Mesh Increment Methodology for Improving Concrete Ultrasonic Tomography

Ensuring the longevity of concrete structures is crucial for increasing their lifespan, and nondestructive tests play a key role in this context. Ultrasonic testing, a widely used nondestructive method, is employed to evaluate the heterogeneity and stiffness of concrete elements. Through advanced ultrasonic signal analysis, ultrasonic tomography enables the internal visualization of a structure’s state. Despite the development of reliable image reconstruction techniques, improving image resolution remains a challenge, particularly when dealing with limited data and mesh density issues. This study presents a method named the mesh increment (MESINC) method to enhance image resolution by incrementally densifying the mesh, even with a small number of tests around a concrete element. Two image reconstruction techniques—the simultaneous iterative reconstruction technique and algebraic reconstruction technique—are applied for image generation. Numerical simulations and experimental concrete sections are used to validate the effectiveness of the proposed method compared to regular image generation methods. The results demonstrate that the proposed MESINC method reduces reconstruction errors, enhances image contrast, and improves the identification of internal inclusions with better-defined shapes and positions. The findings suggest that this methodology can contribute to more accurate diagnostics of concrete elements, offering potential for improved nondestructive testing in civil engineering applications.