Systematic assessment of a multi–solid waste cementitious material: Feasibility and environmental impact.

This study systematically assessed the feasibility of replacing ordinary Portland cement (OPC) with a multi–solid waste cementitious material (MSC) composed of ground granulated blast furnace slag (GGBS), steel slag (SS), red mud (RM), fly ash (FA), limestone powder (LP), and desulfurized gypsum (DG) in specific proportions of 28%, 25%, 21%, 11.5%, 9%, and 5.5%, respectively. The hydration characteristics were analyzed using hydration heat, XRD, TG–DTG, FTIR, and SEM–EDX tests. The heavy metal content and leaching concentration of the MSC were determined using inductively coupled plasma mass spectrometry (ICP–MS). The unconfined compressive strength (UCS), indirect tensile strength (ITS), and water stability of the MSC-stabilized clayey sand and stone chips were investigated. The results showed that synergistic hydration among multiple solid wastes generated abundant hydration products, including Ca(OH) 2 , C–(A)–S–H gels, and AFt crystals, which formed dense and compact microstructures. Furthermore, Pb and Cd in the raw material were effectively solidified by MSC hydration, with leaching concentrations as low as 0.181 and 0.002 mg/L, respectively. The contents and leaching concentrations of the other heavy metals were significantly lower than their limits. The pH of the MSC mortar leachate was stable at 11.56 with curing age, which complied with environmental safety standards. Moreover, MSC as a binder demonstrated higher UCS, ITS, and water stability in comparison to OPC. When MSC was added at a 6% dosage to stabilize clayey sand and stone chips, the UCS values measured after 7 days of curing were 2.82 MPa and 4.83 MPa, respectively. Finally, the MSC was successfully applied in practical projects, demonstrating its promising application prospects. • The synergistic hydration characteristics of a multi–solid waste cementitious material (MSC) were revealed. • The environmental impact of MSC was investigated. • The mechanical properties of MSC-stabilized materials were evaluated. [ABSTRACT FROM AUTHOR]