Effects of internal CO₂ curing provided by biochar on the carbonation and properties of steel slag-based artificial lightweight aggregates (SALAs)

Diffusion of CO₂ strongly influenced the carbonation efficiency of steel slag. A novel approach for preparing steel slag-based artificial lightweight aggregates (SALAs) was proposed, in which biochar was employed to provide internal CO₂ curing and reduce the bulk density. Owing to the additional diffusion channels and temporary storage tank for CO₂ provided by the biochar, the carbonation degree of steel slag was effectively improved, leading to improved performance of SALAs as well as concrete. For instance, with the addition of 3 wt% biochar, the CO₂ uptake was increased by 24.3%, the crushing resistance was 5.7 MPa, while the bulk density was reduced to 1070 kg/m³. In addition, the SALAs improved the compressive strengths and volume stability of concrete.