Laboratory investigation on pavement performance of indirect coal liquefaction residue in asphalt mixture

Indirect coal liquefication residue (ICLR) is a by-product of coal-to-liquid technology, which is harmful to the ecological environment and human health. In this study, an innovative method of using ICLR to replace limestone fine aggregate in asphalt mixture was proposed to solve the disposal problem of ICLR. A traditional and seven different ICLR contained asphalt mixtures were designed and tested to evaluate whether ICLR can be recycled as a kind of pavement material . Firstly, XRD and FTIR were employed to characterize the chemical composition of ICLR to gain insight into the advantages of using ICLR as fine aggregate. Then, asphalt mixture performance including rutting resistance , low-temperature cracking resistance , and moisture susceptibility was tested on the above-mentioned eight kinds of mixtures to evaluate the impact of ICLR particle size effect and replacement amount. The results demonstrate that using ICLR to only replace one group of three groups of aggregates (0.6–1.18 mm, 1.18–2.36 mm, and 2.36–4.75 mm), the performance of asphalt mixture was better than replacing two or three groups at the same time. It was found that replacing limestone aggregate with ICLR improved the high-temperature performance and moisture susceptibility of the asphalt mixture. The use of ICLR instead of aggregate did not improve the low-temperature performance, or even slightly reduce it, but it still met the specification requirements through reasonable replacement. Finally, the gradation filling theory and asphalt film thickness confirmed the possibility of using ICLR instead of fine aggregate. Therefore, it is concluded that using ICLR in asphalt mixture instead of fine aggregate provides a reliable and value-added solution to recycle ICLR. • ICLR could replace limestone fine aggregate in asphalt mixture to solve its disposal problem. • A reasonable ICLR replacement plan could improve the rutting resistance and moisture susceptibility of asphalt mixture. • The gradation filling theory proved the feasibility of replacing fine aggregate with ICLR, along with asphalt film thickness