How Low Is Too Low? Assessing the Risk of Low Air Voids Using Accelerated Pavement Testing

Various forms of asphalt pavement distress can be attributed, in many cases, to low air voids in mixtures during production and placement.When lowair voids are encountered during production, the specifying agency must decide whether to require the material that has already been placed to be removed and replaced or whether it can be left in place. This study was conducted, in part, in the INDOT/Purdue Accelerated Pavement Testing (APT) Facility to develop a decision-support tool for dealing with such events that is based on projected rutting performance of the pavement system. The responses to repetitive APT wheel passes of test pavements with low air voids in either the surface or intermediate course were measured using a laser based system. The permanent deformation of the top pavement layers is used, in conjunction with simplified mechanistic analysis and engineering judgment, to formulate the desired decision-support tool.