Effect of recycled aggregate gradation on the degree of blending and performance of recycled hot-mix asphalt (HMA)

Abstract

The application of recycled asphalt pavement (RAP) could bring huge economic and environmental benefits. Until now, the role of RAP gradations has not been fully considered in the design. Therefore, this study attempted to investigate the effect of recycled aggregate gradation on the degree of blending and performance of recycled HMAs. Six groups were designed, including the three experimental groups mixing with different particle sizes of RAP, designed as “partial blending groups”, a control group designed as “full blending group”, and two further groups designed as “no blending groups”. Then, the volumetric parameters, degree of blending, water stability, high and low temperature performance of each group were evaluated. It can be found that with the addition of finer particles of RAP materials, more RAP binder was activated, and the DoB in recycled HMAs increased. However, despite the DoB increased, the water stability and thermal cracking performance of recycled HMAs containing fine particles of RAP were still worse than that of recycled HMAs containing coarse particles of RAP, which may be due to the unfavorable distribution of RAP binder in these mixtures. Especially, the low temperature performance of recycled HMAs containing 32% 0–5# RAP was only 1.638 MPa, even close to that of the “no blending group”. In addition, the high temperature performance showed the opposite trend. The shear strength of recycled HMAs increased with the addition of finer particles of RAP. Overall, the fine particles of RAP were recommended to avoid use in the cold and rainy regions.