Determination of voids in the mineral aggregate and aggregate skeleton characteristics of asphalt mixtures using a linear-mixture packing model

Voids in the mineral aggregate (VMA), as a main design parameter in the Superpave mixture design method, is an important factor to ensure asphalt mixture durability and rutting performance. Moreover, an asphalt mixture's aggregate skeleton, related to VMA, is another important factor that affects critical asphalt mixture properties such as durability, workability, permeability, rutting, and cracking resistance. The main objectives of this research are to propose an analytical approach for estimating changes in VMA due to gradation variation and determining the relevant aggregate skeleton characteristics of asphalt mixtures using the linear-mixture packing model, an analytical packing model that considers the mechanisms of particle packing, filling and occupation. Application of the linear-mixture packing model to estimate the VMA of asphalt mixtures shows there is a high correlation between laboratory measured and model estimated values. Additionally, the model defines a new variable, the central particle size of asphalt mixtures that characterizes an asphalt mixture's aggregate skeleton. Finally, the proposed analytical model shows a significant potential to be used in the early stages of asphalt mixture design to determine the effect of aggregate gradation changes on VMA and to predict mixture rutting performance.