Durability performance of concrete incorporating Class F and Class C fly ashes

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.