Large dams, integral to global infrastructure, confront a critical challenge of aging as many surpass the 50-year mark, and some approach a century in service. With over 61,000 such structures worldwide, ensuring the safety of aging dams has become a global imperative. This deterioration is exacerbated by alkali-aggregate reaction (AAR), leading to weakening of concrete, cracking, and jeopardizing dam integrity. Alkali-aggregate reaction emerges as a primary cause of concrete gravity dam deterioration, prompting a comprehensive reassessment of safety using contemporary advancements. In the realm of modern structural engineering, the twenty-first century presents a distinctive challenge: employing advanced computational techniques to assess infrastructure safety against the forces of aging, shaking, and cracking. The second law of thermodynamics, coupled with unpredictable natural forces, demands a re-evaluation of dam safety. This paper delves into the critical issue of AAR in large concrete structures, with a specific focus on concrete gravity dams. The process of aging and the resulting risk of AAR-induced cracking pose a significant threat, compelling dam owners to implement preventive measures. The study introduces a simplified modeling approach based on thermo-mechanical analysis, employing finite element method (FEM) in the time domain. This approach is validated against conventional AAR models, demonstrating its effectiveness in predicting strains and stresses induced by AAR effects. The proposed modeling technique provides a unique way to estimate the mechanical damage to concrete gravity dams due to AAR, and also the computational efficiency of the time domain-based finite element method (TDSFEM) over traditional FEM. This computational advantage is particularly crucial for analyzing large structures like concrete gravity dams, marking a significant stride in ensuring the sustained safe utilization of these critical infrastructures.