The measurement of imaging-based volumetric and morphological indices and their correlation with laboratory and field performance results is a wave of the future in the development of asphalt pavement science and technology. A University of Illinois Aggregate Image Analyzer has been developed and is ready for validation. This proposal makes strong efforts to develop parameters that may be used to supplant in speed, cost, objectivity, and precision/accuracy of the traditional test procedures used to characterize aggregate shape/volume characteristics.
The study began in March 2002. It consisted of 2 main phases. In Phase I, coarse aggregate shape, size, angularity and texture properties were evaluated to define proper imaging based morphological indices. The University of Illinois Aggregate Image Analyzer (UI-AIA) was used for the evaluation. The aggregates that were evaluated included: (1) Samples received from the National Center for Asphalt Technology (NCAT) Pavement Test Track study and (2) representative aggregate samples from the participating states and the Centeral Federal Lands and Highways Division.
In Phase (II) of the study, representative samples received from the participating states were used to prepare asphalt concrete samples in SuperPave gyratory compacter. The samples were then tested for modular and permanent deformation characteristics. Stability and performance of the mixes were determined at the Advanced Research and Engineering Laboratory (ATREL) of the University of Illinois. The intent was to form a laboratory database for studying the influence of particle shape on asphalt concrete mix performance and also to establish proper aggregate criteria. In addition, NCAT test track data were collected for various field mixes for which detailed aggregate shape property indices were developed from Phase (I). Both the laboratory and field data are currently being analyzed for better understanding of aggregate effects on asphalt concrete mixture performance.
The laboratory work is expected to be completed by November 2003 and preparation for final report will begin.
The entire project is expected to be completed by March 2004.
Materials and Construction