This paper presents an experimental study on the durability properties of concretes containing Turkish Class C and Class F fly ashes. A total of 39 mixtures with different mix designs were prepared. In order to characterize the concrete quality, compressive strength of the specimens were obtained. After that, the mixtures containing Class F and Class C fly ashes which had similar compressive strength values to control mixtures at 28 d for each series were used for durability tests. The durability performance of the concretes was assessed from measurements of rapid chloride ion permeability, sorptivity and freezing-thawing resistance tests. The degree of freezing-thawing resistance was evaluated using change of weight, ultrasonic pulse velocity (UPV) and flexural strength after 300 cycles. The test results indicated that Class C fly ash showed higher compressive strength than Class F fly ash. The addition of fly ash improved the rapid chloride ion permeability and sorptivity of concrete. There was a notable reduction in the UPV after the specimens are subjected to freezing-thawing cycles. The amounts of flexural strength loss have been measured in the range of 5.38-29.83%. The use of Class C and Class F fly ashes positively affected freezing-thawing resistance of concretes. (C) 2012 Elsevier Ltd. All rights reserved.