Preparation, microstructure and property of carbonated artificial steel slag aggregate used in concrete

Artificial steel slag aggregates were prepared via carbonating the mixes of steel slag, fly ash and Portland cement, of which the microstructure, property and their impact on the performance of concrete were investigated. Calcium carbonates were the main binders in the aggregates, of which the formation yielded dense microstructures and reduced crushing values. The carbonated artificial steel slag aggregates showed very stable volumes after the autoclaving test at 216 °C. This is due to the depletion of free-CaO contained in the steel slag as a result of carbonation. Concretes with compressive strengths of up to 45.5 MPa at 28d and stable volumes were prepared with the carbonated artificial steel slag aggregates. Owing to the water absorption in the artificial aggregates, higher relative humidity and in turn less autogenous shrinkages were induced in the concrete. This work provides a novel way to utilize steel slag to produce aggregates coupled with CO₂ sequestration.