Flexural Strength Research Articles

Characterization of Geopolymer Masonry Mortars Incorporating Recycled Fine Aggregates

This study evaluates the characteristics of geopolymer masonry mortars (GMMs) made with slag–fly ash binder and up to 100% recycled fine aggregates (RFAs). For each RFA replacement rate, two types of GMMs, namely N and S types based on ASTM C91, were proportioned and tested for mechanical, physical, and durability properties. Results revealed that using geopolymeric binder enhanced the flow, water retention, compressive strength, sorptivity, and abrasion resistance of GMMs compared to cementitious counterparts but reduced the initial setting time by up to 75%. Subsequent RFA additions negatively affected the flow, setting time, density, water absorption, porosity, and bulk resistivity but enhanced the water retention, sorptivity, and abrasion resistance of GMM. It also reduced the compressive, pull-off, and flexural strengths by 36, 44, and 27%, respectively. Furthermore, S-type mortars exhibited improved bulk resistivity, sorptivity, and abrasion resistance compared to N-type counterparts. A multifunctional performance index deduced that the GMM mixes incorporating 100% RFAs were superior to geopolymeric or cementitious masonry mortars made with natural fine aggregates (NFAs). Such findings emphasize the sustainability of GMMs made with RFAs in masonry construction, eliminating the need for water curing while maintaining comparable or even superior properties compared to cement-based mortars made with NFAs.

Upcycling Post-Consumer Paint Pail Plastic Waste

The need for ending plastic waste and creating a circular economy has prompted significant interest in developing a new family of composite materials through recycling and recovery of waste resources (including bio-sourced materials). In this work, a family of natural fiber-reinforced plastic composites has been developed from paint pail waste recycled polypropylene (rPP) and waste wool fibers of different diameter and aspect ratio. Composites were fabricated by melt processing using polypropylene-graft-maleic anhydride as a compatibilizer. The internal morphology, interfacial and thermal characteristics, viscoelastic behavior, water sorption/wettability, and mechanical properties of composites were studied using electron microscopy, high-resolution synchrotron Fourier transform infrared microspectroscopy, thermal analysis, rheology, immersion test, contact angle measurement, tensile test and flexural test. The composite matrix exhibited an internal morphology of coalescent micro-droplets due to the presence of polyethylene and dry paint in the rPP phase. In general, the rheological and mechanical properties of the composites comprising higher-aspect-ratio (lower diameter) fibers exhibited relatively superior performance. About an 18% increase in tensile strength and a 39% increase in flexural strength were measured for composites with an optimal fiber loading of 10 wt.%. Interfacial debonding and fiber pull-out were observed as the main failure mechanism of the composites. The developed composites have potential for applications in automotive, decking, and building industries.

Evaluation of the Performance of Fiber-Reinforced Mortars Based on Dredged Sludge

River-carried solids, especially during floods, lead to dam sedimentation. Dredging extends dam life, but excess unusable sediment storage threatens the environment. The aim of this work is to investigate the influence of the recovery of calcined mud from Chorfa dam on the physico-mechanical and chemical characteristics of mortars fiber bundles. The sludge is used as a partial substitute for cement by volume at rates of 10%, 15%, 20% and 25%. All test specimens had water / binder (W/B) ratio and steel fibers ratio. Testing programme included measuring the fluidity, ultrasonic pulse velocity test, dynamic modulus of elasticity, flexural and compressive strengths. Compared to the control mortar, the fluidity represented by the diameter of M0, M15 and M25 mixtures decreased by approximately 11%, 14% and 22%, respectively. The compressive strength of M15 increased by 17.4% at 28 days, compared with the control specimen. At 7 days, the ultrasonic speed of the M25 mixture decreases by 1.7% compared to that of M15. The dynamic modulus of elasticity of M20 and M25 increases by 13% and 12% as the age ranges from 2 to 28 days. At 28 days, the flexural strength of the M20 blends increased by approximately 64%.

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.

Synergistic effects of sisal/glass fiber hybridization and eggshell powder filler on the performance of eco‐friendly polymer composites

AbstractIn recent years, there has been a significant emphasis on the development of composite materials that are both high‐performing and environmentally friendly. Hybrid polymer composites that are reinforced by both sisal and glass fibers are introduced in this study. Investigation was conducted to evaluate the combined influence of hybrid reinforcements and Egg Shell Powder (ESP) on the mechanical properties of the composites. The hand layup technique was employed to create hybrid laminates by incorporating variable amounts of ESP (0–15 wt%) and employing various stacking sequences. Various mechanical testing was administered to the composites that had been prepared. The results indicated that the glass/sisal hybrid laminates exhibited superior mechanical properties in comparison to the non‐hybrid sisal laminates, which was attributed to the synergistic benefits of incorporating both sisal and glass fibers. The incorporation of Egg Shell Powder significantly improved the material's mechanical properties. The glass/sisal hybrid laminates with 15% ESP laminate demonstrated the maximum tensile strength (195.23 MPa), flexural strength (150.02 MPa), and ILSS (7.55 MPa). Scanning electron microscopy enabled a comprehensive analysis of the hybrid composites' interfacial adhesion and microstructure. This investigation verified that the ESP was effectively dispersed and had a substantial effect on the interface between the matrix and the fibers. The hybrid composites that are generated are environmentally friendly and exhibit extraordinary potential for a variety of applications, offering a sustainable and high‐performing alternative to conventional synthetic composites. These discoveries promote the utilization of bio‐based resources in the composites industry and advance the development of sustainable materials.Highlights The glass/sisal hybrid laminates with 15% ESP laminate showed highest tensile strength of 195.23 MPa Hybrid composites exhibited superior mechanical properties. ESP addition significantly improved interfacial adhesion and strength Water absorption decreased with increasing ESP content up to 15% Development of Eco‐friendly composites suitable for automotive and aerospace applications

Effect of temperature on the microstructure and mechanical properties of TiC/Fe matrix composites fabricated by spark plasma sintering

The effects of sintering temperatures on the microstructures and mechanical properties of titanium carbide particles reinforced iron matrix composites (TiC/Fe MCs) fabricated by the spark plasma sintering (SPS) process with pure element powders have been systematically investigated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back scattering diffractometer (EBSD), and energy dispersive spectroscopy (EDS) have been conducted for microstructural analysis. The results show that with increasing sintering temperatures, the porosity of the composites initially decreases and then increases. Simultaneously, the grain size gradually diminishes while element diffusion becomes more uniform. Upon reaching a critical sintering temperature (1120 °C), the original grain size disappears and carbides undergo decomposition and reprecipitation to reach an equilibrium state, with which optimal comprehensive properties can be achieved (porosity decreases to a minimum of 3.85%, grain size of 2.69 μm, Vickers hardness reaches 595 HV0.5, bending strength is at 662 MPa, coefficient of friction is at 0.74, and wear loss to 0.21 mg). These property enhancements have been attributed to reduced porosity in the composites, decreased grain size, and improved anchoring effect of carbides within the matrix. Additionally, the primary fracture mechanisms and wear mechanisms of TiC/Fe MCs with different process parameters have been analyzed. When the temperature is below 1080 °C, intergranular fracture predominates, whereas transgranular and ductile fractures become predominant above this threshold. When the temperature is below 1120 °C, fatigue wear, oxidation wear, and abrasive wear are predominantly observed. Conversely, when the temperature exceeds 1120 °C, oxidation wear and abrasive wear become the primary mechanisms.

Forming performance and environmental impact of bamboo fiber reinforced polypropylene composites based on injection molding process for automobiles

AbstractTo explore the potential application of plant fiber reinforced composites for automotive component applications, this study prepared bamboo fiber (BF)/nano‐talc/polypropylene (PP) composites based on the injection molding process, comprehensively evaluated the effect of reinforcement materials on the forming properties of composites, including thermal performance, mechanical properties, water absorption, etc. Furthermore, taking a certain automotive injection molded interior part as the object, a life‐cycle assessment from production to the gate was conducted based on the real energy and material consumption during the composite preparation process. The results indicate that adding BF and talc powder increased the thermal stability, density, hardness, viscosity, and crystallinity of the composites while reducing the water contact angle on the surface. Surface‐modified BF and PP showed good compatibility. Talc powder exhibited good dispersibility in PP, and the synergistic effect of BF and talc powder effectively enhanced the composite performance. The tensile, flexural, and impact strength of the composites were improved by 40.64%, 51.48%, and 66.51%, respectively, compared with pure PP. The modulus of the composite increased nearly 2 times compared with pure PP. Additionally, the composite demonstrated good friction and wear properties. The environmental impact of the BF composite manufacturing process was significantly higher than that of pure PP. The substantial consumption of electricity, chemicals, and water resources in the extraction and modification processes of BF were the main factors. The findings of this study contribute to achieving green, high‐performance BF composite manufacturing and the expansion of its applications.Highlights Composites have a higher environmental impact compared to PP. BF and talc can synergistically enhance the performance of composites. BF shows good compatibility with PP. Composites exhibit good friction and wear characteristics.

An Experimental Investigation on Durability Properties of Fiber Reinforced Concrete for M25 Grade

In modern years Fibre reinforced concrete is cement based composite material has been developed. It has been successfully used in construction with its outstanding flexural tensile strength, resistance to splitting, impact resistance and outstanding permeability and frost resistance. It is a successful way to raise toughness, shock resistance and resistance to plastic shrinkage cracking of the mortar. Fibre is added as a reinforcing material possessing certain characteristic properties. Concrete is the most extensively used structural material in the world with an yearly production of over seven billion tons. For a multiplicity of reasons, much of this concrete is cracked. The reason for concrete to undergo cracking may be endorsed to structural, ecological or economic factors, but most of the cracks are formed due to the natural weakness of the material to resist tensile forces. Concrete normally shrinks and force crack when it is controlled. It is now well-known that steel fibre reinforcement offers a solution to the problem of cracking by making concrete tougher and more yielding. It has also been proved by wide investigation and field tests carried out over the past three decades. The present investigation focuses on introduction of steel, glass, carbon fibres, Polyvinyalcohol (PVA) fibres, of polypropylene fibres at the time of mixing and production improves a number of properties of concrete, particularly those related to strength, performance and durability. This review paper is an evaluative report of studies established in the recent years. It describes and gives an Experimental basis for the research.

Mechanical Properties of Permeable Concrete Reinforced with Polypropylene Fibers for Different Water–Cement Ratios

Permeable concrete is a material that allows water filtration, reduces surface runoff, and maintains the natural water cycle. Previous studies have shown that its mechanical properties, particularly its compressive and flexural tensile strengths, are generally lower than those of conventional concrete, with significant variability observed among similar tests. This study investigates the compressive strength, flexural strength, and permeability of polypropylene fiber-reinforced permeable concrete specimens at two water–cement ratios (0.30 and 0.35). The mix design was conducted using the ACI 522R-10 method. Forty-eight cylinders measuring 200 mm × 100 mm were fabricated for permeability and compression tests. Additionally, 12 beams measuring 100 mm × 100 mm × 350 mm were produced and subjected to simple flexural testing in accordance with ASTM C78 guidelines. Compressive strength versus permeability and load versus deflection graphs were plotted, and the fracture energy was calculated for various deflections. The results indicate that the addition of fibers increased permeability and tensile strength but decreased compressive strength. Furthermore, an increase in the water–cement ratio led to higher compressive and flexural tensile strengths.

Challenges of a Circular Economy: The Example of Raw Recycled Tyre Steel Fibres Added to Concrete

This research was conducted to analyse the possibility of using raw, untreated recycled tyre fibres as an effective concrete reinforcement according to circular economy principles. The aim of the article was also to develop a method for dispensing tire fibres on a real scale. Additional treatment and homogenisation of recycled steel fibres entail higher energy consumption, emissions of greenhouse gases, and increased costs. However, obtaining durable and safe concrete effectively reinforced with steel fibres is critical. Finding a balance between environmental friendliness and product durability is a circular economic challenge. Reference concrete with commercial steel fibres (15 kg/m3) and two concretes containing various quantities of non-treated, raw tyre recycled fibres (25 kg/m3 and 45 kg/m3) were industrially produced. Tests were carried out on the properties of the concrete mixture and hardened concrete, such as compressive strength, flexural strength, splitting strength, modulus of elasticity, residual flexural tensile strength, and fibre distribution in concrete. Tests revealed that increasing the amount of raw tyre fibres disturbs the structure and causes air entrainment and the formation of fibre clusters. Smaller quantities of raw tyre fibres turn out an effective concrete reinforcement. The use of non-treated tyre fibres as concrete reinforcement is possible but requires more stringent control of the concrete parameters. Implementation tests on an industrial scale are a novelty in this study, presenting an analysis of the possible dispensing of tyre fibres in a ready-mixed concrete production plant and testing the characteristics of manufactured concrete.

The Effects of Metakaolin on the Properties of Magnesium Sulphoaluminate Cement

Magnesium sulphoaluminate (MSA) cement has good bonding properties and is suitable as an inorganic adhesive for repairing materials in civil engineering. However, there are still some problems with its use, such as its insufficient 1 day (d) strength and poor volumetric stability. This paper aims to investigate the influences of metakaolin (MK) on the physical and mechanical properties of magnesium sulphoaluminate (MSA) cement. The hydration products and microstructures of typical MSA cement samples were also analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the addition of metakaolin reduces the fluidity and shortens the setting time of the MSA cement. The initial setting time and final setting time shortened maximally by 15–27 min and 25–48 min, respectively, with the addition of 10–30% metakaolin. Moreover, the compressive strength and flexural strength of the MSA cement improved significantly with the addition of 10–30% metakaolin at a curing age of 1 d. Compared with the compressive and flexural strengths of the control sample at 1 d, the compressive strengths of the modified samples showed obvious increases of 98%, 101%, and 109%, and the flexural strengths increased by 39%, 31%, and 26%, respectively, although they decreased slightly when the curing ages were 7 d, 14 d, and 28 d. The addition of 10% metakaolin improved the water resistance of the MSA cement immersed in water for 7 d and resulted in even higher water resistance at 28 d. The addition of 10–30% metakaolin improved the volumetric stability of the MSA cement with increasing dosages before 28 d of ageing. XRD and SEM-EDS analyses showed that the metakaolin accelerated the early hydration reaction and optimised the phase composition of the MSA cement. The results indicate that the addition of 10–20% metakaolin improved the strength after 1 d of ageing, water resistance, and volumetric stability of the MSA cement, providing theoretical support for the application of MAS cement as an inorganic bonding agent for repairing materials.

Effect of silane coupling agent on mechanical properties, flame retardancy, and ceramifiable behavior of ceramifiable flame‐retardant silicone rubber composite

AbstractIn order to improve the dispersibility of inorganic fillers and enhance its ceramifiable flame‐retardant efficiency, the ceramifiable flame‐retardant silicone rubber composites were prepared using glass powder, zinc borate, ammonium polyphosphate, mica powder, platinum catalyst as ceramifiable flame‐retardant agent, and various silane coupling agents as interfacial modifier. The micromorphology, mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites, as well as the flexural strength of the corresponding ceramics generated after pyrolysis of the composites were examined. The results reveal that the inclusion of silane coupling agents improves the dispersibility of ceramifiable flame‐retardant agents substantially. The mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame‐retardant silicone rubber composites are all improved. When compared to a composite without a silane coupling agent, the tensile strength of the composite can be improved by up to 1.9 times. Only 0.5phr silane coupling agent is required to raise the vertical combustion rating from V‐1 to V‐0, and the composite with 3 phr KH570 has a LOI value of 38.6. Meanwhile, the heat release rate of the composite is reduced to a certain extent, and the time to ignition and residue are dramatically enhanced after the addition of silane coupling agent in the cone calorimetry test. Moreover, flexural strength of the corresponding ceramics generated after pyrolysis of the composites rapidly increases with increasing silane coupling agent content, which can reach to 24.7 MPa with addition of 3 phr KH570.

Synthesis of magnesium hydroxide flame retardant based on microcrystalline magnesite and its application in epoxy resin

Abstract A nanoscale hexagonal flake magnesium hydroxide (MH) flame retardant was prepared by a hydrothermal method using Tibetan microcrystalline magnesite as the raw material. The synthesized samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FSEM), thermogravimetric analysis-differential scanning calorimetry (TG-DSC), and laser particle size analysis. When subjected to hydrothermal treatment at 180°C for a duration of 8 hours in a solution containing 6 mol/L NaOH, and with the incorporation of 4 wt% of the surfactant polyethylene glycol 2000 (PEG2000), hexagonal flake MH, possessing an average particle size of 378.3 nm, was successfully synthesized. The study conducted an examination of the thermal, mechanical, and flame-retardant properties of both EP and EP/MH composites. The results revealed that the incorporation of 9wt% MH led to a notable reduction in the peak heat release rate, total smoke production, and mass loss rate of the EP/MH composites by 36%, 14.5%, and 33.3% respectively, as compared to the pure EP. Remarkably, the tensile and flexural strength of the composite exhibited minimal impact.

Optimization of nano-filler and silane treatment on mechanical performance of nanographene hybrid composites using RSM and ANN technique

This study utilized response surface methodology (RSM) and artificial neural networks (ANN) to optimize the formulation of polymer composites with three key variables: silane concentration, silane dipping time, and the number of nanoparticles. RSM and analysis of variance were employed to explore the effects of these variables on the composite’s mechanical properties, while ANN was used for analyzing complex interactions between parameters. The results reveal a significant correlation between the predicted and actual response values derived from the models. Notably, silane treatment of fiber was identified as the primary factor influencing the composite’s flexural strength. The study found that all fiber-related properties substantially affected both flexural strength and hardness, with silane dipping time being the most critical factor. Additionally, incorporating nanoparticles improved the fiber matrix’s strength by enhancing agglomeration. ANN achieved a 95% accuracy in predicting flexural strength and hardness. Comparisons among experimental data, the regression model, and ANN confirmed the robustness of the ANN predictions. The optimal composition identified for flexural strength was 5 wt % nanoparticles, 10 wt % silane treatment, and a 20-min dipping time. For hardness, the ideal formulation was 5 wt % nanoparticles, 15% silane treatment, and a 20-min dipping time in silane. This comprehensive approach offers a refined method for developing high-performance polymer composites with tailored properties.

Rate‐dependent mechanical properties and acoustic emission characteristic of recycled aggregate concrete under four‐point bending

AbstractThe application of recycled aggregate is crucial for waste concrete recycling, while the loading rate significantly influences the fracture behavior of recycled aggregate concrete. Herein, we investigate the effect of loading rate on the flexural and fracture behaviors of recycled aggregate concrete, along with associated acoustic emission characteristics. Results show that the flexural strength and energy absorption capacity maximum increase by 15.18% and 38.39%, respectively, as the loading rate rises. As the loading rate increases from 0.05 to 1 mm/min, peak frequency is primarily clustered in 0 ~ 75 kHz and 75 ~ 225 kHz and tends to be dense, while the b value decreases by 19.28%, 23.30%, and 30.17%, respectively. Additionally, the proportion of shear failure also decreases, which relates to the high energy release rate. Further, the multifractal spectrum α − f(α) resembles a quadratic distribution, with both multifractal intensity ∆f and spectrum width ∆α showing a downward trend as the loading rate rises.

Preparation and Characterization of Antibacterial Polycarbonate (PC) Using Quaternary Fluoroalkyl Phosphonium Salts with Various Counter Anions

In order to find an optimal antibacterial agent for Polycarbonate (PC), five quaternary fluoroalkyl phosphonium salts (FAPS) with iodine anions (PPICF-13), tetrafluoroborate (FB-PPCF-13), trifluoromethanesulfonate (TFMS-PPCF-13), methanesulfonate (MS-PPCF-13), and p-toluenesulfonate (pTS-PPCF-13), each with a side chain of 13 fluorine atoms, were incorporated were incorporated into PC with a mass ratio of 2.5 wt.%. The influence of the counter anions on the rheological properties, mechanical properties, appearance and light transmittance, antibacterial activity and cytotoxicity of the antibacterial PCs were investigated. The results showed that all the FAPS could impart PC with above 90% of antibacterial degree. The melt flow rate of the PC was increased due to the plasticizing effect of FAPS. The incorporation of up to 2.5 wt.% FAPS had no negative influence on the flexural strength, flexural modulus and tensile strength of the PC, but reduced the impact strength of the PC to varying degrees, depending on the counter anion. All five of the FAPS influenced the appearance and light transmittance of PC, and the TFMS-PPCF-13, MS-PPCF-13 and pTS-PPCF-13 samples appeared to have less impact on these properties than PPICF-13 and FB-PPCF-13. All antibacterial PCs; except for the antibacterial PC containing PPICF-13, exhibited no cytotoxicity. Considering all the properties, the antibacterial PC containing TFMS-PPCF-13 showed the optimal comprehensive properties based on this research.

Utilizing machine learning to forecast mechanical characteristics of NaOH-Treated jute fiber reinforced composite materials

The prediction of mechanical properties in composite materials is crucial for optimizing their performance in various engineering applications. This study focuses on NaOH treated jute fiber reinforced glass epoxy composites, aiming to predict key mechanical characteristics like flexural strength, tensile strength, and the hardness. A comprehensive dataset of 974 samples was analyzed, encompassing a range of input parameters including fiber content, fiber orientation, matrix type, and processing conditions. Advanced statistical and machine learning techniques were employed to develop predictive models, with XGBoost showing itself to be the best model in terms of predicting each of the three mechanical properties. Feature importance analysis revealed that fiber content is the most significant factor influencing the predictions.

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.

A sustainable high-performance bamboo fiber composite material for cryogenic engineering

Exploring the application and development of biomass materials in the field of special engineering in line with the principles of green development. This work investigates the mechanical and thermal properties response of bamboo scrimber (BS) with different densities and resin contents at room temperature and ultra-low temperatures (-196 °C). The results showed that ultra-low temperatures significantly enhanced the modulus of rupture (increase of 143.9 %), modulus of elasticity (125.0 %), compressive strength (150 %), and shear strength (165 %) of BS due to the cell shrinkage at low temperature and physical phase transition of internal water. The failure modes of BS at ultra-low temperatures transitioned from ductile to brittle, compared with that at room temperature. Furthermore, BS with lower-density exhibited better thermal insulation (thermal conductivity < 0.55 W/mK) and dimensional stability (CTE < 6 1/k−6). These findings established a research base for broadening the application areas of BS for cryogenic engineering applications.

Nano-engineered the interfacial transition zone between recycled fine aggregates and paste with graphene oxide for sustainable cement composites

The high water absorption and porosity of recycled aggregate often led to a compromised interface transition zone (ITZ), thereby adversely impacting the mechanical properties and durability of recycled aggregate concrete. This research presents a feasible, straightforward, and targeted strategy to reinforce the ITZ between recycled fine aggregate (RFA) and paste by utilizing RFA particles adsorbed with graphene oxide (GO), termed WGO@RFA. The experimental outcomes demonstrate that incorporating WGO@RFA can enhance the 28-day compressive and flexural strengths of recycled mortars by approximately 25 % and 20 %, respectively, compared to mortars containing only RFA. Furthermore, it can decrease the water sorptivity and chloride ion diffusion coefficients of recycled mortars (28 days) by about 20 % and 27 %, respectively. Notably, using WGO@RFA particles offers significant advantages, such as enhanced mechanical strengths, reduced transport properties, and a densified microstructure within the ITZ, compared to the conventional method of modifying the cement matrix with GO and then binding it with RFA. Highlighting the application of WGO@RFA shows a targeted strengthening of the ITZ, as the sub-nanometer thickness of GO adsorbed on the uneven RFA surface facilitates localized cement hydration at the ITZ. The findings of this research offer novel avenues for reusing aggregate and developing sustainable concrete.