# Application of Foundry Wastes in Eco-Efficient Construction Materials: A Review
## 5 Valorization of Foundry Waste in Construction Materials
### Waste Foundry Sand (WFS)  
Waste foundry sand (WFS) can behave similarly to other sands, making it suitable for various applications where it can replace virgin aggregates. Its applications in construction include artificial soils, asphalt, bases and sub-bases, supplementary cementitious materials, concrete, landfill construction, structural fillings, etc. [72]. Its application in concrete as a substitute for natural aggregate has been a well-developed topic, as demonstrated in Figure 9. To compare the effectiveness of WFS as a partial or total substitute for fine aggregate in concrete production, [PERSON] et al. [44] created a literature review article. According to recommendations, the ideal amount of natural aggregate replacement with WFS was between 20 and 30% by weight, which resulted in good mechanical properties. It was concluded that higher replacement levels compromise the main mechanical properties of concrete. Also, complete replacement reduces compressive strength and workability, making it unsuitable for concrete structural components. [PERSON] et al. [73] verified the feasibility of creating self-compacting concrete with large quantities of WFS as a sustainable substitute for conventional materials, without compromising the strength and durability of the concrete. The study revealed that the addition of WFS did not affect the workability of the mixture, but as the amount of WFS increased, the dosage of superplasticizer was adjusted to avoid impacts on fluidity. A significant increase in strength properties, especially compressive strength, was also observed at different ages with substitutions of up to 40% and 50% of WFS. The leaching toxicity of heavy metals showed an increasing trend with the increase in WFS substitution but remained significantly below the required limit values. The general conclusion of the study is that the addition of WFS can be beneficial for the properties of hardened concrete, in addition to being a possibility for the application of industrial symbiosis. The application of WFS in both conventional and dry-mix concrete for block manufacture was explored by [PERSON] et al. [74]. Their findings revealed that the compressive strength and the flowability decreased when WFS was incorporated in the mortars. Therefore, a different behavior was observed when up to 100% calcined WFS was used; in this case, the mortar properties were comparable to those of the control samples. For the dry-mix concrete with compressive strengths up to 20 MPa, the use of WFS had minimal impact on its strength. Thus, the concrete blocks produced entirely with WFS exhibited a compressive strength akin to that of the reference blocks. The simultaneous incorporation of fly ash (FA) and WFS in steel-fiber-reinforced concrete was studied by [PERSON] et al. [75]. The objective of the study was to evaluate whether the  
Figure 10: Content percentage of different residues in construction materials. addition of these components would affect the mechanical properties of concrete, including the elastic modulus, tensile strength, flexural strength, and compressive strength. The investigation showed that the addition of waste reduced the workability of the concrete, while the mechanical properties were affected according to the content of the waste incorporation. The replacement of WFS as an aggregate influenced the compressive strength and workability, whereas other properties were more influenced by the steel fiber content. Compared to the control concrete, the optimal parameters were achieved with 34% WFS, 20% FA, and 2.3% steel fibers, providing significant improvements in mechanical properties. Microanalysis revealed that while high concentrations of WFS and FA prevented the hydration of the binder and increased porosity, moderate amounts improved the pore structure. [PERSON] et al. [76] analyzed ultra-high-performance concrete with the incorporation of WFS and its impacts on material characteristics and structural performance.