## 4 The Role of Metallurgy Slags in Sustainable Construction
### Metallurgy Slags in Concrete Production  
Slags have versatile applications across different industries, with concrete production being one of the most common [241]. Their reuse as replacements for binders and fine or coarse aggregates depends on the slags' physical, chemical, and mechanical properties, as well as the specific treatments they undergo before being utilized. Among these, the reuse of iron and steel slags in concrete production stands out for its significant potential to enhance the properties of concrete mixtures while also offering environmental benefits. These slags, including blast furnace slag, basic oxygen furnace slag, electric arc furnace slag, and ladle furnace slag, have unique physical, chemical, and mechanical properties that make them suitable for various applications as substitutes for cement and fine or coarse aggregates. Specifically, blast furnace slag is commonly used as a partial replacement for cement in concrete due to its hydraulic properties, which improve the strength and durability of the concrete mix. Studies have shown that these slags can replace between 20% and 70% of cement, leading to reduced CO\({}_{2}\) emissions and cost savings [242]. Optimal performance is observed with replacement levels between 20% and 30% [243], enhancing compressive and tensile strengths while maintaining good workability. However, challenges such as increased setting times and higher autogenous shrinkage need further investigation, particularly concerning long-term durability and resistance to chloride and sulfate attacks [244]. On the other hand, basic oxygen furnace slag exhibits good mechanical properties, but its use in concrete is limited due to its high volumetric expansion caused by free-CaO and MgO content. Treatments such as carbonation and scrubbing processes have been developed to reduce these components, making these slags a viable option for replacing natural aggregates or as a binder [245]. However, due to the lower hydraulic activity compared to cement clinker, basic oxygen furnace slag is more suitable for unbound applications, such as road construction, and further research is needed to optimize its use in concrete [246]. Similarly, electric arc furnace slag is widely used as a replacement for natural aggregates in concrete production, improving the mechanical properties of full-scale elements, like beams and columns [247]. However, when used as a cement replacement, issues such as slower strength development, increased setting times, and greater autogenous shrinkage have been observed [248]. While these slags show promise for enhancing the density and durability of concrete, further studies are needed to address their performance under freeze/thaw cycles, water permeability, and behavior in aggressive environments. Finally, ladle furnace slag has low hydraulic properties and is prone to volumetric instability, which complicates its reuse in concrete. Some studies have explored using these slags as a partial \begin{table}
\begin{tabular}{c c c c} \hline
**SRM** & **Application** & **Dosage** & **Reference** \\ \hline SS(EAF) & Clay bricks & From 5 to 25\% by weight & [235] \\ \hline SS & Ceramic tiles & 35–40–45\% & [236] \\ \hline SS & Bricks & 90 wt\% & [237] \\ \hline SS & Cementitious material & 10–20–30–40–50\% & [238] \\ \hline SS(BOF) & Ceramics composites & 20–25–45\% & [152] \\ \hline SS(BOF) & Foamed glass–ceramic & SS(BOF)/WG ratios: & \\  & 30/70–35/65–40/60–45/55–50/50 & [239] \\ \hline SS(EAF) & Aggregates in semi-dense asphalt & 13 vol\% of the aggregates & [240] \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._cement replacement in low-strength civil engineering applications, often requiring activation with alkali treatments. However, concerns regarding its workability, shrinkage, and long-term durability persist, necessitating more comprehensive research before real-world applications can be realized [249]. In addition to iron and steel slags, other slags from various metallurgical processes also have significant applications in concrete production.