Evaluation of temperature reduction and pavement performance of floating beads asphalt mixture

To alleviate urban heat island effect and lower asphalt pavement temperature, mineral powder in the asphalt mixture is totally or partially replaced by floating beads with low thermal conductivity (0, 25, 50, 75 and 100% floating beads by total volume of mineral powder). The cooling effect and thermal conductivity variation were tested by irradiation test and thermo-conductivity measurer, respectively; meanwhile, the influence of different proportions of floating beads on asphalt mixture pavement performance was studied through relative testing methods. The results show that adding floating beads, the heat transfer in mixture structure and pavement temperature is effectively reduced. The cooling effect of asphalt mixture with 50% and 75% proportions of floating beads is relatively good, their temperature drop being 3.5 and 4.7 degrees C, respectively; meanwhile, thermal conductivity decreased 24.5% and 36.5%. As the proportion of floating beads increases, rutting resistance and water stability of asphalt mixture increase first and decrease afterwards, while low-temperature performance and skid-resistant performance decrease gradually. According to the influence of different proportions of floating beads on pavement performance, the floating beads' content should be less than 75%. Considering cooling effect and pavement performance variance, the proportion of floating beads in the asphalt mixture is proposed as 50-75%.