Synthetic Turf Surface Temperature Reduction and Performance Characteristics as Affected by Calcined Clay Modified Infill

Synthetic turf research plots containing crumb rubber (CR) infill were established in Knoxville, TN in 2012 and 2013. Calcined clay (CC) was amended to CR in several ratios: a 50:50 (vol vol-1) blend; a 50:50 blend with a polymer coating on CC (50 CR:50 CCC); a 15 mm layer of CC under 15 mm of CR (CR over CC); and a 15 mm layer of CC over 15 mm of CR (CC over CR). A 100% CR and a 70:30 blend of CR to sand (70 CR:30 S) were included for comparison. Surface temperature was measured in the summer of 2012 and 2013 at -10, 0, 30, 60, 90, 120, and 150 minutes following 2.8 cm of irrigation. Irrigation reduced surface temperature 60 to 85% regardless of treatment. By 30 minutes after irrigation, surface temperature increased to 74 to 102% of the temperature recorded 10 minutes prior to irrigation. Temperature on the 50 CR:50 CC and CC over CR treatments 150 minutes after irrigation were 10 to 24% and 20 to 21% lower than the hottest surfaces, which ranged from 95 to 137% of the pre-irrigation temperature. Simulated traffic was applied using the Cady Traffic Simulator for a total of 180 traffic events each year. Trends in surface hardness among treatments were inconsistent over years with values ranging from 70 to 160. CC modified infill treatments resulted in a faster increase of surface hardness with traffic compared to 100% CR and 70:30 S. Traffic affected particle size diameter of infill materials. Infill particles ranging in size from 3.35 to 1.0 mm decreased in diameter an average of 1.0 to 12.0%. Particles ranging from 1.0 to <0.002 mm increased in diameter an average of 0.3 to 3.8%. This increase in size was least pronounced for the 100% and 70 CR:30 S treatments and most pronounced for treatment CC over CR. Significant temperature differences were not consistent among treatments and surface hardness with CC tended to measure higher than 100% CR and 70 CR:30 S. The results of this experiment indicate the use of CC in synthetic turf may be limited.