Chemical degradation of a paraffin wax-based binder used in granular composite sport surfaces

Chemical changes in high-oil wax-based binders used in Thoroughbred horse racing synthetic surfaces are studied over a 7-year period in an effort to understand the effect of changes in the binder on track behavior. A wax or polymer binder is used to hold the sand, fiber, and rubber constituents together in addition to creating a hydrophobic coating on the sand. The binder was extracted from bulk samples obtained from sampling of a racetrack surface at the same location on a single racetrack. During the 7 years, the material components of the track were not altered nor was material added, although normal maintenance including daily harrowing and annual tilling was performed. The binder was separated via solvent extraction from the samples. Differences in chemical composition were determined through oil extraction, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC-FID), and differential scanning calorimetry (DSC). Results show chemical changes in the binder resulting from oxidation of the oil in the wax, as well as changes in wax molecular structure. The goal of this work is to better understand how the binder changes over time to help guide maintenance and replacement decisions. Other potential changes to the surface materials can include the addition of oil stabilizers and binder replenishment. If the time interval between surface replacements can be extended, it would enable racetracks to provide a consistent and potentially safer racing surface at a lower cost.