Are There Options to Stop or Control ASR in Existing Dams?

Many dam owners around the world have been faced with swelling concrete issues at their dams and hydro projects for the past 70 years or more. Several different management strategies have been adopted, although the options appear limited and no “once and forever” fixes have been developed. In some cases alkali-silica reactions (ASR) and associated expansion appear to have diminished after 30 or so years, while in many other cases it continues with more or less vigor. In cases where the ASR continues, given the very long required service life of dams, a hundred years and more, there is a clear need to seek to identify some practical solutions to limit the ASR and its effects in these long-term cases. In such cases the potential role of releasable alkalis from aggregates and recycling needs to be clearly understood to be able to reliably forecast future behavior and develop a long-term management plan. The role of water and humidity must also be understood. The control options are limited but given the long timescale, and often the slow rate of expansion, some very long-term solutions, such as drying the concrete to reduce the expansion rates in some parts of dams and associated structures, may be possible and worth considering in some cases. This paper examines some of the issues involved in such notions and identifies issues that would need to be addressed to determine their feasibility and practicability.