Comparative Evaluation of Grids for the Detection of Internal Defects in Concrete Using Ultrasonic Pulse Velocity: Experimental Approach

Abstract

This study evaluates the efficacy of ultrasonic pulse velocity (UPV) testing in detecting internal defects in concrete through an experimental comparison of various measurement grid configurations and concrete compressive strengths. Concrete blocks measuring 60×60×20 cm were fabricated with simulated internal defects created using polystyrene plates. UPV testing was performed in direct transmission mode to identify and quantify defective areas. Measurement grids with densities of 2.5×2.5 cm, 5×5 cm, and 10×10 cm were utilized, and three compressive strength levels were analyzed: 21 MPa (C21), 25 MPa (C25), and 30 MPa (C30). The findings reveal that the 2.5×2.5 cm grid is the most effective for detecting defects, offering an accurate differentiation of internal variations within the concrete, particularly in higher-strength mixtures. In contrast, less dense grids exhibited greater variability in measurements and reduced sensitivity to smaller defects (6.25 cm2). The selection of grid density should carefully balance the need for precision with practical constraints, such as time and resources. Complementing UPV testing with other nondestructive testing (NDT) methods is recommended to achieve a more comprehensive evaluation of concrete integrity.