Effect of wax additives on asphalt rheological behavior as road paving material

Abstract

In response to the growing demand for sustainable and high-performance roads, various asphalt additives have been developed and introduced to pavement construction. The increasing practice of warm mix in asphalt industry advances the usage of wax additives. However, the concern of wax content poses challenges to the application of wax additives in asphalt pavement via wet process. To address this concern, this study comprehensively investigates the influence of wax content on asphalt binder through rheological and chemical characterization. Specifically, three types of wax additives (Fischer-Tropsch wax, fatty acid amide wax and 64# paraffin wax) were selected at two dosages (2 wt% and 4 wt%) incorporating into four types of asphalt binder (virgin asphalt, SBS modified asphalt, asphalt rubber and high-viscosity & high-elasticity asphalt) to formulate various wax modified asphalts. Rheological properties were characterized to assess the engineering performance. Wax content and chemical mechanisms were characterized to investigate wax modification. Results show that incorporating wax additives enhances the engineering performance of asphalt binders but is difficult to meet wax content requirement. Fischer-Tropsch and fatty acid amide waxes are effective in improving rutting and fatigue resistance, whereas paraffin wax has an overall negative effect. Wax modification promotes the asphalt wax crystallization, leading to a further increased wax content and compromised low-temperature performance on asphalt binders, where modified asphalts can alleviate this adverse effect. Wax additives compromise low-temperature performance of virgin asphalt, but minimally impact modified asphalt. Careful wax content consideration is vital for virgin binders, while more flexibility of adjusting wax additive dosage is beneficial for enhancing overall of modified asphalt. This study is anticipated to prompt the understanding the influence of wax content on asphalt binder and benefit the industrial application of wax additives.