Pull-off Test Research Articles

Impact of Freeze–Thaw Cycling on the Mechanical and Durability Properties of Rapid Repair-Based Overlay Systems

Rapid repair materials (RRMs) have been used in concrete overlay systems to rehabilitate infrastructure for many years. The bond performance between RRMs and a concrete substrate is crucial for maintaining the desired performance and can deteriorate due to freeze–thaw action. In the case of partial depth repairs (PDRs), the mechanical and durability properties at the interface between the substrate and repair materials have not been thoroughly studied resulting in frequent failures. There is limited research on the freeze–thaw durability of RRM overlay–substrate interface, and no standardized test methods exist for evaluating the performance under freeze–thaw cycling. The proposed experimental procedure combines freeze–thaw cycling of an overlay–substrate specimen with pull-off testing of the overlay. Three RRM overlay systems were used consisting of calcium sulfoaluminate cement and ordinary Portland cement (PC), and a ternary blend of PC, calcium aluminate cement, and calcium sulfate cement. A correlation between tensile bond strength and fundamental transverse frequency in composite specimens was observed, and the results demonstrated that RRMs can maintain robust adhesion following 300 cycles of freeze–thaw exposure. Furthermore, the employed testing methodology elicited bond-only failures, underscoring the necessity for continued investigation into optimal conditioning intervals and substrate integrity to enhance the durability of repair systems.

Effect of Water Immersion and Freeze-Thaw Cycles on Pull-off Strength of FRP Epoxy Bonded on Concrete: An experimental study

The durability and performance of Fiber Reinforced Polymer (FRP) composites for strengthening reinforced concrete structures under various environmental conditions are critical for their long-term efficacy. This study investigates the effects of water immersion and freeze-thaw cycles on the pull-off strength of epoxy-bonded FRP concrete slabs, simulating conditions typical for waterfront structures such as piles, beams, and decks. Concrete slabs, fabricated to EN 1766 standards, were reinforced with Basalt (BFRP), Glass (GFRP), and Carbon Fiber Reinforced Polymer (CFRP) sheets using Duratek® AV21 epoxy resin. The samples were conditioned in a controlled laboratory environment (23±2°C, 50±5% RH) for 24 hours before being subjected to water immersion and freeze-thaw cycling tests. Pull-off tests, conducted per EN 1542, revealed cohesive failures in the concrete substrate. The average pull-off strength for the control samples was 3.26 N/mm² for concrete and 3.97 N/mm² for epoxy resin. Water immersion results showed a slight decrease in pull-off strength for CFRP and GFRP, by 9% and 2% respectively, while BFRP exhibited a 14% increase. Freeze-thaw cycling led to increased pull-off strength across all FRP types: 7% for GFRP, 7.3% for BFRP, and 3.75% for CFRP. The findings indicate that water immersion and freeze-thaw conditions have a marginal impact on the pull-off strength of FRP-reinforced concrete. Despite the environmental exposure, all test results remained above the required pull-off strength of 2.5 MPa, demonstrating the robustness of the FRP-concrete bond. The study supports the use of FRP composites for structural reinforcement in harsh environments, highlighting their resilience under adverse conditions. Further research is recommended to explore long-term performance and additional environmental factors to ensure comprehensive durability assessments of FRP-reinforced systems.

Investigation of Chloride Salt Erosion on Asphalt Binders and Mixtures: Performance Evaluation and Correlation Analysis.

Asphalt pavement, widely utilized in transportation infrastructure due to its favourable properties, faces significant degradation from chloride salt erosion in coastal areas and winter deicing regions. In this study, two commonly used asphalt binders, 70# base asphalt and SBS (Styrene-Butadiene-Styrene)-modified asphalt, were utilized to study the chloride salt erosion effect on asphalt pavement by immersing materials in laboratory-prepared chloride salt solutions. The conventional properties and adhesion of asphalt were assessed using penetration, softening point, ductility, and pull-off tests, while Fourier transform infrared spectroscopy (FTIR) elucidated the erosion mechanism. The Marshall stability test, freeze-thaw splitting test, and Cantabro test were applied to study the effects of chloride exposure on the strength, water stability, and structural integrity of the asphalt mixture. Finally, the grey correlation analysis was employed to assess the impact of chloride salt erosion on the performance of asphalt binders and mixtures. The findings highlight that chloride salt erosion reduces penetration and ductility in both types of asphalt binders, raises the softening point, and weakens asphalt-aggregate adhesion, confirmed as a primarily physical effect by FTIR analysis. Asphalt mixtures showed decreased strength and water stability, intensifying these impacts at higher chloride concentrations and longer erosion duration. SBS-modified asphalt binders and mixtures exhibited greater resistance to chloride salt erosion, particularly in adhesion, as demonstrated by the Cantabro and pull-out tests. Grey relational analysis revealed that erosion duration is the most influential factor, with TSR and softening point emerging as the most responsive indicators of chloride-induced changes. These findings offer critical insights for practice, providing evidence-based guidance for designing and constructing asphalt pavements in environments with high chloride levels.

Study on the effect of acid rain erosion on the adhesion properties of asphalt-aggregate interface

ABSTRACT This study investigates the impact of acid rain on the adhesion properties of the asphalt-aggregate interface in asphalt mixtures. By employing surface-free energy theory and the sessile drop method to analyse wetting behaviour, the adhesion work and energy indicator ER were calculated. The interface adhesion characteristics were evaluated using the water boiling method and pull-off tests. It was found that acid rain significantly reduces the interface adhesion work, which worsens with increasing erosion cycles and concentrations. The ER value decreases, adhesion becomes poorer and the lower the pH value, the more severe the damage. The acidic environment accelerates the stripping of the asphalt film and weakens the interactive forces. Acid rain increases the polarity between asphalt and aggregates, reducing the adhesion energy and leading to failure. SBS-modified asphalt exhibits better adhesion performance than 70# petroleum asphalt.

Titanate–polyurethane–chitosan ternary nanocomposite as an efficient coating for steel against corrosion

In this study, a titanate–polyurethane–chitosan ternary nanocomposite was prepared by physical mixing. Sodium titanate nanotubes (Na-TNTs) were prepared by the hydrothermal method, and chitosan was extracted from shrimp shell. Na-TNTs were mixed with polyurethane (PU) of different ratios by weight, and chitosan was added after optimization. All of the nanocomposite samples were characterized by field-emission scanning electron microscopy (FESEM), and the mechanical properties were investigated by abrasion, adhesion pull-off, impact resistance, and T-bending tests. The anticorrosion ability was tested by the salt spray method. The obtained results revealed that the binary composite of PU and 1.5% Na-TNTs exhibited remarkable anticorrosion activity among all the binary composites where the disbonded area 5% compared to blank PU 19% and adhesion 5.1 MPa compared to blank 3.5 MPa, while the ternary composite containing 4% chitosan exhibited the best anticorrosion activity where the disbonded area 2% and also exhibit better adhesion 7.9 MPa.

Interaction Between Concrete and FRP Laminate in Structural Members Composed of Reused Wind Turbine Blades Filled with Concrete.

The lifecycle of wind turbine blades is around 20-25 years. This makes studies on the reuse of dismantled blades an urgent need for our generation; however, their recycling is very difficult due to the specific makeup of their composite material. In this study, the authors determined a concept for the reuse of turbine blade sections filled with concrete for geotechnical structures, retaining the walls, piles, or parts of their foundations. Working out detailed structural solutions to the above problem should be preceded by the identification of material parameters. In particular, getting to know the interface stress-strain characteristics is crucial. Therefore, this research focuses on the cooperation between recycled FRP composites and concrete in load-carrying, including experiments and numerical analyses. Regarding the two types of destructive stress, which may occur at the interface under both compression and bending, two types of tests were executed: the 'push-out test', modelling the interface's answer to shear stress, and the 'pull-off test', demonstrating the interface's reaction to normal stress. Additionally, the strength parameters of the materials used were tested. The numerical model for the push-out process was calibrated on the basis of the tests, and this way the shear bond strength and the coefficient of friction between the concrete and the recycled FRP laminate were assessed.

Fast and Nondestructive Mechanical Characterization of Thermally Sprayed and Laser Cladded Coatings: Automated Surface Acoustic Wave Spectroscopy as a New Tool for Quality Control and Research

AbstractLaser-induced surface acoustic wave spectroscopy (LISAWS) allows quick and nondestructive evaluation of the elastic properties such as the Young’s modulus of coatings, surfaces and surface-near bulk materials. Furthermore, the mechanical weakening due to cracks and pores can be evaluated, as they influence the propagation of surface waves as well. This makes the method a fast, accurate and versatile tool for surface characterization, and it is increasingly used in research and development, and quality control. The short measurement time of the LISAWS method allows the time-efficient distribution of the effective Young's modulus over the coated surface to be determined. For this purpose, an industrial LAwave measurement system was automated to allow for processing of a larger number of samples and fast mappings. The investigated coating materials were thermally sprayed Al2O3 insulation coatings and WC-reinforced 316L steel coatings on brake disks produced by laser cladding, respectively. For the Al2O3 coatings, the correlation between the Young's modulus and its areal distribution is shown for different process parameters, such as spray gun movement direction or spray distance, and compared with results from pull-off tests. For the WC/316L-coated brake disks, the distribution of the wave velocity over the coated surfaces or the two coated sides of different disks with varying coating qualities is used to assess the coating quality and homogeneity.

Influence of Laser Micro-Texturing and Plasma Treatment on Adhesive Bonding Properties of WC-Co Carbides with Steel.

This article presents research on advanced surface preparation methods for sintered carbides (WC-Co, grade B2) commonly used in the tool industry, particularly in the context of bonding these materials with C45 steel using adhesives. Sintered carbides are widely used due to their high hardness, wear resistance, and good ductility, making them ideal for manufacturing tools operating in harsh conditions. Traditional bonding methods, such as brazing and welding, often result in stresses and cracks. Adhesive bonding has therefore emerged as an effective alternative to mitigate these challenges. The research focuses on comparing the results obtained through modern surface treatment techniques, such as laser micro-texturing and plasma treatment, with traditional methods like grinding, abrasive blasting, and electrolytic etching. The influence of these methods on adhesion properties and the strength of adhesive bonds was evaluated through mechanical tests, including static shear and pull-off tests. An approximately 50% increase in the mechanical strength of adhesive joints was observed for surfaces treated with low-temperature plasma (operating voltage: 18 kV, flow of gasses: 20 l/min., treatment time: 60 s) and laser micro-texturing (infrared fiber laser, wavelength: 1064 nm (±5 nm), power: 20 W), as compared to mechanical grinding. The shear strength of the adhesive joints was equal to 32 MPa and 30 MPa on average in the case of treatment with low-temperature plasma made of helium and argon, respectively. The highest strength of an adhesive joint was equal to 34.5 MPa on average in the case of laser micro-texturing.

MICRO-MESO CHARACTERIZATION OF PREFABRICATED CONCRETE-CLT ADHESIVE JOINTS

This study evaluates the use of five commercially available epoxy adhesives (EAs), from low to high cost, as a connection alternative of timber-concrete composites (TCCs) using cross-laminated timber (CLT) and medium-strength precast concrete (25MPa). Five alternative EAs were initially evaluated via pull-off tests to determine the adhesive strength of the interface CLT/concrete, with average results varying from 0.6MPa to 3.6MPa. Subsequently, optical and scanning electron microscopy analyses were implemented to assess the microstructure of post-tested TCC specimens, finding that usually the CLT/concrete interface was not fully glued by the EAs and that there was a positive correlation between the penetration of each EA with the corresponding tension strength of the TCCs. Then, the three EAs with the largest adhesive strengths were further tested by small double-shear (SDS) tests evaluating their shear strength and deformation, as well as damage evolution and failure modes, which were obtained using digital image correlation. The SDS test average results ranged from 2.4MPa to 8.8MPa, and the EA with the best behavior was not the one with the highest tensile strength, but rather with the highest EA penetration into concrete, demonstrating that this property highly positively impacted the shear strength of TCCs. Finally, cost/benefit analyses were obtained, and interestingly, the EA with the best adhesive/shear performance was not the most expensive alternative, opening the discussion that, even though mostly expensive EAs have been used in TCCs, the option of technically valid and low-cost EA is feasible.

Amino-grafted Ti3C2 MXene nano-sheets doped with zinc-phytic acid complex; An advance 2D-nanocarrier toward improving epoxy coating smart anti-corrosion performance

MXene's unique structure and properties endow it with new applications in corrosion studies, drawing the attention of material scientists. In the present study, the MXene sheets modified by 3-Aminopropyltriethoxysilane (APTES) were utilized as carriers of zinc cations and phytic acid (Ph) (F-M@Zn-Ph) and then introduced into the epoxy coating for smart anti-corrosion application. Characterization tests such as X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FE-SEM), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and zeta potential were carried out to validate the synthesis of F-M@Zn-Ph. The fabricated composite coatings' protective, and adhesion properties were studied by EIS, cathodic disbondment (CDT), salt spray (SST), and pull-off tests. Solution phase studies exhibited that the F-M@Zn-Ph sample inhibited mild steel corrosion up to 91 % during 48 h of immersion. Investigating the scratched coatings showed that the total resistance (RT) value for the F-M@Zn-Ph/EP sample enhanced by about 58 % compared to the Blank/EP during 48 h of immersion which denotes the self-healing properties of the coating. EIS results of the intact F-M@Zn-Ph/EP sample displayed the highest log|Z|0.01Hz value (10.83 Ω cm2) after 14 weeks of immersion. Along with the barrier properties improvement, the F-M@Zn-Ph/EP coating showed a small adhesion loss of 4 %.

Boosting the efficiency of water-based intumescent coatings with fumed silica nanoparticles: A synergistic approach

This research looked into how well the water-based intumescent coating (WBIC) with fumed silica nanoparticles (FSNs) worked to keep steel parts safe from cellulose fire. The adhesion strength of the coatings was evaluated using the pull-off test according to ASTM D4541. Flame retardant performance was studied by a lab-scale simulated big panel test at 950 °C for 1 hour. Thermogravimetric analysis (TGA) and the UL94 test were used to study the thermal stability and burning characteristics of the WBIC. An FESEM, an X-ray diffraction (XRD), and a Fourier transform infrared spectroscopy (FTIR) analysis were used to fully characterize the residual chars of the optimized formulation and the control coating. Adhesion strength test results showed that adding 0.2 wt% of FSNs increased paint adhesion strength from 0 to 2 MPa and changed the failure mode from adhesive to cohesive. It was found that at the optimal FSNs content (0.2 wt% SiO2), the lowest steel backside temperature of 181℃ after 1 hour of fire testing was obtained. Adding fumed silica from 0.1 to 0.3 wt% has resulted in a reduction of the char layer's intumescent factor by 5.3–42.1 %. The SEM images indicated that fumed silica enhanced the formation of dense, crack-free char layers with small pore sizes. Thermogravimetric analysis revealed that intumescent coatings' thermal stability and residual weight increased with the addition of 0.2 wt% fumed silica. Additionally, the coating contained 0.2 wt% SiO2 passed the V0 rating in the UL94 vertical burning test. The XRD and FTIR tests also revealed that the leftover chars had rutile titanium oxide, aluminum metaphosphate, and titanium pyrophosphate in them. At high temperatures, these ceramic compounds exhibit thermal insulation performance, preventing heat and oxygen penetration into the char layer.

Influences of thickness and coupled water-temperature-load effects on adhesion/cohesion properties of mastic and mortar in porous asphalt mixtures

ABSTRACT The thickness of the mastic and mortar is randomly distributed in porous asphalt mixtures and has a critical influence on the adhesion/cohesion properties of the mastic and mortar. An advanced pull-off test, combined with a coupled effect tester, was designed to evaluate the adhesion/cohesion properties of mastic and mortar. Pull-off tensile strength (POTS) of mastic and mortar firstly increased then decreased with the increasing thickness of mastic and mortar. The failure mode of mastic changed from brittle adhesive failure to adhesive failure, while the failure mode of mortar changed from cohesive failure to adhesive failure with increasing thickness under dry conditions. However, adhesive failure was found in all thicknesses under coupled effects. As coupled effects increased, POTS and fracture energy of mastic and mortar prominently decreased. The failure modes of mastic and mortar changed from adhesive failure to cohesive failure with temperature increase. A water pressure of 0.2 MPa is critical where POTS dramatically decreases. With increasing coupled effect duration, failure modes of mastic changed from adhesive failure to brittle adhesive failure, while failure modes of mortar show brittle adhesive failure. High-viscosity modified asphalt greatly improved the POTS of mastic and mortar under dry and coupled effect conditions.

Multiscale characterisation on the adhesion and selective adsorption at bitumen–mineral interface

The adhesion between bitumen and minerals is essential for the durability of asphalt mixtures, influenced by bitumen composition and mineral structure. The chemical action theory suggests that polar components in bitumen are adsorbed onto the mineral surface, facilitating adhesion. In this study, environmental scanning electron microscopy with energy-dispersive X-ray (ESEM-EDS) is used to analyse bitumen–mineral interfaces at a microscopic level. Elemental analysis reveals selective adsorption of polar substances from bitumen onto the surfaces of four types of minerals. Results show that alkaline rocks (limestone and albite) have a higher adsorption capacity than acidic rocks (granite and quartz). Additionally, treating mineral surfaces with alkaline solutions enhances adsorption. The adhesion properties of bitumen to various minerals are evaluated using the pull-off test. The correlation between ESEM-EDS and pull-off tests demonstrates that the macroscopic adhesion of bitumen to minerals is linked to the microscopic selective adsorption of polar substances.

Study of the effect of N, N-diethyl hydroxyl amine/multi-layered graphene oxide hybrid on reducing cathodic delamination and increasing corrosion resistance of epoxy coating on steel substrate

In this study, a hybrid of multi-layered graphene oxide (MLGO) and oxygen absorbent corrosion inhibitor N, N-diethyl hydroxylamine (DEHA) was investigated. The nano hybrid was prepared in order to reduce the amount of cathodic delamination and increase the corrosion resistance of the epoxy coating. Epoxy coatings were prepared using the optimal percentage of 0.75 wt. % of the nano hybrid with different ratios between MLGO and DEHA like (1:2), (1:1) and (2:1). Mapping energy-dispersive X-ray spectroscopy, thermo gravimetry analysis and Fourier transform infrared (FT-IR) analysis indicated the uniform distribution of the inhibitor throughout the MLGO structure and the hydrogen bond interactions between them. The results of FT-IR spectroscopy: attenuated total reflectance test after six months confirmed the presence and stability of the inhibitor in the coating. Also, the results of 800 h of salt spray test and the long-term electrochemical impedance test after 7 months showed that the epoxy coating, containing MLGO-DEHA (1:2) had the highest corrosion resistance (2.54 × 107 Ω cm2) and the lowest cathodic delamination (15.9%). The results were also confirmed by cathodic delamination and pull-off adhesion tests.

Multi-scale investigation on water stability and anti-aging performance of granite asphalt mixture modified with composite anti-stripping agents

This study aims to improve the water damage resistance of granite asphalt mixtures. Five types of composite modified asphalt were developed using organic anti-stripping agents AMRIII, LQ-2020, ultrafine hydrated lime (HL), and SBS modified asphalt, and the effects of aging on the mechanical properties of these modified asphalt mixtures were evaluated. Fourier Transform Infrared Spectroscopy (FTIR), pull-off tests, and indirect tensile strength tests were the primary analytical methods used. The results indicated that the anti-stripping agents physically mixed with the SBS modified asphalt without any chemical reaction. The SBS modified asphalt containing anti-stripping agents exhibited better mechanical strength compared to unmodified SBS asphalt, with the combined use of multiple anti-stripping agents proving more effective than individual applications. At five freeze-thaw conditions without aging, the enhancement ratios of indirect tensile strength test results of single addition of AMRIII, LQ-2020, HL and combined addition of AMRIII/HL and LQ-2020/HL were 27.27 %, 36.36 %, 14.29 %, 50.91 % and 46.41 %, respectively. The addition of the anti-stripping agent enhanced the cohesive and adhesive energy. Aging reduced the water stability of the mixtures. Different modified asphalts have various sensitivity to aging, with the combination of AMRIII and HL showing the best aging resistance performance. Additionally, it was found that surface free energy had a strong correlation with water damage indicators, suggesting its potential for verifying the water stability of asphalt mixtures.

Development of Biodegradable and Recyclable FRLM Composites Incorporating Cork Aggregates for Sustainable Construction Practices.

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0-3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

Characterization of Interface Transition Zone in Asphalt Mixture Using Mechanical and Microscopic Methods.

An enormous surge in the pavement sector requires the evaluation of interface bonding in asphalt composite, since the assessment of bonding brings considerable cost savings. Microscopic and mechanical analyses were performed to study the status of the interface transition zone of four groups of asphalt mixtures, using thin-slice preparation to obtain asphalt mixture slices with a flat surface for microscopic analysis. The interface transition zones were characterized using good knowledge of blending or diffusion phenomena by conducting tests both at the micro and macro levels to determine mixture quality. Asphalt mixture components were observed using fluorescence microscopy imaging and evaluated by the gray value change law. Asphalt mixture groups, (virgin, recycled of 30% aged and 70% unaged, 6%, and 4% rejuvenator dosage mixtures) under the same process parameters, which are a mixing time of 270 s and a mixing temperature of 150 °C, been considered optimum for component fusion in a hot asphalt mixture were used. This study relied on the influence of morphology law, assessed through rutting tests for high temperature performance, semi-circular bending tests for low temperature performance, and pull-off tests for interface bonding strength. The relationship between interface transition zones and macro performance was studied. The self-developed pull-off method was a research innovation which can be used as an alternative to study interface transition zones in asphalt mixtures, and provides the necessary data needed with 3D surface failure mode calculations. The device measured the bonding strength of a single aggregate in distinct positions using the bitumen penetration test method. The main goals were to determine a correction factor, identify the appropriate alteration, and compute the actual fracture surface area. Using scanning electron microscopy for interface characterization and micro-morphologies of mortar transition zone, our analysis provides adequate knowledge about interface position and the components present. The applied approaches to characterize asphalt mixture interfaces proved workable and reliable, as all methods have similar trends with useful information to determine asphalt pavement quality.

The role of nanomaterials in enhancing adhesion properties between bitumen and aggregate particles

During production and construction stages of asphalt mixtures, rheology of bitumen must be set at certain level. In addition, the adhesion strength between bitumen and the aggregate particles should be high enough so that during the service life of the pavement, asphalt mixture can resist various distresses. There are different methods of controlling rheological properties of bitumen binders and increasing adhesion properties of asphalt mixtures. One of the most effective methods of modifying bitumen binders of asphalt mixtures is using nanomaterials. In this research, two bitumen types of 60/70 and 85/100 penetration grades, three aggregate types (limestone, siliceous, and granite) and four nanomaterials; namely, nanohydrated lime (NHL), nanosilica (NSiO2), nanolime (NCaCO3) and, nanoclay bentonite (NClay) were used at 2, 4, and 6 % of the weight of bitumen. X-ray diffraction and X-ray fluorescence tests were performed and, microscopic images of thin-sections of aggregates and asphalt mixtures were taken with the aim of evaluating petrographic properties of aggregates and bonding characteristics of the bitumen binders with aggregate particles. Physical and rheological properties of the nano-modified bitumen binders were evaluated, performing dynamic shear rheometer and rotational viscometer tests. Boiling water and pull-off tests were also carried out in order to investigate the coating ability and the adhesion strength that is performed at the aggregate surface in the interface with the bitumen binders. Digital images were analyzed using Digimizer Software. The results indicated that the addition of nanomaterials at certain optimal percentage, affected viscosity and improved rheological behavior of bitumen binders at different temperatures; and, increase adhesion properties of the bitumen coating the aggregate particles. Comparing the effects of different aggregates, it resulted that the binder coating limestone aggregates performed better than the siliceous and the granite aggregates. Adhesion and rheological properties of the 60/70 pen bitumen that was modified with nanomaterials were better than those of the pure 85/100 pen bitumen. Nano-modified binders at 4 % NHL, or 2 % NSiO2, or 4 % NCaCO3, or 4 % NClay exhibited the best behavior. Among these, nano-modified binders containing 4 % NHL resulted in better performance. Finally, correlation between adhesion and rheological behavior of mixes were adequate for nano-modified binders in order to improve charcteristics of asphalt mixes at mixing operation and construction stages.

Evaluation framework for bitumen-aggregate interfacial adhesion incorporating pull-off test and fluorescence tracing method

The interfacial adhesion between bitumen and aggregate is crucial to maintain the mechanical performance of asphalt pavement. Numerous indicators characterize the bonding ability of bitumen to aggregate; however, indicators based on limited conditions are used infrequently to effectively evaluate the interfacial adhesion between bitumen and aggregate. This study introduces a method to assess adhesion and moisture damage resistance at the bitumen-aggregate interface by combining the pull-off test with the fluorescence tracing method. The improved pull-off test considers different bitumen film thicknesses, ambient temperatures, material combinations, and moisture damage conditions, and the fluorescence tracing method and surface energy parameters are utilized to precisely detect the extent of bitumen adherence to the aggregate. The findings of this study are summarized as follows. (1) The bitumen stripping ratio characterizes the influence of ambient temperature and bitumen film thickness, and the pull-off strength/work quantifies the influence of ambient temperature and material combination. (2) The indicators derived from surface free energy theory exhibit lower sensitivity to material combinations compared with the pull-off performance indicators, with a coefficient of variation for both adhesion and stripping work of approximately 6 % compared to 14.29 %–70.13 % for the pull-off performance indicators. (3) The pull-off strength indicator dominates the pull-off performance evaluation, with the bitumen stripping ratio necessary at 0°C and pull-off work significant at 40°C to evaluate adhesive properties. In addition, the bitumen stripping ratio increment should be considered alongside pull-off strength loss ratio when estimating anti-moisture damage performance. (4) The fluorescence tracing method shows great potential in terms of enhancing the accuracy of bitumen stripping ratio detection in the pull-off test, with bitumen stripping ratio discrepancies at 0°C–40°C ranging from 0.98 % to 7.16 % for 70#-Limestone and 2.10–9.21 % for 70#-Granite. The methodology presented in this study represents a promising framework to determine the interfacial adhesive properties of asphalt mixtures with high accuracy.

New hybrid organic-inorganic conversion coating applied on the Al2024 substrate: Electrochemical, adhesion and surface study

Health problems caused by chromate conversion coatings promoted new research for discovering environmentally-friendly conversion coatings. In this study, Ti-Zr conversion coating (Ti-Zr) was deposited on the aluminum surface in the presence of nickel sulfate (Ti-Zr-Ni) and adipic acid (Ti-Zr-AA). Polarization and electrochemical impedance spectroscopy (EIS) measurements were employed to evaluate the anti-corrosion properties. Surface analysis was carried out using field emission scanning electron microscope (FE-SEM) and Atomic force microscopy (AFM). The results revealed that the Ti-Zr-Ni treatment inhibited the corrosion progression to a significant degree. The polarization resistance showed a significant increase (Rp= 58835 ohm.cm2) in Ti-Zr-Ni treatment in comparison with Ti-Zr conversion coating (Rp= 4450 ohm.cm2) and Ti-Zr-AA sample (Rp= 15058 ohm.cm2). The presence of Ni in the Ti-Zr composition, not just gave rise to the synergism but also played an important role as catalyst to further help avoiding further material degradation. Moreover, the presence of additives (nickel sulfate and adipic acid) enhanced the anti-corrosion resistance of coating by modification of surface morphology according to FE-SEM and AFM images. Anti-corrosion properties and adhesion strength of samples in a fully coated system were also investigated by EIS and pull-off tests, respectively, which revealed that the delamination of the Ti-Zr-Ni sample was lowest among others, and this sample showed better barrier performance even after 6 weeks of immersion in the corrosive environment.