found in serial dilutions between 1:2000 and 1:32,000; the intra-run and inter-run precision was <5% and <15%, respectively; and AGP was stable in serum stored for at least 8 days at room temperature, at 4 °C and at −20 °C. Cats with confirmed FIP had significantly higher serum AGP concentrations (median: 2954 µg/mL (range: 200–5861 µg/mL)) than those with other inflammatory diseases (median: 1734 µg/mL (305–3449 µg/mL)) and clinically healthy cats (median 235 µg/mL (range: 78–616 µg/mL); pKW < 0.0001). The AGP concentrations were significantly higher in the effusions from cats with FIP than in those from diseased cats without FIP (pMWU < 0.0001). The AGP concentrations in the serum of cats with FIP undergoing GS-441524 treatment showed a significant drop within the first seven days of treatment and reached normal levels after ~14 days. In conclusion, the VetBio-1 SPARCLTM assay offers a precise, fast and cost-effective method to measure the AGP concentrations in serum and effusion samples of feline patients. The monitoring of the AGP concentration throughout FIP treatment provides a valuable marker to evaluate the treatment’s effectiveness and identify potential relapses at an early stage. Full article
(This article belongs to the Section Animal Viruses)
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14 pages, 1122 KB  
Article
Sustainable Hybrid Lightweight Aggregate Concrete Using Recycled Expanded Polystyrene
by D. González-Betancur, Ary A. Hoyos-Montilla and Jorge I. Tobón
Materials 2024, 17(10), 2368; https://doi.org/10.3390/ma17102368 - 15 May 2024
Cited by 7 | Viewed by 2559
Abstract
Global concrete production, reaching 14×1013m3/year, raises environmental concerns due to the resource-intensive nature of ordinary Portland cement (OPC) manufacturing. Simultaneously, 32.7×109 kg/year of expanded polystyrene (EPS) waste poses ecological threats. This research explores [...] Read more.
Global concrete production, reaching 14×1013m3/year, raises environmental concerns due to the resource-intensive nature of ordinary Portland cement (OPC) manufacturing. Simultaneously, 32.7×109 kg/year of expanded polystyrene (EPS) waste poses ecological threats. This research explores the mechanical behavior of lightweight concrete (LWAC) using recycled EPS manufactured with a hybrid cement mixture (OPC and alkali-activated cement). These types of cement have been shown to improve the compressive strength of concrete, while recycled EPS significantly decreases concrete density. However, the impact of these two materials on the LWAC mechanical behavior is unclear. LWAC comprises 35% lightweight aggregates (LWA)—a combination of EPS and expanded clays (EC) — and 65% normal-weight aggregates. As a cementitious matrix, this LWAC employs 30% OPC and 70% alkaline-activated cement (AAC) based on fly ash (FA) and lime. Compressive strength tests after 28 curing days show a remarkable 48.8% improvement, surpassing the ACI 213R-03 standard requirement, which would allow this sustainable hybrid lightweight aggregate concrete to be used as structural lightweight concrete. Also obtained was a 21.5% reduction in density; this implies potential cost savings through downsizing structural elements and enhancing thermal and acoustic insulation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal the presence of C-S-H, C-(A)-S-H, and N-A-S-H gels. However, anhydrous products in the hybrid LWAC suggest a slower reaction rate. Further investigation into activator solution dosage and curing temperature is recommended for improved mechanical performance on the 28th day of curing. This research highlights the potential for sustainable construction incorporating waste and underscores the importance of refining activation parameters for optimal performance. Full article
(This article belongs to the Special Issue Advances in the Design and Properties of New Ecoconcrete Formulations)
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20 pages, 4920 KB  
Article
Effect of Microwave Pretreatment on the Properties and Microstructure of Low-Concentration Carbon Dioxide Early Cured Cement-Based Materials
by Xiao Liang, Maosen Li, Lu Wang and Shuhua Liu
Buildings 2024, 14(4), 1074; https://doi.org/10.3390/buildings14041074 - 12 Apr 2024
Cited by 5 | Viewed by 1593
Abstract
The utilization of microwave drying technology has expanded across various sectors due to its rapid processing speed, reduced operation time, lower sample temperatures, and consistent heating. In this research, microwave pretreatment was implemented prior to carbonation curing with low concentrations, and an array [...] Read more.
The utilization of microwave drying technology has expanded across various sectors due to its rapid processing speed, reduced operation time, lower sample temperatures, and consistent heating. In this research, microwave pretreatment was implemented prior to carbonation curing with low concentrations, and an array of tests including moisture content, compressive strength, carbonation depth, CO2 absorptivity, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were utilized to investigate the effect of microwave pretreatment on the properties and microstructure of cementitious materials under early carbonation curing with low CO2 concentrations. The findings reveal that microwave pretreatment significantly decreases the moisture content within the test specimens, expediting the ingress of CO2 and improving the compressive strength of the specimens. At the same time, the effectiveness of microwave pretreatment in reducing moisture content diminishes as the pretreatment time increases. The absorption of CO2 is relatively rapid in the early stage of carbonation curing, with over 50% of the CO2 absorption occurring within the 0–6 h period of carbonation curing. The hydration products and microstructure of the uncarbonated part inside the specimens are generally consistent with the normal curing state. The formation of CaCO3 contributed to the densification of the specimen by infilling its internal voids, thereby enhancing its compressive strength. Although carbonation curing enlarges the average pore size of the samples, it also serves a filling function, making the samples more compact and reducing the porosity. Full article
(This article belongs to the Special Issue Green Building Materials and Intelligent Construction Technology)
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15 pages, 3882 KB  
Article
Experimental Investigation into the Evolution of Probabilistic Characteristics of Early-Age Concrete
by Giuseppe Ciaramella Moita, Eduardo M. R. Fairbairn, Romildo D. Toledo Filho and Pierre Rossi
Buildings 2024, 14(3), 668; https://doi.org/10.3390/buildings14030668 - 2 Mar 2024
Cited by 1 | Viewed by 1257
Abstract
This paper presents original findings on the heterogeneity of the mechanical properties of concrete of an early age, dependent on the evolution of the hydration reaction. The properties investigated are the compressive strength, the Young’s modulus, and the flexural tensile strength. To achieve [...] Read more.
This paper presents original findings on the heterogeneity of the mechanical properties of concrete of an early age, dependent on the evolution of the hydration reaction. The properties investigated are the compressive strength, the Young’s modulus, and the flexural tensile strength. To achieve this, we employed a testing apparatus in which the samples underwent curing in a chamber that followed the same temperature profile as an adiabatic calorimeter. This method enabled us to monitor the hydration progress across multiple samples. We used a function derived from the literature, with specific adaptations, to model the evolution of normalized properties in relation to hydration. Heterogeneity was quantified through the use of the dispersion coefficient. The key finding of this study is that the dispersion coefficient for the analyzed mechanical properties diminishes with the advancement of hydration, until reaching a specific threshold. Beyond this point, the impact of microcracking on the various properties becomes increasingly pronounced, varying according to the particular property being examined. Moreover, this paper presents initial functions designed to offer formulas that assist in modeling concrete within probabilistic numerical simulations from the early stages of its development. Full article
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15 pages, 4768 KB  
Article
Application of Tamarind Shell as a Green Additive in Natural Rubber
by Weenusarin Intiya, Kannika Hatthapanit, Puchong Thaptong and Pongdhorn Sae-oui
Polymers 2024, 16(4), 493; https://doi.org/10.3390/polym16040493 - 9 Feb 2024
Cited by 7 | Viewed by 3759
Abstract
The feasibility of using tamarind shell as an eco-friendly additive in natural rubber (NR) was studied. Tamarind shell powder (TSP) was prepared with different particle size ranges before being characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), [...] Read more.
The feasibility of using tamarind shell as an eco-friendly additive in natural rubber (NR) was studied. Tamarind shell powder (TSP) was prepared with different particle size ranges before being characterized by various techniques such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis, etc. The results of the FTIR and elemental analysis confirmed that TSP was mainly composed of amino acids (proteins), celluloses, and tannins. The thermal analysis revealed that TSP contained approximately 9% moisture, and its main constituents were stable up to 200 °C, which is higher than the normal processing temperature of rubber products. The addition of TSP to NR led to reductions in scorch time and cure time due to the presence of moisture and proteins. This phenomenon was more obvious with the decrease in TSP’s particle size. Even though the small addition of TSP (≤10 phr) did not cause any change in hardness, it significantly impaired the mechanical properties of the rubber vulcanizates, particularly tensile strength, elongation at break, and abrasion resistance. Such deterioration depended greatly on the TSP particle size, i.e., the finest particles (S-TSP) showed the least deterioration of mechanical properties. In summary, TSP can be considered a low-cost, eco-friendly bio-additive for rubbers. Nevertheless, it must be used with great care to avoid undesirable impacts on mechanical properties. Full article
(This article belongs to the Special Issue Modification and Application of Natural Polymers)
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24 pages, 9460 KB  
Article
Resistance of Concrete with Various Types of Coarse Aggregate to Coupled Effects of Thermal Shocks and Chemicals
by Muhammad Monowar Hossain, Safat Al-Deen, Sukanta Kumer Shill and Md Kamrul Hassan
Materials 2024, 17(4), 791; https://doi.org/10.3390/ma17040791 - 6 Feb 2024
Cited by 6 | Viewed by 1725
Abstract
Rigid pavements at military airfields experience surface deterioration within 6–18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form [...] Read more.
Rigid pavements at military airfields experience surface deterioration within 6–18 months of construction. The cause of this degradation is mainly due to combined exposure to repeated heat shocks from jet engine exhaust and spilled aviation oils (hydrocarbons). Surface degradation occurs in the form of disintegration of aggregates and cement paste into small pieces that pose severe risks of physical injury to maintenance crews or damage to an aircraft engine. Since coarse aggregates typically occupy 60–80% of the concrete volume, aggregates’ thermal properties and microstructure should play a crucial role in the degrading mechanism. At high temperatures, concrete with lightweight aggregates is reported to have better performance compared to concrete with normal-weight aggregate. Thus, the present study carried out a detailed investigation of the mechanical and thermal performance of lightweight aggregate concrete exposed to the combined effects of high temperatures and hydrocarbon oils simultaneously. To replicate harsh airfield operating conditions, standard-sized concrete cylinders were exposed to elevated temperatures using an electric oven. Additionally, a mixture of equal parts of aircraft engine oil, hydraulic oil, and kerosene was applied before each exposure to high temperatures. To identify the resistance of different concrete with various lightweight coarse aggregates, pumice, perlite, lytag (sintered fly ash), and crushed brick were used as lightweight coarse aggregates in concrete. Also, basalt aggregate concrete was used as a reference. After curing, cylinders were tested for the ultimate strength. Later, after every 20 cyclic exposures, three cylinders from each aggregate type were tested for residual comprehensive strength, thermal, chemical, and microstructural (SEM) properties. Overall, concrete with crushed brick aggregate and lytag used in this study showed superior resistance to the simulated airfield conditions. The findings of this study will provide valuable insights to select an appropriate coarse aggregate type for military airfield pavement construction, aiming to effectively minimize surface spalling. Full article
(This article belongs to the Special Issue Durability and Time-Dependent Properties of Sustainable Concrete)
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18 pages, 3945 KB  
Article
Alkaline Activation of Binders: A Comparative Study
by Bianca Ignacio Almeida Alves, Markssuel Teixeira Marvila, José Alexandre Tostes Linhares Júnior, Carlos Maurício Fontes Vieira, Jonas Alexandre and Afonso Rangel Garcez de Azevedo
Materials 2024, 17(3), 667; https://doi.org/10.3390/ma17030667 - 30 Jan 2024
Cited by 7 | Viewed by 1912
Abstract
Binders formulated with activated alkali materials to replace Portland cement, which has high polluting potential due to CO2 emissions in its manufacture, have increasingly been developed. The objective of this study is to evaluate the main properties of activated alkali materials (AAM) [...] Read more.
Binders formulated with activated alkali materials to replace Portland cement, which has high polluting potential due to CO2 emissions in its manufacture, have increasingly been developed. The objective of this study is to evaluate the main properties of activated alkali materials (AAM) produced by blast furnace slag, fly ash, and metakaolin. Initially, binders were characterized by their chemical, mineralogical and granulometric composition. Later, specimens were produced, with molarity variation between 4.00 and 5.50, using the binders involved in the research. In preparing the activating solution, sodium hydroxide and silicate were used. The evaluated properties of AAM were consistency, viscosity, water absorption, density, compressive strength (7 days of cure), calorimetry, mineralogical analysis by X-ray diffraction, and morphological analysis by scanning electron microscopy. The results of evaluation in the fresh state demonstrate that metakaolin has the lowest workability indices of the studied AAM. The results observed in the hardened state indicate that the metakaolin activation process is optimized with normal cure and molarity of 4.0 and 4.5 mol/L, obtaining compressive strength results after 7 days of curing of approximately 30 MPa. The fly ash activation process is the least intense among the evaluated binders. This can be seen from the absence of phases formed in the XRD in the compositions containing fly ash as binder. Unlike blast furnace slag and metakaolin, the formation of sodalite, faujasite or tobermorite is not observed. Finally, the blast furnace slag displays more intense reactivity during thermal curing, obtaining compressive strength results after 7 days of curing of around 25 MPa. This is because the material’s reaction kinetics are low but can be increased in an alkaline environment, and by the effect of temperature. From these results, it is concluded that each precursor has its own activation mechanism, observed by the techniques used in this research. From the results obtained in this study, it is expected that the alkaline activation process of the types of binders evaluated herein will become a viable alternative for replacing Portland cement, thus contributing to cement technology and other cementitious materials. Full article
(This article belongs to the Section Construction and Building Materials)
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