Pavement performance of light-coloured composite-modified binder and mixture for tunnel applications

Traditional asphalt pavements absorb substantial light and lower luminance contrast inside tunnels, causing visual fatigue for drivers. Light-coloured pavements enhance light reflection to improve tunnel visual environments and traffic safety. This study prepares a light-coloured composite-modified binder using naphthenic oil, C9 resin, SBS and EVA through a dedicated light-coloured synthesis process. Response Surface Methodology (RSM) quantifies the effects of synthesis parameters and identifies the optimal formulation: an oil-resin ratio of 1.69, 6.05 wt% SBS and 11.67 wt% EVA. Conventional performance, DSR and BBR tests confirm the binder meets SBS I-C asphalt specifications. A 16-mm nominal maximum aggregate size dense-graded light-coloured mixture containing 30% TiO2 exhibits uniform TiO2 distribution and excellent high-temperature, low-temperature and moisture stability. Evaluations via the HSV colour model show its brightness value is 2.6 times that of conventional asphalt, demonstrating remarkable lightening performance.