Decrease In Flexural Strength Research Articles

Preparation and characterization of fumed silica added PMMA denture base materials

This study was carried out to investigate the chemical, mechanical, and structural properties of increasing amounts of fumed silica added to PMMA denture base material. The effect of adding fumed silica at three different concentrations (0.5%, 1%, and 2% by weight) to PMMA was studied using Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), density, flexural strength, hardness, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The results showed that the highest flexural strength values (105.64 MPa) and hardness (20.07 microvickers) were obtained with 1% wt. of fumed silica material. According to DMA results, fumed silica samples containing 1% wt. had the highest energy storage (3.24 GPa at 30 °C) and glass transition temperature. As a result, fumed silica in PMMA denture base material reached its maximum saturation limit at 1% wt. A more brittle behavior was observed in samples containing 2% fumed silica, which accumulated on the surface, as confirmed by AFM. The molecular bonds at the resin-fumed silica interface weaken due to the agglomeration of fumed silica. Consequently, the flexural strength and hardness decrease, along with the glass transition temperature and storage modulus. The potential applications of this research are vast, inspiring further exploration and innovation in denture-based materials.

Eco‐friendly enhancement of mechanical properties in 3D carbon felt reinforced epoxy/aluminum sandwich composites via NaCl‐based anodizing and triton X‐100 modification

AbstractTo address the challenges of achieving strong adhesion between aluminum face sheets and composite cores (3D carbon felts) in sandwich structures, this work presents a novel approach that prioritizes safety, environmental sustainability, and ease of processing. The 3D CFs/Epoxy core was modified with Triton X‐100 in amounts from 0 to 10 wt% of the epoxy resin. The aluminum alloy face sheets were anodized at voltages from 0 to 11 V, using a NaCl‐based anodizing process. The technique of anodizing can enhance the bond between the aluminum face sheets and the 3D CFs/epoxy core, resulting in improved mechanical performance of the composite, including flexural and compressive testing, as well as dynamic mechanical analysis. The composite, embedding 3D CFs foam in epoxy resin, has a storage modulus 65.1% higher than pure epoxy at 2070 MPa. In addition, increasing Triton X‐100 content (1–10 wt%) decreases the storage modulus from 1886 to 1314 MPa and the glass transition temperature from 68.3 to 62.8 °C. Additionally, with Triton X‐100 concentrations of 1 to 10 wt%, the flexural modulus of the epoxy reinforced by 3D CFs drops from 3951.8 to 2400 MPa, and the flexural strength decreases by 55.3% from 174 to 112 MPa, indicating reduced structural rigidity. For sandwich composites with anodized aluminum face sheets, a 7 V anodizing voltage boosts the flexural modulus from 17.8 GPa (0 V) to 36.2 GPa. At 7 V, compressive strength and strain rise by 346.9% and 995.5%, respectively. Flexural toughness peaks at 11239 KJ/m3 with 5 wt% Triton X‐100.Highlights Developed new sandwich epoxy composites consisting of anodized aluminum sheet treated with NaCl and modified 3D carbon felts epoxy composites using Triton X‐100. Aluminum face sheets underwent an anodization at different voltages (0, 5, 7, 9, and 11 volts), aiming to enhance the bonding between the aluminum sheets and the 3D CFs/epoxy core. Triton X‐100 was utilized to modify the epoxy matrix at various concentrations (0 to 10 wt%) for improving the flexibility of the sandwich core. The sandwich composites incorporating the un‐anodized face sheet have shown flexural modulus of about 17.8 GPa. The modulus achieves its maximum value of 36.2 GPa when anodized at 7 V, indicating a 103% increase. The flexural strength of sandwich composites increases by 13% (272 MPa) when the Triton X‐100 concentration is raised to 5 wt%, compared to the 240 MPa flexural strength of the Al face sheet anodized at 7 V.

Optimization of Ultra-High Performance Concrete Based on Response Surface Methodology and NSGA-II.

This study systematically investigated three influential factors-water-to-binder ratio, cement/sand ratio, and steel fiber content-that significantly impact the performance of ultra-high-performance concrete (UHPC). Utilizing the Response Surface Methodology (RSM) with a Central Composite Design (CCD), 20 carefully designed mix proportions underwent comprehensive experimental testing. Through rigorous statistical analysis, models were established to elucidate the complex relationships between the specified factors and the overall properties of UHPC. Variance analysis reveals significant effects of the three factors on UHPC performance, with workability and compressive strength increasing with higher cement/sand ratios while flexural strength decreases. Moreover, increased water-to-binder ratios exhibit substantial negative impacts on both 28-day compressive and flexural strengths. Despite adversely affecting workability, higher steel fiber dosages contribute positively to mechanical performance. Furthermore, Monte Carlo sampling and the multi-objective non-dominated sorting genetic algorithm-II (NSGA-II) were employed to validate the reliability of the statistical model and to conduct multi-objective optimization. The final UHPC mix design obtained consists of a cement/sand ratio of 1.12, a water/binder ratio of 0.16, and a steel fiber content of 2.94%. Experimental results yielded a slump flow of 802 mm, compressive strength of 122.7 MPa, and flexural strength of 24.3 MPa.

The Effect of Erosive Media on the Mechanical Properties of CAD/CAM Composite Materials.

This study aimed to investigate the effect of acidic media storage (gastric acid and Coca-Cola) on the mechanical properties of CAD/CAM materials. Three types of materials were tested: a polymer-infiltrated ceramic network (PICN) (Vita Enamic (En), VITA Zahnfabrik, Germany), a resin composite block (RCB) (Cerasmart (Cs), GC Corp, Japan), and a conventional resin-based composite (Gradia direct (Gr), GC Corp, Japan), which was used as a control. Beam-shaped specimens of each material, with dimensions of 16 mm × 4 mm × 1.5 mm, were prepared (90 in total). The specimens were divided into subgroups (10 each) and stored for 96 h in either gastric acid, Coca-Cola, or distilled water. Flexural strength and elastic modulus were evaluated using a three-point flexural strength test with acoustic emission (AE) monitoring. Vickers microhardness was measured before and after storage in gastric acid and Coca-Cola. Data were statistically analysed using two-way and one-way ANOVA, the Tukey's post hoc, and independent t-test at a significance level of 0.05. The results showed that Cs and En maintained their flexural strength and elastic modulus after acidic media exposure, while Gr experienced a significant decrease in flexural strength following gastric acid storage (p < 0.01). Initial crack detection was not possible using the AE system, impacting the determination of flexural strength. Exposure to acidic media decreased all materials' microhardness, with Gr showing the most notable reduction (p < 0.0001). Gastric acid had a greater impact on the microhardness of all tested materials compared to Coca-Cola (p < 0.0001). In conclusion, storage in erosive media did not notably affect the flexural strength or elastic modulus of CAD/CAM composites but it did affect hardness. CAD/CAM composite blocks demonstrated superior mechanical properties compared to the conventional composite.

Effect of machining damage on the surface roughness and flexural strength of CAD-CAM materials

Computer-aided design and computer-aided manufacturing (CAD-CAM) materials are available for different types of restorations. However, the longevity of the material is affected by chipping, milling damage, flexural strength, and surface roughness, and a standard edge chipping test or standardized measurements are unavailable for monitoring edge chipping of rotary instrument-milled materials. The purpose of this in vitro study was to analyze the surface roughness and edge chipping of different CAD-CAM diamond rotary instrument-milled dental material bars, correlate the effect of machining damage with material strength, and compare the flexural strength of rotary instrument-milled and sectioned CAD-CAM blocks. Five dental CAD-CAM materials were tested: lithium disilicate glass-ceramic (IPS e.max CAD), leucite-reinforced glass-ceramic (IPS Empress CAD); feldspathic porcelain (Vitablocs Mark II); feldspar ceramic-polymer infiltrated (Enamic), and composite resin (Lava Ultimate). Rectangular bars were designed and milled for each material (n=10). The surface roughness of the bars was measured using a profilometer. All edges of 3 selected bars were analyzed with scanning electron microscopy (SEM) for the chip length, depth, and area. The 3-point bend test was used to test the flexural strength of rotary instrument-milled and saw-cut bars with the same dimensions. Analysis of variance and the Tukey honestly significant difference post hoc test were used to determine the difference among the groups (α=.05). IPS e.max CAD had the highest surface roughness and Lava Ultimate the lowest. Lava Ultimate had the smallest chipping factor and IPS Empress CAD the largest. The surface location significantly affected the chipping depth, area, and length (P<.05). A strong correlation was found between the decrease in flexural strength and the chipping length on the central tensile side of the rotary instrument-milled materials (R2=.62, P=.01), as well as the chipping depth (R2=.44, P=.01). Edge chipping was significantly associated with the material type, milling surface, and edge location and strongly correlated with a decrease in flexural strength.

Using Municipal Solid-Waste Incinerator Fly Ash, Wash Water, and Propylene Fibers in Self-Compacting Repair Mortar, Greenhouse Gas Emissions Potential

Wash water, municipal solid waste incineration (MSWI) fly ash, and propylene (PP) fibers were employed simultaneously to produce self-compacting repair mortar (SCRM). Different SCRM mixtures were utilized, incorporating 35, 70, and 140 kg/m3 of MSWI fly ash, along with 0.1% of PP fibers. The research focused on investigating the workability, mechanical properties, and global warming potential (GWP) of SCRM. The incorporation of MSWI fly ash and wash water in SCRM resulted in reduced workability, necessitating an increase in the use of superplasticizer. Adding MSWI fly ash decreases compressive strength. The minimum compressive strength was observed when employing 140 kg/m3 of MSWI fly ash and wash water instead of tap water simultaneously. By increasing the proportion of MSWI fly ash content and correspondingly reducing the cement content in SCRM samples, there was a decrease in flexural strength. The ultrasonic pulse velocity (UPV) of all SCRM samples falls within acceptable range. Adding MSWI fly ash to SCRM reduces fracture toughness, and the concurrent use of wash water and MSWI fly ash significantly decreases fracture toughness. Incorporating PP fibers into SCRM resulted in increased compressive strength. Utilizing wash water and MSWI fly ash in SCRM significantly reduces GWP. The avoidance of wash water consumption mitigates the environmental impact of SCRM.

Thermal shock resistance of additively manufactured alumina

AbstractThe mechanical behavior and cracking patterns of thermally‐shocked additively manufactured alumina were investigated. The flexural strength of test specimens that had been heated to temperatures ranging from 200°C to 1000°C and then rapidly quenched in water was determined at ambient temperature by four‐point bending. Results indicated that the surface cracking patterns had a multifractal structure and that an increase in the thermal shock temperature led to an increase in the density and uniformity of the crack network. The flexural strength results were analyzed with Weibull statistics, where the Weibull moduli for most of the thermal shock conditions tested were found to be statistically indistinguishable. It was also found that a significant decrease (∼50%) in flexural strength occurred for heating temperatures ≥300°C. The effect of the manufacturing method on cracking patterns is discussed, as well as the implication of the material behavior for practical applications of these materials.

Research Progress in the Application of Calcium-based Expansive Agents as Compensation for Autogenous Shrinkage in High-strength Concrete

In this study, comprehensive investigation of the shrinkage compensation mechanisms of calcium-based expansive agents (CEAs), their effects on the properties of (ultra) high-strength concrete (HSC/UHSC), and the existing problems in applying this methodology was conducted. Analyses showed that the rational use of CEAs under certain conditions could greatly or completely inhibit the development of autogenous shrinkage of HSC/UHSC, and significantly reduce the risk of associated cracking. However, it was found that the hydration of the CEAs affected the hydration process of other binders, thereby altering the microstructure of concrete. This was in turn observed to lead to a degree of decrease in compressive strength, flexure strength and elastic modulus, and the decrease rate increasing as with the rise in proportion of CEAs. Moreover, when attempting to improve the shrinkage compensation effects, increasing the amount of CEA presented a risk of delayed expansion cracking of HSC/UHSC. Neither the expansion mechanism, expansion conditions, nor the inhibition methods have yet been fully clarified in the current stage. Lastly, newly proposed Ca-Mg composite EAs were outlined, and the research prospects of Ca-Mg composite EAs in HSC/UHSC were explored.

Effects of perlite content and jute fiber reinforcement on flexural behavior of the gypsum/perlite composite core-based sandwich structures

Gypsum wallboards are widely used as a building material, but limitations exist in their weight and brittleness. The incorporation of various fillers in the gypsum makes them lightweight, stiff, and capable of resisting catastrophic failure but with the cost of strength. Sandwiching the filled gypsum using a low-cost material as skin may be an innovative approach to improve the flexural properties. In this work, sandwich structures were fabricated using jute fiber reinforced and unreinforced perlite-filled gypsum as cores and low-cost brown paper as skins. The density, flexural strength, modulus, and toughness of the resulting sandwich structures were investigated. It is found that the increase in perlite content in pure gypsum and jute fiber-reinforced gypsum significantly enhances the flexural strength, modulus, and toughness of the sandwich structures. However, previous research on jute fiber-reinforced and unreinforced gypsum/perlite composite panels (without skin) showed a decrease in flexural strength due to an increase in perlite content. The maximum flexural strengths of unreinforced sandwich (URS) and jute fiber reinforced sandwiches (JRS) at a perlite content of 15 g are found to be 13.29 % and 40.79 % greater than the control sandwich with pure gypsum core. The maximum flexural toughness of the JRS at a perlite content of 20 g and that of the URS at a perlite content of 15 g are respectively 118.31 % and 79.14 % greater than the control sandwich. A significant difference in load-displacement curves between JRSs and URSs is noticed despite the similar failure sequence i.e. core cracking→skin yielding→skin tearing.

Exploring flexural performance and abrasion resistance in recycled brick powder-based engineered geopolymer composites

BackgroundDue to growing global concerns regarding the management of construction waste, this study investigates the feasibility of creating engineered geopolymer composites by replacing traditional industrial by-products (slag) with construction waste, specifically recycled brick waste powder.ResultsPolyvinyl alcohol fibers were incorporated into the engineered geopolymer composite mixtures. The substitution of slag with recycled brick waste powder was carried out at varying percentages: 0, 20, 40, 60, 80, and 100%, resulting in six different engineered geopolymer composite mixtures. The study evaluated the flexural strength, sorptivity, water absorption, and abrasion resistance of the engineered geopolymer composites, and also, microstructural characterization was conducted using scanning electron microscopy. The findings demonstrated that incorporating recycled brick waste powder into the engineered geopolymer composite mixes resulted in a decrease in flexural strength by 35.59% and a notable increase in midspan deflection by 339% when slag was replaced. Concurrently, there was a significant rise in water absorption and sorptivity by approximately 304 and 214%, respectively, when slag was entirely substituted with recycled brick waste powder. Conversely, abrasion resistance decreased, with the inclusion of recycled brick waste powder resulting in an 84% increase in volume change. The scanning electron microscopy (SEM) analysis showed active geopolymerization of recycled brick waste powder within the engineered geopolymer composite mixtures.ConclusionsThe results of this investigation demonstrate that it is feasible to produce engineered geopolymer composites using recycled brick waste powder instead of slag. The greater ductility and increased midspan deflection point to areas that require further optimization, even in spite of the observed decreases in flexural strength and abrasion resistance. The SEM examination reveals an active geopolymerization, highlighting the potential of recycled brick waste powder to produce environmentally friendly and sustainable construction materials. These results offer a good starting point for further studies that try to maximize the durability and performance of these composites.

Research on the Performance of Steel Strand-Reinforced Reactive Powder Concrete with Mixed Steel Fibers and Basalt Fibers under the Salt Dry–Wet Erosion

In this study, the properties of steel strand-reinforced reactive powder concrete (RPC) with mixed steel fibers and basalt fibers were investigated. The volume ratios of steel fibers and basalt fibers ranged from 0% to 2%. The reinforcement ratio of steel strands was 1%. The flexural strength and toughness were measured. Moreover, the impact toughness was determined. The studies were carried out under an erosion environment with chlorides and sulfates. The electrical resistance and the ultrasonic velocity were obtained to assess the salt corrosion resistance performance of steel strand-reinforced RPC. The results show that the addition of basalt fibers and steel fibers can improve the mechanical strength, ultrasonic velocity, flexural toughness, and impact toughness and decrease the performance degradation of the steel strand-reinforced RPC under the conditions of dry–wet alternations of NaCl and Na2SO4 solutions. Basalt fibers and steel fibers can improve the steel strand-reinforced RPC’s flexural strength by rates of up to 13.1% and 28.7%, respectively. Moreover, the corresponding compressive strength increases by 10.3% and 18.3%. The flexural strength decreases by 11.2~33.6% and 7.3~22.7% after exposure to the NaCl and Na2SO4 dry–wet alternations. Meanwhile, the corresponding compressive strength decreases by 22.1~38.9% and 14.6~41.3%. The electrical resistance increases with the addition of basalt fibers and decreases with the increasing dosages of steel fibers. The steel strand-reinforced RPC with the assembly units of 1% steel fibers and 1% basalt fibers shows the optimal mechanical properties and salt resistance considering its wet–dry alternation performance. The properties of steel strand-reinforced RPC decrease more rapidly after undergoing NaCl erosion than Na2SO4 erosion.

Effect of chewing simulation in different Ph solutions on flexural strength of monolithic zirconia

Abstract Aim In vitro study is to evaluate the effect of chewing simulation in different ph solutions on flexural strength of monolithic zirconia. Patients and methods Forty zirconia bars (N = 40) were cut off zirconia disc using IsoMet. Each bar was 2 mm thickness, 25 mm length and 5 mm width. Specimens were divided into four groups (n = 10). The first group (control) was ready for universal test of flexural strength. Second, third, and fourth group were ready for chewing simulation but in different PH solutions acidic, neutral, and alkaline respectively. These solutions were collected from the lab (acidic-PH = 4, alkaline PH = 10). Twenty extracted human premolars (divided vertically into two halves by IsoMet) were collected for study as antagonist material for chewing simulation. After chewing simulation of these groups, the flexural strength was measured for them and SEM. Results Group 1 (control) showed the highest flexural strength with the mean value (745.21 ± 69.47) followed by group 3 (neutral) (720.40 ± 92.47), then group 2 (acidic) (507.56 ± 111.99), and finally group 4 (alkaline) (497.26 ± 172.90) with the least flexure of strength. There was significance between group 1 (control) and group 2 (acidic) and highly significant with group 4 (alkaline). There was no significance with group 3 (neutral). SEM showed that no cracks in control group. Group (2) surfaces were very smooth with amorphous structure showing disperessed small pores. Group (3) air voids were found entrapped between zirconia grains. Group (4) the surface was rough showing large compact flacks’ fragmentation and branched cracks. Conclusions This study clearly illustrates the significance of flexural strength in different pH of an aqueous solution in terms of the chewing of zirconia ceramics. Cyclic loading decreases flexural strength of 4% yttrium zirconia in neutral but not significantly. In alkaline and in neutral there were significant decrease in flexural strength with chewing due to degradation of stabilizers and transformation tetragonal phase to monoclinic phase. This degradation was in alkaline group more than in acidic group.

Impact of water content and salts on the mechanical properties of masonry materials used in historic structures

Abstract The protection of built cultural heritage is increasingly important due to climate change. Given that flooding is one of the most serious threats to the conservation of heritage objects, the goal of this study was to evaluate the effect of water and soluble salts on the mechanical strength of materials commonly used in old structures. An experimental analysis was conducted by wetting several types of conventional building materials (such as stone, lime mortar, and fired-clay brick), each characterised by distinct mechanical properties and porous structure. The impact of contamination with three types of soluble salts commonly found in historic buildings was also assessed. The results showed that the level of water saturation can have a significant effect on the mechanical properties of all the tested materials. In some cases, the sample heterogeneity surpassed the effect of water content on the mechanical behaviour. Brick and stone samples showed a similar trend in the strength behaviour. Brick had a flexural strength decrease of around 15% after 7 days of submersion in water and also after storage in an environment with high relative humidity. Mortar mixtures were more sensitive to the effect of water and salt solutions compared to stone and bricks. One-cycle of salt contamination followed by drying increased the mechanical strength of the tested materials.

Development and Characterization of Pineapple Leaf Fibre Reinforced with Graphene and Fibre Glass Composites for Aerospace Application

Natural fibre-based compositessuch as Pineapple leaf fibre (PALF)are valued for their environmental friendliness and unique properties, can be combined with graphene and glass fibres to create advanced aerospace composites. This study investigates the effects of graphene content and PALF composition on the mechanical properties of the composite. PALF is made using environmentally friendly methods, with graphene treated for better integration and fibre glass added through layering. This study compares the strength and flexibility of two samples with different PALF-to-fibreglass ratios: 50:50 and 70:30, and one sample with a 70:30 PALF-to-fibreglass ratio reinforced with 1% graphene, using tensile and flexural tests. The 70:30 composition ratio results in a lower maximum tensile strength and Young’s modulus, but a higher bending stress than the 50:50 ratio due to the higher volume of PALF in the sample. 70:30 PALF/fibreglass reinforced with 1% graphene is stiffer, resulting in a higher Young’s modulus compared to the sample without graphene. There is a slight decrease in flexural strength for the 70:30 PALF/fibreglass ratio reinforced with 1% graphene, while still maintaining superior bending stress strength compared to 50:50 ratio compositions. From the SEM test, PALF/fibreglass samples exhibited fibre pull-out, while 70:30 samples reinforced with graphene showed fibre breakage. Graphene enhanced the bonding between fibres and resins, leading to the breakage.Without graphene, weaker bonding led to fibre pull-out. Therefore, the PALF/fibreglass reinforced with graphene has the potential for aerospace applications, particularly in components subjected to high bending stress, such as aircraft wings or the horizontal tail.

Effect of adding natural coconut oil on the antifungal, flexural strength, and hardness properties of heat cure acrylic resin (an in vitro study)

Purpose. This study's objective was to estimate the effect of various quantities of the addition of natural coconut oil according to concentrations (1%, 2%, 3%) on the heat cured denture base material's anti-fungal, flexural strength, and hardness properties. Material and method. A total of 120 samples were created and (divided into three groups each groups contain forty samples) built regarding the attitude test: Candida albicans adherence test, flexural strength test, and hardness test. Next, each group was subdivided into three subgroups (control 0%, 1%, 2% and 3%) based on the various quantities of the added natural coconut oil, with (n=10 samples for each subgroup). Each group was assessed at 48 hours. One-way ANOVA and other statistical methods were used to analyze the data, Duncan and Dunnett’s tests for comparison means among all groups with control at p ≤0.05. Results. A One-way ANOVA showed a significant difference in the mean values of Candida albicans adherence, with the additive of natural coconut oil groups (1%, 2%) showing the highest antifungal effect compare with (3% additive groups). Adding 1% coconut oil had no significant difference on hardness and flexural strength, while adding 2% and 3% additive of coconut oil groups showed a significantly decrease than control groups at p ≤ (0.05). Conclusion. The antifungal properties of heat-cured acrylic resin are enhanced by the addition of coconut oil. However, when used in high concentrations (greater than 1%), it can result in a decrease in hardness and flexural strength.

Variations in the physical and mechanical behavior of basalt fiber reinforced NHL mortars exposed to different curing conditions

This paper investigates experimentally the short-term behavior of natural hydraulic lime (NHL) mortars reinforced with ballast fiber for use as structural repair mortars in historic and contemporary buildings. The physical and mechanical properties of mortar mixes reinforced with 0.143–0.215 mm equivalent thick and 12 mm long fibers in volumetric percentages of 1 %, as well as of unreinforced mortars, produced with different compaction methods and cured under different environmental conditions, have been evaluated. A cost-effectiveness analysis has also been carried out to determine the economic impact of these factors in their practical application. It is found that basalt fiber reinforcement provides lower water absorption coefficients and significantly improves the shore hardness, compressive strength, and post-critical flexural behavior of NHL mortars at early ages. Furthermore, it is observed that the compaction procedure can improve the packing density of the mortars providing higher densities, lower water absorption coefficients and higher mechanical strength values. Finally, it is verified that the curing parameters affect unevenly the basalt fiber reinforced NHL mortars and unreinforced NHL mortars, with greater deterioration being observed in the former when sufficient moisture is not ensured. Decreases in hardness, flexural and compressive strength, as well as increases in the water absorption coefficient are important. Consequently, the economic profitability of basalt fiber reinforcement depends on ensuring optimal moisture conditions during curing, especially when the mixes have already lost excess water after the first 2–3 days. The study provides quantitative and qualitative data to determine the appropriate curing parameters for basalt fiber reinforced NHL mortars that are viable in practice for their industrial performance.

Studying the usability of recycled aggregate to produce new concrete

One of the most significant environmental issues worldwide is garbage, particularly waste from construction materials, which is generated in substantial numbers. However, in the building industry, the significant extraction of natural resources such as cement, natural sand, and natural gravel poses a critical environmental challenge, depleting these resources at an alarming rate. There are some solutions that developed countries are resorting to, namely the division of construction waste into groups, where it is reused under the name of recycling construction waste to produce new, environmentally friendly building materials. The aim of this research includes a laboratory process study as it includes the use of the following ratios: 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%, under the process of replacing coarse plain aggregates including coarse recycled aggregates and studying the most important mechanical properties of concrete. This research was carried out using fresh concrete properties such as workability tests and hardened concrete properties such as compressive strength, splitting, and flexural tensile strength examined at the durations of 7, 14, and 28 days. The research includes the investigation of the three main properties of concrete. After conducting the tests, the results have shown that the main property of recycled concrete is lower strength than that of conventional concrete, but it can be said that it is within the limits that can be used for construction. The results also showed that compared to normal aggregates, development in the recycled aggregate percentage rates reduces the operational workability of concrete. The research proved that the maximum decrease in compressive, flexural, and tensile strength, density and the slump were 19.4, 18.3, 19.6, 19.5, and 25.0% respectively compared to the control concrete samples.

Effect of MgO addition on the structural evolution, crystallization and properties of self-glazed ceramics sintered from granite sludge

Recycling of granite sludge has both economic and environmental benefits. In this paper, high glossiness self-glazed ceramics were prepared from granite sludge with the addition of TiO2, Ca(OH)2 and MgO by combining two-step sintering and low-temperature crystallization. The effect of MgO addition on the phase evolution, crystallization and properties of the glazed ceramics was studied to reveal its role in the diopside precipitation. With increasing MgO content, the reduced glass viscosity accelerates the dissolution of quartz and anorthite into the liquid glass phase, resulting in a decrease in flexural strength above 1 % MgO. Meanwhile, the addition of MgO increases the non-bridging oxygen to lower the glass transition temperature. The increase in the Al/Si ratio of the glass phase and the mixed alkaline earth effect contribute to an increase in the crystallization temperature. After thermal treatment at 950 °C, the precipitated diopside increases the crystallinity of the glazed glass-ceramic from 6.4 % to 19.3 % at 3 % MgO, resulting in a surface glossiness of 99.7 GU and a flexural strength of 64.1 MPa. High glossiness self-glazed ceramics with an aesthetic appearance could be used in decorative building tiles for scalable utilization of granite sludge.

Mechanically robust high magnetic performance Sm2Co17 sintered magnets via microstructure modification with Al2O3 doping

In this work, a small amount of Al2O3 powders (≤0.3 wt%) were incorporated into the Sm2Co17-type sintered magnets, obtaining both high mechanical and magnetic properties. It is found that 0.1 % weight percentage of Al2O3 doping is enough to enhance the flexural strength by about 20 % (∼ 180 MPa for the case of the c-axis parallel to height). Meanwhile, the (BH)max remains around 219 kJ/m3, and Hcj is 2052 kA/m, which is over 95 % of that of the original magnets without doping. The promising improvement in flexural strength is mainly attributed to the grain size effective refinement caused by Sm2O3 particles including newly-formed ones from the reaction of the Al2O3 powder and Sm in the matrix. Furthermore, the grain size of the magnets decreases significantly with increasing of Al2O3 doping up to 0.3 wt%. Especially, the grain size of 0.3 wt% Al2O3 doped magnets is refined by 37 %. However, the flexural strengths (for the c-axis parallel to height and the c-axis parallel to width cases) of the magnets decrease sequentially and are even lower than that of the original magnet. The microstructure investigations indicate that the decrease in flexural strength may closely be correlated to the larger cell size and the incomplete cell boundaries phase. The obtained results infer that the flexural strength is susceptible to not only grain size but also the cellular structure of the magnets.

Mechanical behavior of glass fiber-reinforced hollow glass particles filled epoxy composites under thermal loading

The use of hollow glass particle-filled fiber-reinforced composites for aircraft applications requires proper understanding of their behavior under in-service temperature conditions in order to exploit their usage in the exterior parts of aircraft and other space vehicles. In this study, the glass fiber reinforced composites containing 0–30 vol% of glass microspheres were subjected to testing for monotonic tensile and flexural loading from room temperature to the test temperature (40°C – 120°C). The evolution of microscopic damage under different temperatures was elucidated by digital image correlation (DIC) strain fields. The strain fields revealed a transition from homogeneous to non-homogeneous pattern as the temperature increases due to softening of the matrix. As the glass microsphere contents in the matrix increased, the tensile and flexural properties of the composites decreased, and their reduction was highest for the specimen containing a 30 vol% microsphere by volume. The tensile properties are slightly decreased by increasing the temperature. The tensile specimens tested at room temperature exhibited limited delamination and fiber pullout, while extensive delamination and fiber splitting occurred in the specimens tested at 120°C. The flexural results of the glass fiber reinforced composite specimens exposed at 120°C demonstrated a considerable decrease in flexural strength compared with room temperature for 0 vol%, 10 vol%, 20 vol% and 30 vol% glass microsphere volume fraction. Finally, the Weibull parametric investigation was performed to model the degradation of modulus for various GMS contents with temperature variations.