Using recycled e-waste microplastics to improve the environmental and functional performance of permeable concrete: a TOPSIS and VIKOR analysis

In the current environmental crisis, where there is an urgent need to protect natural resources, minimize carbon dioxide (CO₂) emissions, and reduce microplastic pollution, this study suggests a novel approach. It recommends incorporating textured recycled microplastics, of uniform size and shape, into low-impact technologies used for rainwater management, such as permeable concretes, which will increase their environmental benefits within a circular economy. The present study evaluated the effects of partial substitution of natural coarse aggregate (0 to 9%) and gamma dose (0 to 1000 kGy) of recycled polycarbonate from electronic waste (recycled e-Polycarbonate) on the mechanical, hydraulic, physical and environmental performance of permeable concrete. The results, derived from experimental tests and Life Cycle Assessment (LCA), were analysed by two Multiple Criteria Decision Making (MCDM) methods (TOPSIS and VIKOR). Both models found that the concretes that have outstanding permeability, supported by a solid porous structure, and that also have desirable attributes such as low density and low GHG emissions, are the mixtures: 9% 0 kGy, 6% 1000 kGy and 9% 500 kGy. Demonstrating that the higher percentage of recycled e-Polycarbonate (9%) analysed, improves the efficiency of the material and that it can be used both irradiated and not. These three alternatives, based on their characteristics – permeability (9–10 mm/s), compressive strength (12.5–13 MPa), porosity (19–21%), density (1680–1779 kg/m3) and GHG emissions (between 343 and 346 kgCO2eq/m3, according to the GWP-total indicator) – focus on pedestrian applications (squares, bike lanes or sports areas) where the required permeability is 6–12 mm/s with a compressive strength between 10–15 MPa. They also meet the requirements of the ACI Committee 522 report, including the use of synthetic materials such as those that can be used to increase toughness.