Diagnostic procedure for corrosion assessment of existing concrete bridges: Experimental case study

Many existing reinforced concrete (RC) and prestressed concrete (PC) structures built in the last century have now reached or exceeded the term of the design service life and require maintenance interventions to repair degradation-induced damage, especially due to steel corrosion. The conservation of aging structures and infrastructural facilities is an urgent problem, particularly for bridges in view of their social and economic importance. To properly define the restoration interventions and fulfill safety, robustness and durability requirements, it is necessary to inspect concrete structures and assess the state of degradation of materials and corrosion of embedded steel. This paper is aimed at presenting a diagnostic procedure based on effective methods and criteria for corrosion assessment of existing concrete bridges. To this purpose, the paper considers a case study of a bridge recently dismantled and investigated within an ongoing multi-partner research project and discusses the results of in-field nondestructive testing as well as of chemical, physical and microstructural analyses, carried out on the structural members that were subjected to carbonation and chloride-induced corrosion during service conditions. Based on the investigation campaign carried out on the case study, the proposed diagnostic procedure for corrosion assessment of existing bridges is discussed and validated.