Effects of particle size and carbonation on steel slag-based artificial aggregates

The potential of utilising steel slag for the development of artificial aggregates was explored. The effects of particle size and carbonation on the particle strength, phase composition and microstructural characteristics of the artificial aggregates were systematically evaluated. The results reveal that mechanical activation through ball milling significantly refine the particle size dimensions of the steel slag, and the minimum particle size is achieved after 90 min of milling. The carbonation curing process effectively converts free calcium oxide into stable calcium carbonate, with calcite and aragonite phases forming under high and low carbon dioxide concentrations, respectively. These carbonate formations contribute to the increased mechanical properties of the aggregates. The optimised artificial aggregates exhibit superior performance, enabling the production of concrete with good workability and a compressive strength of 35.8 MPa at 28 days. Moreover, a comparative life cycle assessment indicates that steel slag-based artificial aggregates reduce carbon dioxide emissions by 42.3%–63.4% compared to natural lightweight aggregates, which underscores their superior environmental performance. These findings highlight the potential of steel slag as a sustainable raw material within the framework of artificial aggregate production, offering a promising solution for high value utilisation of industrial waste in the construction industry.