Mechanical feasibility and carbon reduction potential of improved dredged soil containing pre-carbonated steelmaking slag: A case study of backfill application in a port mooring facility

The mixture of dredged soil (DS) and steelmaking slag (SS), hereafter referred to as MDS, serves as a sustainable construction material contributing to the realization of a circular economy. By utilizing the carbonation potential of SS, MDS can also function as a carbon capture and utilization (CCU) material, offering additional environmental value. This study explored the application of MDS incorporating pre-carbonated SS, hereafter referred to as CCU-MDS, as a backfill material for a port mooring facility in Japan. The feasibility of using pre-carbonated SS in MDS was examined in terms of mechanical performance, and the potential of CCU-MDS to reduce CO 2 emissions throughout the entire construction project was evaluated. Laboratory experiment revealed that the influence of pre-carbonated SS on the strength development of MDS differed by the type of SS used, with certain types causing a substantial reduction in strength. Nevertheless, the required strength was achieved by adding ground granulated blast furnace slag. Furthermore, CCU-MDS, formulated to meet the required strength for the target facility, achieved negative emissions during raw material production, with CO 2 sequestration exceeding –30 kg-CO 2 /m 3 . This level of sequestration surpassed emissions from machinery operation during MDS construction (10.1 kg-CO 2 /m 3 ), resulting in net-negative emissions below –20 kg-CO 2 /m 3 . Consequently, using CCU-MDS instead of conventional stone in the port mooring facility resulted in a reduction of up to 50% in total CO 2 emissions across the entire construction project. These findings demonstrate that CCU-MDS not only facilitates a circular economy but also makes a significant contribution toward achieving carbon neutrality. • Pre-carbonated steelmaking slag is applied for improved dredged soil. • The use of the improved soil (CCU-MDS) as mooring facility backfill is investigated. • The required strength can be achieved by adding GGBFS as necessary. • CCU-MDS construction achieved net-negative CO 2 emissions below –20 kg-CO 2 /m³. • Using CCU-MDS can reduce total emissions from facility construction by up to 50%.