Exploring the Viability of Utilizing Slag Waste in Concrete through LCA: A Case Study in Giessen, Germany

Abstract

According to statistics from the VDI Centre for Resource Efficiency, approximately 30.1 million tons of cement were utilized for construction purposes in Germany in 2020, resulting in an estimated emission of 28 million tons of CO2. Given that concrete is a key material in almost 30% of residential construction, it is imperative to seek methods to reduce cement and clinker usage. One promising avenue involves integrating waste materials into concrete, offering the dual advantage of lowering cement consumption while effectively managing industrial waste. However, the practicality of this approach heavily relies on the availability and quantity of waste materials. To delve deeper into this concept, a study was conducted in Giessen, Germany, with a focus on managing waste from local steel mills, which produce approximately 0.6 tons of waste per ton of steel. This waste encompasses various materials such as steelmaking slag, electric arc furnace dust, mill slag, and zinc sludge. The study examined four concrete scenarios, each involving different levels of cement substitution with Ground Granulated BlastFurnace Slag (GGBFS). These scenarios included Ultra-High-Performance Concrete (UHPC) with 40% substitution, Conventional Concrete (CC) with 40% and 20% substitution, and CC without waste valorization serving as the control mixture. Evaluations spanning 100 and 200-year lifespans indicated that CC with 40% GGBFS had the least environmental impact over a century. However, over a 200-year period, the durability of UHPC positioned it as the most environmentally friendly option in terms of embodied energy, considering the respective design lifespans of both mixtures. Further analysis, factoring in the reduction in reinforcement within the UHPC mixture, however, it still has the highest environmental for the 100-year design life span (without considering the durability factor).