Increase In Bond Strength Research Articles

Investigating the Effect of Polyetheretherketone (PEEK) Veneers on Bond Strength and Discoloration When Repairing Various Composites.

This study aimed to examine the impact of the strength and color change of composite materials that could be utilized in the repair of polyetheretherketone (PEEK) veneer fractures. The 220 nanoceramic-filled PEEK specimens used in the study were divided into four groups, and color measurements were made on a gray background (n=55): Group N, 1-mm-thick monochromatic composite; Group NN, 2-mm-thick monochromatic composite; Group F, 1-mm-thick 2-mm-diameter short fiber-reinforced composite, placed in the center and polymerized; and Group FF, 2-mm-thick 2-mm-diameter short fiber-reinforced composite, placed in the center and polymerized. The remaining mating surfaces were restored by filling with monochromatic composite and adhesion strength testing by re-measuring the color. The results of the two-way ANOVA indicated that there was a significant color change caused by both thickness and composite type (p<0.001). Additionally, a significant difference in bond strength was observed between the groups. In PEEK restorations, short fiber-reinforced composites significantly increase bond strength, while the use of monochromatic composites of a certain thickness ensures that color change remains within acceptable limits. Although PEEK has a superior mechanical structure, it does not meet the aesthetic expectations and needs to be veneered. However, fractures are frequently seen due to low bond strength. Therefore, this study is important because it aims to provide guidance to clinicians on aesthetic and mechanical methods that can be used in PEEK prosthesis repair.

Effects of laser treatment on bond strength of epoxy resin and calcium silicate-based sealers: a systematic review and meta-analysis of in vitro studies.

This study aimed to systematically review the effect of laser treatment on the bond strength of epoxy resin-based and calcium silicate-based endodontic sealers to root dentine. The search encompassed four databases: PubMed/MEDLINE, EMBASE, Scopus, and ISI Web of Science. Inclusion criteria were limited to in vitro studies conducted on extracted human teeth evaluating bond strength in megapascals (MPa) of either epoxy resin-based or calcium silicate-based sealers, using the push-out test. Two independent reviewers appraised the methodological quality of the selected studies to assess the risk of bias. Meta-analysis was performed for different laser types, endodontic sealers, and control groups. Standard Mean Difference and 95% Confidence Interval values were calculated. 17 studies met the inclusion criteria for qualitative synthesis, and 15 for quantitative analysis. Meta-analyses revealed that certain lasers (Er,Cr:YSGG, Er:YAG) significantly increased bond strength for epoxy resin-based sealers when compared to negative controls (inert solutions), but did not show a significant advantage over EDTA agent. For calcium silicate-based sealers, laser treatment did not show significant enhancement in bond strength compared to either inert solutions or EDTA. The subgroup analysis suggested that erbium lasers, especially in the PIPS mode, potentially increase the bond strength of epoxy resin-based sealers. Laser treatment enhances the bond strength of epoxy resin-based sealers compared to inert solutions, but not more than EDTA. For calcium silicate-based sealers, laser treatment does not significantly improve bond strength over inert solutions or EDTA. Laser treatment increases the bond strength of epoxy resin-based sealers.

Effect of Post Sizes and Citric Acid Treatment on the Bond Strength of Fiber Posts Using Self-Etch Resin Cement in Calcium Silicate–Based Sealer Treated Teeth

Abstract Objectives This study evaluated the effects of different post sizes and citric acid (CA) treatment on the bond strength of fiber posts cemented with self-etch resin cement in teeth obturated with calcium silicate–based sealer. Materials and Methods Seventy mandibular premolars were collected and randomly distributed to either a control group (no sealer) or experimental groups obturated with calcium silicate–based sealer (iRoot SP). The experimental groups were classified by post sizes—1.25 mm (no. 1), 1.375 mm (no. 2), and 1.50 mm (no. 3)—and the irrigants used (distilled water [DW] or CA). Prefabricated fiber posts were fixed using NX3 self-etch resin cement. Push-out bond strength was tested in the coronal and middle sections of the roots. Statistical Analysis The data were analyzed using a one-way analysis of variance (ANOVA), followed by a post hoc Duncan test. Results In the coronal section, post size no. 1 with DW showed significantly lower bond strength compared to the other experimental groups (p &lt; 0.05). In the middle section, the larger post sizes (nos. 2 and 3) with CA treatment resulted in a significant increase in bond strength compared to the control group (p &lt; 0.05). Conclusions iRoot SP negatively affected bond strength in the middle section of the canal. However, using larger post sizes (nos. 2 and 3) with CA treatment improved bond strength in the middle section.

Experimental and theoretical investigation on bond performance between surface-modified bamboo scrimber bars and concrete

With the aim of facilitating the adoption of eco-friendly bamboo scrimber bars as an alternative to the widely used steel bars in concrete structures, center pull-out tests were conducted on 75 specimens to investigate the bond performance between bamboo scrimber bars and concrete. Two innovative modification methods were employed, including the sand coating modification method with varying particle sizes and a newly proposed method involving wrapping with basalt fiber bundles, with a focus on the impact of bundles spacing on bond strength. Additionally, other influence factors, including the concrete compressive strength, development length, and equivalent diameter of bamboo scrimber bars, were investigated. The test results show that compared to unmodified bamboo scrimber bars, those modified with sand and basalt fiber bundles show increases in bond strength of 5.50–5.96 times and 4.82–6.15 times, respectively. The bond strength was most significantly influenced by the development length, which decreases with increasing development length. Besides, specimens with development length less than 75 mm mainly exhibit pull-out failure, while those with development length equal to 75 mm primarily occur concrete splitting failure. Furthermore, a bond strength prediction formula and a bond stress-slip constitutive model for the interface between bamboo scrimber bars modified with sand coating and concrete were established, which show great agreement with the test results.

Effect of calcium phosphate modification on the interfacial transition zone of recycled aggregate and concrete

Recycling construction solid waste is an immediate need due to the substantial amount of construction waste that occupies valuable land and poses environmental hazards. In response to challenges related to the performance and interfacial transition zone (ITZ) when using recycled aggregate (RA) in concrete, a modified formulation with low calcium phosphate (CaP) content was developed to enhance RA's performance. It was found that when the mass ratio of CaP to RA reached 0.001 g/g, the physical properties of RA were significantly improved through a precoating treatment, resulting in a 31.52 % increase in the compressive strength of recycled aggregate concrete (RAC) compared to the control group. An in-depth analysis of the mechanism of action of CaP revealed that the active layer formed by CaP on the RA surface promoted the slow hydrolysis-hydration coupling reaction through the sustained release of Ca2+ and PO₄3- ions. This process and the solid-phase reactions of C-S-H gel, carbonation products, and sulfate ions effectively improved the pore structure, increased the specific surface area by 47.36 %, and reduced crack width by 78.95 %. Furthermore, the bond strength test between modified RA and freshly hardened mortar showed a 30.29 % increase in bond strength, directly demonstrating the effectiveness of CaP in enhancing the ITZ in RAC.

Investigating the adaptability of CsMF3 (M = Ge, Si) perovskites under hydrostatic pressure for improved optoelectronic performance: A DFT-based computational study

The Cesium-based halide perovskites CsMF3 (M = Ge, Si) were examined in detail, using density functional theory evaluated ab-initio calculations, under hydrostatic pressures varying between 0 and 40 GPa. The structural, electronic, bonding, optical, anisotropic elastic, and mechanical characteristics of prospective photovoltaic materials are examined to assess their viability. The structural, thermodynamical, mechanical, and vibrational stabilities are validated through the analysis of the Goldschmidt tolerance factor, formation energy, Born stability criteria, and phonon calculations, respectively. Both the GGA-PBE model and the non-local hybrid sX potential were utilized to estimate the structural parameters and electronic energy band gaps. The calculated band gaps indicate that the compounds exhibit semiconductor behavior at ambient pressure with values 2.074 eV (2.642 eV) for CsGeF3, and 1.097 eV (0.977 eV) for CsSiF3 utilizing GGA-PBE (hybrid sX) potential. However, increased pressure reduces the band gap, resulting in enhanced conductivity and causing a shift from a semiconductor to a metallic state. The charge density map distinguishes between the ionic character of the Cs-F bond and the covalent nature of the Ge/Si-F bond. When pressure is applied, the bond strength increases, leading to a uniform decrease in bond length. The application of pressure also improves the optical functionalities, suggesting that these materials could be effectively utilized in various optoelectronic devices designed for the visible and ultraviolet spectra. In addition, hydrostatic pressure has a significant influence on the mechanical characteristics while retaining stability. Under pressure, both the ductile and anisotropic characteristics become more prominent for CsMF3 (M = Ge, Si) solids.

Bond behavior of confined rebar in recycled brick aggregate concrete using bending pullout test

The pertinence of recycled brick aggregate (RBA) in concrete structures largely depends on their bonding ability with the rebars. Considering the practical detailing of concrete structures where main rebars are usually confined by stirrups, this study conducted bending pullout tests on 12 beam specimens to study the influence of concrete confinement on the bond behavior of rebar in RBA concrete. The investigated variables include RBA%, rebar diameter (d), embedment length (le), and the ratio of concrete cover to rebar diameter (c/d). Bond stress-slip relationships were acquired, analyzed, and average bond strengths were compared to the AS 3600, CEB-FIP codes, and existing MacGregor's model. The average bond strength of confined specimens was nearly double that of the unconfined specimens. A progressive increase in bond strength was noticed with the presence of RBA regardless of confinement. The confined specimens also exhibited higher deformability, ductility, and toughness values than those of the unconfined beams. At 15% RBA content, the maximum toughness value of the confined specimen was 3078.1 J, while the unconfined specimens reached a value of 278.1 J, only. Similarly, the ductility of the confined beam was found in a range of 1.21–1.60 whereas the value is only 1.04–1.10 for the unconfined cases. Moreover, the confined specimens exhibited a significant number of cracks during their failure, while the unconfined specimens experienced a split type brittle failure. Nevertheless, these findings may contribute to the further development of the bond behavior of rebar in RBA-based concrete structures and thus play a role in the sustainability of construction materials.

Study on the adhesive property of sludge-modified magnesium phosphate cement reinforcement coating for steel bars

The synergistic interaction inreinforced concrete systems originates from the strong bond between steel reinforcement and concrete, enabling them to collaborateunder load and optimize structural performance. This study applied various sludge-modified magnesium phosphate cement mixtures to the surfaces of plain round steel bars and ribbed steel bars to prepare steel-reinforced concrete specimens. The characterization of the bond performance of the sludge-modified magnesium phosphate cement reinforcement coating for steel bars and concrete was achieved through analyzing the failure modes, bond strength, and slip values of different groups. Microscopic analysis was performed using a scanning electron microscope. The results revealed that the primary failure mode of the steel-reinforced concrete specimens was steel bar pull-out, with some specimens exhibiting concrete splitting failure. Coating application on plain round steel bars increased bond strength, while on ribbed steel bars, it decreased bond strength. The application of the coating slightly reduced slip values to some extent.

Expanding Lightweight Design Potential by Hybrid Joining of Aluminum Sheets with Aluminum Casting Through Compound Sand Casting and Induction Heating

Combining light metals like aluminum to produce lightweight structures offers a high weight‐saving and contributes to a circular economy in automotive car body construction. Compound casting is a promising process for producing car body parts. Difficulties arise in creating metallic continuity between insert and casting. Insert coatings are used to remove the oxide layer and thereby improve the wettability of the melt. This study uses a hybrid joining method to improve the metallic bond between insert and casting. Induction heating differently influences the strength properties of age‐ and nonage‐hardenable inserts. Compression shear tests characterize the metallic bond strength. Microscopic images show the influence of the process variables on the compound quality. Reproducible sound metallic bonding with low scattering is achieved by enhancing the compound casting process through induction and no insert coating. Cast wall thicknesses down to 4 mm contribute to further lightweight potential as they have the same strength level as the reference sample. A decisive factor is the insert temperature in the compound zone. Thereby, insert preheating conditions play a crucial role. Additional heat treatment of hardenable compounds leads to a further increase in metallic bond strength.

Repair of ordinary concrete using basalt fiber reinforced geopolymer: High temperature resistance and micro structure evolution of adhesive interface

Good bonding properties in the interfacial transition zone (ITZ) between the substrate and the repair material are critical to the success of the repair, and a good repair material can act as a protective layer to reduce the impact of fire on the structure. In this paper, Ordinary concrete (OP), geopolymer mortar (GP), and basalt fiber reinforced geopolymer mortar (GPb) were poured as the three repair materials on the roughened surface of the old substrate. The bonded specimens were exposed to temperatures of 23 °C, 200 °C, 400 °C, 600 °C and 800 °C for 1 h. The interfacial bond strength of the bonded specimens was tested by slant shear test, and the physical phase change of the repair material and the microstructure of the ITZ were analyzed by microscopic test. The results showed that the mechanical properties and high temperature resistance of ITZ were best when the old substrate interfaces were grinded and grooved and GPb was used as the repair material. Compared with S-OP, the bond strength of S-GPb was 26.92 %, 27.43 %, 46.50 %, 44.26 %, and 97.02 % higher at different temperatures. The increase in interfacial bond strength can be attributed to three mechanisms: (1) Mechanical interlocking with the old substrate with a rough surface. (2) The increase in temperature accelerates the volcanic ash reaction, and the formation of hydration products further fills the voids at the ITZ, maintaining the strength and compactness of the ITZ. (3) The addition of basalt fibers can form an anchoring effect at the interface, reducing the risk of interfacial spalling and cracking caused by material shrinkage in the ITZ.

Effect of Er:YAG laser surface treatment on surface properties and shear-bond strength of resin-cement to three translucent zirconia: an in-vitro study

Achieving optimal bonding to translucent zirconia poses certain challenges as there is no consensus on ideal surface treatment method. Therefore, the aim of present investigation is to evaluate effect of Er:YAG laser treatment on wettability, surface roughness and shear-bond strength of three Yttrium oxide-stabilized zirconium-oxide polycrystal translucent zirconias. 120 specimens (n = 40/zirconia type) were prepared from three commercially-available translucent zirconias (Dentsply Sirona, USA); Translucent, High-Translucent and Ultra-Translucent zirconia. Specimens were sub-divided (n = 20/surface-treatment) into control and Er:YAG laser surface-treated groups. Regarding water wettability test; goniometer was used to measure contact angle before and after laser treatment. Surface roughness was measured using atomic force microscope. For shear-bond strength (SBS) test; the control group was sandblasted. All resin-bonded zirconia specimens were thermocycled for 5000 cycle and subjected to shear force using universal testing machine with 0.5 mm/min crosshead-speed. Results were statistically analyzed using two-way-analysis-of- variance (p ≤ 0.05). There was significant decrease in average contact angles (p-value < 0.001) in all zirconia groups after laser treatment. For roughness test; insignificant difference in average Ra in Translucent zirconia group. However, significant increase in mean Ra was revealed after laser treatment for High and Ultra-Translucent zirconias. For SBS test, results revealed insignificant difference in average bond strength after laser treatment in Translucent and High-translucent zirconia groups. Significant increase in mean bond strength of Ultra-Translucent zirconia was recorded. Er: YAG laser treatment significantly affected surface properties and shear-bond strength of Ultra-Translucent zirconia. Er:YAG laser irradiation may be a promising zirconia surface treatment method.Graphical

Effect of enamel deproteinization with 5.25% sodium hypochlorite on the bond strength of orthodontic brackets. An experimental study.

In the search for alternatives to increase the bond strength of brackets, when necessary, this study proposes to apply the enamel deproteinization protocol to eliminate the proteins in the surface enamel to achieve better etching patterns and thereby increase bond strength. The aim of this study was to evaluate the effect of sodium hypochlorite as a deproteinizing agent on the bond strength of metal brackets. Forty bovine teeth were randomly and equally divided into two groups. The experimental group (n=20) underwent a deproteinization treatment with sodium hypochlorite at 5.25% for 60 seconds prior to acid etching of the enamel with 37% phosphoric acid and bracket bonding with Transbond XTTM resin. The control group (n=20) underwent enamel etching with 37% phosphoric acid and bracket bonding with Transbond XTTM resin. Shear strength and the adhesive remnant index were evaluated and the Students t and Chi-square tests were used (P<0.05). The bond strength values of the control group (27.72±6.42 Mpa) were not significantly lower compared to the experimental group (29.21± 7.96 Mpa) (p=0.259). The adhesive remnant index showed a similar behavior in both groups, with the amount of adhesive remaining on the enamel being less than 50% in most samples of both the control and experimental group. Deproteinization treatment of bovine tooth enamel with 5.25% sodium hypochlorite for 60 seconds prior to enamel acid etching does not improve the bond strength of a resin in orthodontic bracket bonding. Key words:Deproteinization, sodium hypochlorite, bracket bonding, orthodontics.

Mesoscale modeling of new-to-old concrete interface under combined shear and compressive loads

A mesoscale model of new-to-old concrete interface under combined shear and compressive loads is established, and a parameter study is conducted to evaluate the influence of interface roughness, bond strength, and fracture energy. The mesoscale model is numerically generated using a random aggregate technique, in which the number of aggregates is calculated using the Fuller grading curve and Walraven formula and the aggregates are randomly placed using the Monte Carlo simulation. The concrete damaged plasticity model is employed to simulate the mechanical behaviors of new and old mortars, as well as the interfacial transition zone between the mortar and aggregate. The linear elastic model is utilized to simulate the behavior of aggregates, while the cohesive-friction model is employed to represent the behavior of new-to-old concrete interface. The effect of interface roughness, bond strength, and fracture energy on the interface shear strength and post-peak shear strength using the double-shear test specimens is investigated. The results indicate that increasing the roughness of old concrete surface leads to significant increases in both the interface shear strength and post-peak shear strength, but the larger interface roughness is not necessarily better. As the interface bond strength increases, the interface shear strength remains the same, whereas the post-peak shear strength shows a large increase with the lower interface roughness. Moreover, the interface fracture energy imparts the minimal influence on the interface shear strength and post-peak shear strength, but the higher interface fracture energy can improve the overall constitutive behavior of new-to-old concrete interface if the roughness of old concrete surface is low. The numerical mesoscale model presented can provide the theoretical guidance and technical support for effective design and construction of new-to-old concrete interface and structures.

Push-Out Bond Strength of Fiber Posts to Overflared Root Canals in Different Root Regions: Effect of Reinforcement Techniques.

Objectives: This study aimed to investigate the effect of different reinforcement techniques on the push-out bond strength of fiber posts to over-flared root canals. Materials and Methods: Forty-eight extracted human single-canal premolars were endodontically treated, over-flared, and randomly divided into four groups (N=12) including SARC: luting with self-adhesive resin cement, DCC: luting with dual-cure core build-up resin composite, CRR: relining root canal walls with bulk-fill resin composite, and DAP: relining fiber post with bulk-fill resin composite. After 24 hours, the roots were sectioned to obtain three cervical, middle, and apical 3mm slices. The push-out test was performed and failure pattern was examined. Kruskal-Wallis and post-hoc Dunn-Bonferroni tests were used for statistical analysis (P<0.05). Results: In all three regions, the lowest and highest bond strength was found in the SARC and DAP groups, respectively. In the middle region, there was a statistically significant difference between the bond strength of the SARC group and that of the DCC (P=0.044), CRR (P=0.021), and DAP (P<0.001) groups. There was no significant difference in the apical region. The lowest bond strength was observed in the apical region, and the highest was related to the cervical region. Adhesive failure was the most common failure pattern in all groups. Conclusion: Based on our results DCC, CRR and DAP methods increased bond strength in the middle and cervical sections of over-flared root regions. Considering that DCC is the easiest and most practical method, we propose that CRR and DAP can be replaced with this method in clinical procedures.

Unraveling the oxygen evolution in layered LiNiO2 with the role of Li/Ni disordering

Oxygen loss is widely recognized as a major factor in the structural degradation of Ni-rich layered cathode materials, while a study on the detailed oxygen evolution process and the role of inevitable Li/Ni disordering defects is still lacking. Using ab initio calculations with van der Waals correction, we performed an in-depth study on the oxygen evolution in layered LiNiO2 and considered the role of Li/Ni disordering. We find that excess Ni in Li slab act as a pillar role for the structural framework and increases bond strength of adjacent oxygen ions, both of which are beneficial to the thermal and kinetic stability of lattice oxygen in LiNiO2, thus inhibiting the oxygen evolution. For Li/Ni exchange and Excess Li defects, the Li ion in Ni slab preferred to return to the vacancy in Li slab with delithiation in both surface and bulk LiNiO2. This situation induces the weaken binding and fast migration of lattice oxygen, even Ni slab collapse and oxygen release in the surface. Furthermore, the ab-initio molecular dynamics simulations for LiNiO2 surface reveal three stages of oxygen loss in the pristine state: (i) the formation of pre-O-O dimer; (ii) the pre-O-O dimer oxidizing to O-O dimer; (iii) O2 release with oxygen oxidation and Ni migration. The Li/Ni exchange and Excess Li defects accelerate this process because of Li ion in Ni slab returning to Li slab, while the Excess Ni defects will inhibit this process. We hope this work will improve the understanding of oxygen evolution in layered LiNiO2 and provide theoretical guidance for the design of Ni-rich layered cathode materials with improved stability.

Nonlinear finite element modelling of the bond behavior of near-surface mounted Fe-SMA bars

Strengthening of concrete members with near-surface-mounted (NSM) iron-based shape memory alloy (Fe-SMA) bars can increase the load-carrying capacity and reduce deflections/crack widths owing to the unique self-prestressing ability of the Fe-SMA. However, the bond behavior of Fe-SMA bars is critical for the effectiveness of the NSM strengthening method, as inadequate bond strength can result in premature bond failure, rendering the strengthening technique ineffective. This study presents the results of a non-linear finite element (FE) model that was developed and validated to simulate the bond behavior and failure patterns of NSM Fe-SMA bars grouted into concrete. The variable parameters of the study included the effect of the compressive strength of the grout and the concrete block, the effect of cover depth and the activation of the Fe-SMA bar on the bond behavior. Investigations showed that the bond resistance and failure patterns of the NSM bars were significantly affected by the compressive strength of the concrete block and grout. The results showed that increasing the compressive strength of the grout by two times resulted in a 35 % increase in bond strength while increasing the compressive strength of the concrete block by three times resulted in a 30 % increase in bond strength. Additionally, the load transfer between the grout and concrete block was strongly influenced by the grout's compressive strength, where a higher strength of the grout resulted in a stiffer bond and increased contribution of the concrete block to resisting loads. Similarly, increasing the cover depth by four times from 5 mm to 20 mm increased the bond strength by more than twice and ultimately led to a change in failure mode from a splitting crack in the grout to a splitting crack in the concrete block. The results of the study also show that prestressing the short NSM bond with Fe-SMA can induce an initial bar slip in the range of 0.025 to 0.14 mm for recovery stresses of 100 MPa to 350 MPa.

Hardening properties and microstructure of 3D printed engineered cementitious composites based on limestone calcined clay cement

Comparison of three-dimensional (3D) printing and cast methods on the mechanical properties of cementitious materials is the basis for intelligent construction development. To achieve this, a series of experiments including the uniaxial tensile, compressive, flexural and interlayer bonding tests of mould-cast and 3D printed (3DP) specimens are conducted to investigate the effects of different preparation technologies on the microstructure and hardening properties of limestone calcined clay cement (LC3) based engineered cementitious composites (ECC). Results indicate that the tensile strength and strain capacity of the printed LC3-ECC decrease by 16.6%–22.7 % and 43.3%–54.6 % compared to the cast specimens, while it still possesses a strain capacity of 2 % and multiple cracking behaviour. The compressive and flexural properties of the printed LC3-ECC both show significant anisotropy, the maximum values of which are observed in the Z- and Y- directions, respectively. The interlayer bonding strength increases by 54.3%–91.9 % at 28 d compared to that at 7 d due to the hydration of LC3. The pore structure of the printed LC3-ECC is denser than that of the cast LC3-ECC, with more regular arrangement and finer size of pores. The macro-micro properties correlation analysis proves the better comprehensive performance of printed LC3-ECC relative to casted LC3-ECC, as well as reveals the relationship between pore structure and anisotropy. In terms of material sustainability, 3DP-LC3-ECC has a significant reduction in energy and carbon emissions compared to typical M45-ECC, contributing to the environmental development.

THE INFLUENCE OF ABUTMENT SURFACE TREATMENT ON PULL-OFF BOND STRENGTH BETWEEN (5)YTTRIA STABILIZED ZIRCONIA CROWN AND TITANIUM IMPLANT ABUTMENT

ABSTRACT Aim: The objective of this research was to evaluate the effect of mechanical method and energetic method of surface treatments for Ti-abutment base (Ti-Base, Dentium/Korea) on the pull-off bond strength with (5)Y-TZP crown. Materials and Methods: : Forty titanium implant abutments were used in this study and randomly assigned to four groups (n = 10 for each group) according surface treatment methods of titanium abutment: group (1) act as control without surface treatment for Ti-abutment, group (2) bur surface treatment of Ti-abutment, group (3) sandblast (50-µm aluminum oxide) surface treatment for Ti-abutment, group (4) plasma surface treatment for Ti-abutment. Then, forty implant analogs were placed in the center of acrylic mold. After that abutment was tightened on the each analog with (35 N/cm) torque . Forty (5)Y-TZP crowns fabricated by CAD/CAM system that had special design with occlusal O-hole cemented to all abutments using Allcem dual-cure resin cement. All specimens were then subjected to thermos-cycling with (5000) cycles. With a universal testing machine record pull-off bond strength for all samples, Collected data were analyzed using a one-way analysis of variance at a significance level of (p &lt; 0.01) . Results:, The bur treated abutment (group 2) group showed the highest bond strength values, followed by sandblast treated abutment (group 3) and plasma treated abutment (group 4). Control group was the lowest value of tensile strength. Conclusion: Surface treatments of Ti-abutment had observed effect on pull-off (tensile bond strength) between Ti-abutment and (5)Y-TZP crown Bur and sandblast cause roughness of surface and increase bond strength , plasma cause reactive surface for increasing tensile bond strength.

Experimental investigation on the bond-slip behavior of rebars coated with epoxy and polyurethane systems: A comparative study

This study presents a comprehensive experimental investigation into the effectiveness of various rebar coating systems in mitigating corrosion and maintaining bond strength with concrete. Three coating systems were evaluated: a conventional two-component epoxy system (KC-R), a zinc-rich epoxy system (FR-R), and a moisture-cure polyurethane coating with Micaceous Iron Oxide-Enriched System (MC-R). Accelerated corrosion tests showed that uncoated rebars had a mass loss of about 3.793 ± 0.266 %, while all coated rebars exhibited negligible mass loss. However, coated rebars experienced a reduction in bond strength: KC-R and FR-R coatings resulted in 16.3 % and 48 % reductions, respectively, whereas MC-R showed the least reduction at 9.4 %. Notably, all specimens, whether coated or not, displayed a slight increase in bond strength after corrosion. Additionally, the MC-R coating reduced rebar slip at ultimate bond strength. However, the other coatings increased rebar slip compared to uncoated specimens. Overall, this study underscores the importance of proper rebar coating selection and highlights the effectiveness of the polyurethane coating system in mitigating corrosion while maintaining bond strength with concrete. Additionally, it emphasizes the significance of post-failure analysis in understanding the behavior of coated rebar specimens under different conditions.

Effect of corrosion on bond slipping between steel and concrete in SRC structures

Corrosion critically impacts bond performance in steel-reinforced concrete (SRC) structures. In this study, we investigate the impact of corrosion on bond-slipping between steel components and concrete within SRC structures. Initially, SRC specimens were subjected to electrochemical corrosion tests to induce varying corrosion rates. Then, pull-out tests were conducted to study the specimens' failure modes, bond stress–slip curves, and displacement distribution. The experimental results indicate that lower corrosion rates can increase bond strength due to enhanced steel surface roughness. As the corrosion rate increased from 0% to 5%, the initial bond stress, peak bond stress, and residual bond stress increased by 133%, 101%, and 102%, respectively. However, when the corrosion rate increased from 5% to 15%, these stresses decreased by 57.1%, 49.6%, and 49.6%, respectively. Furthermore, with an increase in corrosion rate from 15% to 20%, the initial, peak, and residual bond stresses decreased by 100%, 67.6%, and 69.0%, respectively. Corrosion considerably affected the initial and peak slipping observed between the steel components and the concrete, yet its impact on residual slip was relatively minor. In addition, a nonlinear finite element model for characterising the corrosion and pull-out tests was developed and validated according to the experimental results. The numerical results showed that the four shear transfer mechanisms, including chemical bonding, micromechanical interlocking, macromechanical interlocking, and rust interface bonding, exhibited distinct behaviours at different loading stages. Finally, a parametric study was conducted using a finite element model. With variations in corrosion rates, four modes of cracking patterns on the concrete surface were observed.