Flexural Strength Research Articles

Structural Behavior of Self-Compacting Bendable Mortar Beams reinforced by GFRP Bars under Monotonic Loads

Flexible or bendable concrete is an Engineered Cementitious Composite (ECC) that exhibits ductile material properties, in contrast to the brittle nature of conventional concrete. The material composition of conventional concrete is modified in order to impart a flexible nature to the material. This research presents the findings of an experimental study examining the flexural response of self-compacting bendable concrete beams reinforced by Glass Fiber Reinforced Polymers (GFRP) bars under a symmetrical two-point load. The experimental work comprised the casting of eight reinforced beams. The dimensions of all beams were identical: an overall height of 150 mm, a width of 100 mm, and a total length of 1,000 mm. The beams were classified into three groups based on the type of variables adopted and the type of the strengthening method employed, the percentage of steel fibers (1%, 1.5%, and 2%), and the percentage of Polyvinyl Alcohol (PVA) (0.2%, 0.3%, and 0.4%) were also considered. The following measurements were taken: the first cracking load, midspan vertical deflections, concrete surface strains, and the ultimate load capacity. Additionally, the crack patterns were recorded and the failure mode was observed, in addition to the mechanical properties of self-mortar bendable concrete (both fresh and hardened). The results indicated that an increase in the PVA ratio from 0.2% to 0.3% and 0.4% resulted in a notable rise in the modulus of rupture and modulus of elasticity, by approximately 16% and 40%, respectively, and 0.09% and 2%, respectively. The ductility of the beams increased with the steel fiber ratio due to enhanced flexural and splitting properties, which is a positive outcome. This allows for more caution to be exercised before the beam reaches its limit of stability. Furthermore, the value of deflection at maximum load increases with the increase of steel fiber content due to the increase in load capacity.

Utilization of Eggshell Powder as a Green Mortar Material

Recycling waste in cementitious materials promotes sustainable construction. It helps to prevent the depletion of natural resources while also reusing abundant recyclable wastes. Eggshells are one of these wastes that is being generated in large quantities because eggs are not expensive and have high nutritional value. On the other side, eggshell has a high content of calcium carbonate. It has a similar composition to the limestone powder used to produce Portland cement. This work investigates the effect of replacing a part of the cement with eggshell powder on mortar properties. The substitution rates were 5 %, 10 %, and 15 % of the cement’s mass. The results were compared with those of an ordinary mortar for the following properties: workability, compressive strength, flexural tensile strength, density in the hardened state, water absorption by total immersion, porosity accessible to water, depth of water penetration under pressure and chemical attack by sulfuric acid. The experimental results show that adding eggshell powder as a partial cement substitute up to 10% improved workability, increased compressive strength by about 10 % and flexural tensile strength by about 20 %, reduced density, and produced a more durable mortar by reducing porosity, water absorption, and water penetration depth under pressure. On the other hand, it decreased resistance to chemical attack by sulfuric acid. Thus, eggshell powder could be used in future construction materials to reduce carbon dioxide emissions.

Mechanical, machinability and water absorption properties of novel kenaf fiber, glass fiber and graphene composites reinforced with epoxy

This paper aims to fabricate a novel kenaf fiber, glass fiber, graphene composite reinforced with epoxy, and to study its water absorption, mechanical and machining properties. Natural fiber composites seek numerous applications nowadays due to its high strength is to weight ratio, high impact resistance, thermal stability, and recyclability. The literature study on natural fiber composites indicates lack of research on Kenaf fibers reinforced with E-glass fibers in conjunction with 0.5% and 1.0% of graphene. Hence, this research focuses on Kenaf fiber with percentage composition of graphene was varied as 0.5%, and 1.0%, by weight of the holding matrix and with/without incorporation of glass fiber. Suitable surface modifications were done by treating natural fibres by 0.5% NaOH for better adhesion of fibre and epoxy resin. Sonication and Cetyl trimethyl ammonium bromide (CTAB) treatments were also done to realize the fine scattering of graphene in the epoxy matrix in order to achieve better mechanical behaviour. Moulds were prepared as per D-638 ASTM standards. The treated fibres were then arranged in the mould by the conventional hand layup technique. The main objectives of this study are to conduct tensile, flexural, Impact, water absorption, machinability, and FTIR test. Result shows that the incorporation of graphene in natural fiber composites showed an increase in tensile strength, flexural strength, and water absorption properties by 27.7%, 53%, and 15% on average, respectively. The composites used in this research find their use in potential applications such as defence, biomedical aids, automobiles, packaging, actuators, etc. These often generate great interest, whenever there is a demand for fabricating lightweight and high strength material.

An Experimental Study on Industrial Concete Pile Foundation in Soft Soil: Comparison of Monolithic and Pile with Welded Joints

This study presents an experimental investigation into the industrial foundation piles. The research carried out employed both destructive and non-destructive testing methods to evaluate the concrete compressive strength and flexural strength capacity of the piles under monotonic loading. The Destructive Test (DT) involves a 28-day cylinder concrete compressive test, while the Non-Destructive Test (NDT) utilizes the Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH) tests. The flexural strength test is conducted using a loading frame, and the results are compared to the GeoPIV-RG, which measures the displacement during the test. The experimental investigations provide insights into the behavior of pile joints when subjected to monotonic load in soft and loose soil. The results indicate a significant difference between the compressive strength obtained from the DT and NDT, with a ratio of 0.64-0.74. Furthermore, the failure occurred at the joints, rather than the welded area, with the ratio of the initial stiffness of the piles with joints to the monolithic pile being 0.15 for zig-zag welded and 0.30 for circular welded, and reaching an average value of 0.225. According to the GeoPIV-RG result, the displacement is similar to the flexural strength test result.

Enhancing mechanical properties of PLA‐based bio composite filament reinforced with horse gram filler for 3D printing applications

AbstractGreen composites for 3D printing have gained significant attention due to the potential of incorporating natural fillers to reduce costs and enhance performance while maintaining environmental benefits. The use of agricultural by‐products, such as horse gram (Hg), not only promotes waste utilization but also seeks to improve the mechanical properties of biopolymers like PLA. In this study, Hg powder was utilized as a natural filler to enhance the mechanical properties of PLA‐based composites. The composites were fabricated with 1%, 2%, 3%, and 4% Hg powder filler content, and the filament was processed through a single screw extruder machine. Their mechanical properties were systematically evaluated to determine the optimal filler ratio. The results indicate that the incorporation of 1% Hg filler into PLA provided superior mechanical performance compared to Neat PLA. Specifically, tensile strength increased by 11.19%, flexural strength improved by 5.32%, and compression strength increased by 5.94%. In contrast, composites with 2% and 3% Hg filler showed a reduction in these mechanical properties, highlighting that the 1% Hg/PLA composite achieves the best balance between strength and filler content. The findings suggest that the 1% Hg/PLA composite offers an optimized combination of tensile, flexural, and compression properties, making it a strong candidate for environmentally sustainable engineering applications such as lightweight structural components, automotive interior parts, and consumer product casings.Highlights One percent Hg filler improved tensile, flexural strength, and hardness through uniform dispersion. Higher filler content (3%–4%) led to agglomeration, reducing composite performance. XRD and SEM analyses revealed reduced PLA crystallinity and structural defects at higher filler levels.

Temperature-dependent effect of nanoscale phase change materials on fresh and hardened cement-based mortar

As smart and innovative materials, temperature-dependent phase change materials (PCMs) can be used to produce environmentally friendly energy-saving concrete. In this study, the fresh and hardened concrete properties of mortars incorporating PCMs in different ratios (0%, 2.5% and 5%) were experimentally investigated. Rheological properties such as slump flow, specific viscosity and yield stress were determined at different temperatures (20–50°C). Time-dependent physical, mechanical and thermal properties such as ultrasound pulse velocity (UPV), electrical resistivity, dynamic modulus of elasticity and compressive and flexural strengths were determined. Thermogravimetric analysis and thermal conductivity tests were also carried out. The experimental findings showed that the workability and hardened properties of mortars decreased with the addition of PCM. However, the rheological properties of the fresh mortar changed depending on the temperature due to the PCM absorbing heat. Therefore, the fresh properties of mortar with PCMs can be controlled by temperature. It was also found that the phase change of mortars with PCM could be obtained by measuring the electrical resistivity or UPV at different temperatures.

Advanced three-dimensional textile technique for fabrication of sisal/flax hybrid fiber green biocomposite with enhanced mechanical, thermal, and sound isolation properties

Natural fibers are regarded as ideal reinforcements for fiber-reinforced composites due to their high specific strength and biodegradability. In this study, three-dimensional orthogonal woven sisal/flax yarn hybrid bio-based epoxy resin composites (3DOWSBCs) were firstly employing a novel three-dimensional orthogonal weaving technique, and their mechanical properties were experimentally examined, and compared with those of traditional lamination composites. Secondly, a finite element model (FEM) was constructed to predict and analyze the shear behaviors of 3DOWSBCs in order to elucidate the strengthening mechanisms of Z-yarns. Additionally, the thermal and acoustic properties also discussed. The results suggested that the flexural strength and shear strength of 3DOWSBCs (141.15 MPa, 22.80 MPa) were 37.9 % and 86.9 % higher than the laminates, respectively. The FEM results demonstrated a strong correlation with the experimental data and revealed that the impact of Z-yarns on the mechanical properties in out-of-plane direction was more significant than that in in-plane direction. Furthermore, 3DOWSBCs had low thermal conductivity (0.29 W/m·K) and high sound transmission loss (63 dB). The environmentally friendly and excellent-performance 3DOWSBCs are a promising semi-structural industrial composites with great potential to alleviate energy consumption and promote sustainable industry development.

Comparison of mechanical and physical behaviors of carbon/basalt/epoxy hybrid composite rod with carbon/glass/epoxy hybrid composite rod used in ACCC conductor core

AbstractThe demand for increased distribution capacity in transmission lines has led to the growing use of hybrid composite rods as the reinforcing core of Aluminum Conductor Composite Core overhead conductors, known as ACCC. These rods usually consist of a carbon fiber‐reinforced epoxy matrix composite core surrounded by an outer shell made of a glass fiber‐reinforced epoxy matrix composite. The outer shell composite can be reinforced with basalt fibers, which are being used more frequently due to their favorable properties. In this research, mechanical properties such as flexural strength, physical properties including density and electrical resistance, and thermal behavior of carbon/basalt/epoxy (CBE) and also carbon/glass/epoxy (CGE) hybrid composite rods fabricated by the pultrusion process have been investigated. The CBE composite exhibited approximately 4% higher mean flexural strength than CGE. Additionally, the CBE composite showed higher thermal stability, as indicated by Thermogravimetric Analysis (TGA). The CGE composite has about 4% higher density than the CGE composite, leading to higher mass per unit length of the resultant ACCC conductor. Finally, the fracture surfaces of hybrid composite rods have been studied using scanning electron microscopy (SEM). The results indicate the better mechanical and thermal properties of carbon/basalt/epoxy hybrid composite rods.Highlights Growing use of hybrid composite rods in ACCC overhead conductors. Hybrid composite rods have a carbon fiber core and glass‐reinforced outer shell. Basalt fibers increasingly used to reinforce the outer shell composite. Pultrusion process used for producing the hybrid composite rods. Fracture surfaces of hybrid composite rods studied using SEM.

Investigation of Concrete Paving Block Characteristics and Performance across Different Shapes and Thicknesses

Concrete Paving Blocks (CPBs) are generally used in pavement structures. Quite often there are differences in the test result characteristics of cube and block-shaped samples. This research aims to analyze the characteristics of differences in height by considering 60 samples from five different factories. The sample dimensions are 200 mm length and 100 mm width with varying heights of 60 mm, 80 mm, and 100 mm. The tests include water absorption, compressive strength, flexural strength, tensile splitting strength, skid resistance, and abrasion resistance. The results of the mortar content show no significant difference between the five sources. According to the findings, the weight loss value depends on strength, and tensile splitting strength is influenced by density, with higher density producing higher tensile splitting strength. It was also found that the compressive strength test method is more realistic when using cube-shaped samples, while beam-shaped samples are more suitable for identifying bending characteristics. Finally, it was shown that the flexural strength value is influenced by density.

The Characteristics of Resin Waste (RW)/Recycled High-Density Polyethylene (R-HDPE) Blends to Enhanced Pavement

Permeable pavement is characterized by open cell structures that enable the drainage of rainfall and snowmelt, as opposed to the runoff observed on impervious pavements. The structural strength of commercial permeable pavement materials is lower than that of conventional pavements due to inherent permeability and structural distinctions. This research focuses on the fabrication of samples using a combination of Resin Waste (RW) and reinforced Recycled High-Density Polyethylene (R-HDPE) in varying ratios of RW (30%, 40%, 50%, 60% and 70% wt/wt). The fabrication process involves a 3-hour heating process at 200°C in a furnace, followed by a 24-hour cure at room temperature. Physical and mechanical properties of the RW/R-HDPE Blends were examined, revealing that the 60% R-HDPE ratio resulted in the lowest density (4.523 g/cm3) and porosity (0.246%). SEM images displayed fewer voids, indicating effective filler dispersion and resin matrix interaction at the 60% resin waste ratio. Tensile strength and stiffness elasticity were maximized at 60% wt/wt of R-HDPE, reaching 3.36 MPa, while the bending strength peaked at 1.1 MPa at the same ratio. The 60% RW/R-HDPE ratio recorded the highest impact strength (26.25 kJ/m2) and energy absorption (1.69 J), showcasing the sample's ability to absorb impact energy through controlled failure mechanisms. In conclusion, the 60% wt/wt RW/R-HDPE Blends exhibit promising potential for enhancing the properties of permeable pavement, particularly in road applications, due to its superior bending and tensile strength.

Calibration and experiments of discrete element flexible model parameters for kiwifruit stalk

A method combining experimental and simulation optimization was used to calibrate parameters to enhance the accuracy of discrete element model parameters during kiwifruit stem separation. First, physical experiments were conducted to determine the intrinsic and contact parameters of kiwifruit stalk. Second, the mechanical parameters of the kiwifruit stalks were determined using three-point bending and shear tests. On this basis, simulation tests were conducted on kiwifruit stalks by combining the Hertz-Mindlin model with a bonding model, and the optimal combination of bonding parameters was confirmed using the bending strength and maximum shear force. Finally, a discrete element model of the kiwifruit was built with the determined bonding parameters and simulated, and the reliability of the model was verified through mechanical tests. The results showed that the density was 867.5 kg/m3, Poisson's ratio was 0.26, the modulus of elasticity was 3.25 × 108 Pa, the recovery coefficient between the fruit stalks and steel parts was 0.365, and the average values of the static and dynamic friction coefficients between the kiwifruit stalks and steel parts were 0.268 and 0.152, respectively. The kiwifruit stem bonding parameters were normal stiffness per unit area kn=7.201×1011 N/m3, shear stiffness per unit area kt=2.379×1011 N/m3, critical normal stress σmax=5.937×108 Pa, critical shear stress tmax = 2.354×109 Pa, and bonded disc radius Rj=0.164 mm. Compared with the results of the mechanical tests, the relative errors of the bending strength and maximum shear of the discrete element model were 2.13% and 2.84%, respectively. The results showed that the discrete element model improves the simulation of the bending and shearing processes of kiwifruit stalks and is capable of characterizing the physical properties of kiwifruit stalks. The results of this study provide a theoretical foundation for the optimal design of end effectors.

Enhancing the mechanical properties of FDM 3D printed PETG parts with high pressure cold isostatic pressing

This study examined the effects of cold isostatic pressing (CIP) as a post-processing method for polyethylene terephthalate glycol-modified (PETG) parts produced by fused deposition modeling (FDM) 3D printing. To analyze the mechanical properties of CIP, 3D printed specimens were subjected to CIP at pressures ranging from 250 to 1000 bar with holding times of 1 to 10 min, followed by tensile, flexural, and interlaminar shear strength tests. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were performed for morphological and chemical property changes. The mechanical properties were generally optimal at 500–750 bar, indicating a significant improvement. SEM analysis revealed that the interlayer gaps and void areas decreased, with the porosity reduced by 4.46 times compared to the untreated samples. XRD analysis showed that the CIP treatment did not significantly alter the chemical structure of PETG and maintained its amorphous characteristics. These results suggest the potential of CIP as an effective post-processing technique that improves the mechanical properties while preserving the basic material characteristics of FDM-printed parts.

Transforming fly ash into value: Sustainable LLDPE-fly ash composites via rotational molding

This study focuses on reducing pollution and promoting sustainability by exploring the use of fly ash (FA), an industrial byproduct, in polymer composites through rotational molding. By incorporating FA into a polymer matrix, the research evaluates the performance of these composites. Results show that the tensile strength increased slightly from 16.54 MPa for pure LLDPE to 17.2 MPa with 5% FA but decreased to 13.5 MPa at 10% FA. The modulus significantly improved, rising from 5.1% to 31.3% with 5% to 20% FA content. Hardness also increased, with a maximum rise of 10.25% at 5% FA and 6.2% at 10% FA. However, elongation at break, bending, and impact strength decreased with higher FA content. The density of the composites increased with up to 10% FA, indicating effective integration of FA particles. These findings demonstrate that FA can be successfully used to develop polymer composites in rotational molding, supporting both environmental sustainability and innovative production practices.

Test and Analysis for Shearing Behavior of Circular CFST Columns

Concrete-filled steel tubular (CFST) structures are well known to possess high strength and ductility. CFST members are used under complex stress states, such as beam–columns, piers, caissons, or other foundation components. Recommendations for the design and construction of concrete-filled steel tubular (CFST) structures were published in 1997 and revised in 2008 in Japan. In the recommendations, calculation methods for the axial strength and flexural strength of CFST columns were established on the basis of experimental results of more than 400 specimens; however, the test results of the columns that failed in shear referred to only 12 specimens in the recommendations. It is necessary to accumulate experimental data on the shear strengths and behaviors of CFST columns. Tests and analyses have been carried out on eight circular CFST column specimens with a shear span ratio of 0.75. The diameter-to-thickness ratio of the steel tube is approximately 34. The shearing capacities of the tests were underestimated by over 20% errors using the calculation method of the CFST Recommendations in Japan. The load versus deformation relations obtained by the tests were well traced by 3D-FEM analysis. The shearing capacities were estimated as an average of 12% errors using 3D-FEM analysis.

An Assessment of Strength Characteristics of Transparent Concrete in Pavement

This study explores the potential of transparent concrete for use in roadway applications, focusing on its ability to transmit light through the incorporation of Plastic Optical Fibres (POFs) within the concrete matrix and evaluating both its mechanical strength and its light transmission capabilities. This material can be applied to various road elements, such as surface illumination, signage, roadblocks, medians, curbs, and areas with changing geometry. The light transmission performance was evaluated using voltage, light sources, and Light-Dependent Resistors (LDRs). A comparative analysis was performed between samples with varying POF content and spacing and traditional concrete. The findings reveal that compressive and flexural strengths remain largely unaffected by the inclusion of POFs up to 1.5% by weight, beyond which a decrease in strength is observed. Additionally, the light transmission efficiency improves significantly with an increase in the POF volume ratios.

Flexural Behavior of High Volume Fly Ash-Self Compacting Concrete Beams to Normal Concrete Beams with Conventional Steel Reinforcement

This research determines the comparison between the flexural behavior of Normal Concrete (NC) beams and High-Volume Fly Ash Self Compacting Concrete (HVFA-SCC) beams. The research data was obtained from full-scale beam tests using four-point loading. Tests were carried out on 6 NC and 6 HVFA-SCC beam specimens with dimensions of 150 mm × 250 mm × 2000 mm. The test specimens varied with main reinforcement of 12 mm, 16 mm, and 19 mm diameter. The results of the studies show that the crack patterns of the NC and HVFA-SCC beams are almost identical to those of the flexural failure mode, while the HVFA-SCC beam has greater ductility than the NC beam. The nominal flexural strength (Mn) of HVFA-SCC beams can be calculated using the Mn formula in ACI 318-19.

Numerical study on the flexural and shear behavior of steel fiber and high‐strength steel combination in ultra‐high‐performance fiber‐reinforced concrete beams under cyclic loading

AbstractFiber‐reinforced concrete consists of hydraulic cement, water, aggregate, and discrete fibers, making it a composite material. These fibers, available in different shapes, sizes, and materials such as steel, polymer, glass, and natural fibers, are commonly utilized in structural applications. The tensile strength of conventional concrete tends to decrease as micro‐cracks develop rapidly under applied stresses. However, incorporating closely spaced fibers can hinder the progression of micro‐cracks, leading to a substantial improvement in both tensile and flexural strengths of concrete. Furthermore, fibers can delay the initiation of tensile cracks, effectively enhancing concrete's ability to withstand tensile strains before failure. As a result, fiber‐reinforced concrete exhibits increased durability and enhanced resistance to impacts compared to plain concrete. This study aims to evaluate and compare the cyclic flexural behavior of a cantilever beam constructed from ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) using reinforcing bars made of high‐strength steel (HSS). The beams contain varying relative proportions of longitudinal reinforcement and steel fibers. Various key performance parameters of the cantilever beam were thoroughly examined, such as load capacity, flexural ductility, failure mode, hysteresis response, energy dissipation, and hardness. The study demonstrated that UHPFRC beams with HSS exhibit good cyclic flexural performance prior to failure.

Mechanical Properties of Recycled Aggregate Concrete with Industrial Waste Ash

This study investigates the performance of concrete incorporating various recycled fine aggregates, including recycled brick aggregates, Fly Ash (FA), and Sugar Cane Bagasse Ash (SCBA). The test results showed that the mechanical properties were adversely affected when utilizing recycled brick or concrete aggregates, whereas FA or SCBA enhanced them. The water absorption potential of recycled bricks was proportional to the reduction in mechanical properties. FA and SCBA enhanced compressive strength and increased flexural strength up to 175.72% and 225.51%, respectively, at 20% replacement. The inclusion of recycled brick and concrete aggregates raised water absorption, while FA and SCBA significantly lowered it, improving the overall performance.

Effect on Mechanical Property of Polypropylene Mixed with Charcoal Waste Ash through Melt Compounding

This study explores the use of charcoal waste ash, a by-product of human activities, as a filler in polypropylene matrices. The samples were mixed using the melt compounding method using an internal mixer at 1wt%, 2wt%, 5wt%, 7wt% and 10wt%. Tensile strength peaked at 29.85MPa at 2wt% while the flexural strength peaked well above pure PP at 45.5MPa at 7wt%. Charcoal waste ash is possible to enhance the mechanical properties of polypropylene, suggesting its potential as a sustainable material in polymer composites.

Characterization and solidification of heavy metals in sintered solid-waste ceramics made from zinc-extraction kiln slag.

Zinc-extraction kiln slag is a hazardous solid waste rich in heavy metals. It is a great challenge to utilize it economically and harmlessly. This study aims to convert this zinc-extraction kiln slag (proportion of 50-60%) into solid-waste ceramics, by simultaneously utilizing other solid waste, fly ash, and desulfurization gypsum. By using X-ray diffraction, leaching experiments, and SEM analysis, the paper studied the solid-waste ceramics 'ability to solidify heavy metals. Under optimal conditions, C5 (zinc-extraction kiln slag, desulfurization gypsum, and fly ash with mass percentages of 60:20:20, at a sintering temperature of 1180°C) shows an excellent performance with 43.02MPa bending strength and 0.74% water absorption. The solidification ratios of Cr, Mn, Ni, Cu, and Zn were all exceed 97%. The main phases in the solid-waste ceramics were diopside and hematite. Diopside can efficiently solidify Zn, Mn, and Ni, while Cr and Cu can be solidified in the minor phase of spinel. During the sintering process, the ceramics produced the liquid phase, which promoted crystallization for solid solution of heavy metals and accelerated densification by elimination of pores. The ceramic system with diopside as the main phase not only shows excellent performance but also effectively solidifies heavy metals. Therefore, it is suitable for the resource utilization of metallurgical solid wastes containing heavy metals.