Thanks to recycling and diversion initiatives over the last decade, the number of tires finding their way to landfills has been greatly reduced. The majority of rubber produced from recycled tires is in the form of crumb, which is most often created by mechanical grinding resulting in particle diameters between 1 and 5 millimeters. Because of the energy required to break and reform the chemical crosslinks that give tire rubbers their strength, much of the tire crumb produced finds application as a filler that is bound together by a continuous matrix. Typical binders include cement, asphalt and polyurethane.
We present results of experiments which explore the potential for tire crumb to be used as permeable construction materials that permit infiltration of water. As precipitation events increase in intensity, stormwater management guidelines increasingly call for infiltration of stormwater so that demands on infrastructure may be reduced. By providing a path by which stormwater can pass underground, impact of precipitation on river levels, erosion, and pollution are all reduced.
The extent to which permeability affects mechanical strength is of importance when manufacturing products such as walkways, road surfaces and other load-bearing materials. We have explored the effect of changing binder fraction and tire crumb particle size on both the compressive strength and hydraulic conductivity of composite samples. Two widely-accessible binder materials with very different mechanical properties were used: polysiloxane-based sealant and polyurethane adhesive. A wide range of sample properties were achieved with adjustment of a minimal number of process parameters and without the need for specialized components or equipment, making the results of these experiments pertinent to applications in remote locations or those where access to equipment is otherwise limited.