A New Approach to Optimizing Aggregates in Asphalt - Evaluated Using Physical Properties Measured in the Goode and Lufsey Study

Abstract

In a previously published article, it was found that maximizing the Percent Packing Efficiency was effective in optimizing aggregates in asphalt to achieve an improved property balance.  This study then found that the Percent Packing Efficiency can be further increased for an optimum aggregate particle size distribution by increasing the ratio, Z, between particles. In addition, the Percent Packing Efficiency has been found to approach an upper limit as the 
number of particles are increased in an optimum particle size distribution with a constant value of Z.  A property analysis of the Goode and Lufsey study data for aggregates in asphalt also found that the minimums for the Mineral Voids and the Air Voids corresponded with maximums of Bulk Specific Density when the Percent Packing Efficiency approaches its maximum value.  These results confirmed that the Percent Packing Efficiency is a significant measure of the particle packing efficiency for aggregate blends in asphalt.

Since Gradation 3 generated in the Goode and Lufsey study had the best balance of properties, this gradation was identified as the standard for their recommended maximum density line. As anticipated, the Goode and Lufsey maximum density standard gradation did yield the maximum Percent Packing Efficiency followed in order by other standard gradations including a Stone Matrix Gradation, a Superpave Gradation and finally a Bailey Gradation.  In general, the analysis of the 24 gradations in the Goode and Lufsey study found that the Percent Packing Efficiency appears to be a very useful tool in predicting the gradation performance.