Volume 40, Issue 7 (December 2012)
Relationship between Degree of Anisotropy of Asphalt Concrete and Its Geometrical Parameters
The property of anisotropy is an inherent characteristic of asphalt concrete (AC) and is mainly created by the nonuniform distribution of aggregates. Although there are some previous studies on the subject, a universal anisotropic model is still unavailable. This paper selects an AC type frequently used in China, AC-20, and tries to establish a usable statistic regression relation to predict the degree of anisotropy. Specimens are fabricated and tested. Then regression equations are obtained, and the effects of different geometrical parameters are investigated. It can be concluded that the average long axis angle is more important than deviation from the gravity center. In resilient modulus experiments of this research, the anisotropic degree of AC-20 ranges from 0.78 to 0.85. It comes mainly from the largest granules in aggregates. The AC type that has the smaller nominal maximum particle size will have less anisotropic tendency. As for AC-20, the anisotropy tendency will be neutralized by granules smaller than 13.2 mm, and the most effective granules have sizes between 4.75 mm and 9.5 mm.