Recycle of lead-zinc tailings in blended cement: mechanical property and stabilization/solidification of heavy metals

Abstract

Due to the increasing output and toxicity of heavy metals, the pollution problems of lead-zinc tailings (LZTs) need to be solved urgently. This paper investigated the properties and heavy metal stabilization/solidification of blended cement containing different replacement ratios of ground LZTs. The compressive strength, hydration products, chemically bound water content and microstructure of specimens were analyzed by XRD, FTIR, TG-DSC and SEM tests. The results showed that the addition of LZTs reduced the compressive strength of blended cement. 10% cement replacement by LZTs can be considered as the optimum for blended cement uses. With the increase of LZTs dosage, Ca(OH)2 content was significantly reduced and the formation of ettringite was promoted. Leaching tests revealed that the leaching concentration of Pb and Zn was much lower than threshold limit. EDS analysis indicated that hydration products (primarily C-S-H gel) played an important role in the stabilization/solidification of heavy metals by means of physical adsorption and encapsulation. This research provides a guidance for the resource utilization of LZTs.