Improvement In Strength Research Articles

Integrated manufacturing of powder metallurgy preparation-thixoforming for Al0.8Co0.5Cr1.5CuFeNi HEA: Excellent formability and enhancement by in-situ generated Al2O3 in liquid phase

Thixoforming displays wild application prospects in manufacturing Cu containing high entropy alloy (HEA) product. In current work, we proposed a novel manufacturing strategy on powder metallurgy preparation-thixoforming for Cu containing HEAs, integrating material preparation, shaping and strengthening objectives. During thixoforming, oxide in-situ generation in liquid phase was utilized to reinforce soft phase, achieving the strengthening of component. Based on this strategy, manufacturing of disc-shaped component for a model Al0.8Co0.5Cr1.5CuFeNi HEA was studied. Compared to 1175 °C thixoforming, room-temperature strength experiences a breakthrough increase at 1200 °C and 1225 °C, accompanied by an increase in yield strength of 323.8 MPa and 314.8 MPa, an increase in ultimate strength of 374.2 MPa and 470.0 MPa, meanwhile, fracture strain improves, which is caused by a considerable amount of in-suit generated Al2O3. Homogeneous and almost defect free microstructure obtained under higher temperature conditions ensures uniformity of mechanical properties for the whole component. As thixoforming temperature increases, preferred orientation of grain fiber shape becomes random, plastic deformation of solid grain (PDS) turns to flow of liquid incorporating solid particles (FLS), sliding between solid particles (SS) during material flow filling, which effectively reduces material damage risk caused by strain localization. In-situ generated Al2O3 in liquid phase helps to hinder crack propagation and blunt crack tip in Cu rich soft phase. Al2O3 only strengthens soft phase, relieving mismatch of strength-plasticity properties between soft and hard phase, accordingly, failure of soft phase is delayed and simultaneous improvement of strength and plasticity is achieved.

Strong and stable ultrafine-grained Al-Mg alloys via polymer-derived in situ nanoparticles

Ultrafine-grained Al-Mg alloys provide immense promise as lightweight metallic materials for load-bearing applications, contributing significantly to energy efficiency and CO2 emission reduction. However, for prevalent bulk ultrafine-grained Al-Mg alloys fabricated by a combined mechanical alloying and thermomechanical consolidation, the presence of remaining polymers, which are used as a process control agent during milling, jeopardizes the mechanical performance of the consolidated materials and thus significantly limit their broad applications. An ideal solution to overcome this critical issue is to turn these polymers into useful nanoparticles, enabling simultaneous improvements in strength and grain size stability. In this study, we present an approach to currently achieve strength enhancement and grain size control by incorporating polymer-derived in situ nanoparticles. Through a combined process involving polymer-assisted mechanical alloying, extrusion at the eutectic temperature, and annealing-driven solid-state phase transformation, we achieved a strong and stable ultrafine-grained Al-Mg alloy. After post-heat treatment at 440 °C (i.e. 0.76 Tm; Tm is the absolute melting temperature of pure Al) for 24 h, the compressive yield strength exhibited minimal reduction from ∼1.3 GPa for the as-extruded alloy to ∼1 GPa for the as-annealed alloy. Similarly, the average grain size only experienced a slight increase, from 106 to 145 nm after post-annealing. These findings offer practical insights into the design of mechanically robust and thermodynamically stable ultrafine-grained metallic materials via a new strategy of polymer-derived in situ nanoparticles.

Enhanced Mechanical Properties of Ceramic Rod-Reinforced TWIP Steel Composites: Fabrication, Microstructural Analysis, and Heat Treatment Evaluation

This study investigates the development and characterization of ceramic rod-reinforced TWIP (twinning-induced plasticity) steel matrix composites, produced using the lost foam casting technique. Mechanical tests revealed a substantial improvement in both flexural strength and ductility, with the composite demonstrating more than double the strength of unreinforced TWIP steel. Furthermore, a simple low-temperature heat treatment further enhanced these properties, increasing the flexural strength of the composite to 1023 MPa while also improving its ductility. The improvement in mechanical performance is attributed to the formation of additional twins in the TWIP steel matrix during deformation following heat treatment, which resulted in further strengthening of the matrix.

The efficient waste-based fine-grained fibre concretes for 3D printing

This study investigates the development of optimized 3D printing mixes using Portland cement grades PC 400-D0 and PC 500-D0, combined with fly ash and various fibers such as polypropylene (PP), polyethylene (PE), and nylon, to enhance the mechanical properties and durability of printed structures. The primary aim is to create a mix that ensures sufficient flowability during the printing process while achieving high tensile strength and resistance to cracking. The methodology involved a series of mix designs with varying proportions of cement, fly ash, and fibers, followed by testing for rheology, compressive strength, and durability. Key findings include achieving a compressive strength of up to 50 MPa and a tensile strength improvement of 20 % with the optimal fiber combination. The incorporation of fly ash resulted in a 15 % reduction in material costs and a significant improvement in workability. The practical implications of this research are substantial for the construction industry, particularly in the context of sustainable and efficient building practices. The optimized mix designs not only reduce costs but also enhance the longevity and structural integrity of 3D printed elements, making them viable for large-scale construction projects. This study provides a foundation for further exploration into advanced 3D printing materials.

Dynamic fracture toughness and crack propagation mechanism of a heterogeneous heterostructured material under combined strengthening mechanisms

Developing fracture-resistant high-strength steels is an attractive prospect for various structural applications. In this work, a combination of carburizing heat treatment (CHT) and shot peening (SP) was used to develop combined strengthening (CS) mechanisms and to improve the mechanical strength and dynamic fracture toughness of 18CrNiMo7-6 alloy steel. Standard tensile tests and split Hopkinson pressure bar tests were conducted to investigate the strength and dynamic fracture toughness of the 18CrNiMo7-6 alloy steel. The crack initiation and propagation of samples were studied using scanning electron microscopy and transmission electron microscopy. Microstructure characterization and molecular dynamic simulations indicated that the excellent dynamic fracture toughness of the CS samples could be attributed to the grain refinement after strengthening and the formation of numerous slip bands at the crack tips, reducing the stress concentration at the crack tips. The Cr23C6 precipitates have a positive effect on the strength improvement of 18CrNiMo7-6 alloy steel. The results showed that this research can be used to guide the design of steels with high-strength and high-dynamic fracture toughness.

The role of ettringite seeds in enhancing the ultra-early age strength of Portland cement containing aluminum sulfate accelerator

The ultra-early age strength of shotcrete with Portland cement-based materials in various supporting constructions is crucial for safety and engineering efficiency. However, concerns exist about the low strength and uncertain mechanism when using aluminum sulfate, the main component of most-used alkali-free accelerators. This study addresses these concerns by introducing ettringite seeds into the Portland cement system with aluminum sulfate. Significant improvement in ultra-early age compressive strength of mortar, i.e., 242 % at 6 h and 201 % at 8 h, was achieved by mere 1 % seed addition. Analyses of hydration heat, composition and microstructure demonstrate that the ettringite seeds mainly affect the mechanical performance by forming a more prolonged and coarser ettringite skeleton, rather than directly accelerating cement hydration. Such an enhanced skeleton was proved to establish stronger interactions between particles in the Monte Carlo simulations. Additionally, the synergistic effect of the ettringite skeleton and C–S–H gel on ultra-early age strength was also explored. These proposed strengthening mechanisms were verified by the C3S and equivalent CaCO3 systems.

Investigation of the Mechanical Properties of Hybrid E-Glass and Mohair Fiber Reinforced Epoxy Composites

Natural fiber composites have significant potential to replace traditional materials used in industries due to their excellent tensile strength, stiffness, low specific weight, and superior thermal and insulating properties. Mohair fiber, also known as the Noble fiber and the Diamond fiber, is obtained from the Angora goat, an animal of Tibetan origin. Renowned for its brilliant luster and resilience, Mohair is a symbol of luxury and exclusivity. The primary objective of this study is to manufacture and test a new natural fiber composite that could potentially outperform existing materials in real-world applications. Specifically, the study aims to investigate the mechanical properties of this composite. Mohair has previously been identified as a fiber many times stronger than a strand of steel of similar dimensions. Incorporating these highly desirable properties of Mohair into an epoxy matrix is one of the novel aspects of this research. The testing procedure begins with the preparation of ASTM molds, concurrent treatment of the fibers, and the preparation of the binding material. Specimens are created both with and without the addition of electrical glass (E- glass) fibers. The next phase is curing, during which the epoxy is allowed to solidify, forming strong bonds. Once developed and cured, the composites are removed from their molds and undergo post-processing and finishing techniques. This study aims to understand the tensile and flexural characteristics of natural fiber composites reinforced with epoxy. Three fiber orientations—uniaxial, biaxial, and criss-cross—are employed to assess the changes in the mechanical properties of the composites. The results indicate that adding E-glass fibers in alternating layers of the composite significantly enhances both tensile and flexural strength. Statistically, the addition of the biaxial arrangement of fibers with E-glass fibers results in an 18.47% improvement in ultimate tensile strength, while the maximum flexural strength increases by 49.90%. Furthermore, the topography of the cracked surface is examined using field emission scanning electron microscopy, and the breaking of the fibers in all three directions is studied.

A Nontoxic and Biocompatible Method for Augmenting Mechanical Strength of Acellular Matrix by Silk Fibroin Impregnation.

Biological scaffolds are plagued by poor biomechanical properties and untimely degradation. These limitations have yet to be addressed without compromising their biocompatibility. It is desirable to avoid inflammation and have degradation with concomitant host collagen deposition or even site-appropriate in situ regeneration for the successful outcome of an implanted biological scaffold. This work aims to achieve this by utilizing a biocompatible method to modify acellular scaffolds by impregnating alkaline-catalyzed citric acid (CA) cross-linking between the extracellular matrix proteins and silk fibroin (SF)/SF-gelatin (SFG) blends. Combinatorial detergent decellularization was employed to prepare a decellularized porcine liver scaffold (DPL). After proving the decellularization efficiency, the scaffold underwent modification by vacuum impregnation with CA containing SF (SF100DPL) and SFG blends (SFG5050DPL and SFG3070DPL) following pre-cross-linking, drying, and post-cross-linking. The subsequent strength augmentation was demonstrated by significant improvement in tensile strength from 2.4 ± 0.4 MPa (DPL) to, 3.8 ± 0.7 MPa (SF100DPL), 3.4 ± 0.7 MPa (SFG5050DPL), and 3.5 ± 0.2 MPa (SFG3070DPL); Young's modulus from 8.7 ± 1.8 MPa (DPL) to 20 ± 1.9 MPa (SF100DPL), 13.3 ± 2.6 MPa (SFG5050DPL), and 16 ± 1.2 MPa (SFG3070DPL); and suture retention strength from 0.9 ± 0.08 MPa (DPL) to 2.3 ± 0.2 MPa (SF100DPL), 2.8 ± 1.2 MPa (SFG5050DPL), and 2.6 ± 0.9 MPa (SFG3070DPL). The degradation resistance of the modified scaffolds was also markedly improved. Being cytocompatible, its ability to incite tolerable inflammatory and immune responses was confirmed by rat subcutaneous implantation for 14, 30, and 90 days, in terms of inflammatory cell infiltration, neoangiogenesis, and in vitro cytokine release to assess B-cell and T-cell activation. Such ECM composite scaffolds with appropriate strength and biocompatibility offer great promise in soft tissue repair applications such as skin grafting.

Effects of accelerated carbonation on fine incineration bottom ash: CO2 uptake, strength improvement, densification, and heavy metal immobilization

Incinerating municipal solid waste (MSW) can effectively reduce its mass and volume while producing electricity. However, this process generates incineration bottom ash (IBA), which is an aggregate-like waste containing heavy metals. Due to the higher heavy metal contents, fine IBA can be removed from total IBA and treated separately to promote the use of IBA. Furthermore, MSW incineration generates carbon dioxide (CO2), which is another concern. In this context, it is beneficial to use accelerated carbonation to treat fine IBA, because it can not only contribute to carbon capture but also provide carbonated IBA that may be utilized as aggregates in civil engineering. The accelerated carbonation process of fine IBA is affected by many parameters. Therefore, this study investigated the effects of CO2 pressure (PCO2), initial water content (wi), and carbonation time on the properties of carbonated IBA, including CO2 uptake, unconfined compressive strength (UCS), density, and leaching of heavy metals. The evolution of mineralogy and microstructure of carbonated IBA was also analyzed. The results showed that IBA with wi of 15% and PCO2 of 200 kPa could achieve a CO2 uptake of 6% of IBA mass. The carbonation time significantly affected UCS and dry density of carbonated IBA. As the carbonation time increased from 0 h to 120 h, the UCS increased from 67 kPa to 691 kPa while the dry density increased from 1.38 g/cm3 to 1.51 g/cm3. Compared with untreated IBA, the leaching concentrations of Cu, Cr, Zn, and Pb from carbonated IBA were reduced significantly. As the carbonation time increased, the microstructure of carbonated IBA became denser. This densified structure was one of the reasons for the strength improvement and dry density increment of carbonated IBA.

A systematic review and meta-analysis on effect of different exercise training on grip strength and upper extremity muscle strength in patients with type 2 diabetes mellitus.

Individuals with type 2 diabetes mellitus (T2DM) are prone to musculoskeletal complications, particularly in the upper extremities (UE), which can significantly impair their grip strength and UE muscle strength. This review will provide valuable insights for developing optimized exercise interventions aimed at enhancing upper limb functionality and improving patient outcomes. To determine the effect of different exercise training on grip strength & UE muscle strength in patients suffering from T2DM. A comprehensive search from electronic databases was performed based on the selection criteria and 13 randomized controlled trials (RCT's) were included in the study. Mean changes in grip strength and UE muscle strength were the primary outcome measures. Included studies ranked high on the PEDro rating scale and eta-analysis was performed by Rev Man 5.4 software. Meta-analysis results indicated that there was a statistically significant improvement in UE muscle strength of experimental group when compared to control group (mean differences [MD]=2.91, 95% confidence interval=0.12, 5.71; p=0.04) with moderate heterogeneity (I2=49%, p<0.07). Grip strength improved significantly in the experimental group when compared to the control group with (MD=2.93, 95% CL=-0.00, 5.86; p=0.05) and moderate heterogeneity (I2=66%, p<0.08). This review indicated a positive role of supervised resistance & aerobic exercises on UE muscle strength in patients with T2DM. Due to lack of RCT's, grip strength needs to be explored by further investigations in these patients.

The effect of silane‐modified carbon black and nano‐silica, individually and in combination, on the performance of ethylene–propylene–diene monomer rubber

AbstractThis study assesses the effectiveness of a specially developed surface‐modified carbon black, both on its own and in combination with nano‐silica, as a hybrid filler for ethylene–propylene–diene monomer (EPDM) rubber compounds. The modification process, which included treatment with a silane coupling agent, resulted in enhanced curing characteristics. The ∆Torque values for compounds incorporating the modified carbon black exceeded those of other formulations by 25.85%. Scanning electron microscopy (SEM) analysis demonstrated improved filler dispersion and better compatibility between rubber and filler due to the surface modification. The silane‐modified carbon black showed considerable enhancements in mechanical properties, particularly in tear resistance, with increases in tensile and tear strength of 22.46% and 34.86%, respectively, following surface treatment. Dynamic mechanical analysis (DMA) indicated the influence of both surface modification and filler type, revealing that the combination of modified carbon black and nano‐silica achieved a reduction in rolling resistance of 20.41% and enhanced ice and wet grip performance by 7.95%. Additionally, modified carbon black displayed varying effects on the glass transition temperature. Thermal gravimetric analysis (TGA) confirmed that the thermal stability of the compounds was consistent, while solvent resistance improved with surface modification, as shown by swelling ratios. Thermodynamic analysis indicated that the surface modification of carbon black positively influences the elasticity and chain mobility of the rubber compounds studied. In conclusion, the careful selection and optimization of filler materials and their modifications are essential for customizing the properties of rubber compounds to satisfy specific performance criteria and applications.Highlights Promising EPDM compounds were prepared with Silane‐Modified CB and Nano‐Silica. Silane‐modified CB effectively improved the curing properties of the EPDM compound. The ΔTorque and cross‐link density of modified CB/EPDM show the highest value. Modified CB/Nano‐Silica/EPDM exhibited significant improvement in tear strength. Modified CB/Nano‐silica/EPDM have lower rolling resistance and higher wet grip.

An Innovative Technique for the Strengthening of RC Columns and Their Connections with Beams Using C-FRP ROPES

The application of the innovative C-FRP ropes for the strengthening of reinforced concrete columns is experimentally examined. Two real-scale specimens with the same geometrical characteristics and the same steel reinforcements were constructed for the needs of this investigation. The primary objective of the study is to investigate the efficacy of the use of C-FRP ropes as externally mounted reinforcement for the strengthening of deficient external columns. In this direction, (a) C-FRP ropes are applied as longitudinal reinforcement of the column for the increase in the flexural strength, (b) C-FRP ropes are applied as external confining stirrups in the critical end parts of the column for the improvement of the concrete strength and the development of local element ductility, and finally (c) C-FRP ropes are applied as external stirrups in the form of diagonal X-shaped reinforcement for the increase in the capacity of the part of the column connected with the beam (joint panel). Both specimens are tested under the same cyclic loading procedure that comprises seven steps and each step includes three full loading cycles. The maximum loads of the strengthened specimen at the three loading cycles of the seventh step were 40%, 72% and 87% higher than the corresponding ones of the unstrengthened specimen. On the other hand, the measured shear deformations of the joint panel of the pilot (unstrengthened) specimen at the sixth and the seventh steps were 43% and 44% higher than the corresponding ones of the strengthened specimen. In general, it is concluded that the strengthened column exhibited improved hysteretic response and the whole behavior was apparently improved compared to the pilot specimen without strengthening in terms of maximum loads per loading step, dissipated energy, and shear deformations of the joint panel. In particular, it is stressed that the measured shear deformations of the joint panel and strain gauge measurements have substantiated that the column and the connection panel of the strengthened specimen remain almost intact, whereas damage and eventually failure have been located in the column and the joint panel of the pilot specimen. Additionally, it is emphasized that the C-FRP ropes can easily be applied in structures with complex configuration without any geometrical restraints.

Microstructure evolution and mechanical properties of NiAlCrFeMo high entropy superalloy after different annealing treatment

A novel NiAlCrFeMo high entropy superalloy was prepared using the vacuum arc melting method, followed by annealing at 800 °C, 1000 °C, and 1200 °C for 10 h. The microstructural characteristics and mechanical properties of the alloy after annealing were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Vickers hardness testing, and high-temperature tensile testing. The results indicate that the as-cast alloy consists of dendritic γ+γ′ phases and interdendritic B2-type β phase, with hemispherical α-Cr phases present within the β phase. Compared to the as-cast status, the volume fraction of the β phase in the annealed state increased from 18.52 % to 26.13 %. Notably, at 800 °C/10h, acicular γp’ phases precipitated within the β phase. The alloy exhibited varying degrees of improvement in both strength and ductility after annealing. The specimen annealed at 800 °C/10h showed the highest strength (σYS = 181.06 MPa) and good ductility (εEI = 12.45 %), with strength increasing by approximately 13.10 % compared to the as-cast status. This improvement is attributed to the coarsening of the α-Cr phase, the transformation in γ′ morphology, and the precipitation of acicular γp’ phase. At 1200 °C/10h, all precipitates dissolved into the matrix, resulting in the lowest strength (σYS = 134.08 MPa) and the highest ductility (εEI = 15.54 %).

Development of high-performance piezoelectric composites for concrete construction through carbonation of calcium and magnesium-based binder

The use of cementitious piezoelectric composite enables structure monitoring of concrete construction, while its piezoelectric and mechanical performance are relatively low. This paper developed a novel high-performance piezoelectric composite through carbonation of calcium and magnesium-based binder (including Ca(OH)2 and Mg(OH)2). The influence of PZT volume, forming regime, and polarization condition on compressive strength and piezoelectric strain coefficient (d33) of the two piezoelectric composites was investigated. Results showed that the use of PZT volume from 20 % to 80 % led to a 6-fold and 3-fold greater d33 value for Ca(OH)2 and Mg(OH)2 piezoelectric composites, respectively. While, such change in PZT volume reduced the compressive strength by 50 % and 55 % for the two piezoelectric composites. This is due to the significantly increased porosity and decreased carbonation degree as indicated by microstructural analysis. The use of a higher forming pressure from 25 to 100 MPa resulted in 60 % and 105 % increases in d33 values for the two piezoelectric composites. Such improvements in compressive strength were 120 % and 135 %, respectively. The d33 values were increased by 45 % and 60 % with the polarization voltage increasing from 1.5 to 3.5 kV/mm for the two piezoelectric composites. Such increases in d33 were 64 % and 94 % when polarization duration extended from 5 to 25 min. This study determined the optimal preparation regime of the two piezoelectric composites that can ensure the best overall performance considering the trade-off among piezoelectric, mechanical, and microstructural properties of the composites. The results of this paper can facilitate the application of novel and high-performance of piezoelectric sensor in smart concrete structures.

A 24-Week Combined Resistance and Balance Training Program Improves Physical Function in Older Adults: A Randomized Controlled Trial

Abstract Jiang, G, Tan, X, Zou, J, and Wu, X. A 24-week combined resistance and balance training program improves physical function in older adults: a randomized controlled trial. J Strength Cond Res XX(X): 000–000, 2024—This randomized controlled trial assessed the feasibility of older adults performing combined resistance and balance training (RBT) and compared the effects of RBT on physical function with those of resistance training (RT) alone and with no exercise training in older adults. In total, 65 community-dwelling adults aged 60–74 years were randomly assigned to an RT (n = 22), RBT (n = 22), or control (n = 21) group. The exercise intervention consisted of RT or RBT for 45 minutes, 3 times per week for 24 weeks. The control group engaged in no exercise training. The compliance rates were 93% in the RT group and 92% in the RBT group. No training-related adverse effect was observed. In the RT and RBT groups, dynamic balance (p = 0.017; p &lt; 0.001, respectively), maximum walking speed (p = 0.014; p &lt; 0.001), upper extremity (p = 0.013; p = 0.009) and lower extremity (p = 0.009; p &lt; 0.001) muscle strength, and spirometry (p = 0.043; p = 0.018) were significantly improved at 24 weeks compared with the control group. Only the RBT group showed significant improvement in normal walking speed (p = 0.002). Compared with the RT group, the RBT group showed additional significant improvements in dynamic balance (p = 0.001) and lower limb muscle strength (p = 0.027). The findings of this randomized controlled trial indicated that RBT was safe and feasible for older adults. Long-term RBT had better effects than either no exercise training or RT alone on improving physical function in older adults. Compared with RT, RBT additionally benefited dynamic balance and lower limb muscle function, which are clinically important factors in preventing falls, frailty, disability, and other geriatric syndromes.

Achieving simultaneous improvement in strength and ductility in Al–Si–Mg–Ce alloy through synergistic morphology modification of eutectic (Si) and Al2Si2Ce phases by Sr addition

In this paper, it was found for the first time that with Sr addition in Al–Si–Mg–Ce alloy, the morphology of eutectic (Si) can be modified from branch to fine fibrous, while the bulk-like Al2Si2Ce phase may replace the elongated needle-like one. Moreover, Mg was observed to segregate along the (Al)/Al2Si2Ce interface and Sr was found to concentrate in the interior of Al2Si2Ce phase. Such heterostructured Sr–Al2Si2Ce was also supported by first-principles calculations. The synergistic morphology modification of eutectic (Si) and Al2Si2Ce phases by Sr addition stimulated the simultaneous improvement in strength and ductility in Al–Si–Mg–Ce alloy.

Synergizing empirical and AI methods to examine nano-silica's microscale contribution to epoxy coating corrosion resistance

Epoxy-nanomaterials offer a promising solution to combat corrosion threatening civil infrastructure. To examine the impact of nano silica on corrosion resistance, varying amounts of nano silica, ranging from 0.0 to 3 wt%, were introduced into the epoxy matrix. Mechanical properties were studied through studying the dog-bone tensile strength and tribological aspects were assessed through mass loss abrasion tests. Corrosion resistance performance was studied using electrochemical impedance spectroscopy (EIS) and salt spray tests. Nano structure of the coated specimens was studied after salt spray tests using SEM-EDX analysis. Micro Chromatography (M-Ct) technique was employed to investigate the pore formation in the epoxy matrix. Besides, atomic force microscopy (AFM) was introduced to study surface roughness. The test results displayed a notable improvement (5–10 %) in tensile strength upon the introduction of nano silica. Taber tester results showed a reduction in mass loss with the addition of nano silica. Electrochemical impedance spectroscopy (EIS) studies further established a significant increase in corrosion resistance, having an impedance of 12 GOhm.cm2 for epoxy matrix samples containing 2.5 % nano silica after a 768-h salt spray test. SEM-EDX analysis revealed the absence of iron content in the epoxy matrix reinforced with uniformly distributed nano silica. Surface roughness assessments illustrated that nanolaminates contributed to an increase in overall roughness, minimizing surface irregularities in the epoxy matrix. Micro-CT scanning results proposed a decrease in epoxy matrix porosity upon the addition of nano silica. AI based prediction model helped to understand the relationship between surface roughness and corrosion. In summary, the experimental findings suggest valuable insights for future advancements in the development of protective coatings for worldwide civil infrastructures.

Characterization and optimization of desulfurized construction gypsum modified with functionalized nanocellulose

This study focuses on the development and characterization of a novel composite material based on flue gas desulfurization (FGD) gypsum modified with functionalized nanocellulose. The incorporation of 0.1 wt% nanocellulose into the FGD gypsum matrix resulted in significant improvements in mechanical strength, water resistance, and thermal insulation properties. The flexural and compressive strength of the optimized composite increased by 32 % and 27 %, respectively, compared to the control sample. The water absorption decreased by 22 %, and the softening coefficient increased from 0.72 to 0.85, indicating enhanced water resistance. The thermal conductivity of the composite was reduced by 31 %, showcasing its potential as an energy-efficient building material. SEM analysis revealed a refined microstructure with improved interfacial bonding between the nanocellulose and gypsum matrix, while FTIR spectroscopy confirmed the presence of chemical interactions between the components. The moisture buffering capacity of the composite was also superior, with a 38 % higher moisture buffering value than the control sample. These findings highlight the potential of functionalized nanocellulose as a reinforcing agent in FGD gypsum-based composites, offering a promising solution for the development of high-performance, eco-friendly building materials.

Mechanical performance and reinforcing mechanisms of foamed concrete strengthened by carbon fibers

Foamed concrete (FC) is a lightweight and environmentally friendly building material that offers versatile applications in civil engineering. However, FC is inherently weak in withstanding tensile and compressive loads. While incorporating fibers into FC has been shown to resist crack propagation and enhance its mechanical properties, the specific mechanisms through which carbon fibers affect FC's tensile and compressive behaviors remain unclear. This study aims to address this gap by incorporating short-cut carbon fibers into FC to achieve a micro-reinforcement effect and enhance its compressive and tensile performance. The mechanical properties, failure modes, and microstructure evolution of carbon fiber-reinforced FC at different density levels, carbon fiber lengths, and contents were comprehensively explored. Digital Image Correlation (DIC) was utilized to analyze crack propagation, and an optimal mix ratio experiment was conducted. The results demonstrate that incorporating carbon fibers effectively enhances the mechanical performance of FC, with a more significant impact on specimens with a density of 500 kg/m3. Furthermore, the maximum improvements in tensile and compressive strengths reached 250 % and 88.5 %, respectively. This study suggests that optimal reinforcement ratio can be achieved through mix ratio adjustments and curve fitting formulas, thereby optimizing the tensile and compressive performance of the specimens.

Experimental Investigation on Axial Strength Improvement of Cold-Formed Steel Jacketed Concrete Stub Columns

This paper presents an experimental study on the behavior of low-strength concrete columns confined with cold-formed steel under axial compression. The laboratory test specimens consist of four groups of rectangular concrete stub columns in the size of 130 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes $$\\end{document} 200 mm cross section and 300 mm height; the first group composes of the unconfined specimens, while the other three contain the confined specimens under 0%, 25% and 50% sustained axial loads. The jackets are made of two G450-grade channel cold-formed steel sections of 2.4 mm thickness welded together. No bonding material is used between the core concrete and the steel jacket. From the results, it is found that the cold-formed steel jacketing can increase the axial strengths of the unconfined concrete specimens by approximately 40-65%. The strength increase comes mainly from the confinement action, as only small axial deformation is detected in the jacket. Based on the given amount of prescribed preloads in this study, the presence of preload in the column does not have a significant effect on the increase in strength of the confined concrete columns. The measured strength enhancement ratio and the confinement ratio of the tested specimens are compared using five existing strength predictive equations. The performance of the unbonded cold-formed steel jacketing technique adopted in the stub columns is observed to closely conform with the predictive confinement model of the concrete-filled tubes.