SELECTING CRITERIA AND WATER PERMEABILITY MEASUREMENT OF RECYCLED AND ARTIFICIAL MATERIALS FOR GREEN ROOF LAYERS

European Aggregates Association Annual Review reported that the Northwestern European countries (Belgium, France, Germany, Netherlands, and the UK) produce 90% of recycled aggregates and 67% of artificial aggregates in Europe. Partially replacing the natural materials with coarse recycled and artificial materials for substrate and drainage layers of green roof systems can be considered as a viable solution to lessen the environmental impact by preserving natural resources in Northwestern Europe. On the other hand, water permeability is one of the main indicators for green roof materials. In this study, some materials available in the Northwestern European markets were selected and their water permeability was measured according to German FLL guidelines. This study also answered the question: to what extent can the water permeability be provided for the substrate and drainage layers by the inclusion of recycled and artificial materials than by conventional green roof materials? For the drainage layer, different coarse granular aggregates were suggested: Recycled Coarse Aggregate (RCA), Incinerated Municipal Solid Waste Aggregate (IMSWA) and Lightweight Expanded Clay Aggregate (LECA). The results were compared with the Natural Coarse Aggregate (NCA). For the substrate layer, the water permeability of commercial substrate materials with and without coarse recycled materials was measured and compared to each other. The results showed that NCA offered a water permeability 1.5 times higher than LECA, although the results of RCA and IMSWA did not differ significantly. Moreover, the water permeability of the substrate with and without coarse recycled materials was within the guidelines' range, indicating that they met the water passing criteria for the substrate layer.