Abstract
This paper aims to evaluate the influence of the microwave heating time on the self-healing properties of fibre-reinforced asphalt mixtures. To this purpose, self-healing properties of dense asphalt mixtures with four different percentages of steel wool fibres were evaluated as the three-point bending strength before and after healing via microwave heating at four different heating times. Furthermore, the thermal behaviour of asphalt mixtures during microwave heating was also evaluated. With the aim of quantifying the efficiency of the repair process, ten damage-healing cycles were done in the test samples. In addition, self-healing results were compared with the fibre spatial distribution inside asphalt samples evaluated by CT-scans. Crack-size change on asphalt samples during healing cycles was also evaluated through optical microscopy. It was found that the heating time is the most influential variable on the healing level reached by the asphalt mixtures tested by microwave radiation. CT-Scans results proved that fibre spatial distribution into the asphalt mixtures play an important role in the asphalt healing level. Finally, it was concluded that 40 s was the optimum heating time to reach the highest healing levels with the lowest damage on the asphalt samples, and that heating times over 30 s can seal the cracks, thus achieving the self-healing of asphalt mixtures via microwave heating.
Highlights
Asphalt mixtures are composite materials made of aggregates and bitumen
Regarding to heating of asphalt mixtures, it can be observed that the surface temperature of the samples (Tmax in Table 2) increased with the increase of the microwave heating time, and that this temperature was higher in samples with higher fibres contents
This paper has studied the effect of the microwave heating time on the self-healing properties of
Summary
Asphalt mixtures are composite materials made of aggregates and bitumen. They are widely used in the pavement industry around the world. Mechanical resistance and durability of asphalt mixtures can be reduced due to their permanent exposure to traffic loading and environmental conditions [1]. With the aim of improving the behaviour of flexible pavements against these factors, different types of fibres can be added to the asphalt mixtures [5], such as: cellulose and mineral fibres [6]; polymeric fibres like polypropylene and polyester [7]; and steel wool and other waste fibres [8]. Due to the higher tensile strength of metallic fibres compared with asphalt mixtures they can improve the tensile resistance and cohesive force when added to the mixture [5]
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