Description
Internal swelling reactions (ISR) is a term used to refer to the chemical reactions that result in the expansion and, eventually, damage of the concrete elements in which they occur. Alkali-silica reaction (ASR) and delayed ettringite formation (DEF) are the most common reactions of this type, both of which are relatively frequent in concrete dams. The concrete deterioration caused by ISR can be observed in several forms at the level of the structure. The external manifestations include relative movements, displacements and deformations, cracking, surface discoloration around the cracks, scaling or spalling and surface pop-outs.
The detection and the assessment of these structural symptoms in large concrete dams is usually made through visual inspection and interpretation of the monitoring instruments data, such as stress-independent embedded strainmeters, geodedic levelling, plumb lines and internal or external jointmeters.
The Portuguese information system, designed to serve as a national database, has its own data structure and includes the results measured from large concrete dams of all types, including dams with more than 60 years. This information system is used by dam owners and the National Laboratory for Civil Engineering (LNEC) to assess the structural behaviour over the years and determine the need for an intervention.
In what concerns to the rehabilitation of these ISR-affected hydraulic structures, the historically most successful intervention types are presented as function of the respective anomaly.
