Enhancement In Flexural Strength Research Articles

Study on the Effect of Fly Ash on Mechanical Properties and Seawater Freeze–Thaw Resistance of Seawater Sea Sand Concrete

When using seawater and sea sand as mixes, the mechanical properties and durability of concrete are adversely affected because the raw materials themselves contain harmful ions. Fly ash is the tailings formed in the process of industrial production, the use of which does not require the burning of clinker, reducing CO2 emissions. Moreover, it belongs to a new type of cementitious materials with low emissions and high environmental protection. Fly ash enhances the properties of concrete and reduces the effect of harmful ions on concrete. Based on the above considerations, the corresponding specimens were prepared and subjected to cubic compressive strength, flexural strength, and seawater freezing and thawing resistance tests by using fly ash admixture as the main variable. A combination of macro-analysis and micro-analysis was used to investigate the effect of fly ash on the performance of seawater sea sand concrete. The results showed that fly ash significantly enhanced the mechanical properties and resistance to seawater freezing and thawing of seawater sea sand concrete. The best improvement in compressive strength and resistance to seawater freezing and thawing was achieved at a substitution rate of 20%. The maximum increase in compressive strength was 13.22%. The maximum reduction in mass loss rate was 57.26% and the strength loss rate was 43.14% after the specimens were subjected to seawater freezing and thawing 75 times. The maximum enhancement in flexural strength was 17.06% for a substitution rate of 10%. Through microanalysis, it can be seen that the incorporation of coal ash can enhance the compactness of concrete through the microaggregate effect as well as the volcanic ash reaction to promote the secondary hydration reaction, so as to strengthen the seawater freeze–thaw resistance of seawater sea sand concrete. Finally, the damage prediction model established using the mean GM (1, 1) model of gray system theory meets the requirements of the first level of prediction accuracy and can accurately predict the damage of seawater sea sand concrete under seawater freezing and thawing.

Simultaneous enhancement of magnetic properties and flexural strength in 2:17 type SmCo magnets induced by spherical WO3 particles doping

The influence of spherical WO3 particles doping on the flexural strength and magnetic properties of Sm(CobalFe0.23Cu0.07Zr0.02)7.8 magnets was investigated. As the doping amount increased from 0 wt% to 2.0 wt%, the magnetic properties initially exhibited an increase followed by a decrease, with coercivity increasing from 32.77 kOe to 36.01 kOe and remanence increasing from 11.16 kGs to 11.28 kGs at a doping amount of 0.5 wt%. Moreover, the flexural strength consistently rose from approximately 80 MPa to 127 MPa, representing a significant increase of about 59 %. The presence of WO3 particles optimizes the magnet’s orientation and Cu distribution in the cell boundary phase, thereby enhancing both remanence and coercivity. Additionally, a significant decrease in grain size from 72.04 μm to 33.41 μm was observed, accompanied by a noticeable increase in the content of Sm2O3 phase, which positively contributes to the enhancement of flexural strength. Our research presents a novel technical approach for simultaneously enhancing the magnetic and mechanical properties of 2:17 type SmCo magnets.

Impact of basic oxygen furnace slag on the hydration microstructure, mechanical properties, and carbon emissions of supersulfated cement

Supersulfated cement (SSC) is recognized as a cementitious material with low CO2 emissions, consisting predominantly of ground granulated blast-furnace slag (GGBS) and a minor activator content. The production of GGBS production constitutes the primary source of CO2 emissions in SSC. In contrast, carbon emissions from the production of basic oxygen furnace slag (BOFS) are lower, and BOFS inherently exhibits substantial carbonization potential. Therefore, in this study, BOFS is employed as a replacement for GGBS in formulating an innovative low-emissions binder denoted as BOFS-modified supersulfated cement (BMSC). This study investigates the influence patterns of BOFS substitution for GGBS on the strength properties of BMSC. Furthermore, a series of experiments involving QXRD, TGA, SEM, and MIP were conducted to systematically investigate the mechanistic impact of BOFS on the hydration microstructure of BMSC. The findings reveal that substituting 10 % of GGBS with BOFS contributes to an enhancement in both flexural and compressive strength of specimens at 7 and 28 days. BOFS exerts a positive influence on the formation of ettringite in BMSC. The C2S and C4AF within BOFS also demonstrate distinct hydration activity. Additionally, BOFS can reduce large pores in the early hydration paste and contribute to narrowing the average pore size. Moreover, the evaluation of the Global Warming Potential (GWP) demonstrates that the replacement of slag with BOFS can lead to a further reduction of up to 30 % in the carbon emissions of SSC.

Effects of autogenous shrinkage microcracks on UHPC: Insights from a machine learning based crack quantification approach

Owing to its high pozzolanic reactivity and contribution to packing density, silica fume is almost an indispensable part of UHPC, but it brings potentially serious problem of high autogenous shrinkage. Nanocellulose (NC) is very effective in controlling shrinkage but would also result in different microstructure, whose impact is not clear. This study aims to explore the compensatory effect of NC on high shrinkage of UHPC. An image process method based on machine learning and stereological methods is proposed to quantify the autogenous shrinkage induced microcracks. Results show that the addition of NC reduces the crack width and area by 57.45∼70.55% and 63.2–83.8%, respectively. The MIP analysis reveals that the incorporation of NC introduces a larger proportion of pores. In terms of mechanical properties, the higher content of pores brought by NC has a negative effect on compressive strength, however, the enhancement of flexural strength by NC can reach 66.02%. Excellent correlations between 0 and 50 nm porosity and compressive strength, crack density and flexural strength are observed with R2 of 0.94 and 0.98 respectively. This study provides a theoretical basis for the potential control of porosity and cracks of UHPC to meet the different mechanical performance requirements of components.

Nano clay treated jute fiber reinforced epoxy composites: Thermo‐kinetic, morphological and mechanical analysis

AbstractCurrent scientific research prioritizes sustainable and cost‐effective materials due to the depletion of traditional non‐renewable sources. Natural fiber reinforced composite materials emerge as promising solutions. However natural fibers being hydrophilic in nature are less compatible with hydrophobic epoxy matrix, to address this issue nano clay treatment of jute fibers have been done and epoxy composites were formed with their reinforcement. Through FT‐IR, thermal, mechanical, and morphological analyses, both treated and untreated composites are evaluated. The treated composites exhibit a notable 19% increase in activation energy (FWO and KAS methods) compared to untreated ones (217.5–259 KJ/mol), indicating improved thermal stability. Moreover, the treated composite demonstrates a significant 38% boost in tensile strength (30–41.4 MPa) and a 28% enhancement in flexural strength (50–64 MPa), highlighting the impact of alkali‐nano clay treatment in reinforcing structural integrity. These enhancements suggest the potential applicability of composites manufactured with alkali‐nano clay treated jute fibers (A/NC/J fiber) across various industries. This innovative approach not only bridges the gap in sustainable material development but also offers cost‐effective solutions for commercial utilization.Highlights Analyzed alkali‐nano clay treatment effects on jute fiber in epoxy composites. Studied activation energy (FWO, KAS) for untreated and treated composites. Treated composites show a 19% increase in activation energy: Thermal stability Significant improvements: 38% rise in tensile, 28% increase in flexural strength.

Multi-scale analysis and structural application of the synergistic enhancement effect of silane coupling agent on the interface between PVA/rubber and cement

This study employs polyvinyl alcohol (PVA) fibers and silane coupling agent (SCA) to augment rubberized concrete mechanical prowess. A multiscale investigation delves into the synergistic enhancement mechanism of SCA on the interfaces of PVA/cement and rubber/cement, considering macroscopic mechanical properties, microscopic structural characteristics, and nanoscale interface interactions. Initially, fundamental mechanical performance tests reveal a notable enhancement in compressive and flexural strength with the inclusion of SCA and PVA fibers in rubberized concrete. Subsequently, observations of corresponding composite concrete slices are conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results manifest gel and polymer filling interface gaps, with SCA fostering a tighter amalgamation of the two interfaces, effectively rectifying interface defects and elucidating its bonding effects at the microscopic interface. Molecular dynamics (MD) modeling and simulation analyses of PVA/C-S-H and rubber/C-S-H, pre- and post-SCA modification, demonstrate that SCA mitigates interface effects, reinforcing hydrogen bonding, van der Waals interactions, Ca-H coordination bonds, and stability. This augmentation enhances interface adhesion energy, fortifying the weak interface bonding between PVA fibers, rubber, and inorganic silicate (C-S-H). Ultimately, portal frame experiments substantiate that incorporating fiber rubberized concrete into structures not only fails to diminish but marginally enhances the load-bearing capacity of the framework. This research furnishes concrete and innovative solutions for sustainable development while providing a valuable reference for the future application of PVA fiber rubberized concrete materials in practical engineering endeavors.

Enhancement of Flexural Strength in Fiber–Cement Composites through Modification of Sisal Fiber with Natural Rubber Latex and Expanded Perlite

This study presents a novel approach in enhancing the flexural strength of sisal fiber cement composites by employing a dual coating technique with natural rubber latex and expanded perlite to the sisal fibers. The effects of different fiber content (0.25, 0.5, 0.75, 1, 1.25, and 1.5 wt%) and fiber length (1, 2, and 3 cm) on the physical and mechanical properties of sisal fiber cement were also studied. The physical properties, including bulk density and water absorption, were evaluated via the Archimedes method. Flexural strength was measured using the 3-point bending method, and microstructure was observed using a scanning electron microscope (SEM) and an optical microscope (OM). As the fiber content and length increase, the bulk density of the sisal fiber cement decreases. However, composites utilizing coated fibers consistently exhibit a higher bulk density than those utilizing uncoated fibers, attributed to enhanced adhesion and reduced porosity. The water absorption of sisal fiber cement increases with fiber content, but it is mitigated by the natural rubber latex coating, which prevents fiber–water absorption, and by expanded perlite, which reduces voids in the matrix. Composites containing coated fibers consistently exhibit superior flexural strength compared to those with uncoated fibers. The highest flexural strength values of 5.58 MPa were observed in composites utilizing 3 cm of coated fiber with 0.25 wt% fiber content. Microstructure analysis reveals a well-bonded interface in coated fibers, emphasizing the positive impact of coating on mechanical performance. The incorporation of coated sisal fibers effectively improves adhesion, water resistance, and flexural strength, offering sustainable and durable construction materials. The achieved results can serve as the guidelines for the development of a high-performance bio-based construction materials with improved durability and reduced environmental impact.

Enhanced mechanical performance and damping behavior of CFRP composites through exfoliated MWCNT functionalization

In evaluating high-performance multiwall carbon nanotube (MWCNT) based carbon fiber composites, effective chemical functionalization of fillers for sufficient exfoliation and precise interface interactions with resin matrix are challenging to attain due to significant interlayer cohesive energy and inactive surfaces of composites. Herein, we demonstrate an effective way to produce carbon fiber-reinforced polymer (CFRP) composite with amended interfacial characteristics via incorporation of MWCNT through oxidation followed by silane functionalization with their exfoliation levels (0/48/60/72 h). The surface functional elements, morphological changes, elemental groups, quantitative information, and thermal degradation of silane functionalized MWCNTs were characterized by FESEM/HR-TEM, XRD, UV, and TG-DTA analysis, respectively. The influence of silane functionalized MWCNT reinforcement on CFRP's mechanical properties were examined using tensile, flexural, ILSS, and damping behavior was analyzed through impulse excitation technique (IET). The resulting silane-modified MWCNTs with 60 h oxidation (OAC-60) infused CFRP demonstrated significant enhancement in flexural strength (73.8%), tensile strength (58.2%), interlaminar shear strength (28.5%) compared to pure-CFRP.

Enhancement of Flexural Strength by Slip Casting Cordierite Ceramics with h-BN Nanoparticles

In this study, we enhanced the flexural strength of cordierite ceramics by incorporating h-BN (hexagonal boron nitride) nanoparticles, facilitated by the slip casting process. Initially, commercial cordierite powder with an average particle size of 10 mm underwent a ball-milling process to reduce the size to 2.5 mm and simultaneously achieve a narrower particle size distribution. The resulting slurry, composed of 67% solid content, exhibited improved stability during the slip casting process for both pristine cordierite and the mixture containing 1 – 2 wt% h-BN nanoparticles. After sintering, the bulk material containing 2wt% h-BN nanoparticles demonstrated a remarkable flexural strength of 174.8 MPa, a significant improvement compared to the initial 119.5 MPa obtained without the addition of h-BN. It is worth noting that the introduction of h-BN nanoparticles did not induce substantial changes in dielectric constant and thermal conductivity, indicating that the desired mechanical enhancement did not compromise other crucial material properties. This research demonstrates a successful approach to concurrently optimize the flexural strength, dielectric constants, and thermal conductivity of cordierite ceramics. This breakthrough opens up new avenues for advanced applications in a wide range of fields, from electronics to aerospace, where high-strength, thermally stable materials are in demand.

Cyclic behavior of existing RC bridge piers strengthened by exterior ECC and BFRP/ECC composite jacketing at pier base

Engineered cementitious composites (ECC) are a class of high-performance fiber-reinforced cementitious composites. This study proposes using ECC and BFRP grid-reinforced ECC (BFRP/ECC) as external jackets at the base of existing RC bridge piers to enhance seismic performance. Seven 1/5-scale RC bridge piers were tested under reversed cyclic loading, including one unmodified pier as reference and six reinforced piers with varying jacket thickness, height, interface, and BFRP grid mesh size. The test results demonstrate that both ECC and BFRP/ECC composite jacketing effectively enhance ductility. The hysteretic response of the reinforced piers with different interfacial properties, however, varied significantly. The piers with interfacial shear keys exhibited enhanced flexural strength, ductility, and energy dissipation capacity but sustained severe damage as jacketing thickness and height increased. Conversely, the piers with smooth interfaces showed insignificant improvements in flexural strength but significant enhancement in ductility with marginal damage. This behavior can be attributed to the fact that the exterior jacketing in specimens with interfacial shear keys was under bi-axial tension-compression stress state due to flexural compression and lateral expansion of the plastic hinge, while the jacket in specimens with smooth interfaces acted solely as lateral confinement.

Collaboration of Fenton reaction with a tannin acid-based hyperbranched waterborne polyurethane sizing agent for synergistic enhancement of the CF/PA6 composite interfacial properties

The adhesive strength between the sizing agent and carbon fiber (CF) plays a pivotal role in determining the interfacial properties of composites. Unfortunately, this critical aspect has been consistently overlooked. In this study, a hyperbranched waterborne polyurethane (HWPU) sizing agent was prepared by biogenetic derived raw materials including gallic acid as well as tannic acid. Meanwhile, iron ion was introduced onto the surface of CF by Fenton reaction, forming a heterogeneous structure to elevate the mechanical interlocking between the CF and resin. Chelation of TA with iron ion on the fiber surface effectively enhanced the adhesion between sizing agent and CF. The mechanical properties of the newly designed composites were systematically investigated. The results showcase a significant enhancement in both flexural strength and interlaminar shear strength (ILSS) compared to untreated CF, marking improvements of 54.3% and 60.0%, respectively. Furthermore, the interfacial shear strength (IFSS) test exhibited a 71.2% augment. In conclusion, this approach presented a highly promising concept aimed at improving the interfacial performance of CF composite materials.

Novel short Agave americana based biocomposite and nanobiocomposites for automotive applications

Short fibers of Agave Americana (AA) was extracted from its plant leaf, was chemically treated with Ac2O, HCOOH, H2O2, KMnO4 and NaOH, and then characterized by Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), thermo-gravimetric/differential thermo-gravimetric (TGA/DTG), and field emission-scanning electron microscopy (FE-SEM). PVA stabilized copper nanoparticles from chemical reduction method was characterized using field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDAX), powder X-ray diffraction (PXRD), Dynamic light scattering analysis (DLS), UV–visible absorption spectroscopy, Fourier Transform infrared (FT-IR) spectroscopy and Thermogravimetric analysis/differential thermogravimetry (TGA/DTG). Bio-composites (AA + Polyester Resin (PE) and hybrid nano bio-composites (AA + Polyester Resin (PE) + Cu) were prepared from the untreated and treated AA fibers and further characterized. The synergistic effect of chemical treatment on morphological (SEM), thermal (TGA/DTG), mechanical properties (flexural, tensile, impact and compressive strength) followed by % water absorption were examined. The average surface roughness values (Ra) of chemical treated fiber was identified to be in decreasing manner along with compression strength of biocomposite in the order of untreated (10.74 μm, 44.01 MPa) > NaOH (8.55 μm, 45.07 MPa) > HCOOH (3.49 μm, 24.10 MPa) Ac2O (3.24 μm, 22.10 MPa) > H2O2 (2.51um, 17.9 MPa) > KMnO4 (1.52 μm, 15.1 MPa) treated fibers. Subsequently, the addition of 2s@PVA led to reverse the order namely, the compressive strength of the bionanocomposites were Untreated (10.74 μm, 9.0 MPa) < NaOH (8.55 μm, 0.1 MPa) < HCOOH (3.49 μm, 3.6 MPa) < Ac2O (3.24 μm, 7.6 MPa) < H2O2 (2.51um, 13.3 MPa) < KMnO4 (1.52 μm, 44.1 MPa) treated fibers. Similarly, the biocomposite where the fibres were treated with NaOH, HCOOH were more rough and had, good interconnection between fiber/PE matrix along with enhanced mechanical properties. On addition of nanobiocomposite, only KMnO4 treated fiber composite possed significant mechanical properties. Therefore, mixing CuNPs@PVA with KMnO4 treated fibers led to significant boost to the mechanical properties and minimised the % water absorption properties when compared to the untreated AA/PE biocomposites. The KMnO4 treatment of the AA fiber and addition of copper nanoparticles caused the enhancement of thermal properties, tensile strength and flexural strength. But, these nanobiocomposites were observed to have low impact strength; while, H2O2 treated nanobiocomposites had highest impact strength. The chemical treatment of the AA fiber with NaOH, Ac2O and KMnO4 developed the water resistance of the respective biocomposites. All the nanobiocomposites with chemically treated AA fibers (except Ac2O) were found to have high water resistance. So, they can be used in automotive industry for non-structural applications.

Enhancement of flexural modulus and strength of epoxy nanocomposites with the inclusion of functionalized GNPs using Tween 80

In this work, epoxy nanocomposite was prepared with the inclusion of unfunctionalized as-received GNPs (ARGNPs) and functionalized GNPs using surfactant Tween 80 (T80GNPs) in the epoxy resin using a mechanical stirrer. ARGNPs were used as it is, while T80GNPs were prepared through the adsorption of surfactant onto GNPs’ surface using a sonication procedure in an ultrasonic bath. Characterization of nanoparticles using SEM shows that ARGNPs indicated a softer image representing a thinner layer of graphene stacks compared to T80GNP which has a tangible solid-looking image resulting from the sedimentation during the process of filtration. Elementally, both ARGNPs and T80GNPs were found to contain carbon, oxygen, and sulfur, as indicated by the EDX spectrum, with the C/O ratio for T80GNPs being 34.7% higher than that for ARGNPs, suggesting the adsorption of Tween 80 molecules on the GNPs after functionalization. FTIR spectroscopy confirms the attachment of Tween 80 molecules on GNPs surface with T80GNPs spectrum indicated higher peak intensity than ARGNPs. Flexural testing demonstrated that the addition of 0.9 wt.% ARGNPs and 0.9 wt.% T80GNPs to the epoxy increased the modulus of the nanocomposites to 72.1% and 82.6%, respectively, relative to neat epoxy. With the same amount of particle content, both nanocomposites showed increased strength, with ARGNPs and T80GNPs exhibiting strengths of 70.5% and 87.8%, respectively, relative to neat epoxy.

Investigation into the Performance Enhancement of Calcium Phosphate Mineralization-Compacted Chinese Fir

The utilization of wood as a construction material offers inherent advantages, including its renewability, good process property, wide availability, and carbon sequestration. However, its susceptibility to combustion and limited mechanical properties also constrain its applications. In this work, calcium phosphate was in situ deposited in dignified Chinese fir wood, followed by hot-pressed densification. Thermogravimetric analysis (TG) reveals that mineralization and densification alleviate the thermal decomposition and combustion behavior of wood, which greatly promotes the formation of the dense char layer during wood combustion. Therefore, the maximum heat release rate (HRR), total heat release rate (THR), and total smoke production rate (TSP) of the as-prepared mineralized dense wood were significantly reduced by 37%, 32%, and 56% compared with the control one. Further, the mineralized dense wood showed a remarkable enhancement in flexural strength and flexural modulus of elasticity, 203% and 220% higher than the natural wood, respectively. This study demonstrated a straightforward and eco-friendly approach to fabricating structural wood possessing exceptional flame retardancy and mechanical characterization, which holds immense potential for application in energy-efficient green buildings.

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%.

Unveiling the enhancement of mechanical properties in cryogenic-treated Sm2Co17 permanent magnets without sacrifice of magnetic properties

SmCo permanent magnets are used in some of the strongest permanent magnets, particularly for applications between about 200 and 550 °C. However, their brittleness limits their practical use. Improving their mechanical properties is therefore of great practical significance. Cryogenic treatment is firstly applied in SmCo permanent magnets to enhance the mechanical properties. The flexural strength has been increased by 14.3% along the weakest orientation, and the impact toughness has been increased by 7.0%. After cryogenic treatment, the intrinsic coercivity is slightly increased, and the other magnetic properties are almost unchanged, which is different from other methods to improve mechanical properties at the expense of magnetic properties. The enhancement of flexural strength and impact toughness primarily stems from a decrease in residual stress. This study provides an effective and convenient approach to enhance the mechanical properties in Sm2Co17 permanent magnets without sacrifice of magnetic properties.

Three-dimensional printing with waste acrylonitrile butadiene styrene: Processing and characterization

Three-dimensional (3D) printing of waste plastic such as acrylonitrile butadiene styrene (ABS) is challenging because multiple heating cycles and irregular cooling cause accumulation of stress in 3D-printed structures, which significantly affects mesostructured and fiber-to-fiber bond strength. Hence, this study demonstrates the ability to print high-quality parts via 3D printing using ABS waste. The different weight proportions (100, 90/10, 80/20, 70/30, 60/40, 50/50) of recycled ABS (RABS)/virgin ABS (VABS) are selected for experimentation. It is found that increasing VABS content in RABS significantly improved the physical properties of samples. Due to VABS blending in RABS, the average enhancement in flexural strength (Sf), flex modulus (Ef), and work of fracture (WOF) are 11.49%, 5.45%, and 17.31%, respectively, when compared with 100% RABS samples. Similarly, the average increase in Young’s modulus (E), tensile strength at yield (Ty), and ultimate tensile strength (UTS) are 7.71%, 5.19%, and 3.51%, respectively. The samples printed with 50% RABS/50% VABS blends show superior mechanical properties than others, also the properties of 90% RABS/10% VABS and 80% RABS/20% VABS are very close to 100% VABS samples. Hence, this study provides unique opportunities for the sustainable use of waste ABS using 3D printing technology.

Performance enhancement of recycled coarse aggregate concrete by incorporating with macro fibers processed from waste GFRP

Reprocessing into coarse aggregates of concrete is a sustainable solution for the disposal of construction and demolition (C&D) waste. The use of recycled coarse aggregates however leads to a degradation in the mechanical properties of the resulting concrete, which then limits the use of recycled aggregates concrete (RAC) in structural elements. The incorporation of discrete fibers shows to be effective in eliminating the mechanical degradation problem of RAC, and this paper has therefore proposed to use macro fibers recycled from waste glass fiber reinforced polymer (GFRP) to reinforce RAC, thus improving the robustness of using RAC in structural elements. The effect of incorporating macro fibers on the mechanical properties of RAC has been first examined through a series of compression and bending tests. The tensile constitutive law of concrete was then derived based on the load-deflection response of the beam specimens using an inverse analysis. The results revealed that the mechanical properties (e.g., compressive toughness, flexural strength, flexural toughness) of RAC can be significantly enhanced by adding macro fibers. For concrete with 50% recycled aggregate (RA), the increase of macro fibers (from 0% to 0.5%, 1%, and 1.5%) leads to the enhancement of flexural strength from 3.13 MPa to 3.54, 4.69, and 5.97 MPa, and the toughness (T150) from 1.4 J to 35.5, 59.2 and 77.6 J, respectively. Such enhancements in the mechanical properties of RAC demonstrate the feasibility of the proposed method.

Mechanical properties of basalt fiber reinforced ambient-cured lightweight expanded polystyrene geopolymer concrete

This study investigated the mechanical properties of ambient-cured lightweight expanded polystyrene (EPS) geopolymer concrete (LEGC) specimens with densities ranging from 1321 to 1912 kg/m3 (i.e., EPS dosing of 40%, 30%, 20%, and 10%) by dosing basalt fiber (BF) with volume contents of 0.2%, 0.4%, 0.6%, and 0.8%. First, density, workability, quasistatic compression, splitting tensile, flexural and ultrasonic pulse velocity (UPV) tests were carried out with the LEGC specimens. Based on the test results, the quasistatic compressive strength enhancement rates of LEGC specimens dosed with EPS volume contents of 10%, 20%, 30% and 40% under the effect of optimal dosing of BF were 10.39%, 19.71%, 16.61%, and 15.18%; the split strength enhancement rates were 14.08%, 21.54%, 26.83% and 19.44%; the flexural strength enhancement rates were 7.35%, 17.82%, 22.56% and 17.34%; and the UPV enhancement rates were 2.82%, 1.90%, 3.12% and 2.95%, respectively. Consequently, empirical formulas were established for predicting the quasistatic compressive strengths, splitting tensile strengths, flexural strengths, and UPV values of the LEGC specimens. The prediction equations were also compared with the empirical equations proposed by previous researchers. Finally, to characterize the damage mechanisms of the LEGC specimens, computerized tomography (CT) and scanning electron microscopy (SEM) analyses were also performed on damaged LEGC specimens.

Exploring the synergistic effect of fly ash and jute fiber on the fresh, mechanical and non-destructive characteristics of sustainable concrete

The utilization of waste fly ash and natural jute fiber has drawn attention to producing sustainable concrete. However, there is a lack of studies to analyze the synergistic effect of jute fiber and fly ash on the properties of concrete. Hence, the aim of this study is to investigate the combined effect of fly ash concentration and the different sizes of jute fiber on the fresh, hardened, and non-destructive testing properties of concrete. Concerning the purpose, the concrete mixes were prepared with 0.2 % and 0.4 % jute fiber incorporating 0 %, 5 %, 10 %, and 15 % replacement of cement by fly ash in concrete. For the assessment of properties, slump, density, and compacting factor test was conducted at the fresh state of concrete, whereas mechanical properties such as compressive, splitting tensile, and flexure strength test were conducted at 7 and 28 days. In addition, the non-destructive test (NDT) was also carried out to predict the destructive compressive strength by rebound hammer at 28 days. The microstructure property of optimum mix concrete was analyzed by scanning electron microscopy (SEM). It is observed that the incorporation of jute fiber decreased the slump, density, and compacting factor but increased the compressive, splitting tensile, and flexure strength, whereas the fly ash improved both fresh and hardened properties. Compared to the standard mix, fly ash-based JFRC mixtures have compressive strength improvements varying from 1.7 % to 25.9 %. The 10 % fly ash and 0.2 % volume of jute fiber exhibited a maximum of 11.64 % and 10.72 % splitting tensile and flexural strength enhancement at 28 days, respecting the control mix. In addition, the NDT strength assessment obtained 5.5 % less than destructive strength on average. From the SEM point of view, it is obtained that the 10 % fly ash with 0.2 % jute fiber composition matrix exhibits a better bonding interface and the cracking resistance nature of the concrete mix.