Interfacial Bond Strength Research Articles

Experimental Investigation on Shear Strength between Ultra-High-Performance Concrete and Normal Concrete Substrates

Tunnel engineering in China has developed to the stage of both construction and maintenance, and the problem of structural defect is widespread. The cast-in-situ jacketed arch treatment takes a long time and has a great impact on traffic. It is urgent to develop prefabricated treatment technology, and the guarantee of mechanical properties of the prefabricated UHPC-post-cast NC interface is the key problem. Through the oblique shear test, combined with the XTDIC full-field strain monitoring system, the failure process and failure mode of UHPC-NC specimens were studied and analyzed under different interface keyway numbers (0, 1, 2, and 3), interface agents (meshless interface agent, cement slurry, silica fume modified cement slurry, modified cement slurry mesh, cement slurry, and expansion agent), and NC pouring grades (C30, C35, C40, and C50), as well as the influencing factors of shear strength, shear stiffness, and the slip model of the bonding interface. The results show that there are four typical failure modes in UHPC-NC under compression and shear, including complete interface failure (Class A), interface failure + NC shear failure (Class B), NC compression failure (Class C), and interface failure + NC compression failure + NC slip failure in the keyway (Class D). The complete interface failure type (Type A) without keyway treatment has sudden failure, and the keyway has the ability to disperse load and limit interface slip. The principal strain decreases along the normal sides of the interface, and the influence range of UHPC and NC sides is about 16.2 mm and 17.5 mm, respectively. In practice, the thinnest part of the treatment structure should not be less than 2 cm. The shear strength of the prefabricated UHPC-post-pouring NC interface is generally low, and the maximum shear strength of 13.9 MPa obtained by the test is still lower than the recommended value of 14–21 MPa of ACI 546.3R-14. In treatment design, the interface shear reinforcement can be introduced to ensure the cooperative bearing capacity. The shear strength of the prefabricated UHPC-post-poured NC interface is slightly affected by the interface agent and postpoured concrete grade and increases linearly with the increase in the number of keyways. When the number of keyways is equivalent to the roughness index, the relationship between the shear strength and the roughness is as follows: f s = 1.664 + 3.030 R z . Under the action of keyway, the interface slip of UHPC-NC can be simplified into four stages: the interface slip stage, the keyway strengthening stage, the shear yield stage, and the specimen failure stage. Based on this, a prefabricated UHPC-post-pouring NC interface slip model was proposed, and the experimental results of key parameters such as interface bond strength, stiffness, and slip amount at different stages were obtained by fitting. In the keyway strengthening stage, the shear stiffness increases linearly first and then tends to be stable with the increase in the number of keyways. The maximum shear stiffness is about 20 MPa/mm, and the maximum interfacial slip increases with the increase in the number of keyways, which improves the overall shear resistance. The results can be used in the design of a tunnel-fabricated treatment segment.

Interfacial bonding properties of styrene-butadiene rubber and ethylene vinyl acetate emulsion-modified OPC–CAC–G repair mortar

Inorganic repair materials such as ordinary Portland cement–calcium aluminate cement–gypsum (OPC–CAC–G), which consist of ordinary Portland cement, aluminate cement, and gypsum, have advantages of fast hardening, high early strengths, and minimal expansion; however, they also have the disadvantages of low bond strengths and weak interface areas, which often lead to repair failure. The interfacial bonding properties of repair materials can be improved by adding highly flexible polymers. In this study, the effects of styrene-butadiene rubber (SBR) and ethylene vinyl acetate (EVA) on the interfacial bonding properties of OPC–CAC–G bonding and the mechanism of the effect of the microstructure are examined using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results show that and EVA are both effective in improving the interfacial bond strength of OPC-CAC-G repair mortars. SBR is suitable for the modification of repair mortars with an optimum dose of 20%; EVA is suitable for the use as an interface agent on the surface of damaged concrete substrates with an optimum concentration of 40%.

External-Shell Oxygen Enabling the Local Environment Modulation of Unsaturated NbN3 for Efficient Electrosynthesis of Hydrogen Peroxide.

Single-atom catalysts with a tunable coordination structure have shown grand potential in flexibly altering the selectivity of oxygen reduction reaction (ORR) toward the desired pathway. However, rationally mediating the ORR pathway by modulating the local coordination number of the single-metal sites is still challenging. Herein, we prepare the Nb single-atom catalysts (SACs) with an external-shell oxygen-modulated unsaturated NbN3 site in carbon nitride and the NbN4 site anchored in nitrogen-doped carbon carriers, respectively. Compared with typical NbN4 moieties for 4e- ORR, the as-prepared NbN3 SACs exhibit excellent 2e- ORR activity in 0.1 M KOH, with the onset overpotential close to zero (9 mV) and the H2O2 selectivity above 95%, making it one of the state-of-the-art catalysts in the electrosynthesis of hydrogen peroxide. Density functional theory (DFT) theoretical calculations indicate the unsaturated Nb-N3 moieties and the adjacent oxygen groups optimize the interface bond strength of pivotal intermediates (OOH*) for producing H2O2, thus accelerating the 2e- ORR pathway. Our findings may provide a novel platform for developing SACs with high activity and tunable selectivity.

Deterioration of mechanical properties at the anchor-mortar interface considering the effect of two-phase corrosion

Factors in the environment may cause corrosion of the anchor rod and mortar, thus degrading the mechanical properties of the anchor rod-mortar interface and eventually leading to failure of the anchor structure. In this paper, a method is designed to accelerate the migration of corrosive ions (Cl-，SO42-) from solution to penetrate the mortar, resulting in the corrosion of both the mortar and the bolt. Taking corrosion of the steel bar as the control, the deterioration law for the interfacial anchor-mortar bond during two-phase corrosion was studied. The mechanical properties deteriorating mechanism of the anchor-mortar interface was revealed based on changes in the composition and amount of corrosion products and the damage extent of anchor rods and mortars. The test results showed that, in acidic environments, the rib height of the bolt decreased due to corrosion, which led to a decrease in the mechanical bite force of the interface. The needle and rod-shaped ettringite generated by the mortar during corrosion can destroy the internal structure of mortar, promote more corrosive solution to participate in the chemical reaction, and reduce the radial binding force on the steel bar. In an alkaline environment, corrosion of the rebar is slow. The plate ettringite formed by the mortar during corrosion provides a filling effect and delays the corrosion reaction of the rebar. Corrosion of the reinforcement and mortar results in deterioration of the interface bond strength between the bolt and mortar. Based on the test results, the current model of bond slip was modified to include deterioration of the anchor and mortar material properties and weakening of the restraining effect of the mortar. A model for the anchor-mortar bond-slip relationship was proposed and included corrosion of both materials. The results of this research will provide guidance for future studies of the failure mechanisms of anchorage structures and evaluations of the durability of anchored slopes.

Interface bond strength of engineered cementitious composites (ECC) in pavement applications

Interface bond strength of engineered cementitious composites (ECC) in pavement applications

Effects of simulated seawater on static and fatigue performance of GFRP bar–concrete bond

Due to their excellent resistance to chloride ions, glass-fiber-reinforced polymer (GFRP) bars are employed to replace steel bars in seawater–sea-sand concrete (SWSSC). The performance of the concrete beams reinforced with GFRP bars depends on the bond between GFRP bars and SWSSC, which is significantly influenced by the marine environment and fatigue loading. Thus, the present study uses pullout tests to investigate the effects of simulated seawater on the static and fatigue properties of the GFRP bar–concrete bond. The impacts of the immersion time, environmental temperature, concrete type, and fatigue loading level are examined. The static interfacial bond strength and the corresponding slip of GFRP bar–SWSSC and GFRP bar–river-sand concrete (RSC) composites increase with the immersion time and the environmental temperature. Coupling the immersion environment and fatigue loading does not affect the failure mode of the GFRP bar–SWSSC and GFRP bar–RSC composites. Fatigue loading eliminates the defects in the interface between the GFRP bar and concrete, and the effects of eliminating the interfacial defects lessen with the immersion time and the environmental temperature. The fatigue load controls the performance degradation of the interfacial bond between the GFRP bar and concrete under coupling fatigue loading and immersion in simulated seawater. Meanwhile, there is no difference in the bond strength of the GFRP bar–RSC and GFRP bar–SWSSC composites under coupling fatigue loading and immersion in seawater. Nevertheless, the GFRP bar–SWSSC composite offers better static bond stiffness than the GFRP bar–RSC composite.

Effects of Filler Properties on Fatigue Performance and Bond Strength of Asphalt Mastics

Mineral fillers are a vital part of asphalt mastic and mixtures that are known to have a major role in the mixtures’ performance. A better understanding of the effects of the filler properties on asphalt mastic is important to control the distresses of the asphalt mixtures. This study evaluates the effects of physical and chemical properties of filler on fatigue and bond strength of asphalt mastic. Twelve asphalt mastics are prepared in the laboratory using three types of asphalt and four types of fillers. A filler to binder ratio of 1 (by mass) is used for all mastic sample preparation in the laboratory. Rigden voids (RV), fineness modulus (FM), calcium oxide (CaO), and methylene blue value (MBV) are used as properties of the filler for characterizing the fillers. The fatigue cracking behavior of asphalt mastic is evaluated using linear amplitude sweep (LAS) test, and asphalt bond strength (ABS) test is used to evaluate the interfacial bond strength between aggregate samples and mastics. The results from LAS test showed that the rolling thin-film oven (RTFO) aged mastic with a high percentage of FM containing filler has a better fatigue life than RV, CaO, and MBV containing filler. For pressure aging vessel (PAV)-aged mastic, the overall test result indicated that the fatigue cracking resistance of mastic is dependent on the interaction between base asphalt binder and filler type. The failure criteria of the LAS test method is an important parameter to characterize the mastic properties. The LAS and ABS test methods reveal that mastics prepared with high MBV and low CaO containing filler have better bond strength and worst fatigue performance. The bond strength performance of the mastic prepared with high FM filler is worse than base asphalt. FM, MBV, and CaO are major filler properties that could influence the asphalt mastic’s fatigue and bond strength performance.

Debonding failure of continuously reinforced bonded concrete overlay at early ages

ABSTRACT The structural behaviour and debonding mechanism of continuously reinforced bonded concrete overlay (CRBCO) on deteriorated concrete pavements subjected to environmental loadings are evaluated analytically and experimentally. It is shown that the temperature gradient in concrete significantly affects the debonding potential at the interface between CRBCO and existing continuously reinforced concrete pavements (CRCPs) and that the normal stress at the interface is the dominant cause of debonding failure. The results of factorial experiment show that the debonding potential can be reduced by decreasing the elastic modulus, coefficient of thermal expansion (CTE) and thickness of CRBCO, and by increasing the interfacial bond strength.

Effect of Chlorhexidine on Immediate and Delayed Bond Strength between Resin and Dentin of Primary Teeth: A Systematic Review and Meta-Analysis.

Objectives: The purpose of this study was to systematically review the literature and use meta-analysis to investigate whether chlorhexidine (CHX) application after acid etching as an adjunct treatment has any influence on the immediate and delayed bond strength to primary dentin. Materials and Methods: In this review, PubMed, ISI (all data bases), Scopus and Cochrane were searched according to the selected keywords up to April 30, 2018. The full texts of all published articles that met our primary inclusion criteria were obtained. The studies were analyzed in two parts: in vitro studies that evaluated the effect of CHX application during the bonding procedures (application after acid etching) on immediate and delay dentin bond strength of resin-dentin interface. Results: The initial search yielded 214 publications, of which 8 were selected after thorough methodological assessment. None of the clinical studies fulfilled the eligibility criteria. Our results indicated that in comparison to the control group, CHX significantly reduced immediate resin-dentin bond strength (P=0.043). These values were increased after aging (P<0.001). Conclusion: Based on this invitroMeta-analysisCHX application, improveresin-dentin bond strength durability in primary teeth.

Nanoscale insights into the interfacial characteristics between calcium silicate hydrate and silica

The interfacial characteristics between cement paste and silica are far from being fully understood, especially from the nanoscale perspective. Herein, molecular models were used to provide comprehensive insights into the interfacial characteristics between calcium silicate hydrate (C-S-H, the main binding phase of cement paste) and silica. Chemically, various types of bonds existed at the interface, including H-bonds and Ca–O bonds, and proton (H+) exchange occurred between C-S-H and silica. An increase in the water content of C-S-H could depress the deprotonation of the Si-OH groups on the silica surface. Structurally, an atomic-level interfacial transition zone (ITZ) with a low density was identified, which was attributed to the rich presence of –OH groups at the C-S-H–silica interface. The water molecules and calcium ions in the ITZ diffused faster than those in the bulk C-S-H. Mechanically, the interfacial bond strength was inversely related to the water content of C-S-H, with the higher water content reducing the interfacial interactions. Under loading, the interfacial fracture underwent three stages: crack propagation, atomic chain bridging (responsible for the interfacial residual strength), and complete failure. These atomic-level findings provide hitherto unknown mechanisms of the interfacial interactions between cement paste and silica.

Interfacial bonding performance of textile reinforced ECC and seawater sea-sand concrete under a dry-wet environment

In order to promote the application of cementitious composites in the marine environment, it is crucial to clarify the interfacial bonding properties of cementitious composites to concrete. Therefore, the interfacial bonding performance of a new cementitious composite, textile reinforced ECC (TRE), to seawater sea-sand concrete (SWSSC) in a chloride salt dry-wet environment was investigated by single shear test. The interface behavior was evaluated from the failure modes, average bond strength, load-slip curves, and fracture energy of TRE-SWSSC interface. The main research factors included the erosion environment, the thickness of TRE composite, and the dry-wet cycles. The study showed that the failure mode of specimens with a small thickness of TRE composite are mainly the fracture and sliding of matrix in the free length of TRE. The failure pattern of the TRE-SWSSC interface with 20 mm thickness changed from the fracture and sliding of matrix in bond length of TRE to that in free length of TRE with the increase of dry-wet cycles. And the failure of specimens in immersion environment was interfacial peeling. The average bond strength of TRE-SWSSC interface increased with the thickness of TRE. After 270 days of environmental action, the interfacial average bond strength in the dry-wet environment was 15.94 % higher than that in the immersion environment. The load-slip curves were smoother for specimens with smaller TRE thickness, and the descending section of the load-slip curves became steeper with the increase of TRE thickness. The interfacial fracture energies of the specimens with different TRE thicknesses showed different growing trend with the dry-wet cycles. With the increase of the dry-wet cycles, the interfacial fracture energy of the specimens with a TRE thickness of 10 mm gradually increased, but the interfacial fracture energy of the specimens with a TRE thickness of 20 mm gradually decreased.

Effects of alloying elements on diamond/Cu interface properties based on first-principles calculations

Diamond/copper composites with high thermal conductivity and a variable thermal expansion coefficient are promising materials for thermal management applications. However, achieving the desired thermal conductivity of the composite material is difficult due to detachment or weak bonding between diamond and Cu. The interfacial properties of diamond/Cu composites can be improved using metal matrix alloying methods. In this study, we investigate the effects of alloying elements (B, Cr, Hf, Mo, Nb, Si, Ti, V, Zr) on the interfacial properties of diamond/Cu using first-principles calculations. Results showed that all alloying components could increase the interfacial bonding of diamond/Cu. Analysis of the electronic structure revealed that increased interfacial bonding strength after doping was the result of the stronger bonding of the alloying element atoms to the C atoms. The C atoms in the first layer of diamond at the interface formed wave peaks near the Fermi energy level after doping with B or Si atoms, facilitating electron–phonon interaction at the interface. The phonon properties of B4C and SiC were similar to those of diamond, which facilitated phonon–phonon coupling. B and Si were shown to be better alloying elements when interfacial bond strength and heat transfer were considered.

Bonding performance monitoring between CFRP and timber column interfaces based on piezoelectric ceramics

To address the problem that carbon fibre reinforced polymer (CFRP) composite material is not easy to directly measure the bond strength of the CFRP-timber column interface during the process of strengthening timber column, a real-time monitoring method of CFRP-timber interface bond strength based on piezoelectric ceramic active sensing is proposed to determine the interface bond strength directly from the structural response signal. A total of 15 specimens were designed for the active monitoring test and tensile test, and the monitoring signals at different enhancement times were compared and analysed using wavelet packets, power spectral density, and short-time Fourier transform, and it was found that the amplitude and power spectral density of the signals increased as the reinforcement time increased. The mapping relationship between wavelet packet energy and bond strength is obtained, providing a more efficient and robust way of monitoring the bond strength between CFRP and timber columns during reinforcement.

Investigating on Molding Process of Steel-polyurethane Flexible Composite Components and the Interfacial Bonding Strength

Investigating on Molding Process of Steel-polyurethane Flexible Composite Components and the Interfacial Bonding Strength

The interfacial reaction between diamond (100) surface and CuNi-based filler alloys containing Cr by first-principles calculations

Brazed diamond tools have the advantages of high holding strength for diamond abrasives, superior grinding performance, formability, etc. The elements used commonly in filler alloys such as Cr, Cu, and Ni have an important impact on the interfacial bond strength and diamond thermal damage. In this work, the interactions between Cu, Ni, and Cr of the filler alloy and the diamond (100) surface were investigated using first-principles calculations. The results indicated that the adsorption energy of Cu adsorbed on the diamond (100) surface was low, suggesting that C atoms are extremely difficult to dissolve into Cu-based filler alloys, which makes Cu-based filler alloys less wettable with diamond. While the adsorption energy of Ni adsorbed on the diamond (100) surface was greater, which may form Ni 3 C weak carbide. Therefore, Ni-based filler alloys are usually wettable with diamonds. However, Ni 3 C of poor stability may decompose C atoms at the interface, which may lead to greater corrosion of diamonds. The adsorption energy of Cr adsorbed on the diamond (100) surface was the highest among Cu, Ni, and Cr, while the co-adsorption of Cr and C can grow into stable carbides. With the extension of time, the carbides can grow to form continuous layers of carbides. The results are generally consistent with the experimental results. • Analysis of graphitization on diamond surfaces using first-principles calculations. • The co-adsorption and deposition processes of Cr and C were investigated, which provided the conditions for the formation of chromium carbides. • Interfacial reaction processes, such as C precipitation and carbides nucleation growth, were investigated at the atomic level using first-principles calculations.

Bond strength prediction of UHPC-NSC interface

The application of ultra-high-performance concrete (UHPC) on top of normal-strength concrete (NSC) is a practical rehabilitation approach to maintaining degraded and damaged concrete members. However, a successful repair operation and consequent adequate performance are very much dependent on the ability of the interface between UHPC and NSC to present a superior performance of bonding under various surface conditions. Consequently, predicting the strength of the bond at the interface joining the existing NSC and the newly placed overlaying UHPC - with sufficient certainty - has become a vital and required step in assessing and maintaining UHPC rehabilitated NSC structural elements. In this work, Artificial Neural Network (ANN as well as Gene Expression Programming (GEP methods are utilized to predict the bond strength between the overlaying UHPC and the substrate NSC using a comprehensive database set consisting of 264 experimental data points gathered from the literature. A parametric ANN analysis is performed to examine and assess the effect of each parameter on the interfacial bond strength. The following five factors are identified as key parameters through the GEP and ANN analyses: curing method, age of UHPC, the compressive strength of NSC, interfacial surface treatment, and moisture conditions. The developed ANN and GEP models have good accuracy and closer predictions of the bond strength of the slant shear test and the splitting tensile strength with root mean square error (RMSE) values of 5.0, 4.3, and coefficient of variation (COV) values of 37%, 24%, respectively.

Influence of bioceramic intracanal medication on the bond strength of bioceramic root canal sealer.

To investigate the influence of the remaining volume of a new intracanal medication based on bioceramic compounds on the bond strength (BS) and formation of an adhesive interface between calcium silicate-based and epoxy resin-based root canal sealers. For this purpose, the specimens were distributed according to the intracanal medication (n = 26): Bio-C Temp (BCT) and Ultracal XS (UXS). The roots were scanned in microCT, and after 7 days, the medication was removed. Then a new scan was performed to evaluate the volume of medication remaining. Subsequently, 40 specimens were redistributed into 2 subgroups (n = 10) and filled according to the sealer used: AH Plus (AHP) and Bio-C Sealer (BCS), to assess the bond strength by using the push-out test, and the adhesive interface by confocal laser fluorescence microscopy (CLSM) and scanning electron microscopy (SEM). The t test showed a smaller remainder of BCT (1.77 ± 0.86) compared with UXS (10.47 ± 5.78), irrespective of the root third evaluated. The BS showed that teeth with BCT + BCS had higher bond strength values (3.70 ± 1.22) when compared to the other groups: BCT + AHP (2.15 ± 1.07), UXS + BCS (3.18 ± 1.09) and UXS + AHP (2.11 ± 1.02) (p<0.001). The cervical third had higher BS when compared with the middle and apical thirds (p < 0.001), and higher number of adhesive failures. The adhesive interface in SEM and CLSM images showed better adaptation for the association between BCT + BCS. Intracanal medication and silicate-based endodontic sealer appeared to interact chemically by forming a biomineralizing layer, allowing for an increase in the bond strength and forming an adhesive interface between the materials, with no or less gap formation.

INTERFACIAL BOND STRENGTH BETWEEN MICRO-SYNTHETIC FIBER-REINFORCED PATCH REPAIR MORTAR AND CONCRETE SUBSTRATE BASED ON PUSH-OFF TEST

A micro synthetic fiber-reinforced mortar has been developed as a patch repair material. The bond strength of this material is a crucial parameter for successful repair applications. The state of stress occurring at the interfacial plane between the repair material and the concrete substrate influences the bond strength requirements of patch repair material. Therefore, bond strength envelope criteria should be established using, among others, the interfacial adhesion and friction coefficient parameters. This research aims to determine the composite’s interfacial bond strength parameters (adhesion and friction coefficient) between micro-synthetic fiber-reinforced patch repair mortar (MSFRPRM) and concrete substrate by push-off tests. At this stage, the smooth joint texture limits the investigation. The fiber volume fraction and age of repair are considered. The tests were conducted at the age of 1, 3, 7, and 28 days. In addition to the laboratory experiment, this research used ATENA Science GiD to numerically simulate the push-off test and study the influence of the fiber volume on the adhesion and friction coefficient. The results show that at a fiber volume of 0.06%, the adhesion and friction coefficients increase from 1.15 to 2.33 MPa and 0.74 to 0.85, respectively, corresponding to age. Numerical simulation indicates that the maximum adhesion and friction coefficient occurs at the fiber volume fraction of 0.06%. Thus, the overall simulation results can be used in the future as a parameter to establish MSFRPRM and concrete substrate bond strength envelopes that will be useful for evaluating the suitability of MSFRPRM as repair materials under various states of stress. Keywords: Bond Strength, Concrete Patch Repair, Concrete Substrate, Micro-Synthetic Fiber-Reinforced Repair Mortar, Push-Off Test DOI： https://doi.org/10.35741/issn.0258-2724.58.1.20

Molecular insights into the interfacial adhesion mechanism between carbon nanotubes and epoxy resin.

In recent years, carbon nanotubes (CNTs) have garnered widespread attention and have been deemed the preferred option for the creation of epoxy composites, owing to their outstanding mechanical properties. Despite this, the interaction between pure CNTs and epoxy resin is primarily dependent on van der Waals forces and therefore, the interfacial forces are weak, making it challenging for effective load transfer. To enhance the mechanical properties of the composites, surface functionalization is often deemed a more favorable method for improving interfacial bond strength. This study employs molecular dynamics simulations to examine the interfacial bonding characteristics between functionalized CNTs and epoxy resin. The results demonstrate that functional group modification can significantly improve the interfacial adhesion between CNTs and epoxy resin, and the incorporation of functional groups can enhance the crosslinking degree of the epoxy resin at the interface. The hydrogen bond network established between the CNTs and epoxy resin after functional group modification, and the high stability of the bond cooperation, are factors contributing to the excellent interfacial performance.

Contribution of fiber–matrix interface enhancement on flexural properties of Ultra–high–performance concrete

Herein, the effect of steel fiber–matrix interface reinforcement on the macromechanical properties of ultra–high–performance concrete (UHPC) is studied. Two types of nano–SiO2–coated steel fibers are prepared using the sol–gel method. Single–fiber pull–out tests are conducted, and flexural and compression tests of UHPC with fiber contents of 1 vol%, 2 vol%, and 3 vol% are performed. The results reveal that the enhancement of interfacial adhesion significantly influences the macromechanical properties of UHPC. However, the granular nano–SiO2 on the surface of the modified steel fibers increases the roughness of the steel fiber and reduces the fluidity of fresh UHPC mixture. Analysis of the images of crack section reveals that appropriate vibration can reduce the influence of the steel fiber surface roughness on the distribution of fibers in UHPC. A flexural load–deflection response model for UHPC that considers steel fiber–matrix interface bond strength and fiber orientation is established.