New technologies have enabled the pavement engineer to develop a better picture of the pavement structure. Two of these new technologies are ground-penetrating radar and infrared thermography. Each of these techniques allows the pavement engineer to nondestructively evaluate subsurface defects within and under the pavement. Infrared thermography is now widely used to determine the location of delaminations within the pavement.
In the case of delaminations or debonded sections of pavement, the thin delaminated area will heat faster than the adjacent thicker section, and the infrared scanner will detect temperature differences between the two areas. This process is widely used to inspect bridge decks. It is used to determine the extent of deterioration beneath asphalt overlays on the deck and thus save the costs of removal of the asphalt and any waterproofing membrane.
Ground-penetrating radar can be used to determine a number of characteristics useful to the pavement engineer in developing a rehabilitation scheme. Radar is used to determine the condition of joints in concrete pavement, to locate and size voids beneath the pavement, to determine the thickness of pavement, and to determine the composition of the pavement structure.
Case histories are presented to discuss each of these technologies and their applications. These technologies are presently being written into ASTM standards for particular applications, including determination of delamination using infrared thermography and determination of pavement layer thickness using ground-penetrating radar. Limitations in the use of the techniques are also discussed.