Abstract:
A monitoring system has been detecting progressive
displacements in Fagilde dam, completed in 1984.
Site inspection revealed the existence of random cracking,
surface discoloration, and superficial dissolution of cement
in the spillway surfaces and in the upstream face of the
dam. The macroscopic signs of deterioration, which could
be due to different mechanisms, showed an uneven distribution
in the exposed surfaces of the structure. Crushed
limestone and alluvial siliceous sand were used as aggregates.
Alkali–aggregate reaction was considered to be the
likely cause of concrete distress. In order to investigate the
causes of cracking and of the movements registered in the
wall, drill core sampling was performed and the concrete
investigated for the occurrence of expansive reactions.
Concrete petrography was complemented by other tests in
order to assess the probable evolution of the reactions in
the structure in the near future. Residual expansion tests,
soluble alkalis evaluation, and unconfined compression
tests were carried out. Alkali–aggregate reactions and
internal sulfate reaction were considered to be the main
causes of damage in the concrete. In this study, microscopy
showed to be an essential tool in the identification of the
main causes of deterioration.
