Abstract

For the Superpave Gyratory Compactor (SGC), the concept of locking point was developed to identify the compatibility of asphalt mixes and to alleviate potential aggregate crushing in the mould, which is defined as the gyrations related to specimens’ height change. Inspired by this concept, for Marshall impact compaction, previous studies redefined the impact locking point as the blow number at the acceleration pulse of each blow reaching a stable stage. Unlike the gyratory locking point, the impact locking point is based on the change in acceleration, which might be related to the change in the specimen stiffness. However, determining the impact locking point by comparing the two successive blow’s acceleration pulse is time-consuming and inconvenient based on previous studies. To improve this, a modified method is proposed based on the change in the peak acceleration during impact compaction and applied on test results from three typical Marshall compactors, and a comparison to locking points of gyratory compaction is also made to verify the validity. The results indicate that the modified method is applicable for the American Marshall compactor. For Chinese Marshall compactors, further study should focus on the accelerometer’s alternate installation method to avoid noise effects.

Keywords:Marshall compactor; Accelerometer; Dynamic response; Superpave gyratory compactor