Recycled construction and demolition materials in permeable pavement systems: geotechnical and hydraulic characteristics

Permeable pavements are increasingly being used as urban stormwater management systems. Permeable pavement systems enable stormwater to infiltrate through the pavement surface and into the filter layer. Three common recycled construction and demolition (C&D) materials; crushed brick (CB), recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) were investigated in combination with nonwoven geotextile to assess their suitability as filter materials in permeable pavements. A series of laboratory tests was undertaken to assess the geotechnical and hydraulic characteristics of the C&D materials in permeable pavement applications. As a worst case scenario, stormwater mixtures were prepared in the laboratory with a slightly higher than the average pollutant concentrations in stormwater runoff events occurring in urban areas. Constant head permeability tests were carried out to investigate the stormwater filtration capacity and clogging behaviour of C&D materials. A series of hydraulic conductivity tests was also conducted to investigate the effect of variations in the properties of filter media, sediment particle sizes, density of the filter media and clogging effects over time. This research found that the geotextile layer increases pollutant removal efficiency of the C&D materials; however has potential to cause more clogging due to continuous accumulations of sediments in a long period. In terms of usage in permeable pavement filter layer, C&D materials were found to have geotechnical and hydraulic properties equivalent or superior to that of typical quarry granular materials. The Model for Urban Stormwater Improvement Conceptualisation (MUSIC) was furthermore employed to predict the pollutant removal efficiency of the C&D materials and the predicted results were validated with the laboratory experiments.