Interaction state and element leaching of waste incineration fly ash-asphalt mortar based on fillerization

Abstract

Fly ash from diverse sources had various physical and chemical properties, resulting in different modified asphalt properties. Therefore, this paper aimed to investigate the interaction between fly ash and asphalt from different sources and the performance of fly ash-asphalt mortar and further sought the best-replaced amount of fly ash. The fillers included limestone, Dongguan fly ash, and Guangzhou fly ash. First, the filler's physical and chemical properties and microstructure were evaluated. Secondly, asphalt mortar was prepared according to the replaced amount (0%, 25%, 50%, 75%, 100%) and powder binder ratio (0.7). Then, the basic performance test, micro test, high-temperature rheological test, and low-temperature rheological test were conducted on asphalt mortar to investigate the interaction between fly ash and asphalt, as well as the high-temperature performance, elastic recovery ability, and low-temperature crack resistance of asphalt mortar. Finally, the segregation and heavy metal leaching of fly ash-asphalt mortar (FA-AM) were evaluated by the segregation and ICP test. The results indicate that fly ash had a small particle size, a rugged surface, well-developed porosity, abundant mineral components including potassium salt, sodium salt, and calcium carbonate, strong interaction with bitumen, and excellent compatibility. Adding fly ash and increasing the replacement amount improved the high-temperature performance of asphalt and enhanced the elastic recovery ability, but the low-temperature performance was weakened. The enhancement of Dongguan fly ash's high-temperature performance was more significant, while the low-temperature performance of Guangzhou fly ash was marginally superior to that of Dongguan fly ash. However, there was no discernible difference between the two types of fly ash in terms of elastic recovery ability. Segregation had no noticeable effect on the heavy metal absorption concentration of FA-AM, and the storage stability was excellent. Asphalt had the best stabilization effect on Zn, Cu, and Pb in FA-AM (Dongguan) and Pb and Cr in FA-AM (Guangzhou). The recommended replacement amount of Dongguan fly ash and Guangzhou fly ash was 25%∼50%.