Validation of Superpave Fine Aggregate Angularity (FAA) Values

Principal Investigator(s):

Mihai Marasteanu, Professor, Civil, Environmental and Geo-Engineering

Co-Investigators:

  • Gene Skok, Former University Researcher, Civil, Environmental and Geo-Engineering

Project summary:

One of the aggregate properties used to evaluate fine aggregate materials for Superpave mixture design is the fine aggregate angularity. This property of the aggregate is measured with a standard Fine Aggregate Angularity (FAA) test. The test measures the voids in a sample results from the flowing of the aggregate into a standard container from a -standard height. Higher voids assumes more angularity. The Superpave criteria for FAA were developed based on the consensus of a number of experts. The current MnDOT Specifications 2350 and 2360 have FAA requirements.

The final project report presents the results of laboratory testing to validate the use of Fine Aggregate Angularity (FAA) measurements with the Superpave method of Hot Mix Asphalt (HMA) design. A search of literature and Minnesota FAA data was conducted in preparation for FAA testing of aggregates and HMA design. Laboratory tests of aggregates included sieve analysis, specific gravity and FAA. Additional work was also performed by acquiring digital imaging data for the aggregates. Testing of asphalt mixtures included dynamic modulus tests and asphalt pavement analyzer tests. Testing was performed on four asphalt mixtures representing a range of Minnesota FAA values. Dynamic modulus testing was performed at three temperatures and five frequencies. Data from the dynamic modulus tests were processed using nonlinear regression. The resulting master curves of dynamic modulus vs. frequency were referenced to test temperature 54C. Asphalt pavement analyzer data at 54C was analyzed with respect to rutting curve. Laboratory test results for aggregates and mixtures were analyzed together using statistical methods to develop correlation coefficients and linear trends. It was found that dynamic modulus and rut resistance values are strongly related to aggregate blend FAA. Some additional parameters from digital imaging also predicted modulus and rut resistance very well and should be included in future reference.

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