Sustainable production of liquefied stabilized soil using waste clay, fine incineration bottom ash, carbide sludge, and GGBS for backfilling applications

Incineration has been widely adopted as a solution to the increasing volume of municipal solid waste (MSW). However, this process generates substantial amounts of incineration bottom ash (IBA), which poses environmental risks due to heavy metal content, especially in the fine fraction (FIBA). In this context, this study proposes producing liquefied stabilized soil (LSS) from FIBA, marine clay (MC), and ground granulated blast furnace slag (GGBS) for backfilling applications. FIBA serves as an alkaline activator for GGBS hydration, while MC functions as the primary soil matrix. GGBS acts as the primary binder. Carbide sludge (CS), another industrial byproduct, was used as a comparison to FIBA. The performance of the fresh and solidified LSS, including flow value, unconfined compressive strength (UCS), and leaching of heavy metals was investigated. The results showed that with proper contents of FIBA, water, and binder, the flow value of FIBA-GGBS-clay and CS-GGBS-clay satisfied the workability requirements. With increasing CS content, the UCS of CS-GGBS-clay initially increased sharply, then gradually reached an optimal value, and slightly decreased in some cases. Nevertheless, as FIBA content increased, the UCS of FIBA-GGBS-clay generally increased linearly. With similar Ca(OH) 2 contents, FIBA-GGBS-clay had a higher strength than CS-GGBS-clay due to the soil skeleton effect of sand-sized particles in FIBA. The synergy of CS and FIBA enabled CS-FIBA-GGBS-clay to achieve high early strength while addressing the high heavy metal content issue of FIBA. Overall, this approach can be adapted to meet the varying strength and heavy metal requirements of LSS in different applications.