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Search Results (3,460)

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Keywords = flexural properties

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16 pages, 5382 KiB  
Article
Evaluation of the Mechanical Properties and Fatigue Resistance of the ZrO2CeYAl2O3 Composite
by Marcio Paulo de Araújo Mafra, Nélio Silva Júnior, Claudinei dos Santos, Jorge Luiz de Almeida Ferreira, José Alexander Araújo and Cosme Roberto Moreira da Silva
Ceramics 2024, 7(4), 1600-1615; https://doi.org/10.3390/ceramics7040103 (registering DOI) - 31 Oct 2024
Abstract
This work aimed to evaluate the fatigue limit of the zirconia ceramic composite stabilized with yttria and ceria reinforced with alumina platelets (ZrO2CeYAl2O3) and characterize the mechanical properties of sintered specimens. Bar-shaped specimens were compacted by uniaxial [...] Read more.
This work aimed to evaluate the fatigue limit of the zirconia ceramic composite stabilized with yttria and ceria reinforced with alumina platelets (ZrO2CeYAl2O3) and characterize the mechanical properties of sintered specimens. Bar-shaped specimens were compacted by uniaxial pressing in a rigid die and sintered at 1500 °C-2 h. Subsequent characterizations included quantitative phase analysis by X-ray diffractometry, determination of density, modulus of elasticity, microhardness, fracture toughness, four-point flexural strength, and fatigue limit. Observations of fracture mechanisms were carried out using confocal and scanning electron microscopy (SEM). The sintered samples presented values above 98% of relative density. Complex microstructures with equiaxed, homogeneously distributed submicrometer grains and planar alumina platelets were observed by SEM. The composite samples showed high values of fracture toughness due to the transformation, during the test, from the tetragonal to monoclinic phase, causing an increase in volume and creating compression zones around the crack, making it difficult to propagate. The average flexural strength reached 445.55 MPa, with a Weibull modulus (m = 16.8), revealing low flexural rupture stress data dispersion. In the composite evaluated in this work, the occurrence of the tetragonal → monoclinic transformation that occurs in the Ce-TZP present at the triple points and grain boundaries during cyclic loading produces “crack tip shielding”, that is, a restricted elastic zone (zone shielding) that surrounds the crack tip. This phenomenon leads to a reduction in the stress intensity factor at the tip of the crack and slows down its growth, generating an increase in the fatigue resistance of the composite. Full article
(This article belongs to the Special Issue Mechanical Behavior and Reliability of Engineering Ceramics)
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27 pages, 11653 KiB  
Article
The Flexural Behavior of Reinforced Ultra-High Performance Engineering Cementitious Composite (UHP-ECC) Beams Fabricated with Polyethylene Fiber (Numerical and Analytical Study)
by Ahmed M. Yassin, Mohamed Ahmed Hafez and Mohammad Mohie Eldin
Buildings 2024, 14(11), 3484; https://doi.org/10.3390/buildings14113484 - 31 Oct 2024
Abstract
Ultra-high performance engineered cementitious composite (UHP-ECC), which is a new and ductile version of concrete, has attracted researchers recently due to its exceptional mechanical properties: its very high compressive strength (from 100 to 200 MPa) and very high tensile strain capacity (not less [...] Read more.
Ultra-high performance engineered cementitious composite (UHP-ECC), which is a new and ductile version of concrete, has attracted researchers recently due to its exceptional mechanical properties: its very high compressive strength (from 100 to 200 MPa) and very high tensile strain capacity (not less than 3% and up to 8%). However, the available experimental literature is small due to its very high cost. To overcome the high cost of the experiments of UHP-ECC, the finite element modeling package ANSYS was used to create a new modeling technique using the Menetrey–Willam constitutive model, recently added to ANSYS. This technique was validated using previous experimental results for UHP-ECC beams and found to be accurate and effective. The previous FE model was used to conduct a parametric study and the variables—the compressive strength of the concrete, the percentage of the volume content of polyethylene fibers, the tensile reinforcement ratio, and the span-to-depth ratio—were found to be effective upon the flexure behavior of the reinforced UHP-ECC beams. As the analysis and design of UHP-ECC beams fabricated with polyethylene fiber are not available yet through design codes, an analytical model including some equations was deduced to calculate the flexure capacity of such beams. The results of the parametric study were used to investigate the validity and accuracy of the analytical model. The proposed equations demonstrated a good estimation compared with the numerical analysis results. Full article
(This article belongs to the Section Building Structures)
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23 pages, 21704 KiB  
Article
Surface Modification of Graphene Oxide and Its Strengthening and Toughening Mechanism for Alumina-Based Ceramic Materials
by Yangyang Hu, Zhenzhen Feng, Yonghui Xie, Hongyang Wang, Qinglong Ji, Jiaoni Wang and Chonghai Xu
Crystals 2024, 14(11), 949; https://doi.org/10.3390/cryst14110949 (registering DOI) - 31 Oct 2024
Abstract
This study investigated the effects of incorporating reduced-graphene-oxide-coated alumina (Al2O3–RGO) nanoparticles and unmodified graphene oxide (GO) onto the microstructure as well as the mechanical properties of Al2O3/TiB2 matrix ceramic materials. The microstructure observation revealed [...] Read more.
This study investigated the effects of incorporating reduced-graphene-oxide-coated alumina (Al2O3–RGO) nanoparticles and unmodified graphene oxide (GO) onto the microstructure as well as the mechanical properties of Al2O3/TiB2 matrix ceramic materials. The microstructure observation revealed that, compared with GO addition, the addition of Al2O3–RGO nanoparticles significantly improved RGO dispersion in the ceramic materials and reduced defects such as pores caused by graphene agglomeration. In addition, the uniformly dispersed RGO nanosheets were interwoven with each other to form a three-dimensional grid structure due to grain growth and the disappearance of pores during sintering, which increased the contact area and interface-bonding strength between the RGO and ceramic matrix. According to the results of microstructure observation and analysis, the good interfacial strength not only facilitated load transfer from the ceramic matrix to the RGO but also induced the fracture mechanism of the RGO, which consumes more fracture energy than the traditional toughening mechanism. The results of mechanical properties analysis showed that the hardness, flexural strength, and fracture toughness of the obtained ATB–RG3.0 ceramic material was measured at 19.52 GPa, 1063.52 MPa, and 9.16 MPa·m1/2, respectively. These values are 16.82%, 27.92%, and 26.87% higher than those of the ceramic material with 3.0 vol.% GO. Full article
(This article belongs to the Special Issue Advanced Technologies in Graphene-Based Materials (2nd Edition))
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27 pages, 16336 KiB  
Article
Hybrid Fiber Reinforcement in HDPE–Concrete: Predictive Analysis of Fresh and Hardened Properties Using Response Surface Methodology
by Hany A. Dahish and Mohammed K. Alkharisi
Buildings 2024, 14(11), 3479; https://doi.org/10.3390/buildings14113479 - 31 Oct 2024
Viewed by 92
Abstract
Plastic waste accumulation has driven research into recycling solutions, such as using plastics as partial aggregate substitutes in concrete to meet construction needs, conserve resources, and reduce environmental impact. However, studies reveal that plastic aggregates weaken concrete strength, creating the need for reinforcement [...] Read more.
Plastic waste accumulation has driven research into recycling solutions, such as using plastics as partial aggregate substitutes in concrete to meet construction needs, conserve resources, and reduce environmental impact. However, studies reveal that plastic aggregates weaken concrete strength, creating the need for reinforcement methods in plastic-containing concrete. This study used experimental data from 225 tested specimens to develop prediction models for the properties of concrete containing macro-synthetic fibers (MSFs), steel fibers (SFs), and high-density polyethylene (HDPE) plastic as a partial substitute for natural coarse aggregate (NCA) by volume utilizing response surface methodology (RSM). HDPE plastics were used as a partial substitute for NCA by volume at levels of 10%, 30%, and 50%. MSFs were added at levels of 0, 0.25%, 0.5%, and 1% by volume of concrete, while SFs were added at levels of 0, 0.5%, 1%, 1.5%, and 2% by volume of concrete. The input parameters for the models are the ratio of HDPE, the dose of MSF, and the dose of SF. The responses are the slump value, the compressive strength (CS), the splitting tensile strength (TS), and the flexural strength (FS) of concrete. The significance and suitability of the developed models were assessed and validated, and the parameters’ contribution was investigated using analysis of variance (ANOVA) and other statistical tests. Numerical optimization was used to determine the best HDPE, MSF, and SF ratios for optimizing the mechanical properties of concrete. The results demonstrated that replacing NCA with HDPE plastics increased the workability and decreased the strength of concrete. The results demonstrated the applicability of the developed models for predicting the properties of HDPE–concrete containing MSFs and SFs, which agreed well with the data from experiments. The created models have R2 values more than 0.92, adequate precision more than 4, and p-values less than 0.05, showing high correlation levels for prediction. The RSM modeling results indicate that the inclusion of MSFs and SFs improved the mechanical properties of HDPE–concrete. The optimum doses of MSFs and SFs were 0.73% and 0.74%, respectively, of volume of concrete, leading to improvement in the mechanical properties of HDPE–concrete. This approach reduces plastic waste and its detrimental environmental impact. Further development of models is needed to simulate the combined effects of different fiber types, shapes, and dosages on the performance and durability of plastic-containing concrete. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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14 pages, 3375 KiB  
Article
Impact of Different Post-Curing Temperatures on Mechanical and Physical Properties of Waste-Modified Polymer Composites
by Bernardeta Dębska, Bruna Silva Almada and Guilherme Jorge Brigolini Silva
Materials 2024, 17(21), 5301; https://doi.org/10.3390/ma17215301 (registering DOI) - 31 Oct 2024
Viewed by 117
Abstract
One of the key trends affecting the future of the construction industry is the issue of ecology; therefore, current activities in construction aim to reduce the use of raw materials, which is made possible by including recycled materials in composites, among other methods. [...] Read more.
One of the key trends affecting the future of the construction industry is the issue of ecology; therefore, current activities in construction aim to reduce the use of raw materials, which is made possible by including recycled materials in composites, among other methods. This article describes the results of tests conducted using four types of epoxy composites, i.e., composites modified with waste rubber (WR), composites modified with waste polyethylene (PE) agglomerate, glycolysate obtained using polyethylene terephthalate (PET) waste, and control unmodified mortars (CUM). Selected properties of the mortars were monitored during their maturation under laboratory conditions, as well as after post-curing at elevated temperatures in the range of 60 °C–180 °C. With the increase in the reheating temperature, an increase in the flexural strength of all types of mortars was noted, with the highest more than twofold stronger than the unmodified composites. The compressive strength increased up to a temperature of 140 °C, and then decreased slightly. The highest value of 139.8 MPa was obtained using PET mortars. Post-curing also led to a slight loss of mass of all samples in the range of 0 to 0.06%. Statistical methods were employed, which made it possible to determine the post-curing temperature and composite composition for which the determined properties are simultaneously the most beneficial, especially for the prefabricated elements. Full article
(This article belongs to the Special Issue Advanced Polymers and Composites for Multifunctional Applications)
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22 pages, 28555 KiB  
Article
Ultrasound-Enhanced Friction Stir Welding of Aluminum Alloy 6082: Advancements in Mechanical Properties and Microstructural Refinement
by Marat Rebrin, Andreas Gester, Dmitrii Ozherelkov, Christiane Wächtler, Toni Sprigode, Martin Mädlow and Guntram Wagner
Metals 2024, 14(11), 1241; https://doi.org/10.3390/met14111241 - 31 Oct 2024
Viewed by 134
Abstract
This study examines the effects of ultrasound-enhanced friction stir welding (USE-FSW) on the mechanical properties and microstructural characteristics of aluminum alloy AA6082-T6, commonly used in automotive, aerospace, and construction industries. The investigation included tensile and bending tests, as well as detailed microstructural evaluations [...] Read more.
This study examines the effects of ultrasound-enhanced friction stir welding (USE-FSW) on the mechanical properties and microstructural characteristics of aluminum alloy AA6082-T6, commonly used in automotive, aerospace, and construction industries. The investigation included tensile and bending tests, as well as detailed microstructural evaluations using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and energy-dispersive X-ray spectroscopy (EDS). The results indicate that USE-FSW led to an approximately 26% increase in tensile strength compared to similar samples produced by conventional friction stir welding (CFSW). Additionally, the elongation at break improved by around 52%, indicating better ductility. Flexural strength also showed a notable improvement of over 70%. Microstructural analysis revealed a finer grain structure in the stir zone, contributing to these mechanical enhancements. However, the changes in texture and grain orientation were relatively modest, as shown by EBSD and Kernel Average Misorientation (KAM) analyses. Overall, USE-FSW offers incremental improvements in weld quality and mechanical performance, making it a promising technique for producing joints with slightly enhanced strength and ductility. Full article
(This article belongs to the Special Issue New Welding Materials and Green Joint Technology—2nd Edition)
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25 pages, 13328 KiB  
Article
Study of the Structure and Properties of Concrete Modified with Nanofibrils and Nanospheres
by Alexey N. Beskopylny, Sergey A. Stel’makh, Evgenii M. Shcherban’, Valery Varavka, Besarion Meskhi, Levon R. Mailyan, Maksim Kovtun, Sergei Kurlovich, Diana El’shaeva and Andrei Chernil’nik
Buildings 2024, 14(11), 3476; https://doi.org/10.3390/buildings14113476 - 31 Oct 2024
Viewed by 163
Abstract
The application of modifying nanoadditives in the technology of cement composites is currently a relevant and widely researched topic in global materials science. The purpose of this study was to investigate new nanoadditives—nanofibrils made from synthesized wollastonite (NF) and nanospheres from corundum (NS)—produced [...] Read more.
The application of modifying nanoadditives in the technology of cement composites is currently a relevant and widely researched topic in global materials science. The purpose of this study was to investigate new nanoadditives—nanofibrils made from synthesized wollastonite (NF) and nanospheres from corundum (NS)—produced by LLC NPK Nanosystems (Rostov-on-Don, Russia) as a modifying additive. During the experimental investigations, the mechanical properties of cement pastes and concrete were examined. This included an analysis of the density, compressive and bending strength, as well as water absorption of concrete that had been modified with NF and NS additives. X-ray phase and microstructural analyses of concrete were performed. It was established that modification of cement composites with NF and NS additives had a beneficial effect on their properties, and the optimal amount for both types of additives was 0.3% by binder weight. The highest recorded enhancements in compressive and flexural strength of concrete with 0.3% NF were 7.22% and 7.04%, respectively, accompanied by a decrease in water absorption by 4.70%. When modifying concrete with 0.3% NS, the increases in compressive and flexural strength were 2.71% and 2.48%, and water absorption decreased by 1.96%. Modification of concrete with NF and NS additives did not have a significant effect on the change in concrete density, which was no more than 1%. Based on the results of phase analysis, it was established that concrete with NF and NS additives were characterized by the presence of five main phases: quartz, portlandite, calcite, larnite, and olivine-Ca. It was found that compositions with 0.3% NF and NS differed from the control composition by the presence of such a phase as olivine-Ca. Microstructural analysis confirmed the effectiveness of NF and NS additives. The microstructure of the modified concretes was distinguished by the extensive occurrence of clusters composed of calcium silicate hydrate zones. The conducted studies prove the possibility of using NF and NS as modifying nanoadditives in the technology of cement composites. The addition of nanofibrils from synthesized wollastonite is the most effective and promising and is recommended for use in real construction practice. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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18 pages, 6764 KiB  
Article
Evolution of Holes and Cracks in Pre-Carbonized Glassy Carbon
by Yi Yang, Wei Wang and Haihui Ruan
Materials 2024, 17(21), 5274; https://doi.org/10.3390/ma17215274 - 30 Oct 2024
Viewed by 180
Abstract
Being a type of carbonaceous material, glassy carbon possesses thermomechanical properties akin to ceramics, offering both mechanical and chemical stability at high temperatures; therefore, it can be applied in electrochemistry and high-temperature manufacturing. However, the direct pyrolysis of a bulk precursor leads to [...] Read more.
Being a type of carbonaceous material, glassy carbon possesses thermomechanical properties akin to ceramics, offering both mechanical and chemical stability at high temperatures; therefore, it can be applied in electrochemistry and high-temperature manufacturing. However, the direct pyrolysis of a bulk precursor leads to internal pores and cracks, usually resulting in fracture. Our characterization results show that at temperatures below 400 °C, large pores do not form, and pre-carbonized glassy carbon (PGC) formed at 350 °C has a dense microstructure without cracks. It exhibits a high compressive strength of ~370 MPa and flexural strength of ~190 MPa, making it suitable for load-bearing applications. Additionally, the PGC-350 material shows small mass loss (~5%) and reasonably low thermal expansion (2.5 × 10−6/°C) when heated to 350 °C again. These properties suggest the potential of PGC for high-temperature applications. As a demonstration, PGC formed at 350 °C was employed to fabricate molds to press chalcogenide glass blanks, which exhibited favorable molding results for various surface morphologies. Full article
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17 pages, 1234 KiB  
Article
Study on the Effect of Jute CNFs Addition on the Water Absorption and Mechanical Properties of Geopolymer Concrete
by Siti Syazwani Nordin, Ervina Efzan Mhd Noor, Nurhidayatullaili Muhd Julkapli and Aeslina Abdul Kadir
Buildings 2024, 14(11), 3444; https://doi.org/10.3390/buildings14113444 - 29 Oct 2024
Viewed by 242
Abstract
This study investigates the influence of thermoplastic polyurethane (TPU) reinforced with jute cellulose nanofibers (CNFs) on the water absorption and mechanical properties of geopolymer concrete. The integration of TPU/jute CNF nanocomposites into geopolymer concrete is explored as a strategy to enhance both its [...] Read more.
This study investigates the influence of thermoplastic polyurethane (TPU) reinforced with jute cellulose nanofibers (CNFs) on the water absorption and mechanical properties of geopolymer concrete. The integration of TPU/jute CNF nanocomposites into geopolymer concrete is explored as a strategy to enhance both its durability and mechanical performance. Geopolymer concrete, a sustainable alternative to traditional Portland cement concrete, is known for its low carbon footprint, but it suffers from high brittleness and water absorption. The water absorption behavior of the modified concrete was assessed, revealing a significant reduction in water uptake due to the hydrophobic nature of TPU and the reinforcing effect of jute CNFs. Additionally, the mechanical properties, including compressive and flexural strengths, were evaluated to understand the impact of the nanocomposites on the structural integrity of the concrete. The addition of TPU/jute CNFs notably enhanced the splitting tensile strength (63.5%), compressive strength (59%), and water absorption (0.59%) of the composite, indicating a promising route for developing high-performance construction materials. The integration of 6 wt% of TPU/jute CNF nanocomposites was found to be optimal, resulting in a uniform matrix, reduced micro-cracks, and improved compressive strength due to enhanced adhesion between the nanocomposites and the geopolymer matrix. Furthermore, a curing temperature of 100 °C was identified as ideal, minimizing unreacted fly ash and enhancing adhesion strength, while higher temperatures (140 °C) led to material deterioration due to rapid water loss. The findings demonstrate that the addition of TPU/jute CNF nanocomposites not only improves resistance to water penetration but also enhances overall mechanical performance. This supports the development of more sustainable and resilient construction materials, contributing to global efforts to reduce the environmental impact of the construction industry. Future research should focus on the long-term durability of these composites under various environmental conditions to validate their effectiveness in real-world applications. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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25 pages, 15108 KiB  
Article
Research on Mechanical Properties of a 3D Concrete Printing Component-Optimized Path by Multimodal Analysis
by Bolin Wang, Min Yang, Shilong Liu, Xianda Liu, Hongyu Zhao, Xiangyu Wang, Yishuang Liang and Xiaofei Yao
Sustainability 2024, 16(21), 9388; https://doi.org/10.3390/su16219388 - 29 Oct 2024
Viewed by 360
Abstract
Three-dimensional concrete printing (3DCP) technology with solid wastes has significant potential for sustainable construction. However, the hardened mechanical properties of components manufactured using 3DCP technology are affected by weak interlayer interfaces, limiting the widespread application of 3DCP technology. To address the inherent limitations [...] Read more.
Three-dimensional concrete printing (3DCP) technology with solid wastes has significant potential for sustainable construction. However, the hardened mechanical properties of components manufactured using 3DCP technology are affected by weak interlayer interfaces, limiting the widespread application of 3DCP technology. To address the inherent limitations of 3DCP technology, conventional improvement strategies, such as external reinforcement and the optimization of material properties, lead to increased production costs, complex fabrication, and decreased automation. This study proposes an innovative spatial path optimization method to enhance the mechanical performance of 3D-printed, cement-based components. The novel S-path design introduces additional printed layers in the weak interlayer regions of the printed samples. This design improves the spatial distribution of fiber-reinforced filaments in continuous weak zones, thus enhancing the functional efficiency of fibers. This approach improves the mechanical performance of the printed samples, achieving compressive strengths close to those of cast samples and only a 20% reduction in average flexural strength. Compared to using a conventional printing path, the average compressive strength and flexural strength are improved by 30% and 55%, respectively, when the S-path layout is employed in 3DCP. Additionally, this method significantly reduces the anisotropy in compressive and flexural strengths to 26% and 28% of samples using conventional printing paths, respectively. Therefore, the proposed method can improve the mechanical properties and stability of the material, reducing the safety risks of printed structures. Full article
(This article belongs to the Special Issue Advanced Materials in Sustainable Infrastructure)
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19 pages, 5438 KiB  
Article
Synthesis and Characterization of an Alkali-Activated Binder from Blast Furnace Slag and Marble Waste
by Gülden Çagın Ulubeyli and Recep Artır
Materials 2024, 17(21), 5248; https://doi.org/10.3390/ma17215248 - 28 Oct 2024
Viewed by 348
Abstract
This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, [...] Read more.
This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis. Full article
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15 pages, 2718 KiB  
Article
FDM 3D Printing and Properties of WF/PBAT/PLA Composites
by Mengya Li, Wen Lei and Wangwang Yu
Molecules 2024, 29(21), 5087; https://doi.org/10.3390/molecules29215087 - 28 Oct 2024
Viewed by 329
Abstract
Fused deposition molding (FDM) is a commonly used 3D printing method, and polylactic acid (PLA) has become one of the most important raw materials for this technology due to its excellent warping resistance. However, its mechanical properties are insufficient. Polybutylene adipate terephthalate (PBAT) [...] Read more.
Fused deposition molding (FDM) is a commonly used 3D printing method, and polylactic acid (PLA) has become one of the most important raw materials for this technology due to its excellent warping resistance. However, its mechanical properties are insufficient. Polybutylene adipate terephthalate (PBAT) is characterized by high toughness and low rigidity, which can complement the performance of PLA. The biodegradable polymers produced by blending the two have thus been used to replace petroleum-based plastics in recent years, but the high cost of the blends has limited their wide applications. Introducing plant fibers into the blends can not only maintain biodegradability and improve the overall performance of the plastics but also reduce their costs greatly. In this study, the PBAT/PLA blends with a mass ratio of 70/30 were selected and mixed with wood flour (WF) to prepare ternary composites using a FDM 3D printing technique. The effects of WF dosage on the mechanical properties, thermal properties, surface wettability, and melt flowability of the composites were investigated. The results showed that the proper amount of WF could improve the tensile and flexural moduli of the composites, as well as the crystallinity and hydrophobicity of the printed specimens increased with the content of WF, while the melt flow rate decreased gradually. Compared to PBAT/PLA blends, WF/PBAT/PLA composites are less costly, and the composite containing 20 wt.% WF has the best comprehensive performance, showing great potential as raw material for FDM 3D printing. Full article
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26 pages, 14117 KiB  
Article
Mechanical Properties and Microstructure of Alkali-Activated Cements with Granulated Blast Furnace Slag, Fly Ash and Desert Sand
by Yunpeng Liu, Xihao Yang, Wendi Tian, Zhenbo Fu, Yimeng Zhao, Binghan Li, Shiji Li, Da Xu, Shige Yu, Zhiyu Yao, Tian Zhao, Xinfeng Ouyang, Guangfei Wang, Hai Yu, Dan Li, Rongxin Guo, Yen Wei and Kangmin Niu
Buildings 2024, 14(11), 3422; https://doi.org/10.3390/buildings14113422 - 28 Oct 2024
Viewed by 422
Abstract
In this study, desert sand was used as supplementary materials in alkali-activated cements (AAC) with granulated blast furnace slag (GBFS) and fly ash (FA). For the first time, a systematic investigation was conducted on the effects of various treatment methods and contents of [...] Read more.
In this study, desert sand was used as supplementary materials in alkali-activated cements (AAC) with granulated blast furnace slag (GBFS) and fly ash (FA). For the first time, a systematic investigation was conducted on the effects of various treatment methods and contents of desert sand on the strength and microstructure of AAC. This study also analyzed the X-ray diffractometer (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray Microanalysis (SEM-EDX), Mercury Intrusion Porosimetry (MIP), pH values, and Fourier-transform infrared spectroscopy (FT-IR) properties of AAC pastes containing differently treated desert sand to uncover the mechanisms by which these treatments and dosages influence mechanical properties of AAC. Untreated desert sand (DS), temperature-treated desert sand (DS-T), and ground desert sand for two different durations (20 mins and 30 mins) all exhibited some pozzolanic activity but primarily acted as fillers in the AAC pastes. Among the samples, DS-T demonstrated the highest pozzolanic activity, though it was still less than that of fly ash (FA). The optimal dosage for the modified desert sands was determined to be 10%. However, The optimal dosage of different modified desert sands is 10%. The flexural strength of DS-G30-10 reaches 6.62 MPa and the compressive strength reaches 72.3 MPa, showing the best comprehensive mechanical properties. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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16 pages, 6090 KiB  
Article
Research on Deterioration Behavior of Magnesium Oxychloride Cement Under High Humidity and High Temperature
by Lingyun An, Ziyi Wang, Leichao Meng, Chenggong Chang, Zhifu Zhou and Fengyun Yan
Materials 2024, 17(21), 5226; https://doi.org/10.3390/ma17215226 - 26 Oct 2024
Viewed by 428
Abstract
To clarify the deterioration behavior of magnesium oxychloride cement (MOC) under conditions of high humidity and high temperature, we first placed MOC slurry samples in a simulated environment with a relative humidity of 97 ± 1% and a temperature of 38 ± 2 [...] Read more.
To clarify the deterioration behavior of magnesium oxychloride cement (MOC) under conditions of high humidity and high temperature, we first placed MOC slurry samples in a simulated environment with a relative humidity of 97 ± 1% and a temperature of 38 ± 2 °C; then, we observed the changes in the macroscopic and microscopic morphology, water erosion depth, bulk density, phase composition, and mechanical properties of the samples. The results show that, over time, under the promotion of high temperature, water molecules infiltrate the MOC samples. This results in the appearance of cracks on the macroscopic surface of the MOC samples due to the volume expansion caused by the hydrolysis of P5 (5Mg(OH)2·MgCl2·8H2O) and the hydration of unreacted active MgO in the samples. The microscopic morphology of the samples changes from needle/gel-like, to flake-like, and finally leaf-like. Simultaneously, the major phase composition turns into Mg(OH)2. Since the structure of the samples becomes looser and the content of the main strength phase decreases, the overall compressive strength and flexural strength are both reduced. The compressive strength of the MOC slurry samples (0 day) is 93.2 Mpa, and the flexural strength is 16.4 MPa. However, after 18 days of treatment, water molecules reach the center of the MOC samples, and the MOC samples completely lose their integrity. As a result, their compressive and flexural strengths cannot be obtained. Full article
(This article belongs to the Special Issue Properties and Applications of Cement-Based Composites (2nd Edition))
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20 pages, 12022 KiB  
Article
Study on the Effect of Basalt Fiber Content and Length on Mechanical Properties and Durability of Coal Gangue Concrete
by Zixin He, Xiao Zhao, Meichen Ye, Wei Zuo, Xiaoxiong Nie and Jianjun Zhao
Sustainability 2024, 16(21), 9310; https://doi.org/10.3390/su16219310 - 26 Oct 2024
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Abstract
The massive accumulation of coal gangue not only causes a waste of resources but also brings serious environmental pollution problems. To promote the utilization of coal gangue resources, mitigate environmental pollution from coal gangue, and address the shortage of natural aggregates, this study [...] Read more.
The massive accumulation of coal gangue not only causes a waste of resources but also brings serious environmental pollution problems. To promote the utilization of coal gangue resources, mitigate environmental pollution from coal gangue, and address the shortage of natural aggregates, this study investigates the use of coal gangue to replace coarse aggregate at a 40% replacement rate to prepare coal gangue concrete (CGC). The current research on the modification of gangue concrete by BF has been less often compared with the research on the effect of basalt fiber (BF) on the properties of ordinary concrete, so in this study, BF with different admixtures and lengths were added into CGC. Additionally, basalt fibers (BFs) of varying amounts and lengths were incorporated into CGC. The study explored the effects of BF on the tensile strength, splitting tensile strength, and flexural strength of CGC. It was found that the mechanical properties of CGC improved significantly when the BF dosage was 0.10–0.15% and the length was 18 mm. This is evidenced by an increase in the compressive strength of 3.94–5.11%, split tensile strength of 11.20–16.18%, and flexural strength of 8.23–12.97%. BF was able to refine pore space, prevent crack development, and bridge cracks in CGC. To further investigate the effect of BF on the long-term service performance of CGC, the effects of BF on the appearance, quality, and compressive strength of CGC in sulfate and freeze–thaw environments were examined. The results indicated that a BF dosage of 0.10–0.15% significantly enhanced the sulfate erosion resistance and freeze–thaw resistance of CGC. This is shown by a 36.76–46.90% reduction in the rate of loss of compressive strength of CGC under the freeze–thaw cycling and a 6.21–8.50% increase in the corrosion resistance factor of CGC under a sulfate attack. BF improved the pore structure and reduced seepage channels, thereby enhancing the durability of CGC. Full article
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