Determining the Permeability Coefficient of Concrete Using New Fractal Model and Examining the Effect of Different Thermal Cycles on Concrete Permeability

Continuous thermal variations cause negative changes in concrete’s physical and chemical properties and can lead to increased permeability. On the other hand, existing methods for measuring concrete permeability are destructive, and the existing theoretical models do not consider the curing age of the concrete. In this study, these issues aimed to be addressed. Concrete samples were prepared and subjected to various thermal variation cycles. Subsequently, the in-situ and non-destructive “cylindrical chamber” method measured the samples’ permeability. Additionally, a new fractal model was employed to assess permeability, incorporating the effect of curing age on permeability. As mentioned earlier, the results obtained from this model showed a 6% difference compared to the laboratory method, indicating the proper accuracy of the new model. This insignificant difference confirms the high accuracy and reliability of our new approach. Furthermore, the “cylindrical chamber” test results demonstrated that 40, 80, 120, and 160 thermal variation cycles increased the concrete’s permeability by 1.4, 1.78, 1.12, and 1.16 times, respectively. In addition, the volume of water that penetrated also increased, consistent with the increasing number of thermal cycles. It is worth mentioning that the mercury test results illustrate that the size of different pores decreases as the curing age increases.