Recent Advances in Understanding the Behavior of Shockpads for Outdoor Synthetic Sports Pitches

Shock-absorbing layers perform vital roles in the user comfort, safety and ball interaction characteristics of synthetic sports pitches. The layer typically comprises a porous composite of granulated recycled rubber bound in a polyurethane resin, compacted to form a flat continuous pad upon which the carpet is laid. A lack of published information regarding sports shockpads has prompted research at Loughborough University that aims to investigate the fundamental aspects of shockpad layers, namely their design, construction, characteristic behavior, and test methods. This paper outlines the findings of a detailed study investigating the effect of mix design variables on shockpad properties. Primary mix design variables, binder content, bulk density and rubber size distribution, were varied individually in industry standard shockpads produced using a reproducible hand-construction method. A comparison of tensile strength, ball rebound measurements and Clegg Hammer impact behaivior, showed marked influence of these variables over shockpad performance. The dominance of smaller sized rubber particles in a 2–6mm rubber size produced a softer shockpad (lower Clegg Impact Values), higher tensile strength and slightly decreased ball rebound resilience (more energy absorbed). Higher binder contents increased shockpad strength but had no effect on ball rebound or Clegg Impact Values. Increasing the bulk density of shockpads increased the shockpad tensile strength and decreased Clegg Impact Values (i.e. softer). Further work is ongoing to assess the effect of other design and construction variables. Testing to assess the effect of various carpets placed above the shockpad is also ongoing to assess the whole pitch system’s performance.