Development and application of lead smelting slag eco-cementitious material: Synergistic excitation regulation and heavy metal solidification

Abstract

In order to realise the resource reuse and safety of lead smelting slag (LSS) that contains several harmful heavy metals, LSS eco-cementitious materials (LSSEM) were prepared in this study using calcium and magnesium sources to excite high-volume LSS (78.125%). The results show that the synergistic effect of dual excitation sources can significantly increase the compressive strength of LSSEM from 13 MPa to 34.44 MPa. Performance enhancement mechanisms were investigated using X-Ray Diffraction (XRD), Fourier Transform Interferometric Radiometer (FTIR), Thermal Gravimetric Analysis (TG), Scanning Electron Microscope (SEM), and Mercury Intrusion Porosimetry (MIP). Introduction of calcium and magnesium sources facilitated dissolution of the active components in the LSS to achieve greater excitation. Leaching experiments showed that LSSEM could significantly solidify heavy metals based on the synergistic action of the dual excitation sources. The solidification ratio for each heavy metal exceeded 70%, and the leaching of heavy metals conformed to drinking water quality standards. The slump of pavement concrete prepared with LSSEM was 130 mm, and its 28-d flexural tensile strength and compressive strength were 6 MPa and 49 MPa, respectively, meeting the requirements for pavement concrete design with light traffic load. A conceptual model of the synergistic stimulatory effect of calcium and magnesium sources on LSS excitation was developed. This study promotes solid-waste recycling and provides complementary cementitious materials with lower energy consumption and CO2 emissions for the construction industry.