Nonmonotonic Variation of Rutting Resistance and Fatigue Life for Polyethylene Modified Bitumen with Different Carbon Black Loading

Abstract

Polyethylene (PE) and carbon black (CB) were premixed in this study for bitumen modification. The service performance of PE/CB-modified bitumen (PMB) was mainly explored by multiple stress creep recovery (MSCR) and linear amplitude sweep (LAS) tests to reveal the rutting resistance and fatigue life, respectively. Low-temperature properties were evaluated by glass transition temperature (Tg) measured by dynamic mechanical analysis (DMA). X-ray diffraction (XRD) results suggested that the crystalline structure of PE was almost the same regardless of different CB loading additions. It was found that the both rutting resistance and fatigue life of PMBs showed nonmonotonic variation with CB loading. The mechanism for this variation was closely related to the microstructure induced by phase separation, CB nanoparticle aggregation and PE crystallinity. As revealed by optical and atomic force microscopy, two different phase structures, network and droplet-matrix structure, can be formed in PMBs when the CB loading changes. In particular, a double percolated network structure can be formed, consisting of a PE-rich network in the bitumen-matrix and CB nanoparticle network within a PE-rich phase. With the presence of this structure, the rutting resistance and fatigue life of PMB can be significantly improved.