Using Recycled Construction Waste Materials with Varying Components and Particle Sizes for Extensive Green Roof Substrates: Assessment of Its Effects on Vegetation Development

Using construction waste materials as substrates can reduce the resource consumption of minerals and provide sustainability benefits in green roofs. This research examined the viability of crushed bricks and crushed concrete with varying particle sizes as substrates by conducting a simulated drought experiment and roof experiment. Six composite substrates were prepared, respectively, by mixing peat with small-, medium-, and large-sized crushed bricks and crushed concrete particles (peat-to-inorganic-particle volume ratio of 1:2). The properties of each group were within acceptable parameters, with the crushed brick substrates displaying lower bulk density and higher porosity compared to the crushed concrete substrates. Seldom lineare was selected for the experiments, and the substrate thickness was set at 10 cm. Under the simulated drought conditions, the growth and stress resistance of Seldom lineare in the crushed brick substrates was similar to that in the conventional substrates and poorer in the crushed concrete substrates. Seldom lineare in medium-particle-size brick substrates performed the best, surpassing the traditional group. The growth of Seldom lineare in the small-particle-size concrete substrates was the worst. In the rooftop environment, all groups could support Seldom lineare over 180 days without maintenance, with an overall coverage of more than 60%. The plants in the medium-particle-size brick substrates exhibited the highest cover. In conclusion, the medium-particle-size brick substrate exhibits ideal characteristics in terms of substrate physical properties and plant growth, making it a favorable option.