Recycled Pulp Fiber Reinforced Asphalt Mastic: Investigating Fiber Reinforcement Mechanisms in Different Asphalt States

Abstract

Adding fibers to asphalt can enhance the cohesion of asphalt mastics, thereby improving their deformation resistance and rheological properties. The fibers enhance the performance of asphalt mastic through different mechanisms depending on the temperature environment. In this study, waste printer paper (WPP), waste newsprint (WN), and recycled corrugated paper (RCP) were processed into flocculent recycled pulp fibers by physical methods. Then, the prepared flocculent WPP fibers, WN fibers, and RCF fibers were added to virgin asphalt (SK70)  in proportions of 0.25%, 0.5%, 0.75%, and 1%by mass of asphalt to prepare asphalt mastics. The low-temperature and high-temperature cohesion of asphalt mastics were evaluated by force ductility test (FDT) and Dynamic Shear Rheometer (DSR) tensile test. The high-temperature performance of asphalt mastics was evaluated through the DSR temperature sweep and MSCR tests. The low-temperature performance of asphalt mastics was evaluated using the Linear Amplitude Sweep (LAS) test and Glover-Rowe (G-R) parameter. Meanwhile, the differences among the three types of recycled pulp fibers were analyzed using oil absorption tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results indicate that in high-temperature environments, where asphalt is in a flowing state, the oil absorption capacity of the fibers determines their reinforcing effect on the asphalt mastic. Fibers with higher oil absorption rates exhibit stronger asphalt adsorption. Consequently, WN fibers offer the best enhancement for the high-temperature performance of asphalt mastic. However, in low-temperature environments where asphalt is in a viscoelastic state, WPP fibers exhibit a significantly better reinforcing effect on the asphalt mastic compared to the other two types of recycled pulp fibers. In such cases, the fibers primarily bear the load and transmit stress within the asphalt mastic, and their mechanical properties determine their reinforcing effect on the asphalt mastic. Fibers with better mechanical properties provide the best enhancement to the low-temperature fatigue resistance and cracking resistance of the asphalt mastic. The recycled pulp fiber forms a three-dimensional network structure in the asphalt mastic, which significantly improves the stability of the asphalt mastic, thereby improving its shear deformation resistance, rutting resistance performance, and creep performance.

Keywords: Waste pulp fiber, Fiber-reinforced asphalt, DSR tensile test, FDT, XRD, Cohesion.