Development of an Asphalt Damage Characterization System Using Laser Scanning Detection Technology

Fatigue damage is a major distress in asphalt pavement and has been evaluated using various experimental and analytical approaches over the last two decades. However, a better understanding of fatigue behavior is needed for improved design and repair methods to minimize failures. The first objective of the present research was to develop a new non-contact damage characterization technique to monitor fatigue behavior of asphalt mixes using laser scanning detection system. The second objective of the study was to evaluate the capability of the new technique for measuring the effect of engineered binders modified by a special reaction technique on critical fatigue damage resistance properties. The third and final objective was to investigate mixtures produced with high percentage of Reclaimed Asphalt Pavement (RAP) for damage resistance and compared to the mixes produced with un-modified and modified binders.;The laser scanning technique is a non-contact measuring system that detects changes in surface properties using a parameter called "defect frequency" by scanning a laser beam along the specimen surface. The results of the present laser scanning method were compared to the data obtained from other traditional measuring systems using conventional deflection measuring devices. Analysis of data included the defect frequency and the change in mechanical properties in terms of reduction in initial stiffness, as well as dissipated energy approaches (Ratio of dissipated energy and Energy Ratio).;Fatigue resistance and material response of several mixes were investigated in the present work under various cyclic uniaxial tensile loading conditions by monitoring the intensity of scattered light from the specimen surface. The laser scanning results indicate that this technique is capable of effectively capturing crack initiation and propagation processes. Defect frequency data exhibit excellent agreement with changes in mechanical capacity and dissipated energy properties as damage develops. The number of cycles to failure indicated by laser scanning correlated well with that obtained from traditional and dissipated energy methods. An analysis of the results also reveals superior performance of the modified binders in terms of fatigue resistance, when compared to the base binder. The mixtures produced with the engineered binders and with high RAP content offer better resistance to damage for a wide range of simulated pavement strain amplitudes.