AbstractPhotocatalytic pavements materials are being developed to purify toxic automobile exhaust gas, especially in tunnels where the pollution concentrations are high. This study investigated the photocatalytic efficiency and pavement performance of asphalt mixtures containing steel slag and different contents of CeO2 and TiO2 as photocatalyst materials. Photocatalytic testing equipment was developed to calculate the photodegradation efficiency for CO, CO2, NO, and HC. The pavement performance of the asphalt mixtures was evaluated using rutting tests and low-temperature bend tests. The texture depth was measured to evaluate the antislide performance. The excessive addition of the CeO2 and TiO2 nano photocatalysts had an adverse effect on the pavement performance of the steel slag asphalt mixture. The optimal contents of CeO2 and TiO2 were 7% and 0.6% by weight of the asphalt binder weight, respectively, as obtained by a gray target decision process based on principle component analysis. These findings are expected to contribute to the development of functional pavement materials that improve the surrounding air quality and have a lower environmental impact due to the use of waste slag.