Evaluation of The Effect of Strength, Duration and Water Pressure and Concrete Casting Direction on Concrete Permeability

Due to penetration of harmful agents into concrete and reduction of its durability, having knowledge about the value of concrete permeability is of importance. Permeability tests are conducted using a specified pressure and duration in concrete codes. While pressure value and its duration are important factors effecting permeability. So, the effects of the test pressure value, its duration and the direction of the casting on the permeability of cubic concrete samples made of dried aggregates and different water to type II Portland cement ratios equal to 0.4, 0.5 and 0.6 at the ages of 7, 28 and 91 days are evaluated using ‘‘cylindrical chamber’’ method. ‘‘Twist-off’’ method is also used for determination of concretes strength. The obtained results show that a linear relationship exists between shear stress of twisting moment and compressive strength and permeability of the samples in casting direction is lower than the permeability perpendicular to casting direction and the exponent obtained to approximate the relationship between penetration volume and depth with pressure is approximately constant in a specific age and test direction, regarding the water to cement ratio. This issue wasn’t observed in approximation of the relationship between penetration volume and depth with the pressurizing time using power function. An inverse relationship between compressive strength and permeability of samples was also observed. The relationship between penetration volume and depth was approximated with high accuracy using linear function. The calculated Reynolds number also shows that flow regime is laminar in concrete samples.