Recently, several researchers have proposed asphalt film thickness as a criterion for ensuring the durability of asphalt mixtures. However, they suggested that the standard film thickness equation, which dates back to the 1940s, needs to be examined by modern technology and improved. A presumable background on which the Asphalt Institute surface area factors are based was recovered and analyzed in detail. A fundamentally sound model for film thickness calculation was developed using a model of asphalt concrete in which the aggregates are spherical but have an arbitrary size distribution. A recent result from statistical geometry is applied to determine the film thickness for any volume fraction of aggregates and any volume fraction of effective asphalt. The analytical formulas are presented, the details of the calculation are summarized, and examples are provided.
Abstract