Over the past decade ground penetrating radar (GPR) applications have been under development within the Texas Department of Transportation (TxDOT). In the early 1990s various research studies were undertaken to identify and verify potential GPR applications and to develop signal processing techniques. In the mid 1990s GPR systems moved into mainstream usage, improved software was developed and training schools were conducted. The Texas DOT now has 4 complete air launched GPR systems for pavement evaluation. Several districts use GPR technology on a routine basis as the first step in planning the rehabilitation of major flexible pavements. It has also been used extensively in forensic studies to identify the cause of rapid pavement deterioration. Current research efforts are aimed at using GPR in "real-time" quality control testing of newly placed hot mix asphalt (HMA) overlays, for both thickness and density control. This paper will provide an overview of the Texas development effort. The basics of GPR will be presented and a number of successful case studies will be described. These include using GPR to detect moisture trapped within HMA, and base layers, and its use in detecting localized areas of segregation in newly placed overlays. GPR was initially promoted as a rapid layer thickness measuring tool, but as will be described in these case studies GPR can provide substantially more information than simply layer thickness. (a)
Samenvatting