Browsing by Author "Schlangen, E."
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Item Effect of fibres addition on the physical and mechanical properties of asphalt mixtures with crack-healing purposes by microwave radiation(2016) Norambuena-Contreras, J.; Serpell, R.; Valdés Vidal, G.; González, Álvaro; Schlangen, E.Microwave heating is regarded as a promising technique to promote crack-healing of asphalt mixtures reinforced with steel wool fibres. In addition to serving as a heat source when subject to microwave radiation, steel wool fibres are expected to affect the physical and mechanical properties of the asphalt pavements. However, it is not clear what this effect is, and what is the optimum fibre content that can provide effective crack-healing without having a negative impact on other relevant mixture properties. This paper reports a study of the steel wool fibres spatial distribution and their influence on the physical and mechanical properties of asphalt mixtures. For this purpose, five different dense asphalt mixtures, with the same aggregates gradation and bitumen content, but with five different percentages of steel wool fibres were manufactured. Then, their mechanical properties such as particle loss resistance in dry and wet conditions, and stiffness modulus and cracking resistance in Mode I of fracture at four different temperatures were evaluated. Samples of these mixtures were examined using Scanning Electron Microscopy and analysed using X-ray micro computed tomography to study the condition and distribution of fibres within the bitumen matrix. Microscopy results showed that fibres can be damaged during the mixing and compaction processes. A larger variability in the local distribution of fibres for mixtures incorporating a higher fibre content was observed in the tomography analysis, with presence of fibre clusters more than double of the average fibre content of the mixture. Although addition of fibres appears to reduce the bulk density of mixtures, according to tomography analysis differences in average porosity between samples were not statistically significant. Finally, it was confirmed that regardless of test temperature, steel wool fibres did not have a relevant influence on the improvement of particle loss resistance, stiffness modulus and cracking resistance of asphalt mixtures. (C) 2016 Elsevier Ltd. All rights reserved.Item Effect of RAP and fibers addition on asphalt mixtures with self-healing properties gained by microwave radiation heating(2017) González, Alvaro; Norambuena-Contreras, José; Storey, L.; Schlangen, E.Microwave heating of asphalt mixtures containing metal fibers is a promising technology for asphalt pavement rehabilitation. The main characteristic of these types of mixtures is that they have the ability to self-heal their cracks when external microwave heating is applied. Prior to this study, the assessment of crack-healing has only been conducted in mixtures prepared with virgin aggregate materials. This paper, however, presents results of research in which the effect of adding reclaimed asphalt pavement (RAP) and metallic fibers was studied. The volumetric properties of the mixtures indicated that the air voids content increased with the fiber content. The indirect tensile stiffness modulus of the mixtures increased with the addition of RAP. Clusters of fibers were found in the mixtures by means of CT-Scan analysis. The general effect of RAP addition was a decrease in the healing of the mixtures, and the effect of fibers was an increase in the healing. Overall, it is concluded that asphalt mixtures with RAP and metal fibers have the potential for crack-healing via microwave heating.Item Self-healing properties of recycled asphalt mixtures containing metal waste: An approach through microwave radiation heating(2018) González, Alvaro; Norambuena-Contreras, J.; Schlangen, E.The concept of self-healing asphalt mixtures by bitumen temperature increase has been used by researchers to create an asphalt mixture with crack-healing properties by microwave or induction heating. Metals, normally steel wool fibers (SWF), are added to asphalt mixtures prepared with virgin materials to absorb and conduct thermal energy. Metal shavings, a waste material from the metal industry, could be used to replace SWF. In addition, reclaimed asphalt pavement (RAP) could be added to these mixtures to make a more sustainable road material. This research aimed to evaluate the effect of adding metal shavings and RAP on the properties of asphalt mixtures with crack-healing capabilities by microwave heating. The research indicates that metal shavings have an irregular shape with widths larger than typical SWF used with asphalt self-healing purposes. The general effect of adding metal shavings was an improvement in the crack-healing of asphalt mixtures, while adding RAP to mixtures with metal shavings reduced the healing. The average surface temperature of the asphalt samples after microwave heating was higher than temperatures obtained by induction heating, indicating that shavings are more efficient when mixtures are heated by microwave radiation. CT scan analysis showed that shavings uniformly distribute in the mixture, and the addition of metal shavings increases the air voids. Overall, it is concluded that asphalt mixtures with RAP and waste metal shavings have the potential of being crack-healed by microwave heating.