3.1. Particle size distribution
The RR obtained from the sanding process exhibits a morphology normally associated with ambient type grinding of vulcanized rubber as the rubber powder is
convoluted and sponge-like. This appearance is in contrast to cryo-ground rubber particles which are normally angular and smooth. The particle size distribution is
shown in Fig. 1. About 63.9% of the rubber particles were in the size range of 250–500 μm, and this range of sizes was used in this study.