A detailed inspection of a dam in Thailand is reported for its time-dependent gradual expansion towards upstream, contrary to the expected downstream creep deflection owing to hydrostatic loads. In this study, based on petrographic analysis and SEM, a sample of cored concrete from the dam was found to undergo a low to moderate level of ASR. The potential for future expansion was verified using an accelerated laboratory test. The experimental data were used to evaluate the dam performance by conducting an FEM analysis. The numerical model was calibrated with the observed deflection, and the mechanical stresses owing to the combined ASR and hydrostatic loads were estimated for various ages of the dam. In addition, stress and deflection were predicted using probabilistic methods. A sensitivity analysis was also performed to monitor the behaviour of the dam under various environmental conditions and input parameters. It was found that the gradual deterioration by ASR does not pose a high risk to the dam under normal loading conditions.

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