Condition assessment of longitudinal pavement joints using ultrasonic surface waves

Abstract

Poor-quality longitudinal joints can cause premature failure on asphalt pavements; they are characterized by exhibiting low density and high permeability. These conditions generate surface distresses such as longitudinal cracking. Previous ultrasonic methods for condition assessment, e.g., Fourier and wavelet transmission coefficient, require user input, making the automatic data processing difficult. Furthermore, the coupling between ultrasonic transducers and the asphalt surface is not practical for testing in-service roads. This paper presents a new data analysis technique and the results of an experimental program for the condition assessment of longitudinal asphalt joints using ultrasonic surface waves. A new coupling system between the ultrasonic transducers and the asphalt surface is presented. The new data processing technique reduces user input and increases testing reliability. The new coupling system uses polyurethane foam and calibrated weights to provide a spring action on the transducers. The proposed data analysis technique, called instantaneous transmission coefficient (ITC), is based on the evaluation of instantaneous frequencies and damping ratios. The main advantage of the new procedure is that it can be performed automatically, reducing user input and increasing test repeatability. A laboratory scale asphalt slab is used to show the potential of the new methodology and coupling system. Laboratory validation results show good agreement between the new ITC method and previous methods, and a significant reduction in testing time, while improving test reliability.