Search Results (63)

This paper investigates nine PVA fiber-reinforced cementitious composites with varying fiber content (1–2.5%) and types (oil-coated and non-coated). The experimental compositions utilize locally available cement, high volumes of fly ash, silica fume, PVA fibers, and a superplasticizer, entirely omitting natural aggregates. Key parameters evaluated include bulk density, compressive strength, secant modulus of elasticity, flexural tensile strength, fracture energy, and structural design applicability. The results show that FRCs without natural aggregates achieves significantly lower densities (1500–1720 kg/m³). Compressive strength is influenced by matrix density, with the highest value recorded at 30.98 MPa. The high fly ash content reduces the secant modulus of elasticity, while flexural tensile strength follows a similar pattern to compressive strength. Oil-coated fibers generally lower fracture energy, except for the 1.5% PVA content, where the 2.5% composition performs best. All specimens exhibit tension softening rather than the strain-hardening behavior of ECCs. Structural design equations were developed, though experimental validation is necessary. The 2.5% PVA composition increases the compression zone height by 7% while requiring 2% more reinforcement. As a sustainable alternative to conventional concrete, the composites offer promising mechanical properties and structural viability for construction applications. Full article

This study aimed to comparatively evaluate the effects of various surface treatment protocols on the shear bond strength (SBS) between heat-polymerized polymethyl methacrylate (PMMA) and different CAD/CAM framework materials, including cobalt–chromium (Co–Cr) alloys, ceramic particle-reinforced polyetheretherketone (PEEK), and glass fiber-reinforced composite resin (FRC). A total of 135 disc-shaped specimens were prepared from Co–Cr, PEEK, and FRC materials. Surface treatments specific to each material, including airborne-particle abrasion, sulfuric acid etching, laser irradiation, plasma activation, and primer application, were applied. PMMA cylinders were polymerized onto the treated surfaces, and all specimens were subjected to 30,000 thermal cycles. SBS values were measured using a universal testing machine, and the failure modes were classified. The normality of data distribution was assessed using the Kolmogorov–Smirnov test, and the homogeneity of variances was evaluated using Levene’s test. Group comparisons were performed using the Kruskal–Wallis test, and Dunn’s post hoc test with Bonferroni correction was applied in cases where significant differences were detected (α = 0.05). The highest SBS values (~27–28 MPa) were obtained in the Co–Cr group and in the PEEK groups treated with sulfuric acid and primer. In contrast, the PEEK group with additional laser treatment exhibited a lower SBS value. The untreated PEEK group showed significantly lower SBS (~3.9 MPa) compared to all other groups. The Trinia groups demonstrated intermediate SBS values (16.5–17.4 MPa), which exceeded the clinically acceptable threshold of 10 MPa. SEM observations revealed material- and protocol-specific surface responses; plasma-treated specimens maintained topographic integrity, whereas laser-induced surfaces showed localized degradation, particularly following dual-step protocols. Fracture mode analysis indicated that higher SBS values were associated with cohesive or mixed failures. SEM observations suggested that plasma treatment preserved surface morphology more effectively than laser treatment. This study highlights the importance of selecting material-specific surface treatments to optimize bonding between CAD/CAM frameworks and PMMA. Sulfuric acid and primer provided strong adhesion for PEEK, while the addition of laser or plasma offered no further benefit, making such steps potentially unnecessary. Trinia frameworks also showed acceptable performance with conventional treatments. These findings reinforce that simplified conditioning protocols may be clinically sufficient, and indicate that FRC materials like Trinia should be more fully considered for their broader clinical potential in modern CAD/CAM-based prosthetic planning. Full article

Propionic acid (PA) is an important organic acid with applications in food preservation, feed additives, and bio-based chemical production. While industrial PA is mostly derived from petrochemical processes, sustainable microbial alternatives are gaining attention. In this study, we explored a co-fermentation strategy using lactic acid bacteria (LAB) with complementary metabolic capabilities to enhance PA biosynthesis via the 1,2-propanediol (PDO) pathway. Genome-based screening identified a metabolic division between strains capable of producing PDO (e.g., Carnobacterium maltaromaticum IBB3447) and those converting PDO to PA (e.g., Levilactobacillus brevis IBB3735). Notably, we discovered that C. maltaromaticum IBB3447 is capable of PDO 24 biosynthesis, a function previously undescribed in this species. Phenotypic assays confirmed glycerol metabolism and acid tolerance among strains. In co-culture fermentation trials, the highest PA concentration (6.87 mM) was achieved using simultaneous fermentation in a fructose–sorbitol–glucose (FRC-SOR-GLC) medium, accompanied by prior PDO accumulation (up to 13.13 mM). No single strain produced PA independently, confirming that metabolic cooperation is required. These findings reveal a novel LAB-based bioprocess for sustainable PA and PDO production, using cross-feeding interactions and the valorization of industrial waste streams. The study supports future optimization and scale-up for circular bioeconomy applications. Full article

This research investigates the effects of steel (ST) and synthetic (SYN) fibers on the workability and mechanical properties of HPFRC. It also analyzes their influence on the material’s microstructural characteristics. ST fibers improve tensile strength, fracture toughness, and post-cracking performance owing to their rigidity, mechanical interlocking, and robust adhesion with the matrix. SYN fibers, conversely, mitigate shrinkage-induced micro-cracking, augment ductility, and enhance concrete performance under dynamic stress while exerting negative effects on workability. Hybrid fiber systems, which include ST and SYN fibers, offer synergistic advantages by enhancing fracture management at various scales and augmenting ductility and energy absorption capability. Scanning electron microscopy (SEM) has been crucial in investigating fiber–matrix interactions, elucidating the effects of ST and SYN fibers on hydration, crack-bridging mechanisms, and interfacial bonding. ST fibers establish thick interfacial zones that facilitate effective stress transfer, whereas SYN fibers reduce micro-crack formation and enhance long-term durability. Nonetheless, research deficiencies persist, encompassing optimal hybrid fiber configurations, the enduring performance of fiber-reinforced concrete (FRC), and sustainable fiber substitutes. Future investigations should examine multi-scale reinforcing techniques, intelligent fibers for structural health assessment, and sustainable fiber alternatives. The standardization of testing methodologies and cost–benefit analyses is essential to promote industrial deployment. This review offers a thorough synthesis of the existing knowledge, emphasizing advancements and potential to enhance HPFRC for high-performance and sustainable construction applications. The findings facilitate the development of new, durable, and resilient fiber-reinforced concrete systems by solving current difficulties. Full article

The construction and operation of reservoirs have significantly altered the downstream flow regime, and the flood regional composition (FRC) method has been widely used to estimate design flood considering the regulation impact of upstream cascade reservoirs. This paper proposes a novel flood regional composition based on the proper orthogonal decomposition (FRC-POD) method that comprehensively takes into account typical-year flood differences and the multi-site flood source characteristics. The proposed method is applied at Cuntan hydrologic station in the upper Yangtze River and compared with the typical-year flood composition (TYFC) method and the most likely flood regional composition (MLFRC) method. The results show the following: (1) The proposed FRC-POD method can identify main flood sources in the design section and pay more attention to floods from the mainstream and the uncontrolled interval basin. (2) Compared with the originally designed values, the 1000-year design peak discharge and 3 d, 7 d, and 15 d flood volumes estimated by the FRC-POD method are decreased by 41.3%, 40.2%, 36.6%, and 34.7%, respectively. (3) Current FRC methods depend on the selected typical-year flood events and have several solutions, while the proposed method has only one final solution, which is more reasonable in practical application. (4) A comparative study proves that the FRC-POD method could obtain rational design flood estimation and is worth further study. Full article

An accurate constitutive model for fiber-reinforced concrete (FRC) is fundamental for analyzing and designing FRC structures. The recently released fib Model Code 2020 (MC2020) includes significant modifications to the tensile constitutive model for FRC, enhancing its accuracy. However, it has been observed that the applicability of this model for certain types of FRC is limited due to its overly simplified post-cracking mechanical assumptions. This is particularly evident in structural FRC, where the fiber pull-out force reaches its maximum at a large fiber slip, resulting in a load decrease before increasing again after the notched beam cracks. In that case, the bilinear assumption in the stress–strain model of MC2020 for post-cracking is insufficient to reflect the fiber mechanism and the mechanical properties of FRC at small crack widths. Therefore, based on the characteristics of fiber pull-out in structural FRC, this paper proposes a trilinear post-cracking stress–strain model to reflect the fiber pull-out mechanism more accurately and better analyze the performance of FRC structures in the serviceability limit state. Through an analysis of experimental data and numerical simulation studies on steel fiber-reinforced concrete (SFRC) notched beams, the parameters for the proposed trilinear constitutive model are determined and validated, and the results indicate that the stress value at the new inflection point in the post-cracking trilinear model should be 0.8f_Fts (the serviceability residual strength of the FRC). Although the proposed trilinear model seems similar to the trilinear model provided in MC2020, it is developed based on fiber pull-out behavior, whereas the trilinear model in MC2020 was mainly developed to eliminate numerical singularities. Finally, while the models in MC2020 perform well in evaluating the ultimate limit state performance, the proposed constitutive model can serve as a supplement, especially when serviceability limit state performance is considered. Full article

Fiber-reinforced concrete (FRC) mixtures often face challenges in the fresh state, which are typically addressed using high Portland cement (PC) content or chemical admixtures, obstructing sustainability efforts in the construction industry. Therefore, this study employs advanced mixed design techniques, specifically particle packing models (PPMs), to proportion eco-efficient FRC mixtures with reduced cement content (<300 kg/m³) while achieving desirable fresh and hardened state properties. Twelve low-cement (LC) FRC mixtures, containing limestone filler (LF) as an inert material and a partial replacement for PC, were designed with a water-to-cement ratio of 0.64, incorporating two fiber types (polypropylene and steel) at varying contents (0.5% and 1.0% by volume) and lengths (38 mm and 50 mm). PPM-designed mixtures used two coefficients of distribution (q-factors: 0.21 and 0.26) and were evaluated for fresh (VeBe time, slump, and rheology) and hardened (compressive strength and flexural performance) state properties. Results show that PPM-designed FRC mixtures achieved up to 70% higher compressive strength and up to 64% greater flexural capacity compared to conventional mixes (i.e., American Concrete Institute—ACI), despite using 20% less cement. Additionally, PPM mixtures exhibited higher VeBe times (up to 24 s) and yield stress, reflecting improved packing density, while demonstrating shear-thinning behavior for practical applications (i.e., pumped or vibrated concrete). Finally, the findings demonstrate that PPMs enable the development of eco-efficient, low-cement FRC mixtures with similar or improved hardened state performance and reduced environmental impact. Full article

Hazelnut processing generates a variety of by-products, including skins, shells, and defatted (DFT) flour, which contain valuable bioactive compounds. These by-products are rich in polyphenols, fibers, and other molecules that are suitable for incorporation into nutraceutical and cosmetic products. The efficiency of three natural deep eutectic solvents (NADES), such as betaine/sorbitol/water (BS), fructose/lactic acid/water (FL), and fructose/glycerol/water (FG) was compared with a control (C) extractant (ethanol/water). These NADES were combined with two extraction techniques: a conventional method involving heat and magnetic stirring, and ultra-sound-assisted extraction (US). The free radical scavenging capacity (FRC), total phenolic content (TPC), and the polyphenolic profile (HPLC) were evaluated. BS NADES exhibited superior efficiency for the extraction from the skin and shell, while FL was optimal for defatted flour. Although the skin is the least abundant hazelnut processing by-product, it exhibited the highest polyphenol content and antiradical activity, indicating potential for cosmetic applications. The suitability of DFT flour, skin, and the residual panel of extracts for thermochemical and biochemical conversion processes was investigated. Some of the materials were found to be conducive to thermochemical conversion, while others were suitable for anaerobic digestion. Full article

The structural use of fibre-reinforced concrete (FRC) has shown to be an attractive alternative for certain structural elements, being especially suitable to withstand shear stresses in concrete beams. In the case of longitudinal steel bars to support bending stresses, the reductions are of interest. However, in the case of shear stress, it is possible to eliminate the stirrup reinforcement in certain areas. In such a case, the use of FRC may eliminate not only the material but also the tasks of preparing and placing reinforcement, achieving significant savings in labour and allowing a faster execution, avoiding human error, and providing greater security to the work. This study was developed with the aim of assessing a basic practical application of FRC for shear strength. A series of graphics have been made to be used as a calculation tool. The typical structural elements of buildings subjected to bending and shear stress have been tested and analysed. The results for steel fibre-reinforced concrete (SFRC) and polyolefin fibre-reinforced concrete (PFRC) show that fibre can substitute, to some extent, part of the longitudinal reinforcement needed to provide the required flexural strength. Additionally, the fibres can reduce or even eliminate the need for stirrups for shear strength, which leads to savings in cost and execution time. Full article

Due to its high axial bearing capacity and good ductility, the embedded steel plate composite shear wall structure has become one of the most widely used lateral force-resisting structural members in building construction. However, bending failure is prone to occur during strong earthquakes, and the single energy dissipation mechanism of the plastic hinge zone at the bottom leads to the concentration of local wall damage. To improve the embedded steel plate composite shear wall structure, the plastic hinge zone of the composite shear wall is replaced by fiber-reinforced concrete (FRC) and analyzed by ABAQUS finite element simulation analysis. Firstly, the structural model of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is established and the accuracy of the model is verified. Secondly, the effects of steel ratio, longitudinal reinforcement ratio, and FRC strength on the bearing capacity of composite shear walls are analyzed by numerical simulation. Finally, a method for calculating the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. It is shown that the displacement and load curves and failure modes of the model are basically consistent with the experimental results, and the model has high accuracy. The axial compression ratio and FRC strength have a great influence on the bearing capacity of composite shear walls. The calculation formula of the normal section bending capacity of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. The calculated values of the bending capacity are in good agreement with the simulated values, which can provide a reference for its engineering application. Full article

Offshore mariculture is critical for global food security and economic development. Advances in deep learning and data-driven approaches, enable the rapid and effective monitoring of offshore mariculture distribution and changes. However, detector performance depends heavily on training data quality. The lack of standardized classifications and public datasets for offshore mariculture facilities currently hampers effective monitoring. Here, we propose to categorize offshore mariculture facilities into six types: TCC, DWCC, FRC, LC, RC, and BC. Based on these categories, we introduce a benchmark dataset called OMAD-6. This dataset includes over 130,000 instances and more than 16,000 high-resolution remote sensing images. The images with a spatial resolution of 0.6 m were sourced from key regions in China, Chile, Norway, and Egypt, from the Google Earth platform. All instances in OMAD-6 were meticulously annotated manually with horizontal bounding boxes and polygons. Compared to existing remote sensing datasets, OMAD-6 has three notable characteristics: (1) it is comparable to large, published datasets in instances per category, image quantity, and sample coverage; (2) it exhibits high inter-class similarity; (3) it shows significant intra-class diversity in facility sizes and arrangements. Based on the OMAD-6 dataset, we evaluated eight state-of-the-art methods to establish baselines for future research. The experimental results demonstrate that the OMAD-6 dataset effectively represents various real-world scenarios, which have posed considerable challenges for current instance segmentation algorithms. Our evaluation confirms that the OMAD-6 dataset has the potential to improve offshore mariculture identification. Notably, the QueryInst and PointRend algorithms have distinguished themselves as top performers on the OMAD-6 dataset, robustly identifying offshore mariculture facilities even with complex environmental backgrounds. Its ongoing development and application will play a pivotal role in future offshore mariculture identification and management. Full article

Experimental and computational research on the behavior of small-scale and large-scale fiber-reinforced concrete (FRC) beams is presented in this paper. The experimental part included the small-scale bending tests, which were conducted on three 1.3 m long by 0.1 m wide by 0.15 m high rectangular simply supported beams, and the large-scale test that was conducted on 12.8 m long by 0.2 m wide by 1.3 m two-chords girder. The concrete mixture in the large-scale test was designed with environmentally more justifiable supplementary materials (binder and fibers), striving for sustainable excellence. To accurately predict the mechanical behavior of tested models, a numerical model incorporating the real nonlinear materials laws is used. A numerical model based on finite element analysis (FEA) is developed. The FEA model is created using a smeared crack approach with a constitutive law for the tensile behavior of FRC derived from an inverse analysis based on prism bending tests. The numerical model is validated against experimental results and the accuracy of numerical predictions based on finite element modeling showed a good correlation with the test data. The FEA-based model makes it easier to predict how FRC structures fail under transversal loading and can serve as a foundation for creating new design processes. Additionally, the presented research is aimed at the feasibility of recycled steel FRC field application in building structures. The usage of recycled steel fibers could achieve environmental benefits through the adoption of sustainable materials. The present study showcased the possibility of modeling reinforced concrete structural building parts made with recycled steel fibers using available software. Full article

Real-time structural health monitoring (SHM) and accurate diagnosis of imminent damage are critical to ensure the structural safety of conventional reinforced concrete (RC) and fiber-reinforced concrete (FRC) structures. Implementations of a piezoelectric lead zirconate titanate (PZT) sensor network in the critical areas of structural members can identify the damage level. This study uses a recently developed PZT-enabled Electro-Mechanical Impedance (EMI)-based, real-time, wireless, and portable SHM and damage detection system in prismatic specimens subjected to flexural repeated loading plain concrete (PC) and FRC. Furthermore, this research examined the efficacy of the proposed SHM methodology for FRC cracking identification of the specimens at various loading levels with different sensor layouts. Additionally, damage quantification using values of statistical damage indices is included. For this reason, the well-known conventional static metric of the Root Mean Square Deviation (RMSD) and the Mean Absolute Percentage Deviation (MAPD) were used and compared. This paper addresses a reliable monitoring experimental methodology in FRC to diagnose damage and predict the forthcoming flexural failure at early damage stages, such as at the onset of cracking. Test results indicated that damage assessment is successfully achieved using RMSD and MAPD indices of a strategically placed network of PZT sensors. Furthermore, the Upper Control Limit (UCL) index was adopted as a threshold for further sifting the scalar damage indices. Additionally, the proposed PZT-enable SHM method for prompt damage level is first established, providing the relationship between the voltage frequency response of the 32 PZT sensors and the crack propagation of the FRC prisms due to the step-by-step increased imposed load. In conclusion, damage diagnosis through continuous monitoring of PZTs responses of FRC due to flexural loading is a quantitative, reliable, and promising application. Full article

The regulation of upstream cascade reservoirs has significantly altered the downstream hydrologic regime and should be taken into account in design flood estimation. The current flood regional composition (FRC) methods do not consider the unfavorable situations for reservoir flood control operation. In this paper, a novel framework, the most unfavorable flood regional composition (MUFRC) method, was proposed based on flood risk analysis to estimate design flood in the cascade reservoir operation period. The cascade reservoirs in the Yalong River basin were selected as a case study. The results indicated that (1) the proposed MUFRC method would allocate more flood volume to the downstream uncontrolled sub-basin, and the precise definition of flood disaster loss could have a significant impact on the MUFRC method for the rational estimation of design flood. (2) The 1000-year design flood peak, and 3-day and 7-day flood volumes at the outlet section estimated by the MUFRC method are 15,400 m³/s, 3.91, and 8.42 billion m³, respectively, which are higher than the values estimated by other FRC methods. (3) The flood control water level in the downstream reservoir can be adjusted for the reduction in design floods in the operation period, which can additionally generate 460 million kW·h (+1.82%) of hydropower during the flood season. A comparison study and sensitivity analysis further proved that the MUFRC method can rationally allocate flood volume while balancing the flood risk and comprehensive utilization benefits, which is worth further study and practical application. Full article

Material optimization was one of the challenges for achieving cost-competitive solutions when concrete was introduced in construction, leading to new structural shapes for both civil works and buildings. As concrete construction became dominant, saving material was given less significance, and the selection of the structural typology was mostly influenced by construction or architectural considerations. Simple and non-time-consuming methods for building thus arose as the dominant criteria for design, and this led to the construction of less efficient structures. Currently, the awareness of the environmental footprint in concrete construction has brought the focus again to the topic of structural efficiency and material optimization. In addition, knowledge of material technology is pushing the use of cements and binders with lower environmental impact. Within this framework, Fiber-Reinforced Concrete (FRC) has been identified as a promising evolution of ordinary concrete construction. In this paper, a discussion is presented on the structural properties required for efficient design, focusing on the toughness and deformation capacity of the material. By means of several examples, the benefits and potential application of limit analysis to design at the Ultimate Limit State with FRC are shown. On this basis, the environmental impact of a tailored mix design and structural typology is investigated for the case of slabs in buildings, showing the significant impact that might be expected (potentially reducing CO₂-eq emissions to half or even less in slabs when compared to ordinary solutions). Full article