Traditionally the effect of microfines in concrete has been evaluated in specimens subjected to a moist curing regimen. However, this type of curing is not representative of real pavement construction conditions in the field where evaporation of water from new pavement surfaces can occur before curing compounds are applied. This study evaluated the impacts of natural microfines from both aggregate fractions, fine and coarse, under ASTM C33–specified requirements, in the performance of concrete cured under a wet (~90% relative humidity) and a dry (30% to 60% relative humidity) environment. The examined concrete batches were fabricated with seven different aggregates, and their associated microfines fell into two major categories: siliceous stone and dolomitic limestone. Results showed that current ASTM C33 thresholds of microfine content were reliable only when specimens were moist cured. The damage induced by dry curing was exacerbated by the presence of these microfines.