Treatment on the State of Reclaimed Asphalt Material in Warm Recycled Asphalt Mixture Gradation Design

In this paper, the influence of RAP state on warm recycled mixture gradation design was experimentally studied. Different kinds of mixture gradations with different content and state of RAP were synthesized. The concept of “variation degree of gradation” was proposed to quantify the uncertainty of the recycled mixture gradation. It was described as the different passing rate at each sieve size between the two kinds of gradations that respectively synthesized by using the RAP screening result of pre-extracting and post-extracting. Their properties were then tested and compared with each other. The results show that, when the variation degree of gradation is bigger, the state of RAP should be simplified to complete mixing state, that is to say, the recycling mixture gradation should be synthesized by using the RAP post-extracting screening result; but when it is smaller, the state of RAP could also be simplified to black aggregate state, i.e., using the RAP pre-extracting screening result to synthesize gradation is also feasible.