A Master of Science thesis in Civil Engineering by Layane Hamzeh entitled, "Ground Penetrating Radar Technique for Bridge Deck Inspection," submitted in July 2013. Thesis advisor is Dr. Sherif Yehia and Co-advisor Dr. Nasser Qaddoumi. Available are both soft and hard copies of the thesis.
The rapid growth of infrastructure in the UAE has caused a proportional growth in the transportation system. Bridges are among the major elements in the transportation system that requires continuous monitoring and maintenance over time. Replacement of bridges is expensive; hence it is desirable to assess damage using a cost effective maintenance strategy. Therefore, nondestructive testing techniques provide an efficient and feasible method for detecting defects in bridges in a quick manner. Several surveys have shown that ground penetrating radar (GPR) has the potential to be adopted as a non-destructive inspection technique. This work presents an experimental investigation of mix variation, and environmental conditions effects on the detectability of defects using GPR. Sixteen 1.22 m x 1.22m x 0.2 m slabs with simulated common bridge defects were prepared. Four concrete mixes: high strength, normal strength, lightweight, and self -consolidated concrete were used in the investigation. Two main parameters were taken into consideration when simulating the defects in the specimen: depth and size of the defect. Each of the simulated specimens contained delaminations, voids, cracks, corrosion, honeycombing, and missing bars. GPR readings were taken regularly at constant time intervals for all specimens. At the time of data collection, environmental conditions, which include temperature, humidity, and wind speed, were recorded to monitor their effect on the dielectric constant obtained from GPR. It was concluded that voids with diameter less than or equal to 1.27 cm and honeycombing were not detected by GPR for one layer of steel specimens. Cracks with thicknesses of 0.25cm and 0.5 cm were not detected in two layers reinforcement specimen due to congestion of steel. It was suggested that defects were detectable by GPR at different temperatures, so it could be used as a non-destructive inspection technique even at high temperature of 40 °C. In all mixes, the detectable defects were visible in early and late concrete age. However, in lightweight concrete mix, defects were not detectable earlier than 3 months after casting concrete. Furthermore, the mixing model gave an idea about the effect of the mix ingredients on the dielectric constant of each specimen.