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In the last years, the use of adhesive bonding is increasing as an alternative to traditional joining techniques due to their advantages such as ease of application, low weight and the good mechani...

Surface treatment technologies are constantly evolving. Increasingly, surface functionalisation is of major concern to lighten structures, improve product performance and reduce costs. To f...

The aggregate-binder bond is one of the main factors that affect the durability of asphalt mixtures. This can be investigated based on the energy required to fracture the adhesive bond between binder and aggregate. In this study, the effects of Sasobit, Rediset WMX and Rediset LQ on the adhesive bond strength of an aggregate-binder system is investigated using the pull-off test. Test data are compared with the nano-scale adhesion force determined using atomic force microscopy (AFM) using the PeakForce Quantitative Nanomechanical Mapping (PFQNM) method. The impact of warm mix additives, test temperature and binder grade on the practical work of fracture was investigated. It was found that Sasobit, Rediset WMX and Rediset LQ increased the practical work of fracture by 170%, 100% and 143%, respectively, for the aggregate-binder system produced using 40/60 Pen binder, and 70%, 25% and 50%, respectively, for the system produced using 100/150 Pen binder. The contribution of warm mix additives in improving the p...

The bonding that exists between the old concrete and the new concrete depends largely on the quality of substrate surface preparation. The accurate representation of substrate surface roughness can help determine very precisely the correct bonding behavior. In this work, an experimental investigation was carried out to quantify the normal concrete (NC) substrate roughness parameters and evaluate their relationship with the bonding performance of ultra high-performance fiber concrete (UHPFC), used as a repair material. The bond strength was quantified based on the results of the pull-off test, splitting cylinder tensile test, and the slant shear test. Three types of NC substrate surface preparation were used: as-cast (without surface preparation) as reference, wire-brushed, and sand-blasted (SB); the roughness of which was determined using an optical three-dimensional (3D) surface metrology device (Alicona Infinite Focus). It was observed from the result of the pull-off test that failure occurred in the su...

Surface free energy is a thermodynamic material property representing the work required to create new surfaces of unit area in a vacuum. Surface free energy has been used to quantify and screen both the cohesive bond energy of asphalt binders and the adhesive bond energy of asphalt binder–aggregate interfaces in wet and dry conditions. The bond energy is computed based on the surface free energies of the constituent materials. The total work of fracture is the cumulative effect of energies applied to the sample to create two new surfaces of unit area. These energies include the bond energy, calculated from surface free energy, dissipated plastic energy, and dissipated viscoelastic energy. This paper presents experimental results from a series of pull-off tests using asphalt binder-aggregate samples that demonstrate the relationship between bond energy and total work of fracture. In order to fully explore this relationship, temperature, loading rate, specimen geometry, and moisture content were varied.

In this study, a micro-pull-off testing machine is developed for reliable measurement of the adhesive force on micro- and nano-scale contact areas. The measuring scheme and working principle of the equipment are based on a reliable measurement technique that uses a commercial atomic force microscope (AFM). Adhesive-force-only measuring equipment is manufactured to overcome the inherent limitations of commercial AFMs, and an adhesive force map with a 1-μm interval is obtained around a micro-machined pattern of radius 2.25 μm. Use of the proposed technique and equipment could reduce deviations of the measured bond strength of an adhesive protein compared with those we have previously reported. Moreover, the proposed technique and equipment could be further developed to measure the binding force of even a single molecule if a nano-scale pattern is fabricated.

The bond strength between asphalt and aggregate plays a fundamental role in evaluating the moisture sensitivity of HMA Mixtures. In this study the effect of water on adhesive and cohesive properties of asphalt-aggregate systems was investigated using a modified version of the PATTI. The device was used to measure the pull-off strength on different asphalt-aggregate combinations and to evaluate the influence of water immersion at two different temperatures. In particular, six asphalt binders were employed in combination with two aggregate types, having different asphalt affinity. The effect of the aggregate surface temperature during specimen preparation was also tested. In the first phase of the study the within-laboratory repeatability of the test procedure was investigated. The results showed the PATTI test is able to evaluate with good precision the pull-off strength and that its repeatability depends on the failure type (adhesive or cohesive). In the second phase of the study a full factorial...

The force needed to pull a cylindrical stud from a soft elastomeric film depends on their elastic and geometric properties. For a rigid stud and a thick elastomeric film, the pull-off stress (σ) depends on the elastic modulus (E) of the film and the radius (a) of the stud as σ ∼ (E/a)1/2 (soft adhesion). However, when the film is very thin, the pull-off stress is significantly higher than the case with thick films, and its value depends on the elastic modulus and the thickness (h) of the film as σ ∼ (E/h)1/2 (hard adhesion). Here, we study the pull-off behavior of a soft cylindrical stud, one flat end of which is coated with a high modulus thin baseplate. As the flexural rigidity of this baseplate is varied, we observe the transition between the two types of adhesion. We present a simple physical interpretation of the problem, which could be of value in understanding various biofouling and adhesive situations.

The elastic solution to the shaft-loaded blister test (SLBT) was adopted to measure the applied strain energy release rate ( G ) of Kapton® pressure sensitive adhesive (PSA) tape bonded to a rigid substrate. The substrates used were either aluminum or Teflon®, a high-energy surface and low-energy surface, respectively. The values of G were calculated from three different equations: (1) load-based, (2) hybrid, and (3) displacement-based. An experimental compliance calibration was utilized to measure the film's effective tensile rigidity, ( Eh ) eff , the results of which are presented in an appendix. Plastic deformation at the contact area of the shaft tip and adhesive results in an overestimated displacement ( w 0 ) (relative to the elastic model), leading to disagreement among the values of G calculated. Estimation of the effective membrane stress in the film, ( N eff ), as well as the reasonable agreement between the value of ( Eh ) determined from a stress-strain experiment and the compliance calibrati...

It is now widely accepted that the inherent chemical resistance of concrete is limited and that the concrete surface needs additional barrier protection when exposed to aggressive environments. Unlike a metallic substrate, the concrete substrate is heterogeneous and porous in nature. Since adhesion is one of the important parameters influencing the durability of any surface coating, the influence of various characteristics of the concrete substrate on coating adhesion has been investigated. It is shown that the adhesion strength of a coating on a concrete substrate depends on the surface strength of the substrate itself. It was found that the cement content of the substrate has a significant influence on the surface strength. Surface strength, like compressive strength, is a function of the hardening process. There is a linear relationship between the surface strength and curing time. The adhesion strength of an acrylic paint coating was found to be slightly higher than the surface strength of the substra...

In this paper, we compare the practical adhesion measurements of alkyd, vinyl, epoxy, and polyurethane paints on cold-rolled steel using the pull-off and three-point flexure tests. It has been shown that (a) in the pull-off test, the ultimate load and ultimate strain values depend on the stud area. During trimming, cracks are created within the system which are responsible for a large decrease in the parameters measured. On the other hand, it is impossible to differentiate between the failure initiation and the failure propagation zones; (b) in the three-point flexure test, the area (W) subtended by the load/displacement curves corresponding to samples with and without stiffener does not depend on the bonded width or on the substrate compliance. After carrying out such a mechanical test, it is also possible to discriminate between failure initiation and failure propagation using appropriate tools for observation, such as scanning electron microscopy, and for analysis, such as electron microprobe analysis ...