A novel method for determining the wax precipitation temperature in wax-based warm mix asphalt

ABSTRACT

To accurately determine the wax precipitation temperature (WPT) of wax-based warm mix asphalt binder, a novel algorithm for WPT calculation was proposed, and the process of wax precipitation in asphalt, as well as the effects of aging, cooling rate, and shear rate on wax precipitation characteristics, were investigated through dynamic shear rheometer (DSR) tests and polarised light microscopy (PLM) experiments. The research findings reveal the following: The refined WPT algorithm exhibits heightened precision compared to the traditional viscosity method, showcasing superior reproducibility and mitigating human-induced errors. During the cooling process, wax molecules become oversaturated, leading to the precipitation of wax crystals and the transformation of asphalt into a solid–liquid two-phase system. The aging of asphalt causes changes in its composition, shifting the phase equilibrium towards favouring wax precipitation. The WPT of asphalt is also influenced by the cooling rate and shear rate, and a larger cooling rate and shear rate will reduce the WPT. Wax crystals are less numerous and more regular in shape at low cooling rates.

KEYWORDS:

• Wax-based warm-mix additive
• wax precipitation temperature
• wax crystal
• rheological characteristic
• viscosity-temperature curve

Disclosure statement

No potential conflict of interest was reported by the author(s).

Acknowledgments

The authors appreciate Analytical and Testing Center of Southwest Jiaotong University for the CLSM microscopy testing.

Additional information

Funding

This study was supported by the Interdisciplinary Cultivation Fund of SWJTU under grant number YH15001124322147, National & Local Joint Engineering Research Center of Transportation and Civil Engineering Materials (Chongqing Jiaotong University) under grant number TCEM-2023-03, National Natural Science Foundation of China under grant number 52178438, Sichuan Science and Technology Program under grant number 2023NSFSC0022 and 23YFSY0003.