Reduction In Tensile Strength Research Articles

WASTE EGGSHELL AND SAWDUST AS REINFORCEMENTS FOR SUSTAINABLE POLYESTER COMPOSITES: MECHANICAL CHARACTERIZATION AND ENVIRONMENTAL DURABILITY ASSESSMENT

This research endeavor undertakes an experimental investigation into the bending and tensile properties of polyester composites reinforced with waste eggshell powder and sawdust particles at 35 wt.%. Valorizing these waste materials as reinforcements contributes to sustainable practices, waste minimization, and environmental pollution mitigation. Composite samples were fabricated using hand lay-up and compression molding techniques. The effects of environmental exposure to water, acidic, and basic media immersion on the mechanical performance were evaluated to assess durability. Experimental characterization through tensile and three-point bending tests determined mechanical properties, stress-strain behavior, and failure mechanisms. Additionally, finite element analysis (FEA) simulations complemented the experiments by providing insights into stress distributions, deformations, and potential failure initiation sites within the composites under flexural loading. The computational models accurately captured the reinforcing effects of the waste materials and the degradation induced by environmental exposure, validating the experimental trends. Incorporating waste natural fibers significantly enhanced polyester's bending strength by 140% (sawdust) and 75% (eggshell), and tensile strength by 13% (sawdust) and 10% (eggshell). However, environmental exposure degraded properties to varying extents, with water immersion reducing tensile strength by 63% (sawdust) and 3% (eggshell), and flexural strength by 63% (sawdust) and 3% (eggshell). The acidic medium caused 58% (sawdust) and 23% (eggshell) reductions in tensile strength, and similar flexural strength degradations. Strikingly, the basic medium decreased eggshell composite tensile strength by 170% and flexural strength by 6%, while sawdust composite strengths declined by 44%.

Magnesium Stearate Fatty Acid Composition, Lubrication Performance and Tablet Properties

Magnesium stearate (MgSt) is a common tablet lubricant. As variations in MgSt properties are known to influence tablet attributes, the impact of MgSt fatty acid composition, particularly the significance of the stearate and palmitate contents, and its effects on tablet properties warrant further investigation. This study investigated the effect of MgSt with different stearate and palmitate contents but comparable physical properties (e.g. particle size, crystallinity, specific surface area and morphology) on lubrication performance and resulting tablet quality attributes, including mechanical strength, disintegratability and drug release. The influence of MgSt concentration and blending duration on the resulting tablet properties was also examined. Tablets produced using the lower stearate content MgSt had slightly higher tensile strength. The effect of MgSt stearate content was more apparent in the disintegration time and drug release, whereby MgSt of lower stearate content resulted in tablets with longer disintegration time and slower drug release. The lower stearate content also resulted in a lower lubrication performance, leading to a lesser reduction in tablet ejection force. As expected, a longer blending time of the tablet formulation blend with MgSt yielded tablets with reduced tensile strength, shorter disintegration time and slower drug release. Tablets with higher MgSt concentration showed a greater reduction in tensile strength, longer disintegration time and faster drug release. The study findings reinforced observations by other researchers and provided a better understanding of the fatty acid composition effects of MgSt on lubrication performance and the resulting tablet properties.Graphical

Preparation of environmentally friendly ionic liquids-toughened polylactic acid/nanofibrillated cellulose composites with high strength and precipitation resistance

Polylactic acid (PLA) is one of the most promising biodegradable materials, but poor toughness severely limits its application. Ionic liquids (ILs) have excellent plasticizing effects on PLA, but strength reduction and plasticizer precipitation remain worrisome. Herein, nanofibrillated cellulose (NFC), with excellent morphology, high modulus and strength, was prepared to reinforce PLA plasticization systems. Moreover, its numerous surface hydroxyl groups were tailored to bond with ILs, reducing plasticizer precipitation. The different sulfonation degrees of NFCs (low LSNFC, medium MSNFC, high HSNFC) and the influence of NFC amounts (0–7 wt%) on the mechanical, thermal and plasticizer precipitation properties of PLA composites were investigated. The results indicate that network-like C2/C3-sulfonated NFCs were successfully prepared through simple processing steps. Noteworthy, the tensile elongations of PLA composites increased with the addition of IL-XSNFC (all three degrees), with no significant reduction in tensile strength and modulus. The addition of 7 wt% IL-HSNFC resulted in an elongation of 25.01 % for PLA composites, which is 3.6 times that of pure PLA. Adding 3 wt% IL-MSNFC achieved ultra-high impact toughness of 3.19 kJ/m2, nearly double that of pure PLA. Interestingly, with increasing sulfonation degree, the amount of ILs precipitation in PLA composites significantly decreased. The precipitation rate of the PLA composite with IL-HSNFC is only 24 % of the counterparts with IL-NFC. This work presents an innovative method to improve interface compatibility, providing a new strategy to reduce plasticizer precipitation and broaden the application scope of PLA.

Experimental study on the static properties of bamboo fiber reinforced ultra-high performance concrete (UHPC)

Bamboo fiber, as a natural and sustainable material, offers low cost, high strength, and environmental benefits, showing significant potential in composite material reinforcement. This study investigates the effects of bamboo fiber on the static properties of ultra-high performance concrete (UHPC) through experimental research. Different fiber lengths (6 mm, 12 mm, 18 mm) and volume contents (0.5 %, 1.0 %, 1.5 %, 2.0 %) were examined for their impact on the workability, mechanical properties, and pore/void structure of UHPC. The results demonstrate that while bamboo fiber incorporation reduces workability, it significantly enhances compressive and flexural strengths. Specifically, a 21.9 % increase in compressive strength was achieved with 18 mm fibers at 1.0 % content, and a 40.5 % increase in flexural strength was observed with 18 mm fibers at 1.5 % content. Mercury intrusion porosimetry (MIP) and computed tomography (CT) revealed that longer fibers contribute to the formation of larger pores, affecting the void structure. Moreover, bamboo fibers degrade over time in alkaline environments, with a 5 % reduction in tensile strength after 28 days, but the crystallinity of the cellulose has increased. Based on the experimental results, 12 mm bamboo fibers at 1.0–1.5 % content provide the best balance of strength enhancement and workability, making them a promising reinforcement material for UHPC.

Exploring the effects of waste plastic aggregate on styrene-butadiene-styrene-modified asphalt binders for sustainable rural pavements

In addressing the imperative need for sustainable and cost-effective solutions in rural pavement development, this study navigates the intricate balance of environmental and financial constraints to ensure the resilience of infrastructure in communities with limited resources. The focal point is the integration of waste plastic aggregate (WPA) into hot mix asphalt, augmented by the inclusion of styrene-butadiene-styrene (SBS) for an elevated level of performance. The findings underscore a gradual decrease in the tensile strength ratio, emphasizing a manageable impact, transitioning from 82.4% in the control to 73.7% at 6% WPA. Noteworthy is the observation of marginal reductions in indirect tensile strength and stiffness, particularly notable at higher WPA levels. Dynamic modulus testing highlights susceptibility to rutting at lower frequencies, while high-frequency results demonstrate stability up to 6% WPA. The Hamburg wheel tracking test signals heightened rutting at 3% and 6% WPA, indicating potential challenges in deformation resistance. Despite a slight dip in strength, the discernible magnitude of this reduction is not substantial. This affirms that the incorporation of WPA achieves a harmonious enhancement of sustainability without compromising critical mechanical properties.

Effect of pre-exposure to chloride environment on the tensile deformation of SS 304HCu at 973 K

304HCu austenitic stainless steel (SS 304HCu) with 3 % copper content is utilized as the tubing material for advanced ultra-supercritical boilers, which operate at temperatures around 973 K and a pressure of 31 MPa. The current investigation aimed to examine the influence of prior exposure to an acidic chloride environment on the tensile characteristics of SS 304HCu at 973 K with the nominal strain rate of 1× 10−3 s−1 in solution annealed as well as thermally aged (973 K/10000 h) conditions. In the prior exposure condition, both the solution annealed and aged specimens were subjected to a pre-determined potential of −0.14 V (Ag/AgCl) for 48 h in 5 M NaCl + 0.15 M Na2SO4 + 2 ml HCl solutions. Thermally aged SS 304HCu showed lower strength in both true UTS and true yield strength compared to the solution annealed specimen tested at 973 K. Exposure to an acidic environment resulted in a considerable reduction in tensile strength and uniform plastic strain. For all the conditions, saturation-stress-based relationship was employed to describe the flow behaviour of the alloy. The relationship adequately fits the true stress-true strain data of SS 304HCu. A systematic variation in strain hardening parameters with respect to different test conditions is noticed. In the case of the aged alloy, the observed microstructure revealed the presence of M23C6 at grain boundaries and copper precipitates in the grain interior. The increased chromium depletion and the higher degree of sensitization led to the formation of localized pits in pre-exposed aged specimen conditions. Consequently, the synergistic influence of precipitation and pitting corrosion significantly affected the tensile deformation behaviour of SS 304HCu alloy in the aged and pre-exposed condition compared to the solution annealed condition.

Effect of water to cement ratio on mechanical properties of FRC subjected to elevated temperatures: Experimental and soft computing approaches

The deterioration of concrete is greatly dependent on the cracks and microcracks development owing to loading or environmental influences. An effective step to avoid the spread of cracks and microcracks is employing of different fibers in concrete and the manufacture of fiber reinforced concrete. On the other hand, fire is one of the cases that always threatens engineering structures. Elevated temperatures cause obvious chemical and physical changes that lead to concrete deterioration. In this study, the effect of adding various fiber with different volume contents in concrete mixture with various cement content was evaluated experimentally. Results indicate that spalling was more dominant in mixture containing steel fiber and with higher amount of cement, while there is not any spalling in mixture containing polypropylene (PP) fibers. Moreover, the reduction in tensile strength of fiber-free concrete specimens is less pronounced in mixtures with higher cement content. In addition, the positive performance of PP fibers compared to steel fibers was proved at higher temperatures and cement contents. Furthermore, by conducting a comprehensive and accurate survey, this research pinpoints gaps in the current literature. Moreover, the gathered dataset serves as input for training a machine learning approach known as Group Method of Data Handling (GMDH). The GMDH network demonstrates a satisfactory accuracy in predicting experimental results, with a MSE of 0.0044.

Effect of thermal shocks on the interfacial bond strength of sandwich composites built with rigid and soft materials produced through extrusion process

The mechanical behavior and adhesion strength of the sandwich composite, which consists of a flexible and a rigid material, were examined using extruded polylactic acid (PLA) and thermoplastic polyurethane (TPU). Three types of binders were combined with the appropriate hardeners to bond the extruded materials. The fabricated specimens are subjected to a different number of thermal shock cycles, with a maximum and minimum temperature of 80 °C and −18 °C, respectively. The sandwich composite's mechanical properties, including tensile, flexural, and impact strength, were assessed after 20, 40, and 80 cycles of thermal shock. The results indicated that the ductility of PLA material was significantly impacted by the thermal shock cycles. After completing the maximal thermal shock cycles, the composites joined with polyester resin exhibited a lower strength reduction in the impact specimens. Maximum tensile strength of 22.3 MPa, flexural strength of 31.6 MPa, and impact strength of 8.3 J were recorded prior to the application of thermal shocks to the specimens. The specimens that were bonded with epoxy resin recorded the maximal tensile, flexural, and impact strength. Following the thermal shock cycles, the composites bonded with epoxy resin exhibited a lesser reduction in tensile and flexural strength, while the composites bonded with polyester resin showed a lower strength reduction for impact specimens. The tensile and flexural specimens encountered a 7.54 % and 20.24 % reduction in strength, respectively, after undergoing 80 cycles of thermal shocks. The impact specimens experienced an 8.62 % reduction in strength.

Experimental Investigation on the Properties of Concrete Containing Waste HDPE Plastic and Copper Slag as Coarse and Fine Aggregates Replacement

Resource concerns have become apparent globally, particularly in the construction sector due to the exploitation of resources for developing globalized infrastructures. This has led to challenges, especially in sourcing construction materials. Consequently, numerous studies have focused on waste management strategies with eco-efficient parameters, particularly in the realm of construction aggregates. While previous research has explored alternatives for these aggregates, there remains ample opportunity for further investigation on the effectiveness and potential of alternative materials in construction projects to promote sustainable resource management. The research aims to fill this gap by examining the impact of using alternatives for both fine and coarse aggregates, specifically copper slag and waste HDPE. This study investigates the effects of partially incorporating waste HDPE plastic and Copper slag on the strength and sustainability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials in the construction sector. Three percentages of High-Density Polyethylene (HDPE) Plastic (10%, 20%, and 30%) and Two Percentages (30% and 40 %) of copper slag were incorporated with the weight of Coarse aggregate and Fine aggregate respectively. Comparisons of conventional concrete with concrete incorporating HDPE waste & copper slag as coarse aggregate and fine aggregates were conducted. From investigation it was found that concrete incorporating 10% of HDPE and 40% of copper slag cured for 7 and 28 days had 10% increase in compressive strength compared to the nominal mix and flexural strength 25% and 40% more than nominal mix. The concrete incorporating 10% of HDPE and 30% of copper slag had 18% reduction in split tensile strength for cylinders cured for 7 days and 55% increase in split tensile strength for cylinders cured for 28 days.

Three-Dimensional Micromechanical Modeling of Martensite Particle Size Effects on the Deformation Behavior of Dual-Phase Steels.

The objective of this study was to examine the influence of martensite particle size on the formation of stress and strain in microstructures of dual-phase steels. In order to achieve this objective, the 3D representative volume element (RVE) method was utilized. Particle size distributions were obtained from the microstructures of DP600 and DP1000 dual-phase steels as they actually exist. Virtual dual-phase steel microstructures were generated according to the above distribution and subsequent validation analyses were performed. In the subsequent phase, microstructures of varying martensite particle sizes (1 µm, 1.98 µm, 3 µm for DP600 and 1.15 µm, 2 µm, 3 µm for DP1000) were formed, and the effects of particle size on deformation behavior under tensile loads were determined. The findings indicated that an increase in martensite particle size resulted in a reduction in tensile strength, accompanied by an increase in deformation amount.

Effects of waste wollastonite filler on hot mix asphalt performance

Asphalt pavement plays a critical role in global infrastructure, necessitating substantial annual investments for maintenance and repair. Enhancing asphalt mixture performance is essential for prolonging pavement life and reducing associated costs. This study explores the use of waste wollastonite, a neutral mineral composed of silica and lime, as a filler material in asphalt mixtures. Comprehensive micro-scale performance tests, including Marshall Stability, resistance modulus, indirect tensile strength, and moisture sensitivity, were conducted on samples incorporating waste wollastonite. The findings indicate that replacing lime filler with waste wollastonite significantly improves asphalt performance; specifically, complete substitution resulted in increases in Marshall Stability, Marshall Quotient, and resistance modulus by 30%, 28%, and 26%, respectively. Furthermore, a 70% replacement of lime with waste wollastonite led to a 9% increase in tensile strength ratio while demonstrating a notable reduction in indirect tensile strength compared to control samples. These results suggest that waste wollastonite is a viable and effective filler option for enhancing the durability of asphalt mixtures.

Characteristics of dynamic mechanics and energy loss in reef limestone concrete during dry-wet carbonation periods

Coral reef limestone is a unique type of rock and soil body characterized by high porosity. Its dynamic mechanical properties under impact loads differ significantly from those of conventional land-sourced aggregate concrete.This study utilizes coral reef limestone as both coarse and fine aggregates to prepare C40 strength concrete. The research investigates the effects of dry-wet carbonation cycles on its dynamic mechanical behavior and energy evolution characteristics using a Split Hopkinson Pressure Bar (SHPB) mechanical testing system.The findings reveal that increasing the number of dry-wet carbonation cycles leads to a significant weakening of the internal structural bonding in coral reef limestone concrete. Notably, the degree of phenolphthalein color change diminishes, while uniaxial compressive strength and tensile strength demonstrate an overall downward trend. The reduction in tensile strength is less pronounced than the decrease in compressive strength. Additionally, the relative dynamic elastic modulus gradually decreases, and a size effect is noted, with a rapid acceleration in mass loss. As the number of dry-wet carbonation cycles increases, dynamic compressive strength declines, and failure modes shift from surface cracking to crush-type failure.The dynamic increase factor (DIF) of the coral reef limestone concrete indicates a high sensitivity to strain rate, with a significant rise in DIF value as the strain rate increases. Various energies generated under impact load exhibit clear strain rate effects. Furthermore, the effects of dry-wet carbonation cycling enhance energy dissipation, especially at 30 cycles, where energy dissipation increases sharply, while a hindering effect on transmitted energy is observed.

Microstructure characterization and formability assessment of electron beam welded Nb-10Hf-1Ti (wt.%) refractory alloy sheets

Formability study on welded blanks of Nb-based refractory alloy C-103 (Nb-10Hf-1Ti (wt.%)) has tremendous potential for utilizing smaller sheets for realization of large-size divergent portions of upper-stage liquid engine nozzle of satellite launch vehicles and thrusters of attitude orbital control systems. In this work, vacuum-annealed monolithic C-103 sheets were electron beam welded successfully to obtain defect-free welds and detailed microstructural and mechanical characterizations were investigated. Columnar epitaxial grains were found in fusion zone (FZ) instead of equiaxed grains in base metal (BM). Detailed SEM and HRTEM analyses revealed spherical shape of nano-sized HfO2 precipitates with monoclinic crystal structure in the C-103 sheet. Further, microhardness across the weld cross-section indicated that the FZ had a uniform and maximum hardness of ∼195 HV0.5 due to formation of finer nano-sized HfO2 precipitates with higher number density, followed by a lowering of hardness in a narrow heat-affected zone. A marginal reduction in tensile strength of ∼6% with a considerable decrease in ductility of ∼29% was noticed for the welded sample. However, fracture occurred in the BM region, indicating good weld integrity. Furthermore, formability of the welded blanks was evaluated in terms of limiting dome height (LDH), forming limit diagram, and deep drawn cup depth. The effect of the presence of WZ on the formability of the C-103 sheet was estimated under uniaxial, plane strain, and biaxial tensile strain paths for the first time, and the results were compared with the monolithic sample. It was noted that the failure limit of the welded specimens decreased compared to that of the monolithic sample, resulting in a lower LDH of approximately 69% and 62% when deformed along plane strain and biaxial tensile strain paths, respectively. However, a marginal variation in LDH was observed for the uniaxial strain path. Also, the welded blank had more resistance to material flow into the die cavity due to the harder weld region, resulting in a reduction of deep drawn cup depth by 52% than that of the monolithic blank. The overall results concluded that the presence of the WZ significantly affected the formability of the C-103 sheet, especially in plane strain and biaxial strain paths. However, the fracture was never found to be propagating along the weld line, indicating the ability of the weld to sustain large plastic strains. This study provides insightful information on the formability of electron beam welded C-103 sheets for the successful fabrication of space components.

Physical and mechanical properties of concrete containing plastic tube fibers

Plastic tube fibers (PTFs) are one form of plastic waste resulting from the production of plastic mats that end up in the landfill. Until today, no attempt has been made to explore the applicability of PTFs as a construction material for a circular economy. This paper investigates the applicability of PTFs as fibers in fiber-reinforced concrete (FRC) production. A series of tests are carried out to investigate the effects of volume fractions (VFs) and the length of the fibers on the physical and mechanical properties of FRC-containing PTFs. The effects of the length and VFs on the unit weight, compressive strength, flexural strength, tensile strength, pulse velocity, thermal conductivity, and microstructure of FRC are examined. Three different lengths of fibers of 20 mm, 30 mm, and 50 mm, and VFs of PTFs of 0 %, 0.5 %, 1 %, and 1.5 % are studied. Results show that although the mechanical properties of concrete decrease as the VFs increase from 0 % to 1.5 %, the rate of reduction becomes smaller as the length of the fiber becomes larger. The maximum reduction of compressive, tensile, and flexural strength was found to be as high as 35 %, 25 %, and 35 % compared to the control sample obtained for 20 mm fiber length having 1.5 % VFs. Formulas to predict the tensile and flexural strengths of concrete containing PTFs as a function of the compressive strength are proposed and found to be providing satisfactory results. From a microscopic view, it is seen that the sample containing higher VFs shows less density and homogeneity of concrete which leads to an increase in the micropores of the concrete. Furthermore, the ultrasonic pulse velocity and attenuation coefficient decrease as the VFs of PTFs increase.

A novel method for through-thickness reinforcement of laminated composites using discrete micro-polarization-induced fiber injection (DMFI) approach

Conventional through-thickness reinforcement methods for laminated composites, such as Z-pin, encounter issues with in-plane property degradation and complex fabrication processes. To achieve rapid and low-damage reinforcement, a novel approach using short-chopped carbon fibers (SCFs) to form a micron-diameter interlaminate structure has been proposed. This method employs a discrete micro-polarization-induced fiber injection (DMFI) technique, where polarized SCFs are electrostatically oriented and injected at high speeds into pre-formed holes in the laminates. The insertion process of SCFs was thoroughly investigated, with optimal interlaminate conditions determined using high-speed cameras and other equipment. The toughening mechanism of SCFs was explored through various characterization methods, including metallurgical microscopy. This innovative method offers several advantages over the traditional Z-pin reinforced method. Notably, present method eliminates the need for prefabrication of Z-pins and fully leverages the excellent mechanical properties of individual carbon fiber in short length. It provides superior interlaminar mechanical properties, achieving a 392% improvement compared to the control group and a 15% improvement compared to 0.1 mm Z-pin reinforcement at the same insertion volume fraction. Additionally, it has minimal impact on the in-plane properties of the laminates, with only a 3.6% reduction in tensile strength and a 4.1% reduction in compression strength. Furthermore, it is environmentally friendly, allowing for the recycling and reuse of waste SCFs.

Microbial degradation of the waste jute fiber and sawdust fiber-based epoxy composites in drainage system

The non-biodegradable nature of polymers presents a considerable environmental hazard, mainly when they accumulate in drainage systems and pollute the water. The application of natural fiber composites has the potential to offer a feasible resolution to address this problem, as natural fibers possess inherent biodegradability. This study examined the degradation ability of epoxy composites made with 5 wt% waste jute fiber and 5 wt% waste sawdust fiber when subjected to drainage water for one year. The composites comprising jute fiber and sawdust demonstrated a reduction in tensile strength by 57 % and 40 %, respectively, because of biodegradation caused by microorganisms. The microorganism consumed the fiber for energy, resulting in significant weight and flexural strength loss. The weathered waste jute and sawdust fiber composite samples displayed an additional peak at a wavenumber of 1700 cm−1 for FTIR analysis, indicating the presence of the C=O group and reflecting CO2 production. The SEM image reveals the presence of clusters, biofilms, and colonies of microorganisms on the surface of the composites, indicating that the microbes were utilizing the fibers and matrix as a substrate for growth and multiplication. This research contributes to the understanding of the degradation mechanisms of sustainable composites and provides insight into the advancement of eco-friendly materials to reduce water pollution.

Influence of hygrothermal aging on the lifetime and mechanical properties of GFRP/Al adhesive joints

The study aimed to investigate the impact of hygrothermal aging on the degradation of mechanical properties and predict the lifetime of adhesive joints between aluminum alloy (AA6061) and glass fiber-reinforced epoxy (GFRP) composites. The adhesive joints were prepared in a single lap joint (SLJ) configuration and subjected to hygrothermal conditions to induce aging. Immersion tests were conducted at a water temperature of 70°C with varying aging periods (10, 18, 40, 54, 60, and 75 days) to assess the long-term performance and predict the lifetime of the joints. The tensile and shear strength of the adhesive joints were evaluated using a tensile test. The test was performed at room temperature (RT) with a speed rate of 1.3 mm/min. Among the different methods available for lifetime prediction, a semi-empirical approach was selected to analyze the changes in the mechanical properties of the adhesive joints. A comprehensive comparison was made between aged and unaged specimens. The experimental results revealed a reduction in the ultimate tensile and shear strength of the adhesive bonds over the 75-day aging period. The semi-empirical relationship used for long-term durability prediction of adhesive joint structures indicated a 78% decrease in ultimate tensile strength for the adhesive joints over a one-year aging period. This highlights the significant influence of hygrothermal aging on the mechanical properties of the investigated adhesive joints. During the aged periods, various failure modes were observed, including adhesive failure, cohesive failure, and structural failure.

Experimental investigation and machine learning models for predicting flexural and tensile strengths of recycled concrete: Bridging the gap between sustainable materials and structural design

The sustainability of structural components requires recycled aggregate concrete (RC) to achieve adequate flexural and split tensile strengths for practical use. These strengths depend on mix design and the properties of recycled coarse aggregates (R-CA). The variability in R-CA sources and the inherent heterogeneity of RC complicate strength predictions. No existing model accounts for this variability, leaving a gap between sustainable materials and structural design. This study develops machine learning-based models to predict the flexural and split tensile strengths of RC, regardless of R-CA source and properties. Key factors such as water absorption, effective water-to-cement ratio, coarse aggregate-to-cement ratio, and R-CA replacement ratio are used for predictions. The impact of different R-CA types on RC and natural aggregate concrete (NC) is also experimentally analyzed. A dataset of 353 test results from this study and 33 prior studies is used, and various machine learning algorithms (MLA) are evaluated. Results show a 41 % and 23 % reduction in flexural and split tensile strengths of RC compared to NC, but acid and mechanically treated R-CA can recover up to 94 % and 93 % of NC's strengths, respectively. Among all MLA models, the gradient boost model depicted the highest accuracy in predictions for the flexural and tensile strengths of both RC and NC. This research introduces new equations and a C/C++ tool for predicting RC and NC strengths, contributing to sustainable concrete design and bridging the gap between research and practical application.

Tannic acid-loaded halloysite clay grafted with silver nanoparticles improved the mechanical, antimicrobial, and degradation properties of linear low-density polyethylene films

Synthetic polymers used for food packaging contribute to plastic pollution due to poor degradability. While they prevent the entry of microorganisms, they may not protect against spoilage microorganisms in the packed food. Nanofillers have been used to improve such properties, but end-of-life degradation remains an issue, making plastic a persistent pollutant. Here, we tested a nanocomposite (Nc) of tannic acid-loaded halloysite nanotubes grafted with silver nanoparticles as a reinforcement to enhance the mechanical, antimicrobial, and degradation properties of Linear low-density polyethylene (LLDPE) films. LLDPE films incorporated with Nc significantly improved tensile strength (TS), elongation at break (EB), and oxygen permeability rate. Nc incorporated (at 5%-and 10%) LLDPE films exhibited a 1.89–2.85 log10 reduction in multi-drug resistant Staphylococcus aureus 1158c in chicken fillets. Both film types demonstrated silver migration below the European Food Safety Authority-mandated acceptable limit. Nc/LLDPE films disintegrated faster when exposed to incandescent light for 6 h, evidenced by significant reduction of weight, TS, and EB. Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy suggested oxidative degradation and breakdown of the polymer. Conclusively, Nc improved the functional properties and degradation rate of LLDPE films when exposed to light, showing potential for enhancing the sustainability of synthetic polymers.

Characterization and life cycle assessment of alkali treated abaca fibers: the effect of reusing sodium hydroxide

The increasing demand for natural fibers, driven by their advantageous attributes such as low density, sustainability, and high specific strength, has promoted the adoption of sustainable alternatives in composites. Although alkali treatments are known to improve fiber properties, they entail challenges regarding NaOH consumption and environmental impact, making it necessary to explore cleaner production strategies. This study evaluated the effects of implementing a circular economy approach through the recirculation of an NaOH solution on the treatment of abaca fibers. The fiber properties were assessed using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile strength testing, along with an evaluation of the carbon footprint through a life cycle assessment. New life cycle inventories were developed to reflect the NaOH recirculation process. Comparative analyses were conducted using polypropylene fibers. The findings indicate that the recirculation of the NaOH solution remains effective for up to eight cycles, producing consistent TGA, SEM, and tensile strength results while achieving a 25 % reduction in the carbon footprint compared to conventional treatment. Additionally, this study highlights the environmental advantages of abaca over synthetic fibers, with increased tensile strength (8–46 %) and carbon footprint reduction (55–86 %) compared to polypropylene fibers. These results highlight the potential of abaca fibers to contribute to the circular economy, enhance resource efficiency, and mitigate climate change.