Effect of old mixture proportion on gradation and performance of recycled asphalt mixture

Recycling technology for asphalt mixture has been widely applied. The old mixture proportion is an important index for the recycled asphalt mixture. According to the relationship of old-mixture gradation, proportion and design gradation of recycled mixture, the authors discussed the effects of old mixture proportion on gradation adjustment of recycled mixture. Recycled mixtures respectively containing 0%, 30%, 50%, 70% (by weight) of old mixture were prepared to analyze the influence of old mixture proportion on high and low temperature performance, water stability and aging resistance of recycled mixture. The results indicate that gradation of recycled mixture can not be adjusted to aiming gradation if the old mixture proportion was too large. With the increase of old mixture proportion, high temperature performance and aging resistance of recycled mixture enhance, but low temperature performance and water stability decay sharply. In practical application, reasonable proportion of old mixture should be determined according to gradation, performance demand and economy of recycled mixture.