Three-point Flexural Strength Research Articles

Effect of rapid cooling on residual stress and surface fracture toughness of dental zirconia

Short-time sintering of dental zirconia not only improves manufacturing efficiency of zirconia prosthetics, but also enables an attractive situation in which prosthetic treatment can be completed within a single visit. Although many studies have clarified the effects of heating rate and dwell time on the properties of dental zirconia during short-time sintering, there are only a few studies on rapid cooling. In this study, we investigated the effect of cooling rate on dental zirconia. It was found that the cooling rate had no effect on the three-point flexural strength, but a fast cooling rate improved fracture toughness at the material surface. Raman piezo-spectroscopy showed that a compressive stress layer formed in the neighborhood of the zirconia surface and that its thickness increased with increasing cooling rate. From the above results, it was concluded that the compressive stress layer formed on the surface by rapid cooling improved the apparent fracture toughness at the material surface.

Effect of rapid cooling on residual stress and surface fracture toughness of dental zirconia

Short-time sintering of dental zirconia not only improves manufacturing efficiency of zirconia prosthetics, but also enables an attractive situation in which prosthetic treatment can be completed within a single visit. Although many studies have clarified the effects of heating rate and dwell time on the properties of dental zirconia during short-time sintering, there are only a few studies on rapid cooling. In this study, we investigated the effect of cooling rate on dental zirconia. It was found that the cooling rate had no effect on the three-point flexural strength, but a fast cooling rate improved fracture toughness at the material surface. Raman piezo-spectroscopy showed that a compressive stress layer formed in the neighborhood of the zirconia surface and that its thickness increased with increasing cooling rate. From the above results, it was concluded that the compressive stress layer formed on the surface by rapid cooling improved the apparent fracture toughness at the material surface.

Effects of Nozzle Temperature on Mechanical Properties of Polylactic Acid Specimens Fabricated by Fused Deposition Modeling.

This paper investigates the effect of nozzle temperature, from 180 to 260 °C, on properties of polylactic acid (PLA) samples manufactured by fused deposition modeling (FDM) technology. The main objective of this research is to determinate an optimum nozzle temperature relative to tensile, flexural and compressive properties of printed specimens. After manufacturing, the samples exhibit an amorphous structure, without crystallization effects, independently of the fabrication temperature. In order to determine the influence of printing temperature on mechanical properties, uniaxial tensile, three-point flexural and compression strength tests were carried out. The obtained results suggest that a relative low printing temperature could reduce the material flow and decrease the density of the final prototype, with a negative effect on both the quality and the mechanical properties of the pieces. If temperature increases up to 260 °C, an excess of material can be deposited, but with no significant negative effect on mechanical parameters. There is an optimum nozzle temperature interval, depending on the considered piece and test, for which mechanical values can be optimized. Taking into account all tests, a recommended extruder temperature interval may be identified as 220-240 °C. This range encompasses all mechanical parameters, avoiding the highest temperature where an excess of material was observed. For this printing temperature interval, no significant mechanical variations were appreciated, which corresponds to a stable behavior of the manufactured specimens.

Effects of dental tissue substructure and size on fracture strengths of lithium disilicate and zirconia ceramics

We aimed to assess the effects of standard resin preparation models with five different thicknesses of occlusal surface on the fracture strengths of zirconia (ZrO2) and lithium disilicate glass ceramics. The specimens of 10 first maxillary molars collected between January 2019 and January 2020 were selected. Standard mathematical models were formed after scanning the resin matrices using software. The full crowns with five different thicknesses of occlusal surface were established, among which the molar specimens prepared by ZrO2 glass ceramic composites alone were assigned into ZrO2 group (n=5, 40 specimens) while those prepared using ZrO2-lithium disilicate glass ceramic composites were allocated into ZTCLDC group (n=5, 40 specimens). When the thickness of glass-ceramic full crowns was 0.5, 0.8, 1.0, 1.2 and 1.5 mm, the fracture load of the specimens in ZTCLDC group was not significantly different from that in ZrO2 group, and there was no significant difference in the three-point flexural strength between ZTCLDC group and ZrO2 group (P>0.05). The fracture toughness was not significantly different between the two groups in the case of the thickness of glass-ceramic full crown at 0.5, 0.8, 1.0, 1.2 and 1.5 mm (P>0.05). The thickness was positively correlated with fracture load, three-point flexural strength and fracture toughness (P<0.05). The fracture strength of lithium disilicate and ZrO2 ceramics is directly proportional to the thickness of ZrO2 and ZTCLDC crowns.

Flexural Strength of Translucent Zirconia Materials Produced with Different Multilayer Technologies: An In Vitro Study.

To evaluate the flexural strength of two translucent multilayered zirconia materials produced with different multilayer technologies. Methodology. Eighty bar-shaped zirconia specimens were prepared from two different multilayered zirconia materials (IPS e.max® ZirCAD Prime and KATANA™ Multilayered Zirconia HTML) and divided into eight groups (n = 10) based on the materials used and the individual layers of the disc for each material: Dentin Prime, Transition Prime, Translucent Prime, Multilayered Prime, Dentin HTML, Transition HTML, Translucent HTML, and Multilayered HTML. The bar-shaped zirconia specimens were cut to include all the layers from translucent to dentin In Multilayered Prime and Multilayered HTML groups. All specimens were fully sintered after cutting from multilayered zirconia discs and subjected to three-point flexural strength test using the universal testing machine. The specimens made of HTML zirconia material showed significantly (P < 0.001) higher flexural strength than those made of IPS e.max® ZirCAD Prime material, with no significant difference (P > 0.05) compared to the specimens in the Dentin Prime group. The Dentin Prime specimens had the highest flexural strength (743 ± 116 MPa) compared to those in the Translucent Prime (514 ± 120 MPa), Transition Prime (575 ± 102 MPa), and Multilayered Prime (531 ± 132 MPa) groups. The flexural strength of the specimens from the individual layers of HTML zirconia material was not significantly different (P > 0.05) among the Dentin HTML (763 ± 56 MPa), Translucent HTML (791 ± 106 MPa), Transition HTML (816 ± 85 MPa), and Multilayered HTML (793 ± 102 MPa) groups. Multilayered zirconia materials produced with different yttria contents by layer have lower flexural strength than those produced with gradient shade technology and the same yttria content for each layer. Therefore, various factors such as the type of prostheses, nesting strategies of prostheses within the zirconia disc, and the desired aesthetical requirements should be considered when selecting the multilayered zirconia materials.

Study of the Determination of Three-Point Flexural Strength Loading in Resin and Reinforcing Ornamental Stones

Theoretical framework: Brazil is one of the world's largest producers of ornamental stones, and is therefore the richest country in granite diversity in the world. Improvements in processing and production techniques have been developed over the years to add value to the final product. The resistance of stones is a preponderant factor for their application in certain environments. Some stone industries try to improve the resistance of the material by resining or reinforcing (resin plus fiberglass mesh) on their material. Method/project/approach: the work studied the behavior of resined and reinforced stones (resin plus fiberglass mesh). three-point flexural strength tests were carried out on pegmatite stones and quartzites. They were divided into groups with just resin and others with resin plus fiberglass mesh. Results and conclusion: The results showed that in the group of Pegmatite stones it was possible to obtain a gain of up to 44% in material resistance when resined and reinforced. However, the Quartzites did not have a significant gain, in some cases they obtained a lower value when reinforced. Only one of the quartzites achieved a 14% gain in resistance. Therefore, it is necessary to carry out a preliminary study with laboratory tests before resining and reinforcing the ornamental stones for sold. Research implications: Compare the three-point flexural strength between samples of pegmatic and quartzite stones and evaluate the resistance of reinforced (resin plus fiberglass mesh) and resin (resin) stones. Originality/value: analyze the influence of resin and fiberglass mesh on the three-point flexural strength of ornamental stones.

Particle surface oxidation modification and particle gradation strategy for the preparation of high-strength SiC ceramics via vat photopolymerization

The high refractive index, high absorbance, and low sintering activity of SiC powders pose challenges in achieving sufficient curing depth of SiC slurries and achieving densification of SiC ceramics. Hence, the preparation of high-strength SiC ceramics by vat photopolymerization is a challenge. This study proposes a strategy of particle surface oxidation modification and particle gradation to address this difficulty. Specifically, the surface of micron and submicron SiC particles is oxidatively modified to enhance the curing depth of SiC slurry, and the gradation of these particles is optimized to improve the sintering activity of the SiC particle system. The percentage of oxidized micron and submicron SiC particles is carefully adjusted to meet the requirements of both vat photopolymerization preparation and sintering. It found that increasing the percentage of sub-micron particles in the particle grade system had a negative impact on the rheological and curing properties of the slurry but contributed to the stability of the slurry and the performance of the sintered ceramic parts. Ensuring that the percentage of sub-micron particles reaches 50% or higher and reducing direct contact between micron particles to form sintered necks are two key conditions for the preparation of high-strength SiC ceramics. Additionally, it found that interlayer bonding location is the pore defects concentrated in the sintered ceramic parts, providing direction for further optimization of ceramic properties. By implementing the oxidation modification and particle gradation optimization strategy, the densification and three-point flexural strength of SiC ceramic parts were improved significantly. The relative density and three-point flexural strength of SiC increased from 65.7 ± 5.3% to 86.8 ± 3.7% and from 75.0 ± 2.1–170.9 ± 11.6 MPa, respectively. This approach provides a simple and effective method to prepare high-strength SiC ceramics by vat photopolymerization.

Effect of Hydrothermal Aging on the Flexural Strength and Microhardness of Materials Used for Additive or Subtractive Manufacturing of Definitive Restorations.

To evaluate the flexural strength (FS) and microhardness of various CAD/CAM restorative materials intended for definitive use. The effect of hydrothermal aging on the mechanical properties of these materials was also investigated. A total of 210 bar-shaped specimens (17 × 4 × 1.5 mm ± 0.02 mm) were fabricated via either subtractive manufacturing (SM) methods-reinforced composite resin (SM-CR), polymer-infiltrated ceramic network (SM-PICN), fine-structured feldspathic ceramic (SMFC), nanographene-reinforced polymethyl methacrylate (PMMA; SM-GPMMA), PMMAbased resin (SM-PMMA)-or additive manufacturing (AM) methods with urethane acrylate-based resins (AM-UA1 and AM-UA2). Specimens were then divided into two subgroups (nonaged or hydrothermal aging; n = 15). A three-point flexural strength test was performed, and five specimens from the nonaged group were submitted to microhardness testing. Specimens were subjected to 10,000 thermal cycles, and the measurements were repeated. Regardless of aging, SM-CR had the highest FS (P < .001), followed by SM-GPMMA (P ≤ .042). In nonaged groups, AM-UA2 had a lower FS than all other materials except SM-FC (P = 1.000). In hydrothermal aging groups, AM specimens had lower FS values than other materials, except SM-PMMA. With regard to microhardness, there was no significant difference found between any of the tested materials (P ≥ .945) in the nonaged and hydrothermal aging groups. The effect of hydrothermal aging on FS varied depending on the type of restorative material. Regardless of aging condition, SM-CR showed the highest FS values, whereas SM-FC had the highest microhardness. Hydrothermal aging had no significant influence on the microhardness of the tested materials.

Evaluation and Comparison of Mechanical Properties of Lithium Disilicate-Based CAD/CAM Blocks

Lithium disilicate are commonly used in dental restoration due to its aesthetic and mechanical performance. However, the patent expiration of the IPS emax system has led to the emergence of other variations of the system. Data and studies concerning mechanical properties of these recent lithium disilicate-based CAD/CAM are scarce and it warrants for an investigation to provide scientific evidence to support its routine use. The aim of this study was to investigate and compare the mechanical properties of lithium disilicate-based CAD/CAM blocks from four different brands. Four CAD/CAM lithium disilicate brands were investigated; IPS emax, Mazic Claro, Cameo, and Tessera. Specimens (n=10) were prepared accordingly; for flexural strength (16 × 4 × 1.2 mm) and microhardness test (15 × 13 × 2 mm). One specimen from each brand was analysed for the microstructure, elemental composition and distribution before and after heat treatment using scanning electron microscope and energy dispersive x-ray spectroscopy. The three-point flexural strength test (n=10) and microhardness test (n=10) was performed. Data were analysed using one-way ANOVA and Dunnett’s T3 test. The results showed that the highest mean flexural strength was from Group 4 Tessera (540.52 ± 143.33 MPa). For microhardness, the highest mean was from Group 1 Mazic Claro (667.70 ± 9.41 HV). Within the four groups, statistically significant difference is noted for flexural strength and microhardness. As a conclusion, Tessera demonstrated significantly higher flexural strength than IPS emax and Cameo. Mazic and Tessera demonstrated significantly higher microhardness than IPS emax and Cameo. All materials tested were above the threshold of 300 MPa.

Effect of sintering temperature on the microstructures and mechanical properties of ZrO2 ceramics fabricated by additive manufacturing

The optimization of the sintering process for ceramic stereolithography-based additive manufacturing is attracting high interest important due to its correlation with the final properties of the fabricated parts. In this work, a photosensitive zirconia suspension with low viscosity and high solid loading (48 vol%) was prepared using surface-modified zirconia ceramic powders, resulting in an improvement in long-term stability. The correlations between the sintering temperature (1400–1520 °C) and mechanical properties were investigated. The results showed that and the as-sintered zirconia parts exhibited a relatively high density of 99.5 ± 0.1 % and three-point flexural strength of 821 ± 65 MPa as well as excellent fracture toughness (4.37 ± 0.22 MPa m1/2) sintering at 1480 °C, which was attributed to the highly homogeneous microstructure without obvious pores or crack. The obtained insights regarding the correlation between sintering temperature, relative density, and flexural strength can provide practical guidance for the future applications of zirconia ceramics.

Effect of sintering programs and surface treatments on monolithic zirconia.

To investigate the effect of sintering programs and surface treatments on surface properties, phase transformation and flexural strength of monolithic zirconia. Zirconia specimens were sintered using three distinct sintering programs [classic (C), speed (S), and superspeed (SS)] (n = 56, each). One sample from each group underwent scanning electron microscopy (SEM) and grain size analysis following sintering. Remaining samples were divided into five subgroups (n = 11) based on the surface treatments: control (CL), polish (P), glaze (G), grind + polish (GP), and grind + glaze (GG). One sample from each subgroup underwent SEM analysis. Remaining samples were thermally aged. Monoclinic phase volume, surface roughness, and three-point flexural strength were measured. Monoclinic phase volume and surface roughness were analyzed by Kruskal-Wallis and Dunn tests. Flexural strength was analyzed by two-way ANOVA and Weibull analysis. The relationships among the groups were analyzed using Spearman's correlation analysis. Sintering program, surface treatment, and sintering × surface treatment (P ≤ .010) affected the monoclinic phase volume, whereas the type of surface treatment and sintering × surface treatment affected the surface roughness (P < .001). Type of sintering program or surface treatment did not affect the flexural strength. Weibull analysis revealed no significant differences between the m and σo values. Monoclinic phase volume was positively correlated with surface roughness in the SGG and SSP groups. After sintering monolithic zirconia in each of the three sintering programs, each of the surface treatments can be used. However, for surface quality and aging resistance, G or GG can be recommended as a surface finishing method.

Effect of Thermal Aging and Chemical Disinfection on the Microhardness and Flexural Strength of Flexible Resins

This article examines the effects of thermal aging and chemical disinfection on the microhardness and flexural strength of flexible resins. The influence of the resin type on the mechanical properties was also investigated. Two flexible resins, Deflex Classic SR and Deflex Supra SF, produced by the injection method, and a thermopolymerizable acrylic resin—ProBase Hot, produced by the flasking method, were subjected to 1000 cycles of thermal aging and three chemical disinfection protocols (n = 8), with daily immersion and during a recommended time, in Corega Whitening, Corega Oxygen Bio-Active, 2.5% sodium hypochlorite, and distilled water (control). Knoop microhardness and three-point flexural strength were evaluated. Data were analyzed using Wilcoxon, Mann–Whitney and Kruskal Wallis tests (α = 0.05). The results varied between 14.5 KHN and 80.1 MPa for ProBase Hot and 7.3 KHN for Deflex Classic SR and 52.5 MPa for Deflex Supra SF. Thermal aging reduced the microhardness of the flexible resins, but not their flexural strength. The microhardness of Deflex Classic SR was influenced by chemical disinfection with Corega Bio-active (p &lt; 0.001). The flexural strength of Deflex Supra SF was influenced by chemical disinfection with Corega Whitening (p &lt; 0.05). It can be concluded that chemical disinfection led to changes in the flexible resins and should be used with caution to maintain the mechanical properties of the resins. Flexible resins showed reduced resistance to physical and chemical environmental influences, which can affect their longevity.

Characterization of materials used for 3D printing dental crowns and hybrid prostheses.

To compare the filler weight percentage (wt%), filler and resin composition, flexural strength, modulus, and hardness of several 3D-printed resins to direct and indirect restorative materials. Four 3D-printed resins (C&B MFH, Ceramic Crown, OnX, and OnX Tough), one milled resin composite (Lava Ultimate), one conventional composite (Filtek Supreme), and one ceramic (IPS e.max CAD) were evaluated. Filler wt% was determined by the burned ash technique, and filler particle morphology and composition were analyzed by scanning electron microscopy and energy-dispersive spectroscopy, respectively. Organic resin composition was analyzed by Fourier transform infrared spectroscopy. Three-point bend flexural strength and modulus of the materials were determined by ISO 4049 or ISO 6872. Vickers microhardness was measured. Data were compared with a one-way analysis of variance (ANOVA) and Tukey post hoc analysis. Linear regression analysis was performed for filler wt% versus flexural strength, modulus, and hardness. 3D-printed resins were composed of various sized and shaped silica fillers and various types of methacrylate resins. Significant differences were found among filler wt% with some materials around 3% (C&B MFH), others between 33% and 38% (OnX Tough and OnX), others around 50% (Ceramic Crown), and some around 72% (Filtek Supreme and Lava Ultimate). All 3D-printed resins had significantly lower flexural strength, modulus, and hardness than the conventional and milled resin composites and ceramic material (p < 0.001). Filler wt% demonstrated a linear relationship with modulus (p = 0.013, R2 = 0.821) and hardness (p = 0.018, R2 = 0.787) but not flexural strength (p = 0.056, R2 = 0.551). 3D-printed resins contain from 3% to 50% filler content. Filler wt% alone does not affect flexural strength, but strength may be affected by resin composition as well. Although the 3D-printed resins had lower flexural strength, modulus, and hardness than milled and conventional composite and ceramic, they demonstrated nonbrittle plastic behavior. The properties of 3D-printed resins vary based on their composition, which affects their clinical applications.

Improvement of mechanical, biological, and electrochemical properties of Ti6Al4V alloy modified with Nb and Ag for biomedical applications

This study aims to evaluate the mechanical and biological properties of a spark plasma-sintered (SPS) Ti6Al4V alloy modified with 5 and 10 wt% niobium (Nb) together with 2 wt% Ag. Five batches of Ti6Al4V, Ti6Al4V-5 Nb, Ti6Al4V-10 Nb, Ti6Al4V-5 Nb-2Ag, and Ti6Al4V-10 Nb-2Ag were sintered using SPS at 1400 °C for 5 min. X-ray diffraction (XRD) analysis was used to identify the phases of the specimens. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray mapping analyses were also utilized to study the powder morphology, microstructure, and fractured surfaces of the samples. Three-point flexural strength and Vickers microhardness tests were performed and the fracture toughness (K1 C) was calculated subsequently. The bulk parts showed a very high building density, which means that the plasma sintering parameters were optimal. X-ray diffraction (XRD) analysis confirmed the existence of alpha and beta phases by adding niobium and silver. Potentiodynamic, electrochemical impedance spectroscopy, MTT assay, and antibacterial tests were also conducted to evaluate the biological properties of the sintered samples. The maximum values of flexural strength and K1 C were obtained for Ti6Al4V-5 Nb samples up to 1943 ± 12 MPa and 63 ± 1.1 MPa.m0.5, respectively. The hardness values of samples showed no significant difference by adding Nb and Ag. The samples containing Nb exhibit a lower passive current density compared to the pure Ti6Al4V alloy, suggesting that the addition of Nb positively influences corrosion resistance. According to the results of the antibacterial test, Nb slightly deteriorated the antibacterial properties, while after adding Ag, this property improved. The results of the MTT assay revealed that adding niobium and silver had no toxic effect on the samples.

Effect of Storage Temperature on Selected Strength Parameters of Dual-Cured Composite Cements.

Direct restorations are currently the most popular restorations used in dental prosthodontics. Due to the increased requirements for materials used in the fabrication of fixed restorations, there is a need for evaluation of strength parameters of these materials, including dental cements. The present study investigated the change in selected strength parameters of four dual-cured composite cements as a function of storage temperature. The following were investigated: three-point flexural strength (FS), flexural modulus in bending (FM), diametral tensile strength (DTS) and Vickers hardness (HV). Four dual-cured composite cements were tested, i.e., Multilink Automix (Ivoclar Vivadent), seT PP (SDI), MaxCem (Kerr), and Bifix Hybrid Abutment (VOCO). Each of the tested cements was stored for 7 days at one of the selected temperatures: 8 °C, 15 °C, 25 °C, or 35 °C, before the samples were made. Strength properties (DTS, FS) are not strongly dependent on the storage temperature in the range of 8-35 °C. Some statistical differences were observed between the hardness of MaxCem and Multilink Automix storage in various temperatures. FS and FM were lowest for Bifix Hybrid Abutment, MaxCem and Multilink Automix storage at 25 °C, and highest for Bifix Hybrid Abutment, MaxCem, and seT PP stored in 35 °C. The cement with the highest filler content (70% by weight) showed the highest FS and HV.

Effect of sintering temperature and low-temperature aging on microstructure and flexural strength of Fe2O3-doped 3Y-TZP ceramics fabricated by stereolithography-based additive manufacturing

In this study, the effects of sintering temperature and low-temperature degradation (LTD) on the microstructure and flexural strength of 0.06 wt% Fe2O3-doped 3Y-TZP ceramics fabricated via stereolithography-based additive manufacturing were evaluated to assess their suitability for dental applications. The ceramics' comprehensive properties, including density, microstructure, phase composition, and three-point flexural strength, were analyzed over a range of sintering temperature from 1400 °C to 1600 °C. The findings revealed that specimens sintered at 1500 °C exhibited the highest density (6.03 g/cm3), a uniform microstructure, and superior mechanical properties (911.54 MPa). However, sintering temperatures above 1500 °C led to abnormal grain growth and martensitic transformation of tetragonal zirconia to the monoclinic phase, resulting in reduced density and material degradation. To investigate the effects of LTD on the phase structure, microstructure, and flexural strength, the specimens sintered at 1500 °C were subjected to LTD tests at 134 °C and 2 bar for 5, 10, and 20 h, respectively. The results demonstrated an increase in the m-phase content from 2.58 wt% to 21.89 wt% on the ceramics' surface. Atomic force microscopy observations revealed a gradual increase in the m-phase grain with longer aging time. Meanwhile, the flexural strength decreased but remained within the required range for dental restorations. In conclusion, the specimens fabricated via stereolithography-based additive manufacturing and sintered at 1500 °C for 4 h demonstrated high mechanical properties and good LTD resistance. These findings, in conjunction with the positive aesthetic properties obtained in previous studies, highlight their potential as a promising material for dental applications.

Effect of fibre diameter and tensile strength on the mechanical, fracture, and fibre distribution properties of eco-friendly high-strength self-compacting concrete

The development of Steel Fibre-Reinforced Self-Compacting Concrete (SFR-SCC) is a complex task with significant practical implications for the construction industry. However, the absence of established design guidelines and recommendations, and the limited availability of design methodologies, present a significant challenge. Achieving the targeted rheological and mechanical properties while simultaneously minimising production costs requires a comprehensive understanding of the optimal blend of fibre type and quantity and the coarse aggregate content. This paper addresses the impact of steel fibre properties on the rheological and fundamental mechanical properties of eco-friendly high-strength self-compacting concrete (HSSCC), using 40% ground granulated blast furnace slag (GGBS) as a cement replacement. The research focused on 30 mm long hooked-end steel fibres with tensile strengths of 1345 MPa and 3070 MPa, and diameters of 0.55 mm and 0.38 mm, respectively. In addition, the study investigated the combined effect of coarse aggregate content and steel fibre type on the performance of eco-friendly HSSCC. The fresh properties of eco-friendly HSSCC were assessed using the slump flow and J-ring tests. Furthermore, mechanical and fracture properties such as compressive strength, splitting tensile strength, elastic modulus, four-point flexural strength, and three-point flexural strength on notched prisms were also evaluated. The distribution and alignment of steel fibres in the HSSCC were assessed using image analysis techniques, which showed that the steel fibre diameters were a crucial factor in the fibre dispersion. The results demonstrated that using steel fibres with higher tensile strength and smaller diameter significantly enhanced the splitting tensile strength, flexural strength, and fracture energy, compared to steel fibres with larger diameters and lower tensile strengths. Additionally, the study indicated that the elastic modulus and fracture energy of eco-friendly HSSCC reinforced with both types of steel fibre are highly dependent on the content of coarse aggregate used. The study highlighted that the coarse aggregate proportion and the steel fibre characteristics were two vital factors that influenced the rheological and mechanical properties of HSSCC and must be considered during the mix design process to optimise the desired properties while also minimising production costs.

CEBs with GRC: Fabrication, characterization, modeling, and correlation with microstructural fracture features

In this study, earth blocks (EB) and compressed earth blocks (CEB) are fabricated and investigated along with the development of a mathematical model of compressive and tensile loads. The investigated specimens are manufactured from a mixture of soil, ground recycled concrete (GRC) powder and water in weight fractions of 4:1:1. EBs are molded and CEBs are obtained by quasi-static compression in wet state. Material samples extracted from the blocks are tested in dry state for compressive strength and three-point flexural strength according to ASTM standards. The results indicate that CEB exhibits 130% higher compressive load capacity and 63% higher tensile strength compared to EB. Furthermore, the proposed and calibrated mathematical model is able to adequately describe the strength and damage behavior of both materials. Finally, microstructural/micromechanical interrelationships with the modeled material response are established based on a characterization of postmortem CEB samples using EDS elemental analysis and SEM micrographs techniques.

Characterization of artificial stone developed with granite waste and glass waste in epoxy matrix

The production of artificial stone through the incorporation of granite and glass waste into an epoxy resin matrix is not only an ecological alternative capable of reducing the environmental impacts caused by improper disposal of these wastes but it is also technically satisfactory, as it adds economic value and optimizes the characteristics of the artificial stone compared to natural stone. The goal of this research was to produce and evaluate the properties of artificial stone plates manufactured using vibration, compression, and vacuum methodology. Plates were produced with 15% epoxy resin by weight, and aggregates in the proportions of 50% Ocre Itabira gray granite waste and 50% colorless tempered glass waste. During production, the materials were processed under a compaction pressure of 3.68 MPa for 20 min at 90 °C. The following characterization tests were conducted: density, apparent porosity, water absorption, three-point flexural strength, impact resistance, abrasive wear, staining, chemical attack, durability test through wetting and drying cycles, and microstructural analysis. The material achieved a water absorption of 0.13 ± 0.03%, flexural strength of 32.77 ± 3.29 MPa, rupture height of 0.45 ± 0.12 m, and abrasive wear of 1.65 ± 0.02 mm. It demonstrated good interfacial adhesion in the microstructural analysis and exhibited resistance to staining, chemical attack, and durability testing through wet-dry cycles. Therefore, the technical feasibility of the produced material was confirmed, with results consistent with previous studies in the field, demonstrating resistance to the conducted tests and indicating its potential application in the construction industry.

Effect of airborne particle abrasion treatment of two types of 3D-printing resin materials for permanent restoration materials on flexural strength.

This study aimed to assess the effects of airborne-particle abrasion (APA) on the flexural strength of two types of 3D-printing resins for permanent restoration. Two types of 3D printing resins (urethane dimethacrylate oligomer; UDMA, ethoxylated bisphenol-A dimethacrylate; BEMA) constituting different components were printed. The specimen surfaces were subjected to APA using 50 and 110µm alumina particles under different pressures. The three-point flexural strength was measured for each surface treatment group, and a Weibull analysis was performed. Surface characteristics were analyzed via surface roughness measurements and scanning electron microscopy. Dynamic mechanical analysis and nano-indentation measurements were limited to the control group. The three-point flexural strength according to the surface treatment was significantly lower in the UDMA group for large particle sizes and at high pressures; the BEMA group demonstrated low flexural strength for large particle sizes regardless of the pressure. After thermocycling, the flexural strengths of UDMA and BEMA significantly decreased in the group subjected to surface treatment. The Weibull modulus and characteristic strength of UDMA were higher than those of BEMA under different APA and thermocycling conditions. As the abrasion pressure and particle size increased, a porous surface formed, and the surface roughness increased. Compared with BEMA, UDMA featured a lower strain, greater strain recovery, and a negligible increase in modulus according to strain. Thus, surface roughness increased with the sandblasting particle size and pressure of the 3D-printing resin. Hence, a suitable surface treatment method to improve adhesion can be determined by considering physical property changes.