Using numerical simulations, this study investigated the concrete expansion damage caused by the coupled action of freeze-thaw cycles (FTC) and alkali silica reactions (ASR). In the authors’ previous experiments, it was shown that a preceding ASR definitely accelerated the succeeding expansion by FTC. Further, even if the specimens have sufficient entrained air to prevent expansion by sole FTC action, they can expand under the combination of ASR and FTC. The presence of air voids in specimens has little effect on the single ASR expansion rates. These observed experimental trends were analyzed by numerical simulations. Authors have proposed the mixed pore pressure and concrete expansion models for coupled ASR and FTC, and a non-linear finite element system for concrete structures was used to analyze them. These models were used to work out the factors governing the experimental trends. By comparing the experiments and simulations, it appears the air voids contribution can be the key factor on the coupled ASR and FTC expansion process. With effective modeling of microscopic ASR-gel and ice formations inside air voids, the experimental trends can successfully be reproduced numerically.