Innovation and performance of lead smelting slag-based multi-solid waste pavement concrete materials: Ratio design, mechanical properties, hydration products, heavy metal leaching

Abstract

Lead smelting slag (LSS) is a solid waste of lead production with multiple heavy metals that can irreversibly damage natural ecosystems. Therefore, it is imperative to creatively employ LSS to promote ecologically sustainable development. In this study, LSS-ground granulated blast furnace slag (GGBFS)-cement clinker (CC)-desulfurization gypsum (DG) road cementitious materials (LSCG) were prepared by synergistically stimulating LSS using multiple solid wastes to broaden the application of LSS in road construction. Specifically, the study presents an evaluation of the optimal ratio of LSCG road cementitious materials on using an integrated weights method. The hydration process of LSCG cementitious material were determined by XRD, FTIR and SEM, and the pore size distribution and content were investigated by MIP. The results indicated that the inclusion of LSS had a detrimental effect on the mechanical strength of the mortar. LSCG cementitious materials can be manufactured to achieve satisfactory performance for medium and light-grade pavements at LSS content no more than 35%. The recommended cementitious material composition ratio for medium and light grade pavement consists of 15% LSS, 44% GGBFS, 35% CC, 6% DG and 35% LSS, 24% GGBFS, 35% CC, 6% DG, respectively. Additionally, 28d flexural tensile strength of the LSCG-based pavement concrete prepared with the above ratios reach 6.0 MPa and 5.7 MPa, respectively. XRD, FTIR and SEM analysis revealed the primary hydration products of LSCG cementitious materials consist of C-S-H gel, ettringite, portlandite, and calcite. The primary contributor to the mechanical strength of the material is the gel network that arises from the interaction between C-S-H gel and ettringite. MIP analysis revealed the progressive introduction of LSS leads to a notable rise of proportion detrimental pores and multi-hazardous pores within cementitious materials. Simultaneously, the leaching concentrations of LSCG pavement concrete for Cr, Cu, Ni, Ni, Pb, Zn, As, Mn are in accordance with the limits of the Chinese standards “GB 8978–1996″and the “GB5749–2006″. Thus, LSCG cementitious material has good environmental benefits, and application in road construction can further promote the resource utilization of LSS.