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In this study, we investigate the potential of cold atmospheric plasma (CAP) as a non-contact excitation device, comparing its performance with an ultrasound transmitter. Utilizing a scanning Laser Doppler Vibrometer (LDV), we visualize the acoustic wavefront generated by a CAP probe and an ultrasound sensor within a designated 50 mm × 50 mm area in front of each probe. Our focus lies in assessing the applicability of a CAP probe for exciting a small polymethyl methacrylate (PMMA) sample. By adjusting the dimensions of the sample to resonate at the excitation frequency of the probe, we can achieve high vibrational velocities, enabling further mechanical analysis. In contrast with traditional vibration excitation techniques such as electrodynamical shakers and hammer impact excitation, a plasma probe can offer distinct advantages without altering the structure's dynamics since it is contactless. Furthermore, in comparison with laser excitation, plasma excitation provides a higher power level. Additionally, while pressurized air systems are applicable for limited low frequencies, plasma probes can perform at higher frequencies. Our findings in this study suggest that CAP is comparable with acoustic excitation, indicating its potential as an effective mechanical excitation method. [ABSTRACT FROM AUTHOR]

Fatigue resistance is of paramount importance for bituminous materials and so it is the effect of applying rest periods, as this is a more realistic representation of the traffic loading. To this end, to evaluate the healing potential, storage rest periods were introduced during a series of fatigue tests. In this study, the healing investigation was performed on the asphalt and mortar scale, aiming to assess the effect of reclaimed asphalt binder (RAB) on the healing potential. For the mortars, the healing indices derived under different damage levels and rest periods were modelled into a healing master curve, describing the healing index as a function of damage level and rest time. The asphalt tests revealed that the mixtures containing RAB showed higher healing potential compared to the control mix, attributed mainly to the existence of a softer blend as a result of partial blending. Furthermore, chemical indicators were considered to assess the healing potential of the binder blends and compared to the results of the healing tests. For the mortars, the 70% RAB samples showed the lowest healing potential, reflecting the full effect of very high RAB content, when the RAB is fully blended with the virgin binder. [ABSTRACT FROM AUTHOR]

The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack formation and propagation in asphalt pavements and healing of these cracks during the rest periods. The healing effect in asphalt mixtures has been observed and verified by many researchers and different methods exist to evaluate this phenomenon. However, current methods are still inadequate to fully observe and quantify the healing phenomenon in asphalt mixtures. In this study, a digital image correlation (DIC) method is used to calculate the strain map on the surface of cylindrical asphalt specimens during the indirect tensile fatigue test. This strain map is used to detect the location of crack initiations and development of the microcracks during the experiments. Next, the specimens are unloaded and the temperature of the climate chamber is increased to 60 °C for 18 h to investigate the healing phenomenon on the surface of the specimens. It is observed that the strain reduces near the microcrack areas especially at the tip of the microcracks. Furthermore, using DIC it is possible to observe the healing rate and the minimum time required to heal the microcracks on the surface of the specimens. [ABSTRACT FROM AUTHOR]

In this article, we report the use of a Confocal Laser Scanning Microscope (CLSM) to apply a qualitative assessment of atmospheric corrosion on steel samples. From the CLSM, we obtain high-resolution images, together with a 3D heightmap. The performance of four different segmentation algorithms that use the high-resolution images as input is qualitatively assessed and discussed. A novel 3D segmentation algorithm based on the shape index is presented and compared to the 2D segmentation algorithms. From this analysis, we conclude that there is a significant difference in performance between the 2D segmentation algorithms and that the 3D method can be an added value to the detection of corrosion. [ABSTRACT FROM AUTHOR]

Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko's beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and to form their master curve. The master curve plotted by this method is compared with the master curve obtained from the standard four-point bending test, and it is concluded that the proposed method is able to produce a master curve similar to the master curve of the standard method. Therefore, the proposed method has the potential to replace the standard stiffness tests. Furthermore, the standard stiffness methods usually conduct experiments up to the maximum frequency of 30 Hz. However, the proposed method can provide accurate complex modulus at high frequencies. This makes an accurate comparison between the properties of the asphalt mixtures in high frequencies and the development of more accurate theoretical models for simulation of specimens possible. [ABSTRACT FROM AUTHOR]

Featured Application: In this paper waste bottom ash from a thermal power station was treated with lime and sand. This improves certain material characteristics leading to a potential use in a subbase in road construction. Industrial waste causes environmental, economic, and social problems. In Morocco, the Jorf Lasfar Thermal Power Station produces two types of coal ash with enormous quantities: fly ash (FA) and Bottom ash (BA). FA is recovered in cement while BA is stored in landfills. To reduce the effects of BA disposal in landfills, several experimental studies have tested the possibility of their recovery in the road construction, especially as a subbase. In the first phase of this study, the BA underwent a physicochemical and geotechnical characterization. The results obtained show that the BA should be treated to improve its mechanical properties. The most commonly used materials are lime and cement. In the selected low-cost treatment, which is the subject of the second phase of the study, lime is used to improve the low pozzolanicity of BA while calcarenite sand is used to increase the compactness. Several mixtures containing BA, lime, and calcarenite sand were prepared. Each of these mixtures was compacted in modified Proctor molds and then subjected to a series of tests to study the following characteristics: compressive strength, dry and wet California Bearing Ratio (CBR), dry density and swelling. The composition of each mixture was based on an experimental design approach. The results show that the values of the compressive strength, the dry density, and the CBR index have increased after treatment, potentially leading to a valorization of the treated BA for use in a subbase. [ABSTRACT FROM AUTHOR]

The need for stable, chemical resistant and conductive materials is on the rise in recent times. Graphene shows promising electrical conductivity and chemical stability, but the production of a continual, conductive layer is limited and expensive. Silver nanowires (AgNWs) are both conducive and economically viable, but they are sensitive to water and oxygen. In this study, graphene oxide (GO) and AgNWs were synthesized and combined in different mass ratios (3:1, 2.5:1.5, and 1:1) to obtain chemically stable composites with improved electrical properties. Composites were reduced using ascorbic acid. With the increase of AgNWs to GO mass ratio, the surface of the free-standing composite film improved: the root mean square roughness was lowered from 376 nm for GO to 168 nm for the composite with the mass ratio of GO:AgNWs 1:1, while the sheet resistance was lowered from 146 × 106 Ω/□ to 4 Ω/□. For the first time, the effects of gamma irradiation on the structure of the composites were studied. Doses of 15, 25, and 35 kGy were applied. [Display omitted] • Graphene oxide (GO) and silver nanowires (AgNWs) were used to produce composites. • Larger mass of AgNWs in composites reduced surface roughness and sheet resistance. • Chemical reduction increased electrical conductivity, but surface roughness too. • GO was weak while GO-AgNWs composite was more elastic and stronger. • Gamma irradiation improved the electrical properties of the nanocomposites. [ABSTRACT FROM AUTHOR]