GPR chloride inspection of a RC bridge deck slab followed by an examination of the results

Chlorides applied on roads for de-icing can cause serious damage to reinforced concrete structures. On bridge deck slabs, there is usually a waterproofing membrane to prevent the ingress of water and chlorides into the concrete. If the waterproofing is damaged, the protection is insufficient and chloride ions and humidity penetrate into the concrete causing corrosion of steel reinforcing bars. This can finally result in a failure of the structure. GPR has been suggested as a method for detecting chloride contaminations in concrete bridge deck slabs. In laboratory experiments, the method has been applied and validated successfully. In addition, it has been applied to several bridge decks. However, on real bridges a detailed examination of the results is usually not possible. In a field experiment, a bridge deck designated for demolition was inspected for chloride contamination using GPR. Afterwards the results were examined with an extensive probing programme. This paper presents a comparison between results of non-destructive (GPR) and destructive (probing) testing based on a detailed examination of measurement results.