Environmental Implications of the Recycling of End-of-Life Tires in Seismic Isolation Foundation Systems

The extensive generation of end-of-life (ELT) tires worldwide has resulted in adverse environmental effects and threats to public health and safety including tire fires and leaching of contaminants into the soil environment, groundwater, and surface water. It is becoming imperative to investigate more sustainable and large-scale opportunities for the reuse of ELTs. One novel engineering solution is their reuse in structures with enhanced seismic resilience. This is particularly important in countries such as New Zealand and Japan where past earthquakes have caused widespread damage and socioeconomic loss. Research is being carried out to investigate a seismic-resilient engineered foundation-soil system for low-to-medium-density low-rise residential housing composed of a layer of granulated tire rubber (GTR) and gravel, and a flexible rubber–concrete raft foundation. It is essential to ensure that such innovations do not result in long-term negative impacts on the environment as tires contain hazardous compounds used in their manufacturing and the steel fiber within the tires can leach heavy metals (e.g., zinc, manganese, lead, cadmium). Preliminary batch leaching tests undertaken on (1) GTR and (2) GTR: gravel mixtures (20–40% rubber content by volume) indicated leaching of calcium (Ca), sodium (Na), magnesium (Mg), and potassium (K) which was contributed to the gravel and low levels of zinc (Zn), which were attributed to the tires.