Evaluation of crack width and self-healing performance of concrete based on fluid flow characteristics: Comparison between water permeability test and gas diffusion test

Water permeability tests are among the most widely used test methods to evaluate a crack width and self-healing performance of concrete. The average crack width and the overall self-healing performance of each specimen have been determined by the amount of water that penetrates through a crack. Water, which is used as a medium, tends to become viscous due to gravitational pull among its molecules. This viscosity causes the flow velocity in the cross section exhibits parabolic distribution. Also, this is the reason why it is difficult to apply the water permeability test for a specimen with a narrow crack. In an attempt to overcome the limitation caused by the viscosity of the water, a gas diffusion test have recently been proposed, wherein a gas with low viscosity is used to replace water as a medium. However, given that water and gases behave differently when passing through cracks, the two methods may have different characteristics in the estimation of crack width and healing performance. The present study analyzed trends found in the estimation of crack width by these two methods. Despite the fact that the tests were conducted on the same specimen, the results of these two experiments showed different trends. This study analyzed the causes of these differences. It was found that the differences in the characteristics of the fluids and the healing products influenced the trend of the experimental results. The gas diffusion test could be used as an effective method for evaluating the crack width and healing performance of self-healing concrete.