Scanning Laser Detection System Used to Measure Propagation of Fatigue Damage of Asphalt Mixes

Abstract

Fatigue damage is a major distress in pavements that has been studied extensively in various approaches, over the past two decades. It is therefore well recognized that measuring fatigue damage accumulation is difficult, time-consuming, and in many cases highly variable. Better methods for monitoring the progression of damage are thus needed for asphalt mixtures because of their heterogeneity and inherited variability. The primary objective of this research was to develop a scanning laser system that would detect changes in surface properties for the purposes of monitoring damage and characterizing the fatigue behavior of asphalt mixtures. This technique characterizes the surface state with a defect frequency parameter by rapidly scanning a laser beam along the specimen. Results were found to correlate quite well with data from other traditional mechanical tests (50% reduction in stiffness) and estimated dissipated energy approaches. This laser system is believed to offer many advantages for testing asphalt mixtures as compared with the conventional mechanical systems. The new approach provides the opportunity to quantify the microcrack formation rate and to evaluate the fatigue performance of asphalt mixtures without the need for fixtures on the sample. This system also has the potential of being used in situ for pavement monitoring.