Mica is widely distributed in artificial sand. However, the performance of dam concrete can be significantly impaired when the mica content in artificial sand exceeds the standard. In this work, the quantitative and qualitative effects of mica on the mechanical properties and durability of dam concrete were evaluated by investigating the influence of artificial sand with different mica contents on these properties. In addition, a freeze-thaw damage model was established to effectively express the quantitative relationship between the factors influencing the freeze resistance of concrete with different mica contents and evaluation indexes. The results indicate that the dam concrete performance is not significantly affected when the mica content is below 2.9%. Whereas mechanical properties, impermeability, and freeze resistance of dam concrete are adversely affected when the mica content exceeds 2.9%. Among them, the compressive strength of dam concrete decreases by 2.6–9.9%, the split tensile strength decreases by 3.3–11.1%; the permeability height increases by 18.4–75.6%; and the mass loss rate increases by more than 63.3%. In addition, freeze-thaw damage model indicates that mica content is a key factor affecting freeze resistance. Therefore, the upper limit of mica content is recommended to be 2.9%.