Using Ground Penetrating Radar (GPR) to Evaluate Air Voids Content in Hot Mix Asphalt

Abstract

"Air voids content is one of the most important characteristics of Hot Mix Asphalt (HMA). Air voids content that is either too high or too low can negatively impact pavement life and lead to deteriorations such as fatigue cracking, rutting, raveling, bleeding, and moisture damage. Currently destructive testing, such as coring, is typically conducted to evaluate in-situ air voids content of placed HMA. Asphalt coring, by its nature, is highly localized and therefore can easily miss localize areas of low quality. In addition, in large projects, there are some concerns expressed on the aesthetic deficiencies with respect to the number of cores in the wearing course and the introduction of potential weak spots within the pavement structure. In other methods of air voids determination, such as nuclear density gauge, there are also concerns regarding safety, costs associated with radioactive material licensing and requirements for closing off work areas. In this paper the use of a “GSSI PaveScan RDM” GPR model for non-destructive assessment of insitu air voids in HMA is investigated. In-situ air voids content can be determined through plotting of dielectric changes with measured cores’ air voids content. This technique provides an opportunity for continuous measurement of air voids in HMA and, at the same time, faster and reliable in-situ data for QA/QC. These benefits can significantly accelerate pavement construction and so this paper looks to proliferate the adoption of such practice. The case study on Al Khor Expressway, one of the major expressways in Qatar, has demonstrated good repeatability and correlation with measured air voids content."