Decrease In Flexural Strength Research Articles

The Influence of Recycled Coarse Aggregate Content on the Properties of High-Fly-Ash Self-Compacting Concrete

In Vietnam, solid waste from construction activities significantly impacts environmental pollution. Recycled concrete aggregate (RCA), derived from waste concrete, can serve as a coarse aggregate in concrete production. However, compared to natural aggregates, RCA exhibits distinct characteristics, including lower strength, higher water absorption, and an increased angular and rough surface. These properties may influence concrete’s workability, compressive strength, and durability. This research investigates the influence of RCA on the properties of High-Fly-Ash Self-Compacting Concrete (SCC). The study explores various replacement levels of natural coarse aggregate with RCA (0%, 50%, 75%, and 100%), alongside a 50% volume fraction of fly ash. Key concrete properties evaluated include workability, compressive strength, flexural strength, and chloride ion permeability. The findings reveal that using 100% RCA in combination with a high fly ash content (50%) produces SCC that meets workability requirements according to EFNARC standards. However, there are trade-offs: the compressive strength decreases by 4.61%, the flexural strength decreases by 3.1%, and chloride ion permeability increases by 57.57% compared to the control sample (using natural aggregates). Notably, the chloride ion permeability of SCC using 100% RCA falls into the category of low permeability. Doi: 10.28991/CEJ-SP2024-010-04 Full Text: PDF

Effect of temperature on the mechanical behavior of glass fiber reinforced with hollow glass particle-filled epoxy composites

The design of marine ships and aircraft components with hollow glass particle-filled fiber-reinforced composites demands an understanding of their performance under outdoor conditions. The continuous glass fiber-reinforced epoxy matrix filled with hollow glass particles in the range of 0–0.3 vol fraction was prepared by the compression molding machine. The influence of temperature exposure on the mechanical behavior of glass fiber-reinforced hollow glass particle composites was studied by conducting tensile and flexural tests. The temperature exposure varying from room temperature up to 60 °C was used to investigate the effect of service temperature on the hollow glass particle-filled fiber composite specimens. Differential scanning calorimetry (DSC) analysis was conducted to study the glass transition behavior of the composites. The incorporation of microspheres in the glass fiber composites gradually reduced the tensile and flexural strength, while their specific values increased as increasing the microspheres. The hollow glass particle-filled fiber composites tested at 60 °C exhibited a decrease in tensile and flexural strength compared with room temperature. As the température of the test spécimens was nearer to the glass transition value, the polymer chain was softened, leading to a reduction in strength. In contrast, the modulus values remain unaffected by increasing the temperature to 60 °C.

Optimization of physico-mechanical and erosive wear properties of single/multilayer – coated granite filled aluminum alloy composites

Abstract In the present research, uncoated and coated (CrN/SiN–CrN) granite dust reinforced aluminum alloy (AA 1050, AA 5083) composites samples were fabricated using stir casting and their physical, mechanical and slurry erosion behavior were assessed. The study reveal a persistent increase in void content, hardness, impact strength and stress intensity factor for both uncoated and coated alloy with the inclusion of reinforcement. In contrast, flexural strength and corrosion rate decrease continuously with increased granite content and also with the corresponding coating. Multilayer coated 5083 aluminum alloy composite with 6 wt.% granite particle shows maximum hardness, impact strength and stress intensity factor and minimum slurry erosion rate. The entropy method was applied to the operating parameter to rank the fabricated composites. The performance of each operating parameter is determined using the VIKOR (Vise Kriterijumska Optimizacija Kompromisno Resenje) optimization method. The optimal formulation based on Performance-Defining Attributes (PDAs) is observed for multilayer-coated 6 wt.% granite particulate reinforced 5083 aluminum alloy composites.

Topographical and crystalline change on surface by sandblasting improve flexural and shear bond strength of niobia-modified yttria-stabilized tetragonal zirconia polycrystal.

This study aimed to investigate the effects of sandblasting on the physical properties and bond strength of two types of translucent zirconia: niobium-oxide-containing yttria-stabilized tetragonal zirconia polycrystals ((Y, Nb)-TZP) and 5 mol% yttria-partially stabilized zirconia (5Y-PSZ). Fully sintered disc specimens were either sandblasted with 125 µm alumina particles or left as-sintered. Surface roughness, crystal phase compositions, and surface morphology were explored. Biaxial flexural strength (n=10) and shear bond strength (SBS) (n=12) were evaluated, including thermocycling conditions. Results indicated a decrease in flexural strength of 5Y-PSZ from 601 to 303 MPa upon sandblasting, while (Y, Nb)-TZP improved from 458 to 544 MPa. Both materials significantly increased SBS after sandblasting (p<0.001). After thermocycling, (Y, Nb)-TZP maintained superior SBS (14.3 MPa) compared to 5Y-PSZ (11.3 MPa) (p<0.001). The study concludes that (Y, Nb)-TZP is preferable for sandblasting applications, particularly for achieving durable bonding without compromising flexural strength.

Combined Effects of Steel and Glass Fibres on the Fracture Performance of Recycled Rubber Concrete

As an environmentally friendly construction material, recycled rubber concrete (RRC) is commonly used as a road material owing to its excellent flexural strength and crack resistance. Previous studies have shown that the addition of fibres is an effective method for improving the crack resistance of concrete. The purpose of this study is to investigate the fracture performance of RRC reinforced with steel fibres (SFs) and glass fibres (GFs). A total of 28 RRC mixtures were prepared. The results of the fracture test showed that the addition of SFs and GFs significantly enhanced the RRC fracture performance. The maximum increases or decreases in flexural strength, brittleness coefficient, fracture energy, initial fracture toughness, and unstable fracture toughness were 64.9, −34.6, 775.6, 92.0, and 118.4%, respectively. The ideal GF content is usually in the range of 0.4–0.6% and decreases with increasing SF content. In addition, scanning electron microscope (SEM) tests were conducted to explore the mechanism of the effect of hybrid fibres on RRC at a microscopic level. The results show that SFs were always pulled out, while GFs were pulled apart at the initial defects. At the same time, excessive GFs caused more initial defects. These results are expected to provide theoretical direction and experimental support for the practical application of hybrid fibre-reinforced recycled rubber concrete (HFRRRC).

Post-Heat Flexural Properties of Siloxane-Modified Epoxy/Phenolic Composites Reinforced by Glass Fiber.

The post-heat mechanical property is one of the important indices for the fire-resistance evaluation of fiber-reinforced polymers. At present, the primary approach to improving the post-heat mechanical property of a material involves incorporating inorganic fillers; yet, the enhancement is limited, and is accompanied by a reduction in room-temperature performance and processability. This study prepares glass-fiber-reinforced composites with elevated mechanical properties after heat through utilizing two variants of epoxy resins modified with polysiloxane, phenolic resin, kaolin, and graphite. In comparison to the phenolic samples, the phenylpropylsiloxane-modified epoxy resulted in a 115% rise in post-heat flexural strength and a 70% increase in the room-temperature flexural strength of phenolic composites. On the other hand, dimethylsiloxane-modified epoxy leads to a 117% improvement in post-heat flexural strength but a 44% decrease in the room-temperature flexural strength of phenolic composites. Macroscopic/microscopic morphologies and a residual structure model of the composites after heat reveal that, during high temperature exposure, the pyrolysis products of polysiloxane promote interactions between carbon elements and fillers, thus preserving more residues and improving the dimensional stability as well as the density of materials. Consequently, a notable enhancement is observed in both the post-heat flexural strength and the mass of carbon residue after the incorporation of polysiloxane and fillers into the materials. The pyrolysis products of polysiloxane-modified epoxy play a vital role in enhancing the post-heat flexural strength by promoting carbon retention, carbon fixation, and interactions with fillers, offering novel pathways for the development of advanced composites with superior fire-resistance properties.

The Influence of Glass Fiber and Copper Wire z-Binder on the Mechanical Properties of 3D Woven Polymeric Composites

AbstractThree-dimensional composites (3D) have potential applications in various fields due to their enhanced properties compared to conventional two-dimensional composites (2D). This study investigates the effect of different volumes of z-binder made from copper wire and E-glass fiber on the mechanical properties of 3D woven polymeric composites. The tensile, flexural, and fracture toughness behavior of four types of 3D orthogonal woven composites were studied in addition to a comparative 2D composite. The creation of the 3D orthogonal single-ply fabrics involved weaving z-binders using two different copper wire diameters, single fiber bundles, and double fiber bundles, each combined with four layers of woven E-glass fiber. The consolidation process for both 2D fabric and single-fabric 3D woven composites was executed using the hand lay-up technique. The results showed that most 3D woven composites outperformed 2D composites in terms of fracture toughness (stress intensity factor KIC and energy release rate GIC) and flexural strain. However, a decrease in flexural strength and tensile properties was observed for all 3D composites. The specimen with a small copper diameter had the smallest decrease of 5% in tensile strength. Furthermore, a decrease of 9% and 21% was attained by reinforcing with double and single glass fiber bundle z-binders, respectively, as compared with 2D composites. The highest enhancement of 92.5% in flexural failure strain was attained with double glass fiber bundles of z-binder. The maximum improvement in KIC fracture toughness, reaching 126% and 101.5%, was observed in specimens with a single glass fiber bundle z-binder and those with a large copper wire diameter, respectively.

Influence of graphene-based nanostructures processing routes and aspect ratio in flexural strength and fracture mechanisms of 3Y-TZP-matrix composites

In this work, the influence of the aspect ratio of graphene-based nanostructures (GBNs) and content on the mechanical properties of 3 mol% yttria tetragonal zirconia polycrystalline 3Y-TZP matrix composites was analysed. The influence of the dispersion method and sintering parameters on the flexural strength and elastic modulus of the composites was studied, and the fracture surfaces were characterized to determine the fracture mechanisms that occur. The results showed that small amounts of exfoliated graphene nanoplatelets, with reduced lateral size, and few layer graphene, up to 1.0 and 2.5 vol%, respectively, slightly increase the 3Y-TZP flexural strength. This has been attributed to the tortuosity of the crack propagation pathways and strengthening mechanisms. Higher contents cause a decrease in flexural strength and stiffness because of overlapped GBNs, which can promote the crack propagation. The pull-out of GBN was more significant in composites with non-exfoliated graphene nanoplatelets, where no increase on the flexural or biaxial strength was measured.

The Effects of Replacing Sand with Glass Fiber-Reinforced Polymer (GFRP) Waste on the Mechanical Properties of Cement Mortars

The aim of this study is to examine the effect of the partial replacement of sand by Glass Fiber-Reinforced Polymer (GFRP) waste on the mechanical properties of cement mortars. Compressive and flexural tests were carried out on mortars containing 0, 3, 5, 10, and 15% (by volume) of GFRP waste. It appears that the incorporation of 3% GFRP waste did not significantly affect the mechanical strength. However, further increasing the GFRP waste content led to a reduction in the mechanical strength. The flexural strength seemed less affected than the compressive strength, since the decrease in flexural strength at a 10% replacement was only 37%, while it was 54% for the compressive strength. However, an improvement in the toughness of the mortar with an increase in the substitution rate was observed. The reference sample displayed a flexural toughness of 0.351 N·m, while the mortar incorporating 15% of GFRP exhibited a flexural toughness of 0.642 N·m. The reuse of GFRP waste in cementitious materials, therefore, constitutes an interesting recycling solution.

Effects on hybridization of interlayer composites and self-reinforced polypropylene

In recent years, there has been increasing attention to develop a high-strength, lightweight composite as a potential substitution for conventional materials in various sectors, whereby most studies have focused on the mechanical performances of fibre-reinforced plastic (FRP) such as carbon, glass and aramid. In contrast, the hybrid composites are less common, though are viewed to have substantial potential in terms of flexibility and capability to merge the benefits of different composites. In this study, five composite designs consisting of several types of woven fibres and self-reinforced polypropylene (SRPP) sheets have been fabricated using the hand lay-up procedure. Several designs are arranged based on the interlayer hybridization mode. The static mechanical properties of the composite designs were examined through the standard tensile and three-point flexural tests. The outcomes attained from the experimental works revealed that carbon fibre-reinforced plastic (CFRP) produced the best tensile characteristics. The CFRP structure displayed 46% higher tensile strength and a 33% greater elastic modulus compared to the CAFRP specimen. Meanwhile, hybrid carbon/aramid fibre-reinforced plastic (CAFRP) pointedly enhanced flexural properties in comparison with single type and other hybrid composites, whereby CAFRP structure outperformed the CFRP structure, exhibiting superior results with variations of 50% and 19% in flexural strength and modulus, respectively. Though the inclusion of SRPP layers in-between the hybrid setup exhibited a decrease in both tensile and flexural strength, but improved the total strain level. The evidence from this study suggests that FRP composites indicate structures of high strength and stiffness but low elongation, whereas SRPP-based composites improve toughness but reduce stiffness characteristics.

Waste silk selvedge/glass fiber reinforced strip-shaped composite: A critical assessment of twisting and dyeing of silk on mechanical properties

With about 11 million tons of waste silk produced each year, waste silk reinforced composites are an important way of high-value utilization. However, the mechanical stability of waste silk reinforced composites remains to be further studied. In this study, we evaluate the flexural and impact properties of waste silk selvedge/glass fiber reinforced strip-shaped composites with different twisting and dyeing structures. The findings reveal that both twisting and dyeing of silk negatively affect the mechanical properties. The twisting structure introduces yarn discontinuity, leading to a 33 % reduction in impact strength. The dyeing process disrupts silk's β-sheet structure, causing a more disordered β-strand structure and a decrease in flexural strength from 448.4 MPa to 412.4 MPa. Further, we determined that untwisting and undyeing waste silk selvedges are suitable for impact-critical application such as automotive bumper. While the twisting and dyeing waste silk selvedges are suitable for non-structural applications requiring aesthetic appeal, such as automotive interiors.This study identifies critical factors influencing mechanical properties of waste silk reinforced composites, benefiting their engineering applications.

TiO2-kaolinite composite photocatalyst for industrial organic waste decontamination

The industrially feasible TiO2-clay based photocatalysts are essential to overcome the practical barriers that are intrinsic to currently available clay-based photocatalysts. The present study demonstrates the fabrication of heterogeneous photocatalyst consisting of TiO2 and kaolinite (TKCP) that has shown improved catalytic activity and strength, ensuring industrial viable photocatalyst. TKCP is prepared via an economical method, employing mechanical compression and dehydroxylation, forming TiO2-clay hybrid matrix. Amount of clay primarily determines mechanical strength and photocatalytic efficiency of TKCP where TKCP with the lowest clay percentage results in a homogeneous matrix that consists of tiny TiO2 particles embedded clay sheet-like structure. The TiO2 particles embedded clay sheet-like structure is responsible for the high specific surface area and small pore size, increasing the active surface that is available for effective disintegration of organic contaminants. By increasing clay fraction in TKCP, a significant increase in surface defects can be observed due to large clay fragments and TiO2 agglomerates, which results in flexural strength and catalytic activity decrease. Methylene blue degradation on TKCP with the maximum TiO2 percentage results in the highest pseudo first-order rate constant of 0.58 h−1, exhibiting improved photocatalytic activity due to well-organized matrix and high specific surface area (82.79 m2 g−1). TKCP can be obtained in variable sizes and shapes that ensure dynamic wastewater treatment applications.

Optical and mechanical properties of multilayered transparent wood

The versatility of utilizing transparent wood composite (TWC) as structural building component has been envisioned by producing thicker section. The challenges and limitation while preparing transparent wood using thick wood sections can be addressed by the concept of multilayered construction. TWCs were produced using 2 mm thick lignin modified wood veneer sections of three wood species viz., Populus deltoides (Poplar), Melia dubia (Melia) and Grevillea robusta (Silver oak) followed by infiltration of epoxy polymer. To increase the thickness of composite, an easy method of multilayer construction of 2 mm thick epoxy infiltrated wood samples to produce thicker TWC composite was adopted. Assembly of 2 mm thick epoxy infiltrated wood samples one above the other to produce two layer (4 mm thickness), three layer (6 mm thickness) and four layer (8 mm thickness) thicker TWC of Poplar, Melia and Silver oak wood was carried out. The optical transmittance of TWC samples was measured using UV–VIS–NIR spectrophotometer equipped with an integrating sphere. The optical transmittance of multilayered TWC was reduced on increasing number of layers. The three-point static bending test of multilayer TWC indicated an improvement in flexural strength and slight decrease in the modulus of elasticity on increasing number of layers.

Original Research Article Effect of Radiotherapy on Flexural Strength of Luting Cementsan In Vitro Study

Aim - The aim of this study was to evaluate changes in the flexural strength of luting cements due to radiotherapy. Methodology- Total of 90 rectangular specimens of 25×2×2 mm dimension were fabricated by utilizing the putty consistency polyvinyl siloxane rubber mould. They were grouped based on their type. Group A included 30 specimens made of zinc phosphate cement, Group B included 30 specimens fabricated using glass ionomer luting cement, and Group C consisted of 30 specimen’s fabricated using resin luting cement. Once the specimens were set, they were stored in distilled water between the experiments. After 24 hours, 15 from each group of the mentioned cements were subjected to irradiation fractionally upto 60 Gy by a Cobalt-60 external beam machine. Remaining specimens from each group were used as controls. After radiotherapy, the specimens were stored in distil water for 24 hours until performing the 3 point bend test. All the specimens were subjected to 3 point bend test on universal testing machine for checking flexural strength. Statistics- Kruskal Wallis Test followed by Mann Whitney test as post hoc analysis was used to compare the mean values of different parameters between three groups of Irradiated and controlled samples. The level of significance was set at P&lt;0.05. Results- After exposure to fractional irradiation for 4 weeks, in the zinc phosphate luting cement (Group-A) and glass ionomer luting cement (Group-B), showed a slight decrease in flexural strength. The resin luting cement (Group-C) showed slight increase in flexural strength. Conclusion- Among all the groups, the resin luting cement showed a slight increase in flexural strength when compared to the other luting cement groups after fractional irradiation

Analysis of the Impact of Sludge and Slag Waste on the Basic Properties of Cement Mortars

Abstract The article examined the influence of two additives, which are post-production waste from metallurgical processes, on the basic properties of cement mortars. Sludge and slag waste were used for testing. Both wastes were examined in terms of their chemical composition using a spectrometer, their specific density and grain composition were determined. As part of the tests, a series of standard mortars were made and the results obtained for modified mortars were compared to them. The produced cement composites used waste in amounts of 5, 10, 15 and 20% of the cement mass, used as a substitute for standard sand. After preparing the standard mortar and mortars containing additives for each series, consistency tests were performed using the flow table method. After an appropriate maturing time, flexural and compression tests were performed for all mortar series after 7 and 28 days of maturing, as well as water absorption tests. The research shows that the addition of these two wastes thickens the fresh cement mortar (from 0.62 to 15 %). The use of such waste also results in a decrease in flexural strength after 7 and 28 days (for sludge from 5 to 21% and for slag from 2 to 11%). Natomiast wytrzymałość na ściskanie zapraw zmalała o 11% w przypadku dodatku 20% szlamu oraz niemal taka sama co zaprawy normowej po dodaniu 20% żużla.

Shotcrete 3D Printing ‐ Effect of material‐process interaction on the global and local material density

AbstractShotcrete 3D Printing is a 3D printing process in which the concrete is applied layer by layer using a wet mix process. In the print process, a large number of different process as well as material parameters can be varied, which also influence the hardened concrete properties. A systematic understanding of the interaction between material and process is required to define limits for material and process control variables with respect to the resulting component quality. Therefore, in this paper we present results on the effect of concrete volume flow (0.4; 0.8 m3/h), air volume flow (30; 40; 50 m3/h) and accelerator dosage (0; 3; 6 % by weight of cement) on global density, local density distribution as well as flexural strength. The results show that the combination of an increasing concrete volume flow, a decreasing air volume flow and an increasing accelerator dosage lead to a decrease in global density and flexural strength. A high correlation between the global density and flexural strength can be demonstrated despite the layer‐by‐layer fabrication. In addition, an inhomogeneous density distribution over the cross section is shown. Finally, the underlying mechanisms are discussed regarding the influence of the material and process parameters.

Flexural strength evaluation of Persian clay brick masonry with gypsum mortar

This paper addresses the imperative need for understanding the mechanical properties of clay brick masonry with gypsum mortar, the primary construction material in Persian historical buildings, to facilitate accurate restoration efforts. Given the constraints of heritage preservation, destructive tests on large-scale specimens are unfeasible. As a viable alternative, this research employs scaled-down specimens to investigate the flexural strength. For the first time, Persian clay brick masonry with gypsum mortar assemblages have been tested at three scales of 1:2, 1:4 and 1:6 to determine the flexural strength. The paper introduces new relationships between the flexural strength of brick masonry and brick size. Furthermore, it establishes a correlation between the flexural strength of the brick masonry specimens and the flexural strengths of both the brick and the gypsum mortar. Additionally, some specimens incorporate cement mortar instead of gypsum mortar for result comparison. The obtained results reveal the profound influence of mortar type and thickness, along with brick dimensions, on flexural strength. The flexural strength of brick masonry increases with decreasing brick size. By reducing the size of bricks, the ratio of compressive strength to flexural strength decreases, offering key insights for restoration efforts.

Valorization of virgin cork by the design of cork-plaster composites

The aim of this study is to develop a composite insulation material based on plaster and virgin cork from Corsica which has an insufficient quality for cork stoppers. This paper presents the results of design and characterization. In this study, six cork-plaster mixtures with a C/P ratio of 0.025; 0.05; 0.075; 0.10; 0.15; 0.20 were produced. The cork-plaster composites were compared with a reference sample without cork particles in terms of properties. It was observed that the compressive and flexural strength, density, and thermal conductivity decrease with the increase of the cork content. The value of thermal conductivity (0.460 – 0.168 W/(m⋅K)) shows that virgin cork-plaster composites can be used in building applications as non-structural material.

Eco‐friendly geopolymer mortar prepared from geopolymer waste: Mechanical and thermal properties

AbstractAs the demand for sustainable construction practices increases, alternative materials are being explored to reduce waste and carbon emissions. This study investigates the feasibility of utilizing recycled geopolymer binder as a substitute for ordinary sand in the production of geopolymer mortar. The study examines the effects of various replacement rates of recycled geopolymer on the physical, mechanical, and thermal properties of the geopolymer mortar. The results indicate that geopolymer mortar incorporating recycled geopolymer binder as a replacement for ordinary sand exhibits similar mechanical properties to traditional geopolymer mortar, with minor decreases in compressive and flexural strength as the replacement rate increased. The geopolymer mortar also demonstrated lower thermal conductivity than traditional mixes, resulting in increased thermal insulation. These findings suggest that using recycled geopolymer binder as a replacement for ordinary sand in geopolymer mortar production could be a promising approach for sustainable construction practices.

Effect of Graphene Nanoplatelets on Flexural Behavior of Glass Fiber Reinforced Polymer Composites Subjected to Different Temperatures

Glass Fiber Reinforced Polymer (GFRP) Composite are increasing rapidly in Aerospace Industry, Civil and Wind energy sectors, where they can frequently be exposed to different temperature conditions. As the constituent polymer matrix is highly affected by temperature, extreme temperature conditions are critical for GFRP composite structural design. Researchers have recently found nanofillers such as graphene and carbon nanotubes with excellent multifunctional mechanical properties. Graphene Nanoplatelets (GnP) consist of several layers of graphene. GnP is considering an attractive nanofillers as it has improved polymer matrix properties. In this study, the weight percentage of GnP added in GnP-GFRP laminate is 0.25% and 0.5%.GFRP and GnP-GFRP laminates are fabricated by using the hand lay-up method, and the specimens are subjected to a three-point bending test in a thermal chamber with varying the temperature, i.e., 30°C, 50°C, 75°C, and 100°C. This paper investigates the effect of graphene nanoplatelets on the flexural behavior of glass fiber-reinforced polymer composites subjected to different temperatures. Flexural strength and modulus are evaluated, and the appropriate conclusions are determined. GFRP with 0.25% GnP shows higher strength than the neat and 0.5% GnP-GFRP. Here, it has also been shown that flexural strength and modulus decrease significantly with increasing temperature.