Diagnosis and prognosis of internal swelling reactions in Cahora Bassa dam, Mozambique – a case study

Abstract

In recent decades, a significant number of large concrete infrastructures with deterioration problems related to alkali–silica reaction (ASR) and delayed ettringite formation have been identified worldwide. Currently, owing to phenomenological and assessment complexities, it is still difficult to provide recommendations for preventing ASR damage in new structures involving certain aggregates, and to perform a complete assessment of the actual condition of an affected structure and an accurate prediction of its future deterioration. The aim of this paper is to contribute to the ongoing discussion of this topic and presents some of the work performed on the diagnosis and prognosis of internal swelling reactions in concrete from the Cahora Bassa dam, in Mozambique. The Cahora Bassa dam, built between 1972 and 1975, is 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 an analysis of some of the results obtained in the laboratory test campaign (e.g. microstructural analyses, chemical analyses and expansion tests) performed on cores extracted from the structure in 2017 and on the aggregate used in the dam’s concrete.