Long term environmental safety evaluation of incineration fly ash and its use as admixture after freeze-thaw

Abstract

Extensive research has been conducted on the short-term performance of incineration fly ash resource utilization. However, research on the long-term leaching characteristics of heavy metals under external environmental conditions is limited. Therefore, the frost resistance of cement prepared with incineration fly ash as an admixture focused on the leaching characteristics of heavy metals from incineration fly ash and mortar after freeze-thaw were studied by XRD, MIP, SEM, and ICP-MS. The results showed that after 100 freeze-thaw cycles, Cd (HJ 299–2007) in incineration fly ash leached heavy metals exceeding 42.07 % of the GB 18598-2019 limit value. 5 % incineration fly ash enhanced the compressive strength of cement, but exceeding 5 % led to a decrease in compressive strength. After freeze-thaw, incineration fly ash increased the mortar mass loss, strength loss, and porosity. The leaching concentration of heavy metals from incineration fly ash increased under three environment, with the leaching concentration of Ni (HJ 300–2007) after 200 freeze-thaw and the leaching concentration of Cd exceeding 2323.87 % of the limit of GB 16889-2008. Although the concentration of heavy metals in mortar increased with the number of freeze-thaw, the leaching concentration was only 1.73 % of the standard limit, posing no risk of exceeding the limit. Therefore, resource utilization could effectively mitigate the leaching of heavy metals from incineration fly ash under external environmental conditions.