Mechanical and Environmental Performance of Circular Concrete with Recycled Aggregates from Composite Material Waste

The construction sector has a significant environmental footprint, primarily due to its extensive use of natural resources. In the context of ongoing efforts to promote resource efficiency and reduce the consumption of nonrenewable materials, this study explores the physical, mechanical, and environmental performance of a circular concrete incorporating recycled aggregates derived from sink manufacturing waste consisting of a composite material that would otherwise be disposed of in landfills. This waste, composed of approximately one-third methacrylic resin (MMA) and two-thirds mineral filler (virgin quartz), was processed into different particle-size fractions and used as a partial replacement for both fine and coarse natural aggregates. An extensive experimental program involving more than 200 concrete specimens was carried out to assess the behavior of the developed mixtures in both fresh and hardened conditions. The investigation included the evaluation of workability, density, water absorption and permeability, mechanical performance under compressive, flexural, and tensile loading, elastic modulus, shrinkage, and postcracking response. The results indicate that the incorporation of recycled aggregates generally reduced compressive strength and stiffness, with significant reductions observed at higher replacement levels and when fine recycled fractions were used, while tensile-related properties were less affected. Overall, low replacement levels of coarse recycled aggregates provided the best balance between mechanical performance and sustainability, whereas higher replacement levels and the use of fine recycled fractions appear more suitable for nonstructural applications. The environmental performance of the different mixes was evaluated through Life Cycle Assessment. Recycled aggregates were assigned only the impacts associated with the milling process, while the impact of landfill disposal of the composite material, avoided through its valorization, was subtracted. The effect of the avoided impact is more or less significant depending on the impact category. Under the assumptions adopted in the LCA system modeling (cutoff approach with avoided landfill credit assigned to the waste material), the environmental results, referred to 1 m³ of concrete, demonstrate that as the percentage of replacement of natural aggregates with recycled ones increases, environmental impacts decrease. These findings support the implementation of circular economy principles in the construction sector, providing a sustainable strategy for reducing landfill waste and offering a pathway for the valorization of industrial byproducts in civil engineering applications.