Preparation, Properties, and Microscopic Mechanism Analysis of Liquid Natural Rubber–Modified Asphalt

To explore the feasibility and effectiveness of liquid natural rubber (LNR)-modified asphalt and provide new insights into the preparation of rubber-modified asphalt, this study employed an orthogonal experiment to investigate the interactions among different components and determine the optimal preparation scheme for liquid natural rubber–modified asphalt (LNRMA). The LNRMA first was aged using a rolling thin-film oven (RTFO) and pressure aging vessel (PAV). Then the pavement performance, including rutting, fatigue, and low-temperature cracking resistance of LNRMA were studied using dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Additionally, the storage stability of LNRMA was investigated using fluorescence microscopy (FM) and molecular dynamics (MD) simulations, and the temperature susceptibility of LNRMA was evaluated using Fourier-transform infrared spectroscopy (FTIR) and MD simulation. The results indicate that LNRMA with 5% rubber content, 4% KOH content, and 1.5% sulfur content mixed at 165°C has significantly enhanced low-temperature cracking resistance, and its fatigue and aging resistance are improved to a certain extent. Chemical changes occur during the modification process of LNRMA, leading to the presence of saturated alkanes, aromatic hydrocarbons, and olefins in the asphalt binder, which enhance its rheological properties. The addition of LNR can increase the solubility of different components in LNRMA and enhance the compatibility of the asphalt system, thereby improving the storage stability of the asphalt.