Comparison of Marshall Compactor and Superpave Gyratory Compactor for Mix Design and Control of Airport Asphalt Mixtures
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Authors
Rogers, Celyn
Issue Date
2023
Type
Thesis
Language
Keywords
Equivalent Gyrations , Marshall , Superpave
Alternative Title
Abstract
The Federal Aviation Administration’s (FAA) current Advisor Circular “Standard Specifications for Construction of Airports” No. 150/5370-10H (2018) allows the engineer to select compaction by either the Marshall hammer or Superpave Gyratory Compactor (SGC). The specifications require a compaction level of 50 blows or gyrations for asphalt mixtures for airfield pavements serving aircraft of 60,000 pounds or less, and 75 blows or gyrations for mixtures to support aircraft weighing more than 60,000 pounds, respectively. The Marshall hammer compaction was used for many decades prior to the development of the SGC and has been considered to result in mixtures with satisfactory performance. However, since the introduction of the SGC as an option in the FAA Advisory Circular in 2014, the SGC has gradually become the method of choice for most FAA projects. Some concern remains among many airfield asphalt pavement engineers that specimen densities from Marshall and SGC compaction are not equivalent, and the differences result in airfield asphalt mixtures that may perform differently in service.The goal of this research was to determine the equivalent number of SGC gyrations (Neq) that achieve volumetric mix properties equivalent to 50 and 75 blow Marshall hammer specimens. The research consisted of sampling 14 FAA hot mix asphalt (HMA) mixtures from 8 states. The sampled mixtures all conformed to FAA “Standard Specifications for Construction of Airports” No. 150/5370-10H (2018) with both P-401 and P-403 mixtures sampled. These mixtures varied in design with 6 mixtures designed with Marshall hammer compaction and 8 mixtures designed with SGC compaction. The sampled mixtures were tested by compacting via the Marshall hammer method to the specified number of blows based on FAA mixture type. The samples were then compacted via SGC to the specified number of gyrations. The volumetric properties of the compacted specimens were determined, and additional specimens were compacted via the SGC to bracket the volumetric results of the Marshall hammer compacted specimens. By correlating the results, the equivalent number of SGC gyrations (Neq) was determined for 50 and 75 blow Marshall hammer compacted samples. The result show that a Neq value of 87 gyrations with a standard deviation of 19 gyrations is equivalent to 75 Marshall blows for FAA P-401 and P-403 mixtures. Various mixture properties of the sample mixtures were compared to determine which properties have the greatest effect on the Neq value. Voids in Mineral Aggregate (VMA) has the highest correlation to Neq values. A Neq value for 50 blow Marshall mixtures was unable to be determined due to insufficient data.