# Application of Foundry Wastes in Eco-Efficient Construction Materials: A Review
## 1 Introduction
The deal highlights the challenges of the current industrial model, which is overly linear and heavily reliant on the extraction of new raw materials [14]. Complementing this initiative is the EU Action Plan for the Circular Economy, which sets out a roadmap for the EU's transition to a more sustainable and circular economy model. The plan aims to promote sustainable consumption and innovation, focusing on reducing waste. In addition, policies such as the promotion of high-quality recycling, the creation of an internal market for secondary raw materials, and the harmonization of selective waste collection systems are proposed [15]. The construction sector significantly contributes to waste generation, global resource consumption, and greenhouse gas emissions. It is important to switch to a circular production and consumption system to confront these issues. By incorporating alternative materials into construction practices, it is possible to reduce landfill accumulation and minimize the harm to the environment [16]. Concrete, which is the most widely used construction material globally, has a significant impact on the environment due to the extensive extraction of virgin materials during its production [17]. Incorporating industrial waste materials such as slag, tire rubber, stone waste, pond ash, foundry sand, and plastic wastes has proven highly effective in dealing with the shortage of natural aggregates in concrete production. This partial substitution has positive impacts on both the mechanical and durability properties of concrete [18]. Casting operations can generate foundry waste from different types, such as used foundry sand, slag, ash, refractory, coagulant, baghouse dust, pattern shop waste, and debris. Among these wastes, used foundry sand and slag have proven to be promising byproducts for improving concrete performance. The origin of each type of waste is associated with distinct industrial practices, where different industries generate varying amounts of each waste material [19]. Environmental compliance costs are significant across industries, including the concrete industry. Incorporating industrial byproducts like foundry waste can lead to enhancements in energy efficiency and environmental sustainability within the industry [20]. It is fundamental to investigate ways to repurpose byproducts from the foundry industry to promote sustainability, enhance resource efficiency, minimize waste, encourage innovation, and ensure compliance with environmental guidelines. This paper aims to showcase the potential of foundry waste in construction materials by highlighting the diverse range of materials that have been researched in recent years with respect to their incorporation of different types of foundry waste. This review begins by providing an overview of the foundry industry, including its background, processes, waste management, and waste statistics, to contextualize the topic. Subsequently, the evolution of research on foundry waste is presented through a bibliographic analysis. Lastly, the paper analyzes recent advancements in employing foundry waste for the development of construction materials.