Civil Engineering Association

Development of Criteria for Using the Superpave Gyratory Compactor to Design Airport Asphalt Pavement Mixtures

Asphalt mix design for commercial airports in the United States is performed in accordance with guidelines set forth in the Federal Aviation Administration (FAA) Advisory Circular AC 150/5370-10D, “Standard for Specifying Construction of Airports, Item P-401—Plant Mix Bituminous Pavements.” Currently, two methods are used to compact asphalt pavement mixtures used in transportation surfaces. The Marshall method, the standard method for commercial airports, uses an impact device that imparts a repetitive stress to the mixture. The Superpave design method provides a kneading action to compact the mixture under constant strain conditions. Design of asphalt mixtures for airfields has been successfully accomplished using the Marshall method since the 1940s. The Superpave design method was developed and adopted by state departments of transportation beginning in the mid-1990s. Currently, most transportation departments have adopted this concept. Since most of the paving work by the asphalt industry is funded by state departments of transportation and private work (which typically use department of transportation criteria), it is becoming more difficult to find laboratories and contractors that continue to use the Marshall method. Hence, it is important that the Superpave method be adopted for airfield pavements. Prior to adopting Superpave as the primary method, it was necessary to determine the number of gyrations required to provide an adequate compactive effort for airfield pavements. This study evaluated the number of gyrations for a number of mixtures required to provide a density equal to 75 blows with the Marshall hammer. Since the 75-blow Marshall mixtures had performed well in the past, it was believed that providing a density with the gyratory compactor equal to that obtained with Marshall compaction would be a good way to adopt Superpave and still have confidence of good performance. This report describes the details of the study and provides a recommended number of gyrations with the Superpave gyratory compactor to provide a mixture that will perform similar to the 75-blow Marshall mixture. The study recommended that 70 gyrations are required to produce a mix similar to the 75-blow Marshall mixture. Additional research is also needed to correlate field performance of asphalt mixtures designed using Superpave methodologies.