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Environmental Performance of Mature Precast Slabs in Permeable Pavements: Hydraulic Functionality and Pollutant Retention Under Real-Life Conditions
Summary
Researchers monitored porous concrete pavement slabs over five years of urban use, finding a 48% decline in infiltration capacity alongside 7.5-fold higher microplastic loading than new slabs — dominated by fibers of PE, PP, and PET — and demonstrated 42.5% hydraulic recovery after pressure cleaning, positioning the surface layer as a significant microplastic sink in urban stormwater systems.
Permeable pavements are increasingly integrated into urban environments as sustainable systems that enhance stormwater infiltration, mitigate runoff, and contribute to pollutant control. However, long-term accumulation of contaminants within their porous structure may impair hydraulic performance and environmental functionality, particularly regarding microplastics (MPs), an emerging pollutant of growing concern. This study investigates the five-year environmental performance of porous concrete pavement slabs operating under real urban conditions, focusing on infiltration capacity and retention of nutrients, suspended solids, and MPs. A dual methodology combining continuous on-site permeability monitoring with laboratory analyses of aged slabs was used to assess performance decline and recovery after maintenance. Results show a 48% reduction in infiltration over five years, while maintaining effective functionality, and a 42.5% recovery after pressure cleaning. Used slabs exhibited substantial pollutant accumulation relative to new slabs, including increases of +258% in COD, +123% in total phosphorus, +28% in total nitrogen, and +48% in suspended solids. MP abundance reached 10,272 ± 5829 MPs/m2, 7.5 times higher than in new slabs, dominated by fibers (~70%) and polymers such as PE, PP, and PET. These findings highlight the pavement surface layer as both hydraulic infrastructure and contaminant sink supporting improved maintenance and sustainable urban stormwater management.