Steel Slag: A Key Player in Reducing Carbon Emissions in the Concrete and Cement Industry
Steel slag, particularly in the form of ground granulated blast furnace slag (GGBFS), is emerging as a vital component in the effort to cut carbon emissions within the concrete and cement sectors. However, as the steel industry takes steps to minimize its own carbon footprint, the availability of steel slag may diminish in the coming years.
The construction industry is a major contributor to global CO2 emissions, and the steel, concrete, and cement sectors are pivotal players in this realm. To combat climate change, these industries are collaborating on initiatives such as the integration of steel slag into cement and concrete production, a proven method to lower emissions.
Utilizing Steel Slag for Sustainable Cement Production
Steel slag serves as a clinker substitute, which is crucial since clinker is responsible for the majority of cement's carbon emissions. Claude Loréa, Cement, Innovation, and ESG Director at the Global Cement and Concrete Association, explains, “GGBFS is a clinker substitute and a supplementary cementitious material (SCM). By replacing a portion of clinker in Portland cement, we can significantly reduce its environmental impact.”
The history of using steel slag in cement production dates back over 150 years, with its commercial introduction in Germany in 1865. GGBFS was incorporated into Portland cement by 1901, demonstrating its long-standing significance. Today, GGBFS offers numerous advantages, including compatibility with clinker handling and higher substitution rates compared to other SCMs. It enhances concrete properties, resulting in lower heat of hydration, reduced cracking risk, and prolonged strength gain. These benefits contribute to the economic and environmental sustainability of structures.
Challenges Ahead: Availability of Steel Slag
Despite its advantages, the steel industry's transition toward reducing emissions could lead to a decline in available steel slag for the cement sector. As coal-fired power plants and blast furnaces evolve, the supply of key materials like fly ash and GGBFS may dwindle. Loréa notes that alternatives such as ground limestone and calcined clays are being explored to compensate for reduced slag availability and further minimize the clinker binder ratio.
Current data from the Global Cement and Concrete Association indicates that the average clinker binder factor is 0.63, projected to drop to 0.58 by 2030 and 0.52 by 2050. While steel slag remains essential for reducing cement-related CO2 emissions, its acceptance among cement buyers and availability constraints pose challenges.
As the industry pushes for sustainability, it’s crucial for stakeholders to embrace innovations like steel slag while adapting to shifting material availability. Overcoming barriers to acceptance will be key to fully leveraging steel slag’s potential in achieving greener construction practices.
The future of steel slag in the concrete and cement industry is a balancing act between environmental goals and material availability, making collaboration and adaptability imperative for sustainable progress.
