Abstract
This study aims to explore the applicability of diffuse ultrasound to the evaluation of water permeability and chloride ion penetrability of cracked concrete. Lab-scale experiments were conducted on disk-shaped concrete specimens, each having a different width of a penetrating crack that was generated by splitting tension along the centerline. The average crack width of each specimen was determined using an image binarization technique. The diffuse ultrasound test employed signals in the frequency range of 200 to 440 kHz. The water flow rate was measured using a constant water-head permeability method, and the chloride diffusion coefficient was determined using a modified steady-state migration method. Then, the effects of crack width on the diffusion characteristics of ultrasound (i.e., diffusivity, dissipation), water flow rate, and chloride diffusion coefficient are investigated. The correlations between the water flow rate and diffuse ultrasound parameters, and between the chloride diffusion coefficient and diffuse ultrasound parameters, are examined. The results suggest that diffuse ultrasound is a promising method for assessing the water permeability and chloride ion penetrability of cracked concrete.
Highlights
Water permeability and chloride ion penetrability are widely used as indices to evaluate the durability of cement-based materials
The average crack width in each specimen was defined as the area of the crack at the flatThree face divided by thetests, length of the crack
The experimentally determined water flow rate (Q) is well represented by a cubic polynomial function of average crack width based on Equation (5)
Summary
Water permeability and chloride ion penetrability are widely used as indices to evaluate the durability of cement-based materials. Ultrasonic wave velocity [7], transmission of surface waves [8,9], diffusion of high-frequency waves [10,11,12,13,14,15,16], coda wave interferometry [16,17,18], characteristics of guided waves [19], and nonlinear characteristics of ultrasound [20] have been studied for application to the nondestructive evaluation of defects in concrete. Among the available ultrasonic methods, diffuse ultrasound can be applied to monitor and evaluate the process of micro-cracking damage, self-healing [15,16] or volumetric change in concrete [18], and it may be applicable to evaluating the material properties of concrete (e.g., air-voids, setting time) [22,23,24,25]
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