Laboratory Evaluation of the Workability and Compactability of Asphaltic Materials prior to Road Construction

Abstract

Asphalt mix compaction is dependent on many factors, particularly gradation, asphalt grade and content, aggregate size, temperature, and compactor manufacturer. The new development in polymer-modified asphalt has a major impact on asphalt pavement compaction in the field. Although it leads to improving overall mechanical characteristics, there are concerns that mixes become drier and more difficult to compact. This paper aims to develop compaction indices using the Superpave gyratory compactor to evaluate the workability and compactability of the mixes during the routine mix design process and prior to laydown operations. Workability is reflected in the ease of blending the mix components using construction equipment. Compactability is reflected in the mixes’ stability and resistance to densification under traffic loading. To identify adequate thresholds for the compactability indices, performance testing is required to validate the long-term behavior of these mixes. This was accomplished in two phases: laboratory performance testing and field performance testing. The former was conducted using Hamburg wheel tracking, rutting, and dynamic modulus tests, whereas the latter phase was accomplished through accelerated pavement testing. Evaluation of the mixes’ internal structure effect on the compaction indices, in terms of aggregate orientation and number of contacts, was also investigated.