Investigation of compaction characteristics of subbase material using the superpave gyratory compactor

The purpose of this study is to complete an in-depth analysis of data from both the Federal Aviation Administration\u27s (FAA) full-scale testing and Superpave Gyratory Compactor testing to determine if the SGC is a valuable tool for the prediction of airport pavement performance and design. The practicality of the SGC was based on extensive laboratory and field testing of three unbound materials including P-154, P-209, and DGA, which are the subbase and base materials used by the FAA at the National Airport Pavement Test Facility (NAPTF). During the past construction cycles at the NAPTF, it has been found that the flexible pavements failed due to excessive compaction of the subbase material. To better study this phenomena in the laboratory, SGC tests were done at various moisture contents, while varying other variables such as the confining pressure and number of gyrations. The laboratory tests were correlated with field performance characteristics during construction such as changes in density of the soil with each pass of the roller. It was found that the SGC results are capable of replicating the field compaction characteristics irrespective of the roller used. In addition, the laboratory SGC results were correlated with field trafficking data such as magnitude of deflections with each pass of the aircraft gear and a direct correlation has been found. The excessive compaction observed in the subbase layer during trafficking is shown to be due to abrasion and attrition of the aggregate changing the aggregate from an angular to a more rounded aggregate, which reduces interlock and causes more compaction. Ultimately, the study has provided correlations between passes of various landing gear configurations and gyrations in the SGC