The role of tyre crumbs as a substitute for coarse aggregates in stormwater management features

In Australia, it has been estimated that over 48,000,000 waste tyres are being generated annually, with less than 20% of these tyres being properly managed or recycled. Literature has indicated that there are a few methods for tyre recycling at the end of their life, such as the use of crumbed tyre rubber as an adsorbent surface for pollutants in aqueous solutions. The present study aims to determine the function of tyre crumbs as an alternative for coarse aggregates in Water Sensitive Urban Design and its applicability in the removal of pollutants from urban runoff. Nine columns, three control columns, three with a 10% crumb rubber substitution, and three with a 20% crumb rubber substitution, are constructed to depict a typical stormwater filtration system. The current experimental studies focus on the hydraulic conductivity of raingarden filters, also using crumb rubber as a substitute for coarse aggregates in the same percentages as previously mentioned, on unsaturated filters. Results from infiltration studies indicate that the hydraulic conductivities are quite high and varied. 20% tyre crumb substitutions performed the most consistently, with a median unsaturated hydraulic conductivity of 352 mm/hr, which is generally suitable hydraulic conductivity for the removal of pollutants and support of vegetation growth. Although the hydraulic conductivities for majority of other samples were greater than 500 mm/hr, conductivities are expected to decrease as the filters become saturated through infiltration, compaction and clogging.