Compaction Testing of Synthetic Turf Fields, Term Agreement

Baltimore County has multi-purpose synthetic turf sports fields at various locations throughout the County. The fields are designed with a pad and/or rubber infill to absorb the shock of someone's fall. The shock absorbency of a field is tested by what is referred to as a GMAX or shock absorbency test. GMAX tests involve using a specialized piece of equipment that includes a 20 lb. hammer that is dropped from a height of two (2) feet. An accelerometer is embedded in the hammer that measures the rate that the hammer decelerates as it hits the surface. The faster this hammer comes to a stop, the harder the field. The deceleration is measured in units called gravities, thus the term GMAX. The test simulates the impact of a head on the field surface. A newer type of test called HIC test stands for Head Injury Criterion. Similarly to the GMAX test, it measures the collision force to the surface. However, this test is designed to mimic the shape of a head in order to better gauge the likelihood of head injury. The American Society for Testing and Materials (ASTM) has set standards for the testing and safety of synthetic fields. According to ASTM F1936-19, the GMAX results on a field should be no more than 200G.