Using bitumen modifiers to prolong the asphalt mixture’s life has been considered a practical approach in constructing asphalt mixtures. Among various bitumen modifiers, biomass ones have been more noteworthy because of their abundance, cost-effectiveness, renewability, and sustainability. Calcium lignosulfonate (CLS), as a plant-based bitumen modifier, has been studied to enhance the rheological properties of bitumen. However, the feasibility of using CLS as a rutting retarder of asphalt mixtures is still unclear. This study focused on the durability of asphalt mixtures containing CLS powder as a bitumen modifier. Specifically, extensive laboratory tests were conducted to determine the performance of asphalt mixtures against traffic loadings. In this study, to begin, CLS-modified bitumen was manufactured using a high-shear mixer at various CLS dosages (5, 10, 15, and 20 wt.%). Afterward, the optimum bitumen content of asphalt mixtures was found using the Marshall mix design technique. Finally, a series of dynamic tests, including resilient modulus, dynamic creep, and wheel-tracking tests, were combined with Zhou’s three-stage model and Tukey method to determine the influence of CLS on asphalt mixture’s rutting potential. The Tukey method found that asphalt mixtures containing 15% CLS had the highest rutting performance among the samples tested under repetitive loadings. Meanwhile, the surface morphology and elemental analysis of CLS powder were investigated using a field emission scanning electron microscope (FESEM) and by energy-dispersive X-ray spectroscopy (EDX), respectively. The FESEM and EDX results showed that the CLS powder had a bumpy structure and its chemical structure contained metal oxide, carbon, magnesium, calcium, and silicon. The results indicated that the asphalt mixtures became stiff owing to the combination of CLS and bitumen, which significantly affected the rutting improvement of asphalt mixtures. Moreover, Zhou’s three-stage model revealed that the incorporation of CLS into bitumen enhanced the rutting resistance capacity of asphalt mixtures against traffic loadings. 1. Introduction

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