GPR in road investigations – equipment tests and quality assurance of new asphalt pavement

Ground penetrating radar (GPR) was successfully used in road applications in the Nordic countries as a nondestructive test procedure during the last decade. In order to standardise the procedures, boost cooperation and share knowledge between Finland, Sweden and Norway, a joint Mara Nord project was launched in 2010, involving national transport administrations, universities, consultant companies and GPR manufacturers. One outcome of the project will be recommendations to guidelines on different GPR applications. Within the frame of the project test, measurements of the most common GPR units and antennas were carried out. The results show that all tested equipment produce good results, and differences between the varying techniques are highlighted. Quality assurance of new asphalt pavements can be performed with the help of GPR, by relating the measured dielectric value to the void content of the asphalt pavement. The current method used in Finland is analysed. Recommendations and proposals for developing the quality assurance are presented. The project is scheduled to end by summer 2012.