Abstract
Steelmaking slag has emerged as a promising material for low-carbon concrete, owing to its ability to sequester CO₂ through carbonation. However, CO2 sequestration by steelmaking slag and its utilisation is still far from practical application due to the high energy consumption and cost of the accelerated carbonation process. Anticipating that optimising the pre-natural carbonation during storage would reduce the energy and cost for accelerated carbonation, this study focused on the natural carbonation potential of steelmaking slag. In addition, the applicability of naturally carbonated steelmaking slag as aggregate for concrete was investigated. The long-term exposure experiment simulating outdoor storage demonstrated that CO₂ sequestration through semi-natural carbonation reached 18-107 kg-CO₂/t-slag depending on the particle sizes, indicating the significant potential of semi-natural carbonation during storage. CaCO₃ layer was found on the slag surface, and the presence of polymorph CaCO₃ and crystallisation of calcite was suggested. The compressive strength (after 7 days of sealed curing) of concrete incorporating semi-naturally carbonated steelmaking slag was comparable to those made with natural aggregate or steam-aged steelmaking slag, demonstrating the potential for its use as aggregate. The CO₂ emission intensity of concrete using semi-naturally carbonated steelmaking slag was 69 kg-CO₂/m³, representing a 49% reduction compared to natural aggregate. The natural carbonation of steelmaking slag has the noteworthy potential to sequester CO2 at a low cost and in an energy-saving manner. It can also contribute to the decarbonisation of concrete.
Keywords
steelmaking slag, direct carbon sequestration, natural carbonation, concrete aggregate.
DOI
10.5703/1288284318172
Recommended Citation
Nakamura, Sumire and Kawabata, Yuichiro, "Utilisation of Semi-naturally Carbonated Steelmaking Slag as Concrete Aggregate" (2025). International Conference on Durability of Concrete Structures. 2.
https://docs.lib.purdue.edu/icdcs/2025/ddm/2
Utilisation of Semi-naturally Carbonated Steelmaking Slag as Concrete Aggregate
Steelmaking slag has emerged as a promising material for low-carbon concrete, owing to its ability to sequester CO₂ through carbonation. However, CO2 sequestration by steelmaking slag and its utilisation is still far from practical application due to the high energy consumption and cost of the accelerated carbonation process. Anticipating that optimising the pre-natural carbonation during storage would reduce the energy and cost for accelerated carbonation, this study focused on the natural carbonation potential of steelmaking slag. In addition, the applicability of naturally carbonated steelmaking slag as aggregate for concrete was investigated. The long-term exposure experiment simulating outdoor storage demonstrated that CO₂ sequestration through semi-natural carbonation reached 18-107 kg-CO₂/t-slag depending on the particle sizes, indicating the significant potential of semi-natural carbonation during storage. CaCO₃ layer was found on the slag surface, and the presence of polymorph CaCO₃ and crystallisation of calcite was suggested. The compressive strength (after 7 days of sealed curing) of concrete incorporating semi-naturally carbonated steelmaking slag was comparable to those made with natural aggregate or steam-aged steelmaking slag, demonstrating the potential for its use as aggregate. The CO₂ emission intensity of concrete using semi-naturally carbonated steelmaking slag was 69 kg-CO₂/m³, representing a 49% reduction compared to natural aggregate. The natural carbonation of steelmaking slag has the noteworthy potential to sequester CO2 at a low cost and in an energy-saving manner. It can also contribute to the decarbonisation of concrete.
