Quantification of the tyre-track resistance of coloured asphalt mixtures

Abstract

Coloured asphalt pavements have been widely used for a variety of purposes. Passing vehicle tyres may lead to serious surface colour variations of the coloured pavements. However, the resistance to tyre tracks of the coloured asphalt mixtures has not been well addressed. This study investigated the tyre-track resistance capability and the colour recovery capability of the red asphalt mixture specimen fabricated in the laboratory. An acrylic resin seal coat was applied to the right half of the specimen for comparison. The RGB colour values of selected spots on the specimen were acquired at three stages: (1) before the wheel test, (2) after the wheel test, and (3) after washing with water and air dry. Two indices, tyre-track residual rates (Tr) and original-colour loss rate (Lr), were established based on the acquired RGB values in order to quantify the colour variations when the specimen experienced the three stages. The test and analysis results showed that both Tr and Lr could reach approximately 20% after 1000 load repetitions, which indicated that the black tyre tracks were prone to leave on the coloured asphalt mixture. The acrylic resin seal coat successfully protected the coloured asphalt mixture from the tyre tracks, which was demonstrated by the fact that the average Tr and Lr of the left half of the specimen without the seal coat almost doubled those of the right half with the seal coat. Tyre tracks left on the coloured asphalt mixture could be partially removed by washing with water. This method reduced the average Tr and Lr of the right half of the specimen with the seal coat by around 50%, which illustrated the excellent colour recovery capability of the seal coat. These findings are currently used by contractors to construct coloured asphalt pavements in a city park in Wuhan, China.