SmartRock-Based Research on Gyratory Locking Point for Stone Mastic Asphalt Mixture

Abstract

For gyratory compaction, the concept of the locking point was initially developed to identify the compactability of asphalt mixes and to alleviate potential aggregate crushing in the mold. Most previous studies on the locking point were based on specimens’ height change. Recent studies have indicated that the gyratory locking point of cold mix asphalt mixtures could be determined by the rotation angle range indicator using SmartRock. However, height or rotation angle change ultimately reflects a change in volume. Additionally, there is no clear physical and mechanical connection between the volume change and the gyratory locking point. In this paper, a stone mastic asphalt mixture (SMA 13) was selected for gyratory compaction applying various compaction temperatures. The compaction data were recorded by a SmartRock embedded in different positions. Collected data included stress, rotation angle, and acceleration. The major findings are as follows: (1) the specimen’s locking point could be determined based on a representative stress value when the SmartRock was embedded in the specimen’s center, and the results are close to the traditional evaluation results (LP3 or LP2-2-3); (2) the representative rotation angle value reached a plateau earlier than the representative stress value; (3) the representative acceleration value is not suitable for characterizing the interlocking process during gyratory compaction.

Experimental and numerical simulation study on flow behavior of asphalt mixture using smart aggregate

“…Thus, the results recorded by the sensors are an approximate representation of the complex contact between the aggregates, which is the non-negligible reason for the large difference between the contact forces monitored by the sensor and the external load. However, the contact force monitored by smart aggregate is a qualitative description of the interlocking state between aggregates, and the high and stable contact force is a sign of the formation of a high-strength interlocking structure between aggregates in the later compaction stage [15].…”

“…Scholars carried out indoor gyratory compaction and field compaction tests of mixture using smart aggregate sensors [1,13,14], and evaluated the compaction degree of asphalt mixtures at different locations by analyzing the monitoring data of the sensors, and further developed a method to determine the locking point of asphalt mixtures based on the monitoring results of the smart aggregate sensors [15]. However, asphalt mixture is a typical non-homogeneous material, and the grain-scale factors such as size and shape of particles can significantly affect the monitoring results of smart aggregate sensors [1,16].…”