Evaluation of the GPR frequency spectra in asphalt pavement assessment

•This paper discusses the use of frequency analysis in GPR assessment of pavements.•A section of a highway was studied in two different stages of its service life.•Changes in frequencies are associated to changes of the layers thicknesses and moisture.•The spectrum shows divisions that could be in this case associated to different layers. Ground penetrating radar (GPR) is frequently used in pavement assessments, mainly using the evaluation of wave travel times. However, GPR data provide further information that could be used in order to determine the inner conditions and characteristics about materials. In this paper, the possible analysis of the frequency spectrum of GPR signals is analysed and discussed. Several tests were carried out in a portion of a highway in two different stages of its service life. Results highlight the relationship between the shape of the spectrum and the frequency signature with the structure and conditions of the pavement.