Mechanical properties and heavy metals immobilization of lithium slag stabilized by magnesium slag as road subbase material
Xuanhao Cao, Bowen Guan, Jincheng Yu, Jun Li, Wenbo Liu, Hua Zhao, Juanni Nian, Li Dai, Zheng Huang
Abstract
The leaching of excessive heavy metals (HMs) from lithium slag (LS) presents a significant challenge for its use in road engineering, necessitating the development of safe treatment methods. This study employed solidification/stabilization (S/S) technology to develop a magnesium slag-lithium slag composite solidified material (MS-LS). The deformation and displacement characteristics of MS-LS during destruction were analyzed using digital image correlation (DIC). Various microscopic analytical techniques were used to analyze the stabilization mechanisms of MS-LS towards HMs. Results indicated that adding MS significantly improved the compressive strength and resistance to cracking of MS-LS. The minimum strength of the 8 %-MS group reached 2.7 MPa, meeting the strength requirements for subgrade stabilized soil in a first-class highway under heavy traffic load conditions. The development of strength is attributed to improved structural compactness from particle micro-gradation effects and the cementitious hardening action of C-S-H gel. HMs immobilization was achieved through directional adsorption at active sites within the calcium-rich mineral phase and interlayer adsorption within the C-S-H gel, complemented by a physical encapsulation mechanism that reduces HMs leaching. The immobilization rates of Be(II) and Pb(II) in the 8 %-MS group exceeded 95 %, demonstrating the effectiveness of MS in stabilizing these HMs in LS.