There are over 61,000 large dams worldwide, with over a quarter being concrete gravity dams. These structures, with an average age of 50 years and some approaching or exceeding 100 years, face significant challenges due to aging and the detrimental effects of Alkali-Aggregate Reactions (AAR). The evolving operational environment, exacerbated by climate change and seismic hazards, further complicates the safety assessment of these critical infrastructures. This paper investigates the impact of AAR on concrete gravity dams at various life stages. A pseudo-thermo-mechanical approach is considered to simulate the AAR effects on the dam body. A comprehensive analysis is conducted using a 2D model of Koyna Dam, incorporating inline properties of AAR at key life stages: 0, 25, 50, 75, and 100 percent of AAR effect propagation in the dam body. To evaluate the vibration-based characteristics of the dam, it is subjected to seismic ground motions at each stage considered here. The obtained displacements and accelerations have been used to evaluate the damage that occurred at each stage by calculating damage indices at each stage. The damage parameters considered are the frequency and displacement damage index. Each of the evaluated damage parameters is used in determining the extent of AAR damage over the dam body and its progression over time. This also helps to determine the efficiency of the damage parameters considered in determining the location of damage. These insights are essential for developing effective health monitoring mechanisms and refining numerical simulations.