Caculo Cabaça Hydropower Project - Evaluation of the susceptibility of aggregates for participation in expansive alkali-silica reaction

Abstract

It is worldwide recognised that alkali-silica-reaction (ASR) may cause premature deterioration of concrete dams. GAMEK as the representative of MINEA – Energy and Water Ministry of Angola, owner of Caculo Cabaça Hydropower Project (HPP), and its consultant COBA, were concerned with this phenomenon and the problems that it may cause in the future, during the operation stage, namely in the structures’ integrity and the adequate functioning of the equipment, especially the gates integrated in the dam and the waterways of the powerhouses. For that purpose, in the tender specifications, it was requested that the Contractor CGGC carry out a set of laboratory tests in the design stage to evaluate the potential for the development of ASR in the concrete to be used. The assessment also involves the evaluation of the efficiency of preventive measures, such as the use of mineral additions with pozzolanic characteristics. This paper presents and discusses the results from the tests carried out at LNEC to assess the susceptibility of aggregates and combinations of aggregates with pozzolan for participation in expansive alkali-silica reaction (ASR). The results obtained can then be used to establish the dosages of mineral additions that allow mitigating expansive reactions in the concrete, thus guaranteeing the operation of the hydropower project without constraints due to this phenomenon.