Using GPR and FWD to Assist in Selecting the Optimal Pavement Rehabilitation Strategy

A comprehensive evaluation of pavement condition and an understanding of the underlying causes of pavement distress are essential when selecting the optimal rehabilitation strategy. Knowledge of the existing pavement condition is vital to the success of any rehabilitation project. Verifying the presence and extent of subsurface defects and knowing the pavement structural load bearing capacity prevent premature distress from reoccurring. One project on US 287 near Amarillo Texas was investigated in this paper to demonstrate the application of nondestructive testing technologies in the strategy selection process. Ground Penetrating Radar (GPR) was employed to locate subsurface debonding defects in a hot mix asphalt layer that were responsible for the existing chronic pavement distress. Coring, and Falling Weight Deflection (FWD) testing were used to verify the presence and severity of the defects observed in the GPR data. The advantage of nondestructive testing is that it provides a comprehensive evaluation of subsurface conditions throughout the entire project, not only at locations where coring and trenching are performed. GPR was employed to verify a proposed rehabilitation design for US287. Initially visual investigations of the project had assumed the problems were related to the treated base layer and it was thought that full reconstruction would be required. However, nondestructive testing (NDT) found that the main cause of the distress was limited to the top asphalt layer. The GPR and FWD results helped district personnel substantially reduce the cost of pavement repair. The techniques and approaches demonstrated in this paper are widely used within the Texas Department of Transportation and are applicable to a wide range of pavement rehabilitation projects.