Procedure for Monitoring of Brazilian Railway Concrete Bridges Affected by Chemical Reaction

Typical mosaic-shaped cracks have been frequently identified mainly in concrete foundation blocks of some railway bridges built around 1970´s in South-eastern Brazil. These damages are attributed to the Alkali-Aggregate Reaction (AAR) and to the Delayed Ettringite Formation (DEF - Delayed Ettringite Formation). In view of maintaining the bridges in service, it was necessary to carry out a thorough evaluation of the evolution of the process that is destroying the concrete elements, with the aim of looking for indicators that can be monitored for this purpose. All these studies gave rise to a management plan, which strategy is to intervene annually in a greater number of bridges that present damage with the challenge of seeking technically viable solutions, enabling faster and less costly interventions, and still mitigating the risks regarding structural and durability problems in these elements. For this purpose, additional test procedures have been accomplished with the concrete extracted from the bridges, like the Damage Rating Index (DRI), the Stiffness Damage Test (SDT), and in the field, the cracking index (CI) has been applied. These test procedures have been developed to assess the current condition and the potential for further expansion/distress of chemical-affected concrete. From the test results and the damage identified during bridge inspection, assets will be selected to intensify monitoring or carry out interventions, based on the risk of each bridge determined in the Bridge Management System (BMS). A procedure for ranking bridges for maintenance is proposed to define prioritization and actions to be adopted in each case.