*Article* **Effect of Phosphogypsum Based Filler on the Performance of Asphalt Mortar and Mixture**

**Jiuming Wan 1,2, Tao Han <sup>1</sup> , Kaifei Li <sup>1</sup> , Suxun Shu 1,\*, Xiaodi Hu <sup>1</sup> , Wenxia Gan <sup>1</sup> and Zongwu Chen <sup>3</sup>**

	- Changsha University of Science & Technology, Changsha 410114, China

**Abstract:** This study introduced phosphogypsum coupled with steel slag powder to prepare the phosphogypsum based filler (PF) for asphalt mixture. Penetration, penetration index, softening point, ductility, equivalent softening point, moisture stability of asphalt mortars with different steel slag powder content, filler-asphalt ratio, and PF content were studied. Mechanical properties of PF based asphalt mortar (P-AM) were then analyzed to determine the optimum steel slag content in PF. Overall desirability method was used to determine the optimum replacement ratio of PF content in limestone filler. Rheological properties of P-AM were also analyzed through dynamic shear rheometer. Volumetric performance, high-temperature performance, low-temperature performance, and moisture stability tests were carried out on PF based AC-20 asphalt mixture. Results showed that P-AM presented the optimum performance when the content of steel slag powder was 23% by mass of phosphogypsum. Fatigue and rutting factor of asphalt mortar were enhanced by PF. The optimum PF content in replacing limestone filler was 75% through overall desirability evaluation. PF developed the high-temperature performance and moisture stability of asphalt mixture. Additionally, volumetric and low-temperature performance were not significantly affected by PF. It is suggested that using PF which is based on phosphogypsum as a filler of asphalt mixture to partially replace traditional limestone filler was adequate.

**Keywords:** phosphogypsum; steel slag powder; asphalt mortar; asphalt mixture; overall desirability
