Ultimate Flexural Strength Research Articles

Mechanical behaviour of pineapple leaf fibers reinforced Lapox L-12 epoxy composites

To meet the increasing need for composites in sectors such as medical, transportation, safety, and athletics, researchers continuously develop novel composites. This study investigated the effects of boron carbide filler particles in epoxy by fabricating composites from Lapox L-12 epoxy with 20 and 30 wt. % of pineapple leaf fibres (PALF) utilising the hand layup method. The mechanical parameters of the synthesised composites were evaluated according to ASTM standards, encompassing hardness, ultimate tensile strength, yield strength, elongation, and flexural strength. The addition of pineapple leaf fibres to epoxy Lapox L-12 resulted in enhanced hardness, tensile strength, and flexural strength, accompanied by a minor reduction in percentage elongation. Lapox L-12 composites supplemented with 30 wt.% of PALF exhibited enhancements of 60.8% in hardness, 66.2% in ultimate strength, and 101% in flexural strength.

Exploring Ultimate Flexural Strengths of Ultra-High-Performance Concrete (UHPC) Samples through Experimental Analysis in Comparison with Ordinary Concrete Structures

Exploring Ultimate Flexural Strengths of Ultra-High-Performance Concrete (UHPC) Samples through Experimental Analysis in Comparison with Ordinary Concrete Structures

Experimental research on the flexural properties and pore structure characteristics of engineered geopolymer composites prepared by calcined natural clay

The synthesis of high ductility geopolymer composites using excavated natural clay is an economical and environmentally friendly method to realize the utilization of excavated natural clay. This paper presents an experimental research on the flexural properties and pore structure characteristics of engineered geopolymer composites (EGC) prepared by calcined natural clay. The EGC with different slag and fiber contents were prepared and the four-point bending tests were conducted on the EGC. The effect of slag and fiber content on the flexural strength, flexural deflection and flexural toughness were discussed. The microscopic pore structure characteristics of EGC were further analyzed. The optimal mixture ratio of calcined clay-based EGC with the highest flexural toughness was proposed. The results show that fiber can significantly enhance the flexural properties and cracking control ability of EGC. The ultimate flexural strength, flexural deflection, flexural strengthening index and flexural toughness of EGC all increase with increasing fiber content. The results also show the addition of 10.0% slag can increase the flexural strength and flexural toughness, while excessive slag content reduces the flexural properties. The EGC with 10.0% slag content and 2.5% fiber content exhibits excellent flexural properties and cracking control ability. The ultimate flexural strength and flexural toughness index reach 9.75 MPa and 486.11, showing the highest flexural toughness.

Experimental, Numerical, and Analytical Investigation of the Reinforced Concrete Hidden and Wide Beams

AbstractThis research presents an experimental, analytical, and numerical study to predict the flexural behavior of reinforced concrete hidden and wide beams embedded in slabs. The experimentally studied parameters of testing eight specimens include beam depth, beam width, and beam eccentricity from the column. The obtained test results were compared to the predictions of finite element analysis using the ANSYS program. A numerical parametric study was conducted by the ANSYS program to explore other parameters affecting the ultimate flexural strength of beams. The studied parameters encompass concrete compressive strength, steel reinforcement strength, bottom reinforcement ratio, top-to-bottom reinforcement ratio, and web reinforcement ratio. The results revealed that an increase in beam depth led to higher ultimate load and secant stiffness, along with a decrease in deflection. The increase in beam width significantly affected beam depth, resulting in increased ultimate load and secant stiffness and a slight decrease in deflection. The increase in beam eccentricity from the column resulted in a decrease in ultimate load and secant stiffness while increasing the deflection. Comparisons between experimental and numerical results were made against calculations based on the ECP 203-2017 and ACI 318-19 codes, and the comparison yielded satisfactory results.

An improved flexural design procedure of steel plate I‐girders considering elastic lateral torsional buckling at elevated temperatures

AbstractIn the present study, an improved design method is proposed for the flexural design of steel plate I‐girders at elevated temperatures. The proposed method accounts for two important phenomena accompanying the temperature increase in steel I‐girders: (1) alteration of the failure mode and (2) degradation of the material properties. The main strategy of the proposed procedure is to find the ambient‐temperature‐equivalent design parameters of steel I‐girders at elevated temperatures. The basic design relationships are adopted from the flexural design provisions of AISC 360‐16 and then modified to accommodate the elevated temperatures and instability conditions of I‐girders. To evaluate the accuracy and efficiency of the proposed method, a comprehensive finite element study is conducted using ABAQUS. To this aim, 54 numerical models of steel plate I‐girders with different cross‐section slenderness parameters were investigated. All the simulated I‐girders were prone to fail in elastic lateral‐torsional buckling mode at both ambient temperature and elevated temperatures. To corroborate the numerical modeling and analysis process at ambient and elevated temperatures, the results were verified against the available experimental data. Based on the results, the maximum absolute deviation of the ultimate flexural strength obtained from the proposed method from the finite element predictions was 9%.

Effects of palm oil fuel ash and crumb rubber on mechanical and thermal properties of sustainable engineered cementitious composites

The construction sector using natural sand causes rapid depletion and environmental harm, including erosion, biodiversity loss, and aquatic habitat destruction. To address these challenges and advance sustainability, this study systematically investigated the behaviour of engineered cementitious composites (ECC) incorporating 10–30 % ground palm oil fuel ash (GPOFA) and crumb rubber (CR) as a fine aggregate substitution. Two different sizes of GPOFA, P600 (in the range of 300 μm–600 μm) and P300 (less than 300 μm), were utilized to substitute the fine aggregate in the mix. Dry density, workability, thermal conductivity, modulus of elasticity, tensile strength and strain, compressive strength, flexural strength, and ultrasonic pulse velocity (UPV) were investigated. Furthermore, the microstructures and mineralogical compositions of the selected ECC samples were also examined. The results indicate that increasing GPOFA and CR content reduced ECC's flowability and density. Incorporating GPOFA reduced the compressive strength by 23 % for P600, 12 % for P300, and 74 % for CR, for 30 % substitution at 28 days. Both substitutions reduced the modulus of elasticity and UPV of ECC due to reduced packing efficiency and increased porosity. Increasing GPOFA improved the first cracking load slightly but decreased ultimate flexural strength, whereas CR significantly reduced both. In addition, tensile strain and strength dropped more significantly for ECC with CR compared to ECC with GPOFA. ECC with CR recorded the highest shrinkage and the lowest thermal conductivity (0.66W/mK). Overall, P600 outperformed P300, and CR showed the lowest performance in ECC across all parameters studied. This study highlights that partial replacement of silica sand with GPOFA could produce greener ECC with acceptable mechanical properties, while CR effectively reduces the thermal conductivity of ECC. Integrating GPOFA and CR adds significant value to these wastes while simultaneously providing a sustainable solution for waste disposal.

Research on the flexural performance of recycled coarse aggregate concrete beams after carbonation

This paper discusses the flexural behavior of carbonated recycled aggregate concrete (RAC) beams through experimental data. We produced fifteen beams, each varying in recycled aggregate replacement ratios: 0 %, 30 %, 50 %, 70 %, and 100 %. Each replacement ratio included three beams, amounting to different levels of carbonation: non-carbonated, partially carbonated, and completely carbonated. Post accelerated carbonation processes; flexural testing was conducted. The findings reveal that beams incorporating varying amounts of recycled coarse aggregates (RCA) but maintaining identical carbonation levels exhibited a minor reduction in the cracking moment, with negligible variations in ultimate flexural strength and deflection. Moreover, beams sharing the same RCA replacement ratio demonstrated increased cracking moment, ultimate flexural strength, and stiffness with advancing carbonation levels, while deflection tended to decrease. Based on these findings, predictive models for cracking moment and ultimate flexural strength of carbonated RAC beams were developed. Comparisons between experimental outcomes and numerical simulations, particularly within the RAC50 group, indicated nearly identical results.

Column-to-beam flexural strength ratio for rigorous strong-column–weak-beam design for steel–concrete composite frames

This study addresses the limited research and unclear principles surrounding the strong-column–weak-beam (S-C–W-B) criterion in steel–concrete composite frames, a critical aspect of structural engineering. Despite its widespread application in steel frames, the S-C–W-B criterion's adaptation to steel-concrete composite frames remains underexplored. The research aims to clarify and establish consistent guidelines for preventing column hinge formation at the joint, a key concern in S-C–W-B design. Beginning by analysing the definitions of ultimate flexural strength and flexural yielding strength of a section, essential components of the S-C–W-B criterion, the minimum column-to-beam flexural strength ratio (ηc, min) required for a robust S-C–W-B design was deduced. The methodology involves a novel parametric analysis using a fibre beam–column model. This model is used to derive a closed-form equation for ηc, min, which was then verified through time-history analysis using the finite-element software MSC.Marc. The findings indicate that the established ηc, min provides a stringent, nonetheless, reliable criterion for S-C–W-B design in steel-concrete composite frames. This research not only bridges a significant gap in existing structural engineering knowledge but also proposes a practical approach for safer and more efficient design in real-world applications.

In-plane flexural behavior of eccentric rectangular hollow section (ERHS) X-joints: Experimental, numerical and analytical study

This paper investigates the in-plane flexural behavior of an eccentric rectangular hollow section (ERHS) X-joint, where the two braces are continuous at one side and the inner face is aligned with a chord sidewall. The presented X-joints are full lateral offset RHS joints. In this study, laboratory static testing is implemented on two ERHS X-joint specimens and one traditional RHS X-joint specimen under in-plane bending moment (IPBM), and the corresponding numerical simulation is conducted. The results show that the ultimate flexural strength and initial stiffness of the ERHS X-joints with a medium brace-to-chord width ratio (β) are larger than those of the RHS X-joints. The initial stiffness and strength of ERHS X-joints increase with the growth of β. Based on the load transferring mechanism, two analytical models and the relevant formulae are proposed to predict the strength of the ERHS X-joints with β ≤ 0.925 and β = 1.0, and the strength of joints with 0.925 <β < 1.0 can be determined by linear interpolation. The proposed analytical models are validated against experimental data and finite element results.

Explainable AI Techniques for Comprehensive Analysis of the Relationship between Process Parameters and Material Properties in FDM-Based 3D-Printed Biocomposites

This study investigates the complex relationships between process parameters and material properties in FDM-based 3D-printed biocomposites using explainable AI techniques. We examine the effects of key parameters, including biochar content (BC), layer thickness (LT), raster angle (RA), infill pattern (IP), and infill density (ID), on the tensile, flexural, and impact strengths of FDM-printed pure PLA and biochar-reinforced PLA composites. Mechanical testing was used to measure the ultimate tensile strength (UTS), flexural strength (FS), and impact strength (IS) of the 3D-printed samples. The extreme gradient boosting (XGB) algorithm was used to build a predictive model based on the data collected from mechanical testing. Shapley Additive Explanations (SHAP), Local Interpretable Model-Agnostic Explanations (LIME), and Partial Dependence Plot (PDP) techniques were implemented to understand the effects of the interactions of key parameters on mechanical properties such as UTS, FS, and IS. Prediction by XGB was accurate for UTS, FS, and IS, with R-squared values of 0.96, 0.95, and 0.85, respectively. The explanation showed that infill density has the most significant influence on UTS and FS, with SHAP values of +2.75 and +5.8, respectively. BC has the most significant influence on IS, with a SHAP value of +2.69. PDP reveals that using 0.3 mm LT and 30° RA enhances mechanical properties. This study contributes to the field of the application of artificial intelligence in additive manufacturing. A novel approach is presented in which machine learning and XAI techniques such as SHAP, LIME, and PDP are combined and used not only for optimization but also to provide valuable insights about the interaction of the process parameters with mechanical properties.

Optimizing lunar regolith for vat polymerization and sintering: pre-processing & mineral composition impact

Lunar regolith is the most abundant resource on the lunar surface, which can be used for in-situ fabrication and repair technologies. Vat photopolymerization-based additive manufacturing is among the most promising techniques, capable of producing precise ceramic parts of complex shapes from the lunar regolith feedstock for the needs of future crewed exploration missions to the Moon. One of the under-studied aspects of additive manufacturing with lunar regolith is the pre-and post-treatment procedures, which would ensure optimal energy and material consumption and the best printing performance. The goal of the present article was to define the influence of the mineral composition of lunar regolith simulants and the parameters of their pre-processing on the properties of sintered regolith ceramics. It was found that the highland regolith could be sintered to higher relative density compared to the mare regolith. The optimal sintering temperature was determined to be 1150 °C for both types of lunar regolith. An optimal mineral and fractional composition for the regolith feedstock was determined based on the trade-off analysis between lunar regolith sinterability and its printability via vat photopolymerization-based additive manufacturing. Vat-polymerization was performed to produce complex-shaped ceramic parts, yielding 95 % of relative density and a mean ultimate flexural strength of 106 ± 5 MPa, confirming the proposed trade-off point.

Investigation of Mechanical Properties of Natural Fiber Reinforced Hybrid Composite

Abstract: Hybrid composite is a material composed of matrix and two or more reinforcements. Two or more reinforcements in hybrid composite replace the limitation of conventional composites by providing uniform strength to thematerial. Recently, natural fibers reinforced hybrid composites are gaining increased interest due to the encouraging properties of natural fibers such as high strength to weight ratio, low cost, no harm to environment etc. Many studies dealt with natural fibers based composite reported that the hybrid composites has the potential to replace glass fiber based composites and to reduce the weight of conventional composite. This project reports on the manufacturing of the Indian elm and Acacia fibre reinforced epoxy composite laminate as per the ASTM (American Society for Testing and Materials) Standards. This laminate consists of matrix and reinforcement. Epoxy is used as a structural matrix material which is then reinforced by Indian elm fiber, combining Acacia fibres with resin matrix results in composites that are strong, lightweight, corrosion-resistant and dimensionally stable. They also provide good design flexibility, high dielectric strength and act as inflammable materials. Their tremendous strength-to-weight and design flexibility make them ideal in structural components for the aerospace industry. In this project the Indian elm and Acacia fibre reinforced epoxy composite is manufactured into two different parts each having ratios of Indian elm and Acacia fibre to epoxy resin as 60:40, 40:60 respectively and are compared for ultimate tensile strength, impact strength, hardness strength and flexural strength of the material by conducting experiment such as tensile test, flexural test, hardness test and impact test.

Experimental Design and Analysis of MWCNT, Nanoclay and ZnO Nanofillers on Bi-Directional-Chopped Stranded Glass Fibre Reinforced Epoxy Matrix on Mechanical Properties using L9 and L18 Taguchi’s Orthogonal Technique

Stealth, mechanical and thermal properties, resistance to fire by limiting oxygen and retarding flame can lead to save several human lifes travelling and working in civil, commercial as well as defence air transport and could even develop drone and aircraft meant to escape enemy countries radar tracing and monitoring range. GFRP play very important role in engineering application. The composite manufactured using nanofillers have found to posses better propeties in certain application. In the present work, MWCNTs, Nanoclay and ZnO have been used in GFRP. The developed material can be a promising replacement of composites being used for structural applications in the aerospace sector and space technology apart from the automotives to impart light weight, superior bending and tensile strength. Testing of GFRP infused nanofillers was conducted to obtain the ultimate tensile strength and flexural bending strength of the composite. Experimental design with three Nanofillers as parameters at three levels for optimization of output characteristics with superior properties for structural applications was done using Taguchi’s L9 and L18 orthogonal arrays. ANOVA Analysis was also performed for both L9 and L18 arrays. The effects of three nanofillers infused GFRP was investigated and their impact on tensile and flexural strength were evaluated.

Flexural performance and damage of reinforced fly ash and slag-based geopolymer concrete after coupling effect of freeze-thaw cycles and sustained loading

To better represent field conditions, the bending performance of reinforced geopolymer concrete (GPC) beams after the coupling effect of freeze-thaw cycling and sustained flexural load was investigated. Two types of GPC (G10 and G50) with different content of fly ash and slag were included and compared with ordinary Portland cement concrete (OPC). The mechanical strength of concrete and bond strength of rebars in concrete before and after freeze-thaw cycles were measured. It was found that the frost resistance of G10 was the weakest followed by OPC and G50. Three scenarios of bending tests on reinforced concrete beams were included: (1) control (without freeze-thaw damage); (2) individual freeze-thaw cycling; (3) coupling effect before bending. Rebound tests were conducted to evaluate frost damages at different areas of the beams as the base to analyze bending behaviors of the beams. The failure mode, load-displacement(strain) relationship, ultimate flexural strength, and bending stiffness of beams from bending tests are analyzed. All beams in scenario (1) were dominant in flexural failure. For scenario (2), G10 and G50 failed in debonding failure due to significant reduction in bond strength, while OPC failed in diagonal tension failure as OPC could sustain bond stiffness, thus preventing debonding failure. For scenario (3), damages in GPC were exacerbated, while damages in OPC were limited.

Water Absorption, Thermal, and Mechanical Properties of Bamboo Fiber with Chopped Glass Fiber Filler-Reinforced Polyester Composites

This study explores the investigations of bamboo fiber-reinforced polyester composites with chopped glass fiber (CGF) filler, focusing on addressing the challenges of low mechanical properties, limited thermal stability, and high moisture absorption. The two types of composites were fabricated using the hand layup method, that is, long unidirectional 0° bamboo fiber (BF) and randomly oriented short bamboo fiber (BP) reinforced a polyester matrix with chopped glass fiber (CGF) filler. By incorporating CGF filler, significant improvements in mechanical properties were achieved across both types of bamboo fiber, surpassing the limitations of unfilled composites. Notably, the composite formulation consisting of 40% wt. of unidirectional 0° BF and 5% wt. of CGF filler exhibited superior ultimate tensile strength, flexural strength, impact strength, water absorption, and thermal stability. This composite demonstrated remarkable enhancements, with increases of up to 131.22 MPa, 128.76 MPa, 113.3 kJ/m2, 1.94% water absorption, and up to 255°C (representing a 10% improvement) in thermal stability compared to the unfilled composite. Statistical analysis revealed quadratic models for the mechanical properties of long unidirectional 0° bamboo fiber composites, while water absorption exhibited a linear two-factor interaction model. For randomly oriented short bamboo fiber, the models for tensile, flexural, and water absorption properties were linear, while the impact energy model showed a quadratic relationship. These statistical models provide valuable insights into predicting the properties of bamboo fiber-reinforced polyester composites. This research underscores the significance of bamboo fiber-reinforced polyester composites in wall partition systems. This study paves the way for improved performance in these areas. The findings highlight the potential of incorporating CGF filler, enabling enhanced mechanical strength, increased thermal stability, and improved resistance to moisture-related issues. The derived statistical models offer valuable guidance for predicting the properties of these composites, facilitating their application and adoption in the construction industry.

A STUDY ON MULTI-OBJECTIVE OPTIMIZATION OF PULSED TIG WELDING PARAMETERS AND THEIR EFFECT ON JOINT PROPERTIES OF HIGH MANGANESE STEELS USING TAGUCHI-BASED GRA APPROACH

This investigation focuses on the study of the effect of process parameters like peak current ([Formula: see text], base current ([Formula: see text], pulse frequency ([Formula: see text], shielding gas flow rate ([Formula: see text] on mechanical properties like yield strength (YS), ultimate tensile strength (UTS) and flexural strength (FS) of the welded joints during pulsed TIG welding of SAILMA 450 and EN14 B steels. Taguchi’s L[Formula: see text] orthogonal array has been used for conducting the tests. Multi-objective optimization has been performed using Grey relational analysis (GRA) in order to maximize the mechanical strength and to find out the optimal set of parameters. The optimum parametric combination is obtained at a peak current of 220[Formula: see text]Amps, base current of 120[Formula: see text]Amps, pulse frequency of 5[Formula: see text]Hz and shielding gas flow rate of 17[Formula: see text]l/min. Analysis of variance (ANOVA) is used to predict the significant process parameters. It has been observed from the ANOVA analysis that peak current and pulse frequency have more influence on the output responses than the shielding gas flow rate and base current. The results of the confirmatory test show an improvement of 0.5801 in the GRG, which is satisfactory. A microstructure study has been performed using scanning electron microscopy (SEM) for the optimal set of process parameters.

Ultimate flexural strength and Young’s modulus analysis of denture base resins for masked stereolithography 3D printing technology

of the study is to investigate the ultimate flexural strength and Young’s modulus of some materials, which can be used for complete denture fabrication by Masked stereolithography 3D printing technology.Three groups of five specimens each were fabricated. Two of the groups are 3D printed by Masked SLA 3D printer of two commonly used denture base resins. The third group is set to be a control as the specimens were fabricated of a heat-curing acrylic resin. A three-point flexural test tested the objects, and the data collected was used to determine ultimate flexural strength and Young’s modulus calculation. All the results are compared to the ISO Standard 20795-1.The data shows that the mean ultimate flexural strength of the 3D printed specimens is 87 MPa - 89 MPa. Their results are very similar to those for the heat-curing acrylic resin, which means the ultimate flexural strength is 93 MPa. The mean Young’s modulus obtained for the first group of 3D printed specimens is 2263.21 MPa and 2377.44 MPa for the second one. As for the control group, 2396.06 MPa is achieved. When ISO Standard 20795-1 is inspected, all the data obtained covers the minimum requirements.The limitations of the study concern to some additional factors that should be observed for more detailed evaluation. For example, the level of the final polymerization of light-curing resins for 3D printing, their ability to washstand to different defect and denture-bearing area characteristics (the notch for the labial and buccal frenulum, chambers for torus release, etc.), the ability of the materials to withstand to cyclic load, etc.3D printing is faster and cheaper than conventional methods for complete denture fabrication. The knowledge about the mechanical properties of the different materials for 3D printing is very valuable for properly selecting a material and approach for complete denture fabrication.Nowadays, 3D printing is essential in dentistry. For this reason, observation and knowledge of the raw materials properties is very important for the proper choice of a material and/or technology for each clinical case.

Effect of Rebar Harsh Storage Conditions on the Flexural Behavior of Glass FRP Concrete

Nowadays, fiber-reinforced polymer (FRP) has become a widely accepted alternative reinforcement to steel bars in concrete members due to its many sustainability traits, as represented by its high strength-to-weight ratio, corrosion resistance, non-conductive properties, and electromagnet neutrality. However, FRP bar exposure for an extended period of time to harsh environmental conditions and chemicals can have an adverse effect on their mechanical properties. In this investigation, glass FRP bars were exposed to indoor controlled temperature, outdoor direct sunlight, outdoor shade, seawater, and alkaline solution for six months prior to using them as reinforcement in concrete flexural members. This research involves the fabrication and testing of five pairs of 3 m-long concrete beams with 200 mm by 300 mm cross-sections embedded in the tension zone with the exposed GFRP bars. The 10 beams were instrumented with strain gauges and tested following a four-point loading scheme using a hydraulic jack attached to a rigid steel frame. Crack width records from the tests showed the inferior serviceability of the beams that contained rebars stored in an outdoor environment relative to the control beams. GFRP bar exposure to an alkaline solution or outdoor direct sunlight slightly affected the cracking and ultimate moment capacities, reducing them by 5% and 3% in terms of the same parameters as the controlled indoor exposure, respectively. The influence of GFRP bar exposure to open-air shade or sunlight decreased the pre-cracking stiffness by 25% and flexural ductility by 10–20% when compared with the control specimens. The predicted ultimate flexural strength using the ACI 440 provisions gave comparable results to the experimentally obtained values. A simple mathematical equation that envelops the moment–deflection relationship for GFRP over-reinforced concrete beams and only requires information about initial cracking and ultimate flexural conditions is proposed.

Exploring the Impact of TiO2 and MgO Nanoparticles on the Mechanical and Topographical Characteristics of Glass Fiber Reinforced Polymer (GFRP) Composites with Varied Lay-up Sequences: A Taguchi Analysis

A revolutionary composite material, blending Glass Fiber Reinforced Polymer (GFRP) with advanced nanofillers like TiO2 and MgO, showcases remarkable versatility in various industries due to its unique properties. The process involves precise control of key factors, including fiber stacking sequence (F.S.S) and nanofiller integration (MgO and TiO2). The vacuum bagging process is employed in the production of nanocomposite laminates. Experimental studies have been conducted to assess the performance of composites with and without nanofillers, with a specific focus on crucial mechanical properties, namely ultimate tensile strength (U.T.S), flexural strength (F.S), impact strength (I.S), and hardness (H). The Taguchi L9 orthogonal array design optimizes parameters and enhances mechanical properties. Comparisons reveal significant improvements with nanofillers, including a 31.96% increase in ultimate tensile strength and a substantial 68.43% enhancement in flexural strength. ANOVA results highlight the critical impact of fiber stacking sequence on ultimate tensile strength (63.65%), flexural strength (65.70%), and impact strength (9.30%), while nanofillers play a lesser role, contributing 11.71% to ultimate tensile strength, 2.66% to flexural strength, and 3.61% to impact strength. Notably, in composite hardness, nanofillers play a more significant role, contributing 39.22%, while the influence of fiber stacking sequence is lower at 3.29%.

Toughness and strength of PVA-fibre reinforced magnesium phosphate cement (FRMPC) within 24 h

Cement with high toughness and early strength are widely utilized in the field of rapid repair. This study is focused on the development of PVA fibre reinforced magnesium phosphate cement (FRMPC) that possesses these properties. The compressive, flexural, and tensile strengths of the FRMPC were measured at various ages, including 1, 2, 3, 4, 5, 6 and 24 h. The relationships of the element contents, hydration products, hydration process, and the microscopic morphology with the mechanical properties were analyzed. Importantly, the mechanical formation process of the 6 h was analyzed in detail. Results show that the tensile strain of the FRMPC exceeded 3% at all ages, and the flexural strength was greater than 10 MPa at all ages. The compressive strength reached 15.53 and 25.63 and 32.48 MPa after 1 h, 6 h and 24 h, respectively. The ultimate tensile strength, flexural strength and compressive strength of 6 h reached 98%, 90% and 78% of the final strength of 24 h.The incorporation of fly ash and quartz sand mitigates the exothermic rate of hydration and optimizes the filler structure. Furthermore, the addition of fly ash engenders an amorphous phase gelling material and MgSiO3, characterized by effective filler properties.This results in an enhanced integration of PVA fibres with the cement matrix, thereby exhibiting improved toughness.The main hydration product was MgKPO4 × 6 H2O, and its formation rate and amount affected the mechanical properties. The nature of the hydration products and the density of the specimen structure were determined to be key factors in the progression of uniaxial tensile properties. FRMPC's strength, toughness and shrinkage are in a relatively good state, and the potential for its early-stage mechanical properties still can be improved.