GPR applications for bridge deck evaluations in Finland : Saarenketo, T; Soderquist, M K Non-destructive Testing in Civil Engineering, Liverpool (United Kingdom), 14–16 Apr 1993. Vol. 1, pp 211–226. Edited by J H Bungey. The British Institute of NDT (1993)

Abstract

The usefulness of Ground Penetrating Radar (GPR) for examining areas of deterioration in bridge decks was tested in Finland, with the aim of assessing whether the method can be used to estimate pavement thickness, deterioration of the protective concrete and slab and damage to the water proofing. Some tests were also performed to locate cracks in the slab. The surveys were performed using ground coupled dipole bow-tie antennae with frequencies of 900 MHz, 1.0 GHz and 1.5 GHz, and 2.5 GHz TEM horn antennae were also tested. The measured GPR data were compared with information obtained from drill cores and damage mapping during repair of the bridges. The results show that GPR can be used to map areas of deterioration in bridge decks. The radar data image of the weathered areas varies depending on whether the damaged concrete is dry or saturated with water, but the level of deterioration is still difficult to determine from radar data alone in all bridges and some reference drill cores have to be taken. A pavement thickness of more than 40 mm can be determined with sufficient accuracy and failures between the concrete and asphalt pavement and in water proofing are also detectable. The problems with the method as used in Finland have concerned the manual interpretation of the GPR data, which is slow and time-consuming, but efforts are under way to develop software for automatic interpretation. (A) For the covering abstract see IRRD 861706.