Feasibility of using three solid wastes/byproducts to produce pumpable materials for land reclamation

Land reclamation is important for countries with limited land resources, and it requires a huge volume of filling materials. Traditional filling materials such as sand are depleting, which urges the discovery of new filling materials. The rapid growth of population and urbanization has also witnessed increasing solid waste generation. In this context, it is beneficial to turn the solid wastes into filling materials for land reclamation. This study, therefore, intended to reuse three solid wastes/byproducts, namely excavated marine clay (MC), incineration bottom ash (IBA), and ground granular blast-furnace slag (GGBS) to produce pumpable filling materials for land reclamation. Ordinary Portland cement (OPC) was utilized as a reference binder for comparison with GGBS. To this end, the workability (flowability and bleeding), appearance, unconfined compressive strength (UCS), mineralogy and microstructure, and leaching of heavy metals of the proposed materials were investigated. Considering the seawater exposure at land reclamation sites, the integrity of materials in water environments was examined. The results highlighted that for air-cured specimens, to achieve a target UCS of 100–200 kPa, the binder usage of IBA–MC–GGBS could be only half that of IBA–MC–OPC. In water environments, IBA–MC and IBA–MC–OPC generated cracks or were even dismantled, especially when soaked in seawater, posing a significant concern for land reclamation. However, IBA–MC–GGBS showed much higher resistance against seawater than IBA–MC and IBA–MC–OPC. The formation and growth of ettringite was the primary cause of the instability of IBA–MC and IBA–MC–OPC. The hydration of GGBS in IBA–MC–GGBS consumed alkaline minerals, which in turn suppressed the formation of ettringite. The results indicated the feasibility of using IBA–MC–GGBS as pumpable filling materials for land reclamation.