Diagnosis and Prognosis of Internal Swelling Reactions in Cahora Bassa Dam – A Case Study

In the last decades, a significant number of large concrete infrastructures with deterioration problems related to alkali-silica reaction and delayed ettringite formation have been identified worldwide. Currently, due to phenomenological and assessment complexities it is still difficult to provide recommendations for the prevention of ASR damage in new structures, involving certain aggregates, as well as to perform a complete assessment of the actual condition of an affected structure and an accurate prediction of its future deterioration. This paper aims to contribute to the ongoing discussion of this topic and, therefore, presents some of the work performed on diagnosis and prognosis of internal swelling reactions in the concrete from the Cahora Bassa dam, in Mozambique. The Cahora Bassa dam, built between 1972 and 1975, is a part of a hydroelectric scheme located on the Zambezi River. This paper includes a very brief overview of the information available on the concrete and its constituents, at the time the dam was built, and succinctly presents the analysis of some of the results obtained in the laboratory test campaign (namely, microstructural analyses, chemical analyses, and expansion tests) performed on concrete cores extracted from the structure, in 2017, and on the aggregate used in the dam’s concrete.