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The present study evaluated the effect of different rinsing postprocessing solutions on surface characteristics, flexural strength, and cytotoxicity of an additive manufactured polymer for orthodontic appliances. These solutions have been deemed an alternative to the standard isopropanol which is a flammable liquid, known to have toxic effects.Tested specimens were manufactured using direct light processing of an orthodontic appliance polymer (FREEPRINT® splint 2.0, Detax) and post-processed with different post-rinsing solutions, including isopropanol (IPA), ethanol (EtOH), EASY 3D Cleaner (EYC), Yellow Magic7 (YM7), and RESINAWAY (RAY), respectively. All groups were post-cured following the manufacturer's instructions. Surface topography and roughness (Ra and Rv) were evaluated. In addition, flexural strength was measured by a three-point bending test. An extract test was performed to evaluate cytotoxicity. The data were analyzed by the Kruskal-Wallis test with Dunn's multiple comparisons test (p 0.05).Various post-rinsing solutions did not significantly affect the roughness values (Ra and Rv). Specimens post-processed with EtOH (98.1 ± 12.4 MPa) and EYC (101.1 ± 6.3 MPa) exhibited significantly lower flexural strength compared to the groups of IPA (110.7 ± 5.3 MPa), RAY (112.1 ± 5.6 MPa) and YM7 (117.3 ± 5.9 MPa), respectively. Finally, there were no cytotoxic effects of parts cleaned with different post-rinsing solutions.Considering the use of 3D-printed orthodontic appliance materials, different rinsing postprocessing procedures did not affect surface characteristics. However, the flexural strength was significantly influenced, which could be attributed to the chemical ingredients of the post-rinsing solutions. Various post-rinsing treatments had no alternation concerning cytocompatibility.

To evaluate the effect of post-curing times on the color change, flexural strength (FS), modulus (FM) and microhardness at different depths of four 3D printed resins.A characterization of the light emitted by 3D-resin post-curing unit (Wash and Cure 2.0, Anycubic) was performed. The tested 3D printed resins were Cosmos Temp3D (COS), SmartPrint BioTemp (SM) Resilab3D Temp (RES) and Prizma3D BioProv (PRI) were evaluated under five different post-curing conditions (no post-curing or 5-, 10-, 15, and 20 min of post-curing). For color change analysis, 10 mm diameter x 1 mm thick discs (n = 7) were printed, and the luminosity, color and translucency were measured before post-curing as control, and repeatedly after 5 min cycles of post-curing until a total of 20 min was reached for ΔEThe post-curing time significantly influenced the ΔEA fine adjustment of the post-curing time is crucial to produce adequate mechanical properties in 3D-printed restorative resins, while minimizing the color alterations on the restorations. For the evaluated resins, 5-10 min of post-curing will result in adequate mechanical properties, without affecting the acceptability in the color of the material. However, the results are material-dependent, and evaluation of each specific resin is advised.

Pervious concrete provides a tailored surface course with high permeability properties which permit the easy flow of water through a larger interconnected porous structure to prevent flooding hazards. This paper reports the modeling of the flexural properties of quarry dust (QD) and sawdust ash (SDA) blended green pervious concrete for sustainable road pavement construction using Scheffe’s (5,2) optimization approach. The simplex mixture design method was adapted to formulate the mixture proportion to eliminate the set-backs encountered in empirical or trials and the error design approach, which consume more time and resources to design with experimental runs required to evaluate the response function. For the laboratory evaluation exercise, a maximum flexural strength of 3.703 N/mm2 was obtained with a mix proportion of 0.435:0.95:0.1:1.55:0.05 for water, cement, QD, coarse aggregate and SDA, respectively. Moreover, the minimal flexural strength response of 2.504 N/mm2 was obtained with a mix ratio of 0.6:0.75:0.3:4.1:0.25 for water, cement, QD, coarse aggregate and SDA, respectively. The test of the appropriateness of the developed model was statistically verified using the Student’ t-test and an analysis of variance (ANOVA), and was confirmed to be acceptable based on computational outcomes at the 95% confidence interval. Furthermore, the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were used to evaluate the morphological and mineralogical behavior of green prior concrete samples with various additive mixture compositions. The addition of QD and SDA, on the other hand, aided the creation of porous microstructures in the concrete matrix due to fabric changes in the concrete mixture, potentially aided by the formation of cementitious compounds such as calcium aluminate hydrate and calcium silicate hydrate.

Background/Aim: Relining is defined as the procedure used to resurface the tissue side of a denture with new base material, thus producing an accurate adaptation is provided at the denture foundation area. During mastication, relined dentures have to withstand masticatory forces to prevent fracture. The aim of this study was to evaluate the flexural strength of acrylic resin denture base relined with different methods and materials. Material and Methods: Fourteen experimental groups and one control group were determined to consider different reline materials and processing methods. Acrylic resin specimens were prepared with the dimensions of 65x 10x 1.5 mm and reline materials (1.5 mm thickness) were placed on acrylic resins. Reline material was not used in control group specimens. Flexural strength values of relined and control specimens were measured with three-point bending test at a speed of 5 mm/min. Data were analyzed with using one way Anova and Student t tests. Results: The highest flexural strength values were shown in control group (86.51±1.08 MPa). There were significant differences among relined specimens (p< 0.05). For the relined specimens, the highest flexural strength values were found in the relined specimens with denture base material (77.90±1.93 MPa), and the lowest values were found in relined with autopolymerize acrylic material (59.81±1.50 MPa). Conclusions: Relining of the heat cure denture base material significantly decreases the flexural strength for all processing methods and materials.

In this research, flexural properties of mill-run, in-grade red and white oak lumber from a single mill and commercially available laminated hardwood composite were evaluated. Structurally graded green (wet) freshly sawn red and white oak 5 by 10-cm (2 by 4-in) nominal lumber as well as glue-laminated hardwood composite billets were tested in bending and their modulus of rupture (MOR) and modulus of elasticity (MOE) properties were developed. It is well documented that MOR and MOE are two major indicators to evaluate flexural strength of wood lumbers. From these data, summary statistics, design values, and mean separations were calculated and reported. Overall, the red and white oak lumber performed similarly to structural No. 2 grade material. The hardwood composite billets were highly uniform. Each of the three materials demonstrated a reasonably good relationship between MOE and MOR, thereby suggesting that MOE could be used as a selection criterion for strength in a commercial use situation.

The present study comprehensively compared the microstructure, flexural strength, and fracture toughness of zirconia ceramics prepared via two different methods, subtractive milling (SM) and stereolithography (SLA). Disc- or rectangular-shaped zirconia specimens (Prettau (SM) and 3DMix Zirconia (SLA)) were prepared following each manufacturer’s instructions and polished. The microstructures of the two different zirconia specimens were studied by scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectroscopy, and electron backscattered diffractometry. The flexural strength and fracture toughness based on the indentation fracture method were measured for the two different zirconia ceramics. A greater number of small pores and smaller grains were found in the SLA specimen than in the SM specimen. The crystal structure and microstructure analysis revealed that both ceramics had a similar phase composition to each other. No significant differences in flexural strength (p = 0.242) or fracture toughness (p = 0.101) were detected between the two ceramics. The mean flexural strength of the SLA-fabricated zirconia as well as the SM zirconia satisfied the class 5 criteria (>800 MPa) in the ISO 6872 standard.

With recent technological advances, adding nanomaterials as a reinforcement material in concrete has gained immense attention. This review paper aims to report advances in the form of a one-stop shop catering to methods that focus on improving the quality of traditional concrete. Nanoparticles—the elementary form of nanomaterials—are proven to enhance the strength and longevity of concrete. Nanosilica, nanoalumina, nanometakaolin, carbon nanotubes, and nanotitanium oxide are modern nanomaterials that have demonstrated strong evidence of enhancing concrete quality, which supports infrastructure building and long-term monitoring. Nanoconcrete—an exciting prospect extending the boundaries of traditional civil engineering—exhibited increased compressive and flexural strength using elementary compounds. In particular, the rigorous research survey of many articles reveals an increase in compressive strength from 20% to 63% by replacing the cement with different nanomaterials in different percentages and flexural strength from 16% to 47%.

To investigate the effect of acidic media, including beverages and gastric fluids on flexural strength and fatigue of CAD-CAM materials.Four CAD-CAM materials (high-translucency zirconia (Ceramill Zolid HT+), lithium disilicate (IPS e-max CAD), hybrid ceramic (Vita Enamic), and nanohybrid resin composite (Grandio Blocs) were prepared and immersed in one of five media (gastric HCl, white wine, Coca-Cola, orange juice, and artificial saliva) in an incubator (37 ℃, 24 h). Surface topography and roughness were obtained using a scanning electron microscope (SEM) and a stylus contact profilometer, respectively. Initial 3-point flexural strength was measured for half of the bars (n = 20/gp) using a universal testing machine (0.5 mm/min). The other bars underwent 10Zirconia bars has the highest initial flexural strengths followed by lithium disilicate, while resin composite and hybrid ceramic groups had the lowest strength regardless of the erosive medium. Cyclic fatigue significantly reduced initial flexural strengths for all materials except for hybrid ceramic and resin composite. Weibull moduli were the highest for zirconia, lithium disilicate and resin composite and lowest for hybrid ceramic.Erosive media significantly changed surface roughness of CAD-CAM materials except for zirconia and resin composite without jeopardizing the flexural strength of the CAD-CAM materials. Despite the higher flexural strengths for zirconia and lithium disilicate, resin composite and hybrid ceramic were more resistant to cyclic fatigue.

Ultra-high-performance concrete (UHPC) has greater mechanical and durability performance than normal concrete (NC). Using a limited dosage of UHPC on the external surface of NC to form a gradient structure could significantly improve the strength and corrosion resistance of the concrete structure and avoid the problems caused by bulk UHPC. In this work, white ultra-high-performance concrete (WUHPC) was selected as an external protection layer for normal concrete to construct the gradient structure. WUHPC of different strengths were prepared, and 27 gradient WUHPC-NC specimens with different WUHPC strengths and interval times of 0, 10, and 20 h were tested using splitting tensile strength to reveal the bonding properties. Fifteen prism gradient specimens with the size of 100 × 100 × 400 mm and a WUHPC ratio of 1:1, 1:3, and 1:4 were tested using the four-pointed bending method to study the bending performance of the gradient concrete with different WUHPC thicknesses. Finite element models with different WUHPC thicknesses were also built to simulate the cracking behaviors. The results showed that the bonding properties of WUHPC-NC were stronger with less interval time and reached the maximum of 1.5 MPa when the interval was 0 h. Moreover, the bond strength first increased and then decreased with the decline in the strength gap between WUHPC and NC. When the thickness ratios of WUHPC to NC were 1:4, 1:3, and 1:1, the flexural strength of the gradient concrete improved by 89.82%, 78.80%, and 83.31%, respectively. The major cracks rapidly propagated from the 2 cm position to the bottom of the mid-span, and the thickness of 1:4 was the most efficient design. The results simulated by finite element analysis also proved that the elastic strain at the crack propagating point was the minimum and was easier to crack. The simulated results were in good accordance with the experimental phenomenon.

Research has focused on creating new methodologies such as supervised machine learning algorithms that can easily calculate the mechanical properties of fiber-reinforced concrete. This research aims to forecast the flexural strength (FS) of steel fiber-reinforced concrete (SFRC) using computational approaches essential for quick and cost-effective analysis. For this purpose, the SFRC flexural data were collected from literature reviews to create a database. Three ensembled models, i.e., Gradient Boosting (GB), Random Forest (RF), and Extreme Gradient Boosting (XGB) of machine learning techniques, were considered to predict the 28-day flexural strength of steel fiber-reinforced concrete. The efficiency of each method was assessed using the coefficient of determination (R2), statistical evaluation, and k-fold cross-validation. A sensitivity approach was also used to analyze the impact of factors on predicting results. The analysis showed that the GB and RF models performed well, and the XGB approach was in the acceptable range. Gradient Boosting showed the highest precision with an R2 of 0.96, compared to Random Forest (RF) and Extreme Gradient Boosting (XGB), which had R2 values of 0.94 and 0.86, respectively. Moreover, statistical and k-fold cross-validation studies confirmed that Gradient Boosting was the best performer, followed by Random Forest (RF), based on reduced error levels. The Extreme Gradient Boosting model performance was satisfactory. These ensemble machine learning algorithms can benefit the construction sector by providing fast and better analysis of material properties, especially for fiber-reinforced concrete.

The study of composites made from residual organic materials and polymeric resins, has a great projection due to the use of new raw materials and the good physical, mechanical and aesthetic characteristics these materials present in the construction industry. The manufacturing processes of these composites include the necessary pressure application to generate an efficiently compact material, where matrix and reinforcement bonding are efficient. This study defines how the compaction force influences the flexural strength of composites made from polyester resin as polymer matrix, and rice husk as reinforcement material. This is achieved by testing different series of specimens, made by applying different compaction forces in a cold process, to analyse the relationship between compaction and flexural strength. Specimens are made varying only the compaction force, from 2, 5, 8, 11, 14, and 17 tons. The results show that, when the compaction force increases, the flexural strength in the composites also increases, however, there is a pressure range where the flexural strength values are very close, conditioning the use of pressure in relation to the decrease in the specimen section.

This paper presents the feasibility study of adding recycled Polyethylene Terephthalate (PET) fiber obtained from drinking water bottle as admixture material in the concrete. A few numbers of tests were conducted to determine the physical and mechanical properties of recycled PET fiber reinforced concrete such as slump test, compressive strength test and flexural strength test. The effect of incorporating the recycled PET fiber on various volume fractions of concrete by 0.5%, 1%, and 1.5% of weight of cement were experimentally investigated. The test specimens comprising of cubes and beams were prepared and tested at 3, 7, 14 and 28 days after curing process completed. Generally, it was found that the workability of concrete reinforced recycled PET has reduced as the volume fraction of PET fiber increased. The compressive strength of concrete reinforced recycled PET has reached the highest value at volume fraction of 0.5%. However, the flexural strength of concrete was significantly increased by incorporating 1.0% of recycled PET fiber. It can be concluded that the concrete which contains 0.5% of recycled PET fiber has the highest of average percentage of relative. Hence, it can be categorized as the optimum percentage of recycled PET fiber to be utilized in concrete. It is recommended to use recycled PET fiber in concrete for the construction of structures and infrastructures as a green construction material in order to achieve clean and sustainable environment in the year future.

In the manufacturing of bulk graphite, pores produced by vaporization and discharge of volatile materials in binders during carbonization reduce the density of bulk graphite, which adversely affects the electrical conductivity, strength and mechanical properties. Therefore, an impregnation process is introduced to fill the pores and increase the density of bulk graphite. In this study, bulk graphite is prepared by varying the viscosity of the impregnant. The microstructure of bulk graphite is observed. The flexural strength and electrical resistivity are measured. As the viscosity of the impregnants decreases and the number of impregnations increases, it is shown that the number of pores decreases. The density before impregnation is 1.62 g/cm3. The density increases to 1.67 g/cm3 and porosity decreases by 18.6 % after three impregnations using 5.1 cP impregnant, resulting in the best pore-filling effect. After three times of impregnation with a viscosity of 5.1 cP, the flexural strength increases by 55.2 % and the electrical resistivity decreases by 86.76 %. This shows that a slight increase in density due to the pore-filling effect improves the properties of bulk graphite.

This research was funded by Ministerio de Educacion, Cultura y Deporte grant numbers PID2020-115372RB-I00, PYC20-RE-072-UGR, DPI2017-83859-R, UNGR15-CE-3664 and EQC2018004508-P; and Junta de Andalucia grant numbers SOMM17/6109/UGR, B-TEP-026-UGR18, IE20175537 and P18-RT-1653. As well as Erasmus + doctoral studies grant., Thermoplastic resin fiber composites have an easy fabrication process, good mechanical properties, and compatible stiffness to tooth dentin. However, they have not yet attracted much interest in the field of dentistry. The current study was carried out to test a new proposed approach to manufacture a fiber reinforced composite endodontic post and evaluate its flexural strength through a two-point inclined loading test. The proposed fiber post manufacture approach depends upon a braiding technique of the glass fibers' (GF) reinforcing component with thermoplastic polypropylene (PP) resin fibers that will later represent the resin matrix after thermal melting. Posts were made of different core (70%) and sheath (30%) construction (PP/GF ratios) using three different GF types and seizing pre-treatment to both fiber types. Two-point inclined loading test at 45 degrees C applied force angle was used to test the posts' flexural strength. Fiber posts (1.6 mm in diameter) with pure GF (de-sized starch E-GF and pre-silanized S-GF) core, and sheath construction with higher PP/GF ratios, showed the significantly highest two-point bending strength (56.67 +/- 4.89 and 53.96 +/- 1.81 MPa, respectively), among experimental posts groups (except for the commercial control posts). However, posts with PP core type showed the lowest values (21.59 +/- 1.86 and 16.54 +/- 1.94 MPa for de-sized and E-glass sheath fibers, respectively). Based on these findings, the proposed approach was reliable in producing fiber-reinforced composite post with the desired dimensions and fiber distribution. Post construction with a pure GF core and higher PP/GF ratio showed considerably higher flexural strength and GF volume fraction comparable to commercial available post types., Spanish Government PID2020-115372RB-I00 PYC20-RE-072-UGR DPI2017-83859-R UNGR15-CE-3664 EQC2018004508-P, Junta de Andalucia SOMM17/6109/UGR B-TEP-026-UGR18 IE20175537 P18-RT-1653, Erasmus + doctoral studies grant

Dental direct block are dental mill blanks made from Yttrium stabilised, presintered and zirconium oxide blanks for the manufacture of dental prostheses. Dental direct presintered blocks with disk-shapede were used to machining the specimens at different rotational speed (10000,20000,40000) r.p.m by After that, the specimens were put through a uniaxial flexure test using balls and loaded in a universal testing machine at a cross-head speed of 0.5 mm/min until they failed. Computer Numerical Control machine (CNC) then sintered at 1600℃. The rotating speed affected the flexural strength, microstructure, crystal phase, and grain size of the studied zirconia. The characterization of samples were conducted using field emission scanning electron microscopy (FESEM) and analyzed with X-ray diffraction (XRD). The results XRD analysis showed the presence of a tetragonal phase in all rotational speeds. The differences in morphology and grain size due to different in rotational speed and grain size increase with increasing the rotational speed about 36%. The best flexural strength was observed at low speed, while Hardness showed little varation (decreasing10%) with increasing rotational speed.

Zirconia restorations are usually coated with glazing to provide an aesthetic and reduce wear on opposing teeth. Occlusal adjustments such as grinding and polishing to eliminate occlusal or internal interferences can affect the mechanical properties of zirconia. The purpose of this study was to evaluate the effect of glazing, reglazing, and polishing procedures on the biaxial flexural strength of zirconia ceramic. This experimental study used 20 samples of zirconia discs (12x1,2 mm), which were divided into fourth groups (n=5). The first group was zirconia discs without treatment as control, the second group with glazing treatment, the third group with reglazing treatment, and the fourth group with polishing treatment. Biaxial flexural strength was determined using a piston on three balls technique. The data were analyzed using 1-way ANOVA and t-test. The results of this study showed no statistically significant difference between the group with glazing, reglazing, polishing and the control group (p>0.05). The highest zirconia biaxial flexural strength was found in the polished group but not significant statistically (1913.64 ± 594.28 MPa). The reglazing group with the lowest average biaxial flexural strength was (1413.01 ± 365.66 MPa). It can be concluded that there were no differences in biaxial flexural strength between the polishing, glazing, and reglazing group. The use of polishing can be an alternative technique to improve aesthetics besides glazing and reglazing because it does not impair the biaxial flexural strength of zirconia.

This study aimed to determine the effect of the testing method configuration on the bi-axial flexural strength (BFS) of three resin-based dental composites (RDCs). A total of 180 disc-shaped sample...

QF-Bi2SiO5/EP composites had both great mechanical properties and X-ray visualization with the potential to be used as dental fiber posts or orthopedic implants.

Dental implants have been widely used in clinical practice. The 3D modeling software was used to design threedimensional (3D) models (in the shapes of long strips, discs, and screws), i.e., the Ti2.6Al1.2 V0.42 specimens. Meanwhile, the implant material was electrochemically precipitated, and a layer of chitosan nano-coating was added to the surface. To test the bone-binding ability and planting success rate of the material, the mechanical properties of the specimens with different porosity (0%∼70%) were firstly analyzed by the three-point bending method. Then, the screw-shaped titanium alloy specimens were divided into the solid group, the solid coating group, the solid 30% group, the coating 30% group, the solid 50% group, and the coating 50% group. The MC3T3-E1 cells were cultured, and the in vitro biological properties of the specimens were tested from different angles. The biomechanical properties and flexural strength of screw-shaped titanium alloy specimens in different groups were tested by using a universal testing machine. In the experiment, the prepared dental implants had the complete surface, uniform pore distribution, dense coating distribution, and less overall cracks. The elastic gradient of porous titanium specimens would decrease due to the increase of porosity. The cell activity of the test specimen was higher, and the percentage of viable cells exceeded 80%. The MTT test confirmed that the pores of the test specimen could promote the increase of MTT value (P < 0.05), and the test specimen/composite coating had higher ALP levels compared with the test pieces with no surface treatments (P < 0.05). In biomechanical properties and flexural strength tests, the increase of pores increased the biomechanical properties (P < 0.05) and decreased the flexural resistance (P < 0.05), while the increase of coating decreased the biomechanical properties and increased the flexural resistance (P < 0.05). The porous titanium alloy specimens were successfully prepared, and the chitosan-based composite coating was applied. The material was non-toxic, which was beneficial to cell proliferation and had good mechanical properties, thereby contributing to the growth of new bone.

In this study, the flexural strength and fatigue properties of interfacial transition zone (ITZ) were experimentally investigated at the micrometre length scale. The hardened cement paste cantilevers (150 × 150 × 750 μm3) attached to a quartzite aggregate surface were prepared and tested under the monotonic and cyclic load using a nanoindenter. The measured flexural strength of the ITZ (10.49–14.15 MPa) is found to be one order of magnitude higher than the macroscopic strength of ITZ reported in literature. On the other hand, the fatigue strength of the ITZ is lower than that of bulk cement paste at same length scale, measured previously by the authors. The microscopic mechanical interlocking and the electrostatic interaction between aggregate surface and hydration products are thought to contribute to the bond strength of ITZ. This study provides an experimental basis for the development of multiscale analysis of concrete subjected to both static and fatigue loading.

This in vitro study compared the color change (∆E) and biaxial flexural strength (BFS) of two resin nanoceramics (LU and CS) and two polymer-infiltrated ceramic networks (VE and CU) after different surface finishing protocols. A total of 192 discs (12 × 1.2 mm2) were prepared from the materials (n = 48) and then polished with 1200-grit silicon carbide paper, followed by roughening with a 30 µm grit diamond bur. According to the surface finishing applied, the discs from each material category were categorized into four groups: control group (no finishing), polishing (MP), glazing (OG), or a combination of MP and additional polishing (MP+PP). Following surface finishing, all the discs were immersed in a coffee beverage to simulate one year of clinical use. A spectrophotometer and universal testing machine were used to measure the ∆E and BFS, respectively. Fractographic analysis was performed using scanning electron microscopy images. Multivariate analysis of variance was used for the statistical analysis, followed by one-way ANOVA and post hoc Dunnett’s test (a = 0.05). The ∆E and BFS were significantly impacted by material type and surface finishing (p ≤ 0.05). Irrespective of the materials and finishing, untreated LU and OG-treated VE specimens demonstrated the highest (2.98 ± 0.36) and lowest (1.21 ± 0.33) color changes. Regarding BFS, untreated CU and OG-treated CS specimens demonstrated the lowest (121.88 ± 2.08 MPa) and highest (174.17 ± 3.83 MPa) values. Surface finishing using glazing resulted in the highest BFS and lowest ∆E compared to other surface finishing protocols for the tested materials. VE demonstrated the least color changes, and CS showed the highest BFS following surface finishing of the materials tested. Surface finishing is material dependent; thus, it is critical to use the best surface finishing protocol in a clinical setting.

Objectives To test and compare five pressable lithium-X-silicate-ceramics on their mechanical and wear properties. Methods Specimens were pressed and prepared from: i. Amber Press (AP), ii. Celtra Press (CP), iii. Initial LiSi Press (IL), iv. Livento Press (LP), and v. IPS e.max Press (IE). Four-point flexural strength (FS), SEVNB fracture toughness (KIC), three-body wear (3BW), Martens hardness (HM) and indentation modulus (EIT) were measured. For CP, FS and HM were measured with and without additional Power Firing. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov–Smirnov, one-way ANOVA followed by Scheffe test, Kruskal–Wallis-H-, Mann–Whitney-U-, and Spearman–Rho-test (p Results AP and CP presented higher FS than IL. LP presented the highest Weibull modulus. CP showed lower KIC values than AP, and AP was not significant compared to LP and IE. The most 3BW material loss was observed for CP. CP revealed higher HM values than the remaining ceramics. IL presented lower EIT compared to AP and CP. The following correlations were observed between the test parameters: 3BW with FS (r = 0.279, p = 0.015), with HM (r = −0.378, p = 0.001), and with EIT (r = −0.344, p = 0.004); EIT with FS (r = 0.203, p = 0.028); and HM with FT (r = −0.223, p = 0.027) and EIT (r = 0.884, p Significance AP followed by LP showed the highest and IL followed by CP the lowest properties tested. Power Firing of CP improved the flexural strength. Ceramics with high flexural strength and Martens parameters showed lower wear. Materials with high Martens hardness presented lower fracture toughness values and ones with high indentation modulus showed high flexural strength.

Objective To test the impact of zirconia pretreatment and aging on flexural strength and phase structure. Methods For flexural strength measurements, 180 3Y-TZP0.25 specimens were fabricated and pretreated: (i) air-abraded (105-μm alumina, 0.25 MPa), (ii) air-abraded (50-μm alumina, 0.25 MPa), (iii) air-abraded (30-μm silica-coated alumina, 0.28 MPa) (iv) non-pretreated. Each pretreated group (n = 15) was aged: (a) hydrothermal (134 °C, 0.23 MPa, 2 h) (b) in a mastication simulator (1,200,000×, 5/55 °C) and (c) not aged. The fractured specimens were stored dry for 5 years (23 °C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP0.25 (n = 12) and 3Y-TZP0.05 (n = 8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4 MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffe post hoc test and partial-eta-squared (ƞp²) (α = 0.05). Results The highest impact on flexural strength was exerted by the pretreatment (ηP² = 0.261, p Significance Air-abrasion with 30-μm silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP0.25 and 3Y-TZP0.05. For air-abrasion using alumina powder lower pressure should be used.

The flexural strength of Slender steel tube sections is known to achieve significant improvements upon being filled with concrete material, however, this section is more likely to fail due to buckling under compression stresses. This study investigates the flexural behavior of a Slender steel tube beam that was produced by connecting two pieces of C-sections and was filled with recycled-aggregate concrete materials (CFST beam). The C-section’s lips behaved as internal stiffeners for the CFST beam’s cross-section. A static flexural test was conducted on five large scale specimens, including one specimen that was tested without concrete material (hollow specimen). The ABAQUS software was also employed for the simulation and non-linear analysis of an additional 20 CFST models in order to further investigate the effects of varied parameters that were not tested experimentally. The numerical model was able to adequately verify the flexural behavior and failure mode of the corresponding tested specimen, with an overestimation of the flexural strength capacity of about 3.1%. Generally, the study confirmed the validity of using the tubular C-sections in the CFST beam concept, and their lips (internal stiffeners) led to significant improvements in the flexural strength, stiffness, and energy absorption index. Moreover, a new analytical method was developed to specifically predict the bending (flexural) strength capacity of the internally stiffened CFST beams with steel stiffeners, which was well-aligned with the results derived from the current investigation and with those obtained by others.

Chipping remains a big challenge during the clinical application of glass ceramics in dentistry. The fabrication procedure used affects the mechanical properties of dental feldspathic porcelain and is associated with technical failures. This study aimed to compare the effect of the use of manufacturers’ liquids versus H2O on the flexural strength of glass ceramics. Specimens (n = 120, n = 15 per group) (25 × 4 × 1.2 mm) were obtained using four porcelain powders (Creation CC, IPS InLine, Noritake EX-3, and Vita VM 13). Four groups were produced using porcelain powder and modeling liquid, and four groups using distilled water. The specimens were fired, sintered, and polished. Flexural strength was measured using a universal testing machine. Statistical analyses were conducted using post hoc Tukey’s, two-way ANOVA, and Weibull analysis. Flexural strength values (mean ± SD) of the ceramic-manufacturer’s liquid mixture ranged between 67.2 ± 10.2 and 85.8 ± 12.8 MPA (NR &lt, VT &lt, IV &lt, CR), while flexural strength values of the ceramic–water mixture were between 72.2 ± 6.9 and 95.2 ± 12 MPA (CR &lt, NR &lt, IV). While the choice of the ceramic type significantly affected flexural strength, the use of water vs. manufacturers’ liquid showed in almost all cases no significance. To achieve better flexural strength results, InLine should be used with distilled water mixtures, while all ceramic powders except for Noritake can be used with the manufacturer’s liquid mixtures.

Through proper arranging of a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and steel bars in the tensile region of the beam, the advantages of both FRP and steel materials can be sufficiently exploited to enhance the flexural capacity and ductility of a concrete beam. In this paper, a methodology for the flexural strength design of hybrid FRP-steel reinforced concrete (RC) beams is proposed. Firstly, based on the mechanical features of reinforcement and concrete and according to the latest codified provisions of longitudinal reinforcement conditions to ensure ductility level, the design-oriented allowable ranges of reinforcement ratio corresponding to three common flexural failure modes are specified. Subsequently, the calculation approach of nominal flexural strength of hybrid FRP-steel RC beams is established following the fundamental principles of equilibrium and compatibility. In addition to the common moderately-reinforced beams, the proposed general calculation approach is also applicable to lightly-reinforced beams and heavily-reinforced beams, which are widely used but rarely studied. Furthermore, the calculation process is properly simplified and the calculation accuracy is validated by the experimental results of hybrid FRP-steel RC beams in the literature. Finally, with the ductility analysis, a novel strength reduction factor represented by net tensile steel strain and reinforcement ratio is proposed for hybrid FRP-steel RC beams.

The aim of the present study is to determine the loss in the flexural strength capacity of a reinforced concrete (RC) beam due to the presence of cold joint under two conditions: (i) different mix ...

3D printing innovation, as a quick prototyping, utilize plastic or metal as the crude material to print the genuine parts layer by layer. In this way, it is likewise called added substance producing procedure. Contrasted and conventional assembling innovation, 3D printing innovation has evident points of interest in assembling items with complex shapes and structures. Fused deposition modeling (FDM) is one of the most broadly utilized 3D printing advances. Fibers of thermoplastic materials, for example, polylactic acid is for the most part utilized as crude materials. The present examination will concentrate on the effect of the infill density, percent on the flexural strength of polylactic acid. Bending test was performed on different infill density, percent of specimens. According to ASTM D638.14 standards, samples for testing are made in different infill density, percent (20, 30, 40, 50 and 60 %) by using a polylactic acid in 3D machine printing and their tensile tested and the parameters include different fill density, layer high of 0.1 mm , 0.2mm and 0.3 have an effect on the mechanical characterized while the time of printing the sample would be increased with increasing of fill density%. The tensile strength of polylactic acid samples was found at different fill density and a layer thickness. According to test measuring results that the tensile strength, maximum 47.1,47.4, and 48 MPa at 30%,40%,and 50% fill density respectively and 0.1mm height layer and the tensile strength minimum at 60% and 70 % fill density and 0.1 mm height layer thickness. The higher strength results as higher layer thickness 0.3 mm as compared with 0.1 and 0.2 at 30%fill density.

In recent years, the growing trend of using polymer materials in various industries has led to significant improvements in the methods of production and bonding of polymer materials. The present study aimed to optimize the flexural strength of polypropylene sheets welded by the friction-stir method, which is considered as one of the most efficient methods in this field. The surface quality and mechanical properties of the components produced in this method highly rely on the parameters of rotational speed, linear speed, geometry, and tool tilt. Therefore, this research seeks to evaluate the effect of these parameters on three different levels, both experimentally and statistically, in order to investigate the welding flexural strength. By applying the analysis of variance and Box–Behnken response surface methodology, the results revealed the existence of a significant relationship between the properties and parameters of the process and the possibility to examine the effect of the interaction of different parameters in the process using mathematical modeling and Chart analysis. In addition, optimal models were introduced through process optimization so that the flexural strength of the weld joint was increased by up to 96% of that of the base specimen, after conducting further experimental tests, resulting in confirming the optimal model. Finally, the efficiency of the designed model was evaluated by comparing the measurement errors obtained from the experimental results and the prediction of the model.

Purpose: The aim of the present study was to evaluate the effect of artificial aging on the optical properties and flexural strength of ultra-translucent tetragonal/cubic zirconia. Materials and Methods: A total of 30 (N=30) ultra-translucent cubic zirconia discs (DD cube X2) were fabricated. Samples were divided into 3 equal groups (n=10) according to the aging protocol followed including Group (1): (control), samples were not subjected to hydrothermal aging protocol, (n=10), Group (2): Samples were subjected to one-hour hydrothermal aging protocol, (n=10), Group (3): Samples were subjected to 3 hours hydrothermal aging protocol, (n=10). Samples of each group were subjected to optical properties determination using spectrophotometer including (Translucency parameter TP, Contrast ratio CR, Change in color ΔE) and biaxial flexural strength determination using universal testing machine. Obtained values were statistically analyzed. Results: Statistical analysis using ANOVA test revealed no significant difference between the three tested groups. The highest mean value of translucency and biaxial flexural strength were recorded at the control group. While group (3) samples recorded the lowest mean values. Color change (ΔE) was performed for groups (2 and 3) to detect the amount of color change from control group. Group (3) samples recorded higher mean values than group (2) samples. Conclusions: Hydrothermal aging has no effect on the optical properties and flexural strength of tetragonal / cubic zirconia (DD cube X2).

This paper aims to evaluate mechanical behavior (compressive and flexural strength) of reactive powder concrete (RPC) with ferronickel slag (FNS) as quartz sand replacement. Standard laboratory tests were performed i.e. sieve analysis to determine the particle size distribution of the FNS, slump and density tests as well as compressive and flexural tests on the RPC. Promising results were obtained in this study. An increased consistency and density were observed upon increasing the FNS content. The utilization of FNS could lead to a compressive strength value of 86 MPa at 28 days. A higher strength enhancement in the early curing days (7 days) was observed than in the longer curing days (28 days), when FNS mixes were compared to reference mixes. The flexural strength result demonstrated two different phenomena at two different ages, where there was a slight rise at 7 days and relatively no increment at 28 days when FNS mixes were compared to the reference mixture.

The mechanical characteristics of concrete used in rigid pavements can be improved by using fibre-reinforced concrete. The purpose of the study was to predict the flexural strength of the fibre-reinforced concrete for ten input variables i.e., cement, fine aggregate, coarse aggregate, water, superplasticizer/high range water reducer, glass fibre, polypropylene fibre, steel fibres, length and diameter of fibre and further to perform the sensitivity analysis to determine the most sensitive input variable which affects the flexural strength of the said fibre-reinforced concrete. The data used in the study was acquired from the published literature to create the soft computing modes. Four soft computing techniques i.e., Artificial neural networks (ANN), Random forests (RF), Random trees RT), and M5P, were applied to predict the flexural strength of fibre-reinforced concrete for rigid pavement using ten significant input variables as stated in the ‘purpose’. The most performing algorithm was determined after evaluating the applied models on the threshold of five statistical indices, i.e., the coefficient of correlation, mean absolute error, root mean square error, relative absolute error, and root relative squared error. The sensitivity analysis for most sensitive input variable was performed with out-performing model, i.e., ANN. The testing stage findings show that the Artificial neural networks model outperformed other applicable models, having the highest coefficient of correlation (0.9408), the lowest mean absolute error (0.8292), and the lowest root mean squared error (1.1285). Furthermore, the sensitivity analysis was performed using the artificial neural networks model. The results demonstrate that polypropylene fibre-reinforced concrete significantly influences the prediction of the flexural strength of fibre-reinforced concrete. Large datasets may enhance machine learning technique performance. The article's novelty is that the most suitable model amongst the four applied techniques has been identified, which gives far better accuracy in predicting flexural strength.

Cement panels are industrial products that are widely used as construction and insulation materials. In general, cement panels are reinforced with synthetic fibers. In this study, a cement panel reinforced by natural fibers, namely abaca fiber, was developed. Abaca fiber has advantages over other natural fibers in terms of availability, mechanical properties and physical properties. Cement panels were made in several levels of abaca fiber content (0%, 1%, 2%, 3% and 4%) to study the effect of fiber content on the flexural strength and physical properties of cement panel. The material and experiment were prepared and carried out according to Indonesia standard SNI 01-4449-2006. The result of the experiment showed that the fiber content significantly affected the flexural strength, density, moister content, water absorption and thickness development of abaca-cement panels. The maximum flexural strength was 71.88 MPa, produced by cement panel with 3% fiber content, and it was 2.15 time higher than cement panel without fiber. The result of the experiment indicated that the abaca fiber was potential inforcement for cement panel with respect to its flexural strngth and physical properties.

The glass fiber reinforced plastic (GFRP) composite materials are widely used in industries; these composites are coupled into large structures by drilled holes. In the present investigation, the characteristics of such drilled holes and defects were studied using GFRP composite samples with open-hole (at different positions), half-through holes and epoxy filled holes under three-point bend loading conditions. The “composite with epoxy filled holes” envisages maximum flexural strength, "composite with holes at a depth of 2.5 mm" showed intermediate and "composite with an open hole" exhibited minimum flexural strength. However, the flexural strength of the "composite" was increased when the relative distance between the holes was increased. The hypothesis of investigating the effect of defects in the form of Teflon exhibited significant results. The flexural strength was minimum in the case of multiple defects, however, it showed maximum fracture toughness. It was also observed that if the defect is present only at one end, it exhibited maximum flexural strength and minimum fracture toughness value.

A crucial step in the preparation of yttria-stabilized zirconia materials (YSZ) is the final sintering step. Sintering parameters affect phase composition, grain growth and porosity of the material which, in turn, influence both mechanical and optical properties. Discrepancies of + /- 5% are common between actual and displayed firing temperatures depending on sintering furnace brand and condition. The aim of this study was therefore to investigate how such sintering temperature deviations in dental furnaces compared to the recommended firing protocols affected certain material properties of different yttria-stabilized zirconia materials.Disc-shaped specimens were made from four different translucent and high translucent YSZ-powders and analysed regarding crystal structure; unit cell volume for the c, t, and t' -phases along with the tetragonality for the t and t' phases. Biaxial flexure strength and the spectral transmittance through the ceramic specimens were also measured.Deviations of 5% from the sintering temperature recommended for YSZ materials with different yttria content influenced material properties such as light transmittance, flexural strength, crystal phase fractions, tetragonality, and grain growth. Too low temperature resulted in decreased strength for some of the translucent zirconia materials, while others where less affected. Light transmittance varied depending on several factors such as grain size, crystal phase fractions and binder content in the start material prior to pre-sintering.The use of high quality, wellcalibrated furnaces is crucial when sintering YSZ materials to avoid unwanted material changes.Deviations of 5% from the sintering temperature recommended for YSZ materials with different yttria content influence material properties such as light transmittance, flexural strength, crystal phase fractions, tetragonality, and grain growth. Too low temperature results in decreased strength for some translucent zirconia materials, while others are less affected. Light transmittance varies depending on several factors such as grain size, crystal phase fractions and binder content in the start material prior to pre-sintering. Consequently, the use of high quality, well-calibrated furnaces is crucial when sintering YSZ materials to avoid unwanted material changes.

In order to gain acceleration of the osseointegration process after implant placement, micro retention using inorganic elements such as Hydroxyapatite (HA) were commonly used as a coating material in dental implant. Meanwhile, another inorganic material such as Carbonate Apatite (CO3Ap) has been known as bone substitute for decades. The purpose of this study is to investigate the flexural strength of Yttria-Stabilized Zirconia (Y-TZP) as dental implant material after being coated with CO3Ap. Ten specimens of Y-TZP were divided into two groups. The first group was coated with CO3Ap while other groups without coatings were used as the control. Biaxial flexural strength was determined using piston on three balls-technique and data were evaluated by statistical analysis. The specimens surface were analyzed through images taken by Scanning Electron Microscope (SEM). As the result, this study showed that there was no statistically significant found between the group with coating and the control group (p>0.05). The biaxial flexural strength’s mean of the group with coating and control were 212.80 MPa and 209.35 MPa; while micro Vickers hardness’ means were 229.56 HV and 245.40 HV. It can be concluded that there was no difference in the mean flexural strength between Y-TZP before and after coating.

Composite fiber were already developed and looked promising in dentistry. PMMA, optically clear polymer, was combined with high mechanically properties ZrO2-Al2O3-SiO2 (ZAS) ceramic powder to improve the flexural strength value of dental post prototype. ZAS powder, with ratio 60:20:20, were first prepared via sol-gel technique. Afterwards, PMMA was dissolved in acetone then incorporate with ZAS powder 1% wt to gain ZAS-PMMA composite fiber via electrospinning method. Dental post prototype were fabricated into two groups, one group contain ZAS-PMMA composite fibers and one group contain neat BisGMA, as control, with amount of each groups samples was 10. As-prepared samples were tested by Universal Testing Machine (UTM) to evaluate the flexural strength values. Based on unpaired T-test analysis (p value < 0.05), the composite fiber post is significantly higher (48.17 %) than the neat BisGMA post. ZAS-PMMA composite fiber post was potential to be used as dental endodontic post in anterior.

BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength.

Purpose: The purpose of the present study is to assess the effect of different hydrofluoric acid etching durations on the translucency, flexural strength and surface topography of a lithium silicate-based glass ceramic (LS). Materials and Methods: Forty LS (Obsidian) samples will were constructed and divided into four groups (n=10 each) according the duration of hydrofluoric acid (HF) application including group (I); (control) as received samples without surface treatment, group (II); ceramic surfaces etched with HF for 10 seconds; following the manufacturer’s recommendations, group (III); ceramic surfaces etched with HF for 30 seconds and group (IV); ceramic surfaces etched with HF for 60 seconds. All treated samples were evaluated for translucency (TP) using spectrophotometer, flexural strength using universal testing machine and surface topographic analysis using SEM and profilometer. Obtained values were statistically analyzed. Results: The highest mean value of translucency and biaxial flexural strength were recorded at the control group. Values then gradually decreased in the subsequent etching times to reach its lowest level after 60 seconds. While the lowest mean value of surface roughness (Ra) was recorded at control group. The mean Ra value gradually increased with the subsequent increase in etching times to reach its highest level after 60 seconds. Conclusions: Increasing HF acid etching duration negatively affects the translucency of lithium silicate based glass ceramic; while it has no effect on its biaxial flexural strength or its surface roughness (Ra).Key WordsBiaxial flexural strength (FS), LS (Obsidian), surface roughness, translucency.

Silica extracted from rice husk ash (RHA-Si) by pretreatment with hydrochloric acid followed by calcination at 700°C, was prepared. It was investigated with regard to its chemical composition and structure using X-Ray Fluorescence spectroscopy (XRF) and X-Ray Diffractometry (XRD). RHA-Si (0, 0.25, 0.5 and 1% w/w) was incorporated into poly(methyl methacrylate) (PMMA) or acrylic resin powder. Microhardness, flexural strength and dynamic mechanical properties of RHA-Si filled PMMA were then determined. The chemical composition analysis showed that RHA-Si contains a large amount of silica with an amorphous structure. The microhardness of acrylic resin filled with RHA-Si does not change significantly with increasing RHA-Si loading. Flexural strength of filled acrylic resin increases with increasing RHA-Si loadings up to 0.25% w/w. It then decreases with increasing RHA-Si loadings. Dynamic mechanical behavior illustrates that polymer-filler interactions play an important role in reinforcement.

Graphene is a two-dimensional nanomaterial with excellent mechanical, electrical and thermal properties. The application of graphene in cement-based materials has good prospects. However, the mechanical properties of cement-based materials are difficult to be significantly enhanced by ordinary graphene nanoplates. In this paper, nitrogen-doped graphene is first reported as an additive with dosages of 0.01, 0.02, 0.03, 0.04 and 0.05 wt.%, respectively, to prepare iron ore tailings–based cementitious composites. The iron ore tailings–based cementitious composite with 0.02 wt.% graphene shows an extremely high flexural strength of 15.05 MPa at 3 days, which is 134.4% higher than that of the iron ore tailings–based cementitious composite without graphene. The effects of graphene content and curing age on the flexural strength and microstructure of iron ore tailings–based cementitious composites were studied. In particular, the scanning electron microscope was adopted to observe the micromorphology of the composites. It is helpful to understand the graphene reinforcement mechanism for the high early flexural strength of iron ore tailings–based cementitious composites. By altering the morphology of iron ore tailings–based cementitious composites, graphene plays two roles in the composites. One role is to connect C-(A)-S-H gels, ettringite and other hydrated crystals to construct a three-dimensional structure. The other is to attract iron ore tailings distributed on its platform to enhance its flexural strength properties. These findings provide favorable guidance for the performance enhancement and mechanism replenishment of graphene-reinforced cementitious composites.

Flexural strength (FS) and translucency (Contrast Ratio-CR) of three different factory crystallized silica-based glass ceramics, Celtra Duo (CD), N!ce (NI) and Li-Si Block, a lithium disilicate, IPS e.max CAD (LD), and a leucite-reinforced feldspathic ceramic, Empress CAD (EM), in two different translucencies (HT and LT) for use in chairside dental restorations have been compared. CAD blocks of the materials were cut into beams and tiles and processed following manufacturers’ instructions. The beams were tested (3-PBT) to determine flexural strength, Weibull characteristic strength, and Weibull modulus; and tiles were tested to determine CR. All data were statistically analyzed. In addition, SEM analysis of the materials was performed. Differences in flexural strength (FS) and translucency (CR) between the materials were found to be statistically significant. FS decreased as follows (MPa): LDHT 350.88 ± 19.77 (a) = LDLT 343.57 ± 18.48 (a) > LSLT 202.15 ± 17.41 (b) = LSHT 196.93 ± 8.87 > NIHT 186.69 ± 13.06 (c) = CDLT 184.73 ± 13.63 (c) = CDHT 174.15 ± 21.76 (c) = NILT 172.12 ± 11.98 (c) > EMHT 131.16 ± 13.33 (e) = EMLT 127.65 ± 11.09. CR decreased as follows (mean ± sd): CDLT 74.1 ± 1.1 (a); LSLT 74.0 ± 1.1 (ab); NILT 73.3 ± 0.8 (ab); EMLT 73.0 ± 1.5 (ab); NIHT 72.4 ± 1.0 (bc); LDLT 71.3 ± 1.1 (bc); LTHT 65.2 ± 0.9 (de); LSHT 63.8 ± 1.1 (def); EMHT 636 ± 1.2 (ef); CDHT 62.2 ± 0.8 (f). Our findings show that factory-crystallized lithium silicate glass ceramics fulfill ISO standards for Classes 1 and 2. Therefore, they can be considered viable alternatives to produce single-unit restorations with a chairside procedure not requiring thermal treatment.

In this paper, the steel bar was used to prepare steel bar reactive powder concrete (SBRPC). The three-point bending test was adopted to investigate the effect of the number of steel bars on the flexural strength of SBRPC. The acoustic emission (AE) was used to monitor the fracture process of SBRPC in real time. In addition, the parameter RA and AF ratio (RF) was defined to analyze the distribution of shear cracks and tensile cracks during the fracture process. The experimental results showed that with the increases in the number of the steel bar, the flexural strength of SBRPC gradually increased. The fracture stage of SBRPC can be accurately divided according to the curve slope change in hits and cumulative counts. Moreover, the early warning of SBRPC damage can be realized by observing the amplitude of the AE amplitude value. The dynamic changes in the rising angle (RA) and average frequency (AF) values can be used to determine the cracks mode and fracture mode. Based on the results of RF analysis, adding steel bars will improve the proportion for tensile cracks during its fracture process.

The aim of this work was to evaluate the flexural strength and surface hardness of heatcured Polymethyl methacrylate (PMMA) modified by the addition of ZrO 2 nanoparticles, TiO 2 nanoparticles, and E-glass fibre at different wt.% concentrations. Specimens were fabricated and separated into four groups (n = 10) to measure both flexural strength and surface hardness. Group C was the control group. The specimens in the remaining three groups differed according to the ratio of filler to weight of PMMA resin (1.5%, 3%, 5%, and 7%). A three-point bending test was performed to determine the flexural strength, while the surface hardness was measured using the Vickers hardness. Scanning Electron Microscope (SEM) was employed to observe the fractured surface of the specimens. The flexural strength was significantly improved in the groups filled with 3 wt.% ZrO 2 and 5 and 7 wt.% E-glass fibre in comparison to Group C. All the groups displayed a significantly higher surface hardness than Group C, with the exception of the 1.5% TiO 2 and 1.5% ZrO 2 groups. The optimal filler concentrations to enhance the flexural strength of PMMA resin were between 3–5% ZrO 2, 1.5% TiO 2, and 3–7% E-glass fibre. Furthermore, for all composites, a filler concentration of 3 wt.% and above would significantly improve hardness.

Waste glass (WG) is unsustainable due to its nonbiodegradable property. However, its main ingredient is silicon dioxide, which can be utilised as a supplementary cementitious material. Before reusing WG, the flexural strength (FS) and alkali–silica reaction (ASR) expansion of WG concrete are two essential properties that must be investigated. This study produced mortar containing activated glass powder using mechanical, chemical, and mechanical–chemical (combined) approaches. The results showed that mortar containing 30% WG powder using the combined method was optimal for improving the FS and mitigating the ASR expansion. The microstructure analysis was implemented to explore the activation effect on the glass powder and mortar. Moreover, a random forest (RF) model was proposed with hyperparameters tuned by beetle antennae search (BAS), aiming at predicting FS and ASR expansion precisely. A large database was established from the experimental results based on 549 samples prepared for the FS test and 183 samples produced for the expansion test. The BAS-RF model presented high correlation coefficients for both FS (0.9545) and ASR (0.9416) data sets, showing much higher accuracy than multiple linear regression and logistic regression. Finally, a sensitivity analysis was conducted to rank the variables based on importance. Apart from the curing time, the particle granularity and content of WG were demonstrated to be the most sensitive variable for FS and expansion, respectively.

For plain concrete materials, the degradation of concrete by seawater is mainly reflected in the corrosion of sulfate ions. In this study, the variation in the flexural strength of concrete specimens with different water-cement ratios under different sulfate concentrations for 470 days is explored, and the effect of sulfate environment on the decay of flexural strength of concrete with corrosion time is experimentally examined. The results show that the evolution of flexural strength can be divided into three stages: strength attenuation stage, strength recovering stage and strength re-attenuation stage. According to the experimental results, the mechanism of strength attenuation, rebound and re-attenuation is established. Combining the chemical reaction rate equations of continued hydration, delayed growth of ettringite and growth of hydroxy-AFm, a new model for the flexural strength degradation of concrete under sulfate corrosion is proposed. Further, the influence of water-cement ratio and corrosive sulfate solution concentration on the flexural strength of concrete is analyzed. Since the ability of concrete to resist sulfate corrosion can be different for different corrosion systems, a unified method is proposed for evaluating the sulfate corrosion resistance of concrete.

The aim of this work was to evaluate the effects of application time of an acid mixture solution on the surface roughness, phase transformation, and biaxial flexural strength of 3Y-TZP after sintering or air abrasion. For the biaxial flexural strength measurement, 220 3Y-TZP disk-shaped specimens were prepared after as-sintering or air abrasion. The etching solution comprised a mixture of hydrofluoric acid, sulfuric acid, hydrogen peroxide, methyl alcohol, and purified water. The samples were divided into 11 subgroups according to the etching times (Control, 1, 2, 3, 5, 8, 10, 12, 15, 20, and 30 min). The results showed that acid treatment on both as-sintered and air-abraded 3Y-TZP surfaces increased the surface roughness. However, it had no significant effects on the monoclinic phase or flexural strength of as-sintered zirconia. The monoclinic phase and flexural strength of air-abraded zirconia increased sharply after air abrasion, however, they gradually decreased after acid treatment, to a similar level to the case of the untreated surface. Surface treatment with acid mixture increased the roughness, but the lack of increase of monoclinic phase is thought to be because the loose monoclinic particles remaining on the surface were removed through the etching process.