Diagnosis of alkali aggregate reaction in concrete dams: an Indian case study

Abstract

Deterioration of concrete structures have been observed in various dams in India and abroad. One of the critical deterioration mechanism involved in concrete hydraulic structures, such as dams and powerhouses can be attributed to the alkali aggregate reaction. Arch Dam in this case study is double curvature large thin arch dam, which features horizontal as well as vertical arches. Said dam suffered a continuous upstream deflection along with signs of minor distress. This paper provides a case study on systematic evaluation techniques adopted for diagnosis of Alkali Aggregate Reaction in Arch Dam in India. The study on arch dam constructed four decades ago in India included a field inspection of concrete dam structures with subsequent concrete cores drilling for laboratory investigation. The investigation included detailed petrographic evaluation of aggregates covering morphological microstructural and mineralogical analysis as per IS: 2386 Part VIII, mineralogical analysis covering the absence / presence of reactive aggregates prone to alkali-silica reaction, evaluation of concrete using petrographic analysis including study of pore structure and presence of micro cracks and abnormal reactive products, surface morphology study of concrete samples by Scanning Electron Microscopy (SEM) method and residual expansion on concrete cores.