Quantification of Compactability of Bituminous Mixtures with Different Aggregate Gradations Using Superpave Gyratory Compactor and Shear Box Compactor

Bituminous mixtures offer varying compactive resistance due to gradation, binder type, its content, and temperature. Most of the attempts to quantify laboratory-scale compaction resistance have used Superpave Gyratory Compactor (SGC). However, SGC has criticism related to poor spatial uniformity of air voids, whereas the Shear Box Compactor (SBC) is reported to have less spatial variation in air voids. The focus of this study is to investigate and document the sensitivity of SGC and SBC on the variation in aggregate gradation during compaction. In this work, two aggregate gradations designed based on particle packing theory for achieving optimum packing, and a control sample with Bituminous Concrete mid-gradation as per the current Indian Specifications are used. Compaction curves obtained from both the compactors are analyzed in terms of various compaction indices and their correlation to laboratory rutting performance is investigated. It is identified that certain indices of SGC and SBC are sensitive to the rutting performance of the mixtures prepared with different aggregate gradation.