Environmental approaches in the asphalt industry have focused on utilizing waste materials as modifiers. Lignin is a high-potential bitumen modifier due to its characteristics; however, the blending process with bitumen is critical. This study investigates the chemo-thermal characteristics of lignin-modified bitumen under two different blending protocols, including a mechanical and high-shear mixer to evaluate its performance as a modifier. According to the protocols, 5, 10, and 20% of Kraft lignin was added to a PG 58S−28 bitumen. The samples were subjected to analysis using Brookfield Rotational Viscosity (BRV), Dynamic Shear Rheometer (DSR), Fourier-Transform Infrared Spectroscopy (FTIR), Environmental Scanning Electron Microscopy (ESEM), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC) tests. The BRV and DSR test results indicate a remarkable alteration in the rheological properties of lignin-modified bitumen under blending conditions. The FTIR analysis indicated that Kraft lignin did not produce new functional groups. The fibril structures of the bitumens are affected by Kraft lignin content and blending conditions due to ESEM. The Kraft lignin and blending conditions influence the thermal behavior of bitumen. The findings highlight Kraft lignin’s potential as a bitumen modifier, and the fact that its characteristics are influenced by the blending protocol and Kraft lignin content.

There are several methods to improve moisture susceptibility of asphalt mixtures that using additives or modifiers is the most common method in this regard. In this research, a new nanocomposite material was used for improving the moisture susceptibility of the asphalt mixtures. The experimental design included one base asphalt binder, two types of aggregates (granite and limestone) and 2% of nanocomposite (polypropylene/nanoclay). Indirect tensile strength and surface free energy tests were conducted to evaluate the moisture susceptibility of the asphalt mixtures. The surface free energy components of the aggregates and asphalt binders were obtained using universal sorption device and Wilhelmy plate methods, respectively. The test results showed that the tensile-strength-ratio values of the asphalt mixtures containing nanocomposite had improved. In addition, the results of surface free energy test indicated that the nanocomposite could be used to improve the moisture susceptibility of the asphalt mixtures.