Muti-scale analysis of solidification/stabilization (S/S) of Pb-contaminated dredged sediment using nano-SiO2 modified cement

作者：Wei Zhang, Lei Lang, Zhen Qi, Yao-Yi Wang, Qiang Xue, Jiangshan Li · 发表于：Journal of Rock Mechanics and Geotechnical Engineering · 年份：2025 · DOI：10.1016/j.jrmge.2025.01.010 · 被引用次数：13 · 研究领域：Building materials and conservation、Concrete and Cement Materials Research、Calcium Carbonate Crystallization and Inhibition

The remediation of lead-contaminated dredged sediments (LDS) presents significant environmental challenges. This study investigates the solidification/stabilization (S/S) mechanisms of ordinary Portland cement (OPC) modified with nano-silica (NS) across a continuum from nanoscale interactions to macroscopic performance. For this, a series of macroscopic experiments was conducted to evaluate the mechanical performance and lead-encapsulation efficiency, including unconfined compressive strength (UCS) and toxicity characteristic leaching procedure (TCLP). Microstructural and phase transformations were characterized using X-ray diffraction, thermogravimetric analysis, and scanning electron microscope. Molecular dynamics simulations revealed the interactions between NS-modified cement, calcium silicate hydrates (C-S-H) gel, and Illite, focusing on interaction energies, atomic density distributions and structural changes. Macroscopic analyses demonstrated that increasing NS content from 0% to 8% improved Pb-immobilization rate from 88.7% to 97.6% and enhanced UCS from 764 kPa to 1358 kPa. These improvements were attributed to NS enhancing the microstructural integrity of C-S-H gel and filling pores in samples. Nanoscale simulations elucidated that Pb-stabilization occurs through coordination bonds with oxygen atoms in the C-S-H silicon chains and on Illite surfaces, complemented by the formation of stable Pb 3 (CO) 3 (OH) 2 precipitates. Additionally, the simulations revealed that ...