Three-Dimensional Fractal Characterization of Concrete Surface Subjected to Sulfuric Acid Attacks

Sulfuric acid corrosion on concrete structures is more prevalent and its damage evaluation becomes gradually imperative. This study attempts to characterize the sulfuric acid corroded surfaces of concrete in terms of three-dimensional fractal dimension. Accelerated sulfuric acid corrosion tests were conducted using concrete cylinders with six different corrosion durations, and the 3D coordinates of points on the surface of cylinders were captured using 3D laser scanning technique. The fractal dimensions were calculated using the cubic covering method, and the corrosion depth and mass loss of concrete were obtained correspondingly. The results indicated that fractal dimension can be considered as an indicator to evaluate the corrosion deterioration. The surface fractal dimension was positively correlated with the corrosion duration by a power function, where the value increased dramatically in the early stage, and gradually slowed down to maintain constant. Therefore, empirical functions to evaluate the corrosion depth and mass loss of concrete after sulfuric acid attacks were proposed. The parameters to establish the equivalent accelerated relation between experimental and natural conditions were also recommended under different degradation degrees.