Recycling and utilization of high volume converter steel slag into CO2 activated mortars – The role of slag particle size

Converter steel slag is produced in large quantities as by-product of primary steel-making, which is mainly landfilled or used as an aggregate The high reactivity of converter steel slag with CO2 makes it an ideal material for CO2 capture by forming calcite even at ambient temperature and pressure. This reaction can also be used to for the production of green building materials. However, the carbonation of steel slag is strongly controlled by the particle size, which influences CO2 transport and carbonation speed. In this study, low carbon footprint binders consisting of various fine converter steel slag powder (80%) and normal cement (20%) are applied to produce mortars using ambient carbonation. The results indicate that the variation of steel slag particle size influences gas transport and CO2 uptake of carbonated steel slag blended mortars during the curing period, which effects microstructure, strength, and leaching. The application of optimal size range of steel slag (21.75–24.13 µm) in blended mortars leads to a higher compressive strength (31.21 MPa), CO2 uptake (15.9 %), faster carbonation rateas well as sustainability efficiency (0.486 MPa/(kg/m3)), which is obviously superior compared to the larger or smaller size of steel slags mortars. . The leaching properties, especially V and Ca leaching of steel slag blended mortars are observed to be strongly influenced by the CO2 uptake, rather than steel slag particle size. A green binder system is achieved by both the reduction of cement content and the high CO2 uptake by mass of binder.