A comparison of two rotational traction test devices for artificial turf

The Rotational Traction Tester and Lightweight Rotational Traction Tester are the two devices specified in sports pitch certification test standards. They are thought to provide comparable results, when used to characterise the rotational resistance properties of artificial turf pitches. While both devices have been used on polymeric-infilled surfaces for many years, a recently introduced restriction on the use of microplastic infills within the European Union has caused a focus on organic-based materials such as Cork, wood, and Olive pits for use as the performance infill in newly built systems. These infills have different properties to traditional polymeric infills, with many comprised of what is considered to be more rigid particles and thus may respond differently to traction testing. In this study, rotational traction testing was conducted on a Styrene-Butadiene Rubber, Cork, Olive pit, Birch, and Pine pitch with the two standard mechanical devices. Testing included the normal operation of both devices and also the Rotational Traction Tester used without a drop. In addition, two stud designs were included to investigate the response to an alternate geometry—standard cylindrical Fédération Internationale de Football Association studs and a narrower tip conical design of the same length. Overall, peak torque values were found to be significantly affected by the testing configuration across all the pitches. The Rotational Traction Tester used without a drop showed poor agreement with the Rotational Traction Tester used with a drop and Lightweight Rotational Traction Tester peak torque values for every pitch tested. Peak torque values were comparable between the Lightweight Rotational Traction Tester and Rotational Traction Tester when using standard Fédération Internationale de Football Association studs across all pitches. The conical studs were found to significantly increase peak torque on pitches with more rigid infill particles i.e. the Birch, Pine and Olive pitches. In contrast, a decrease in peak torque values on the Styrene-Butadiene Rubber pitch was observed for the conical studs, attributed to the slightly smaller cross-sectional area. The results highlight a need for further investigations into the methods/devices used for sport pitch traction characterisation.