Laboratory Study on Influence of Blending Conditions on Chemo-Thermal Characteristics of Lignin-Modified Bitumen

Abstract

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.

The impact of bio-oil on the structure, rheology, and adhesion properties of lignin-modified asphalt

“…The lignin dispersion was enhanced with more bio-oil, transitioning from semi-continuous phase separation to discrete particulate dispersion [23]. This change in morphology indicates the bio-oil improved miscibility between the hydrophobic asphalt and hydrophilic lignin phases.…”

“…The LMAs showed a coarser microstructure with distributed lignin particles. The size, shape, and dispersion of the lignin phase depended on its dosage [23] (table 3). At 5% lignin content, small spherical lignin particles around 2-5 μm in diameter were dispersed in the asphalt matrix.…”