Factors Affecting the Measurement of Effective Specific Gravity for Reclaimed Asphalt Pavement

Abstract

Proper use of high amounts of reclaimed asphalt pavement (RAP) in recycled asphalt mixtures requires a better understanding of RAP properties before mix design to ensure confidence that RAP properties are not changed by the mix design or asphalt production process. This paper presents the results of an investigation into the measurement of effective specific gravity of RAP and if RAP has any propensity to absorb additional asphalt during mix design or production. Factors of heating time, heating temperature, warm mix additives and amount of virgin asphalt added to RAP were investigated. The factors included two warm mix additives, three mixing temperatures, three asphalt contents and three RAP sources for a total of 34 test conditions and 68 tests. Results indicate that RAP does not absorb noticeable amounts of virgin asphalt or existing RAP asphalt during mix design or under approximate production conditions. A proposed method to improve measurement simplicity for the effective specific gravity of RAP by first coating RAP samples with 2% virgin binder is also discussed.