Search Results (5,601)

This article presents the results of a systematic review investigating the potential of agricultural wastes as sustainable and low-carbon alternatives in reinforced concrete (RC) production. Background: The depletion of natural resources and the environmental burden of conventional construction materials necessitate innovative solutions to reduce the carbon footprint of construction. Agricultural wastes, including coconut shells (CSs), rice husk ash (RHA), and palm oil (PO) fuel ash, emerge as promising materials due to their abundance and mechanical benefits. Objective: This review evaluates the potential of agricultural wastes to improve sustainability and enhance the mechanical properties of RC structural elements while reducing carbon emissions. Design: Studies were systematically analyzed to explore the sources, classification, and material properties of agro-wastes (AWs), with a particular focus on their environmental benefits and performance in concrete. Results: Key findings demonstrate that AWs enhance compressive strength, tensile strength, and modulus of elasticity while reducing the carbon footprint of construction. However, challenges such as variability in material properties, limited long-term durability data, and lack of standardized guidelines hinder their broader adoption. Conclusions: AWs hold significant potential as sustainable additives for RC elements, aligning with global sustainability goals. Future research should address material optimization, lifecycle assessments, and regulatory integration to facilitate their mainstream adoption in construction. Full article

A dysphagia diet is a special dietary programme. The development and design of foods for dysphagia should consider both swallowing safety and food nutritional quality. In this study, we investigated the rheological properties (viscosity, thixotropy, and viscoelasticity), textural properties, and swallowing behaviour of commercially available natural, pregelatinised, acetylated, and phosphorylated maize starch and tapioca starch. The results showed that all the samples belonged to food grade 3 in the framework of the International Dysphagia Dietary Standardization Initiative (IDDSI) and exhibited shear-thinning behaviour in favour of dysphagia patients, except for the sample containing pregelatinised starch, which was grade 2. Rheological tests showed that the samples had good structural recovery properties. At the same starch concentration, the elastic modulus of phosphorylated cassava starch FSMP was significantly greater than that of the starch solution, whereas that of acetylated starch was significantly less than that of the starch solution, and the combination of acetylated starch and protein led to a significant viscosity reduction phenomenon, resulting in FSMPs with good stability and fluidity; this may provide an opportunity for the incorporation of more high-energy substructures. The textural results showed that all the samples possessed textural properties of low hardness, low adhesion, and high cohesion, all of which could be used as food for dysphagia patients. This study may provide a theoretical basis for the creation and design of novel nutritional foods for dysphagia. Full article

This study presents analytical solutions grounded in three-dimensional (3D) thermo-elasticity theory to predict the bending behavior of cross-laminated timber (CLT) panels under thermo-mechanical conditions, incorporating the orthotropic and temperature-dependent properties of wood. The model initially utilizes Fourier series expansion based on heat transfer theory to address non-uniform temperature distributions. By restructuring the governing equations into eigenvalue equations, the general solutions for stresses and displacements in the CLT panel are derived, with coefficients determined through the transfer matrix method. A comparative analysis shows that the proposed solution aligns well with finite element results while offering superior computational efficiency. The solution based on the plane section assumption closely matches the proposed solution for thinner panels; however, discrepancies increase as panel thickness rises. Finally, this study explores the thermo-mechanical bending behavior of the CLT panel and proposes a modified superposition principle. The parameter study indicates that the normal stress is mainly affected by modulus and thermal expansion coefficients, while the deflection of the panel is largely dependent on thermal expansion coefficients but less affected by modulus. Full article

The accurate calibration of snow parameters is necessary to establish an accurate simulation model of snow, which is generally used to study tire–snow interaction. In this paper, an innovative parameter inversion method based on in situ test results is proposed to calibrate the snow parameters, which avoids the damage to the mechanical properties of snow when making test samples using traditional test methods. A coupled Eulerian–Lagrangian (CEL) model of plate loading in snow was established; the sensitivity of snow parameters to the macroscopic load–sinkage relationship was studied; a plate-loading experiment was carried out; and the parameters of snow at the experimental site were inverted. The parameter inversion results from the snow model were verified by the experimental test results of different snow depths and different plate sizes. The results show the following: (1) The material cohesive, angle of friction, and hardening law of snow have great influence on the load–sinkage relationship of snow, the elastic modulus has a great influence on the unloading/reloading stiffness of snow, and the influence of density and Poisson’s ratio on the load–sinkage relationship can be ignored. (2) The correlation coefficient between the inversion result and the matching test data is 0.979, which is 0.304 higher than that of the initial inversion curve. (3) The load–sinkage relationship of snow with different snow depths and plate diameters was simulated by using the model parameter of inversion, and the results were compared with the experimental results. The minimum correlation coefficient was 0.87, indicating that the snow parameter inversion method in this paper can calibrate the snow parameters of the test site accurately. Full article

This study compared the use of cellulose nanofibrils (CNF) and lignocellulose nanofibrils (LCNF) in different concentrations to reinforce the poly(vinyl alcohol) (PVA) matrix. Both nanofillers significantly improved the elastic modulus and tensile strength of PVA biocomposite films. The optimum concentration of CNF and LCNF was 6% relative to PVA, which improved the tensile strength of the final PVA biocomposite with CNF and LCNF by 53% and 39%, respectively, compared to the neat PVA film. The addition of LCNF resulted in more elastic films than the addition of CNF to the PVA matrix. The elongation at break of the PVA biocomposite with 2% of LCNF was more than 100% higher than that of the neat PVA film. The integration of tannic acid (TA) into the PVA-LCNF system resulted in antioxidant-active and more water-resistant PVA biocomposites. The three-component biocomposite films with 2 and 6% LCNF and 10% TA exhibited a more than 20° higher contact angle of the water droplet on the surfaces of the biocomposite films and absorbed more than 50% less water than the neat PVA film. New formulations of biocomposite films have been developed with the addition of LCNF and TA in a polymeric PVA matrix. Full article

The paper presents experimental studies on the influence of a simultaneous, appropriately proportioned combination of microsilica and fly ash additives on the physical and mechanical properties of ultra-high-performance concretes (UHPCs). Concrete mixtures with the addition of microsilica in the amount of 6.7–14.7% and fly ash in the amount of 8.3–26.7% were analyzed, assuming a constant content of cement, water and superplasticizer. Experimental studies were carried out regarding the consistency of the fresh concrete mixtures and on the compressive strength, flexural strength, tensile splitting strength, secant modulus of elasticity, depth of penetration of water under pressure into hardened concrete and water absorption. The analysis of mechanical properties was carried out during a long maturation period from 2 to 90 days. Additionally, the influence of the cost of component materials on the final cost of concrete was taken into account. The test results indicate the effectiveness of the use of microsilica and fly ash additives in ultra-high-performance concretes and possible directions for optimizing their proportions in order to achieve the intended physical and mechanical properties. The best strength properties were obtained for concrete containing 16.7% fly ash and 13.3% microsilica. The highest resistance to water penetration and absorption under pressure was characterized by concretes containing an increased content of microsilica up to 14.7%. Full article

In order to clarify the influence of the uncertain parameters of a bridge numerical model for seismic isolation design on the calculation results of structural seismic demand and to improve the accuracy of bridge seismic isolation design, a refined numerical model of a seismic isolation continuous girder bridge was established. The uncertainty of the model parameters was sorted out at two classification levels of the seismic isolation device system and the non-isolated system, and the sensitivity of the structural parameters was systematically analyzed by using the tornado diagram and the first-order second-moment method. The uncertain factors that have a great influence on the seismic response of the bridge structure in the seismic isolation design are bulk density coefficient, bearing friction coefficient, clay ultimate resistance, damping ratio, elastic modulus, clay ultimate deformation, and isolation bearing fusing force. The impact of the seismic isolation bearing’s melting force is particularly significant during periods of low peak acceleration. It was observed that the selection results remained largely unchanged despite the consideration of the collision effect. This finding serves as a valuable reference for the design and calculation of seismic isolation measures in continuous beam bridges. Full article

Background: The aim of this study was to evaluate the influence of acidic beverages on the mechanical properties of various dental resin-based materials. Material and Method: A total number of 160 samples were prepared using four types of resin-based materials—Group A (n = 40): flowable composite, Group B (n = 40): heavy-flow composite, Group C (n = 40): resin-based sealant and Group D (n = 40): nano-hybrid composite. Then, the samples were distributed into four subgroups according to the submersion solution: a (n = 10): artificial saliva, b (n = 10): coffee, c (n = 10): cola and d (n = 10): red wine. The Vickers microhardness, Young’s modulus of elasticity and scratch resistance were assessed using a CETR UMT-2 tribometer. Results: The obtained results showed that 14-day submersion of the resin-based materials in coffee, cola and red wine solutions significantly (p < 0.05) decreased the microhardness values (VHN), Young’s modulus of elasticity and scratch resistance. Fourteen days of storage in coffee decreased the microhardness values of flow resin from 117.5 to 81.59 VHN (p < 0.001) whereas the values of the nanohybrid resin decreased from 125.5 to 89.4 (p < 0.001). The elasticity modulus of the heavy flow resin showed a decline from 15.57 to 10.50 GPa after 14 days’ submersion in coffee (p < 0.001), and from 21.29 to 13.10 GPa for the nanohybrid resin after immersion in cola (p < 0.001). For the scratch test, the resin-based sealant showed a significant decrease after 14 days of storage in coffee, from 0.34 to 0.02 units. Conclusions: The submersion of conventional nanohybrid, flowable, heavy-flow composite resins and resin-based sealants in coffee, cola and red wine solutions changes the mechanical properties (Young’s modulus of elasticity, Vickers microhardness and scratch resistance). The most resistant resin-based material to acid attack was the conventional nanohybrid composite resin, followed by heavy flow resin, flowable resin and resin-based sealant. Full article

Difficulty in clarifying the deformation characteristics of deep rocks under a high water pressure environment is a technical bottleneck restricting the safe operation of large hydropower stations. In order to study the effect of reservoir water level changes on the mechanical behavior of deep limestone, a series of mechanical tests were conducted under different dynamic high water pressure environments using a self-developed hydraulic loading test device. The test results show that the unsaturated limestone always undergoes compressive deformation during the linear increase in external water pressure, and the saturated limestone changes its deformation state from compression to expansion during the linear decrease in external water pressure. The stress–strain curve of limestone shows apparent hysteresis characteristics during the cyclic increase and decrease in external water pressure. Overall, the rock strain rate showed a significant negative correlation with the external water pressure, and the rock deformation modulus showed a certain positive correlation with the external water pressure. During hydraulic loading, saturated rocks had a smaller range of variation in the strain rate and deformation modulus and were more resistant to deformation than unsaturated rocks. Limestone was subjected to both external water pressure and internal pore water pressure in a cyclic cycle, where pore water pressure promotes pore creation and expansion, while external water pressure prevents water from degrading the pore structure. The periodic change of water pressure has a significant influence on rock mechanics and deformation behavior, and the rock mass will undergo elastic deformation, plastic deformation, and even fracture. Further study of this deformation rule can provide a more accurate theoretical basis for the safe operation of water conservancy projects. Full article

Offshore wind power is a hot spot in the field of new energy, with foundation construction costs representing approximately 30% of the total investment in wind farm construction. Offshore wind turbines are subjected to long-term cyclic loads, and seabed materials are prone to causing stiffness degradation. The accurate disclosure of the mechanical properties of marine soil is critical to the safety and stability of the foundation structure of offshore wind turbines. The stiffness degradation laws of mucky clay and silt clay from offshore wind turbines were firstly investigated in the study. Experiments found that the variations in the elastic modulus presented “L-type” attenuation under small cyclic loads, and the degradation coefficient fleetingly decayed to the strength progressive line under large cyclic loads. Based on the experimental results, a random forest prediction model for the elastic modulus of the submarine soil was established, which had high prediction accuracy. The influence of testing the loading parameters of the submarine soil on the prediction results was greater than that of the soil’s physical property parameters. In criticality, the CSR had the greatest impact on the prediction results. This study provides a more efficient method for the stiffness degradation assessment of submarine soil materials in offshore wind farms. Full article

Microwave-assisted rock breaking is recognized as an effective technology for reducing tool wear and enhancing rock-breaking efficiency. In this study, basalt rock was irradiated with a microwave power of 3 kW and 6 kW for 30 s, 60 s, 90 s, and 120 s. Subsequently, uniaxial compression, uniaxial loading and unloading, and acoustic emission tests were performed. The damage evolution of basalt was assessed through non-destructive acoustic testing methods and nuclear magnetic resonance (NMR) techniques. The results showed that the P-wave velocity, uniaxial compressive strength (UCS), and modulus of elasticity (E) exhibited varying degrees of deterioration as the microwave radiation time increased. An increase in microwave radiation time and power led to heightened acoustic emission activity in basalt and a significant rise in the proportion of shear cracks during uniaxial compression. From an energy perspective, microwave irradiation decreased the energy storage capacity of the basalt specimen prior to its peak point, with increased power and duration. At a microscopic level, porosity and the macroporous fractal dimension increased with extended microwave radiation time and power, indicating that microwave irradiation facilitated the growth of larger fractal pore structures. The findings of this study offer scientific insights for the application of microwave-assisted rock crushing. Full article

Generative adversarial neural networks with a variational autoencoder (VAE-GANs) are actively used in the field of materials design. The synthesis of random structures with nonrepeated geometry and predetermined mechanical properties is important for solving various practical problems. Geometric parameters of such artificially generated random structures can vary within certain limits compared to the training dataset, causing unpredicted fluctuations in their resulting mechanical response. This study investigates the statistical variability of mechanical and morphological characteristics of random 3D models reconstructed from 2D images using a VAE-GAN neural network. A combined multitool method employing different mathematical and statistical instruments for comparison of the reconstructed models with their corresponding originals is proposed. It includes the analysis of statistical distributions of elastic properties, morphometric parameters, and stress values. The neural network was trained on two datasets, containing models created based on Gaussian random fields. Statistical fluctuations of the mechanical and morphological parameters of the reconstructed models are analyzed. The deviation of the effective elastic modulus of the reconstructed models from that of the original ones was less than 5.7% on average. The difference between the median values of ligament thickness and distance between ligaments ranged from 3.6 to 6.5% and 2.6 to 5.2%, respectively. The median value of the surface area of the reconstructed geometries was 4.6–8.1% higher compared to the original models. It is thus shown that mechanical properties of the NN-generated structures retain the statistical variability of the corresponding originals, while the variability of the morphology is highly affected by the training set and does not depend on the configuration of the input 2D image. Full article

This paper focuses on analysing the structural performance of fast-grown hardwood versus softwood glued laminated timber (GLT or glulam) beams with the aim to evaluate the potential structural use of the two main species planted in the country. In Uruguay, the first forest plantations date from the 1990s and are comprised mainly of Eucalyptus ssp. and Pinus spp. No one species were planted for a specific industrial purpose. However, while eucalyptus was primarily destined for the pulp industry, pine, which is now reaching its forest rotation, had no specific industrial destination. Timber construction worldwide is mainly focused on softwood species with medium and long forest rotation. The objective of the present work is, therefore, to analyse and compare the potential of eucalyptus (Eucalyptus grandis) and loblolly/slash pine (Pinus elliottii/taeda) to produce glulam beams for structural purposes. Experimental tests were made on sawn timber and GLT beams manufactured under laboratory conditions for both species. The relationship between the physical and mechanical properties of sawn timber showed that, for similar characteristic values of density (365 kg/m³ for pine and 385 kg/m³ for eucalyptus), and similar years of forest rotation (20–25 years for pine and around 20 years for eucalyptus) and growth rates, the structural yield of eucalyptus was higher compared to that of pine. The superior values of modulus of elasticity found in the hardwood species explained this result. Since there is no strength classes system for South American wood species, the European system was the basis for estimating and assigning theoretical strength classes from the visual grades of Uruguayan timbers. For sawn timber, a C14 strength class for pine and C20 for eucalyptus were assigned. Results showed that pine GLT could be assigned to a strength class GL20h, and eucalyptus glulam to GL24h and GL28h, demonstrating the potential of both species for producing glulam beams. Even though eucalyptus showed a better yield than pine, the technological process of manufacturing eucalyptus glulam was more challenging in terms of drying time and gluing than in the case of pine, which derivates in higher economic costs. Full article

The introduction of 3D printing technology has broadened manufacturing possibilities, allowing the production of complex cellular geometries, including auxetic and curved plane structures, beyond the standard honeycomb patterns in sandwich composite materials. In this study, the effects of cell design parameters, such as cell geometry (honeycomb and auxetic) and cell size (cell thickness and width), are examined on acrylonitrile butadiene styrene (ABS) core materials produced using fusion deposition modeling (FDM). They are produced as a result of the epoxy bonding of carbon epoxy prepreg composite materials to the surfaces of core materials. Increasing the wall thickness from 0.6 mm to 1 mm doubled the elastic modulus of the re-entrant structures (5 GPa to 10 GPa) and improved compressive strength by 50–60% for both geometries. In contrast, increasing cell size from 6 mm to 10 mm significantly reduced compressive strength by 80% (from 2.5–2.8 MPa to 0.5–0.6 MPa) and elastic modulus by 70–78% (from 9–10 GPa to 2–3 GPa). Flexural testing showed that the re-entrant cores, with a maximum load capacity of 148 N, exhibited more uniform deformation, while the honeycomb cores achieved a higher load capacity of 273 N but were prone to localized failures. These findings emphasize the directional anisotropy and specific advantages of auxetic and honeycomb designs, offering valuable insights for lightweight, high-strength structural applications. Full article

The influence of different pore sizes on the compressive strength and elastic modulus of recycled concrete is an important issue in the academic circle. Aiming at this problem, a quantitative characterization model of the compressive strength and elastic modulus of recycled concrete based on pore grading was established in this paper. The compressive strength, elastic modulus, porosity and distribution of pore size of recycled concrete were measured by a concrete test and nuclear magnetic resonance technology, and the influences of different pore sizes on the compressive strength and elastic modulus of recycled concrete were analyzed, and the rationality of the quantitative characterization model was verified. The results showed that the compressive strength and elastic modulus of recycled concrete decreased with the increase in the recycled coarse aggregate replacement rate, and the decrease was more obvious with the increase in the substitution rate. The peak pore diameter in the distribution curve of porosity and pore diameter of recycled concrete increased, and the proportion of pore diameter above 50~200 nm and 200 nm also increased. The pore sizes, including those below 20 nm and 20~50 nm, had a positive correlation with the compressive strength and elastic modulus of recycled concrete, while the pore sizes, including those above 50~200 nm and 200 nm, had a negative correlation with the compressive strength and elastic modulus of recycled concrete. The test results of recycled concrete verify that the quantitative characterization model could better characterize the compressive strength and elastic modulus of recycled concrete. Full article