EVALUATION OF NONDESTRUCTIVE EVALUATION METHODS FOR APPLICATION IN EARLY DETECTION OF DETERIORATION IN CONCRETE PAVEMENTS

Three nondestructive evaluation (NDE) methods for concrete pavements - surface ultrasonic pulse velocity measurements (UPV), the impact-echo (IE) method, and the use of a seismic pavement analyzer (SPA) - were tested on six sections of two continuously reinforced concrete pavements. The results were compared with the actual condition of the concrete as determined by visual inspection, photographic imaging, and examination of cores extracted from the sections. The IE and surface UPV methods were the best in indicating the existence of macroscopic cracks. However, each must be used over a relatively long period of time to determine the deterioration rate of pavement. In addition, to be practical and efficient for application in pavement inspection, mechanization of the instrumentation of each method would be required. Even though the SPA did not compare favorably with the IE and surface UPV methods in detecting cracks and delaminations, it provided information that could be used to derive the overall qualitative condition of each test section. The results with the SPA had a high correlation with a petrographically determined rating for alkali-silica reactivity. This correlation, if verified, can serve as the basis for using the inspection system to collect information that may be used to predict the future condition of a pavement. In comparison with the other methods, the SPA would require the least additional development to be an effective inspection method. Photographic imaging was extremely valuable. Although it did not probe into the concrete as did the three NDE methods/systems investigated, it captured the surface cracks and other surface features that may well be useful indicators of the future condition of the pavements. In view of the recent advancements in the technology of high-resolution digital imaging systems and computers that can make this inspection method quantitative, which it seriously needs to be, photographic imaging deserves attention as an NDE method.