Evaluating Four-Point Bend Fatigue of Asphalt Mix Using Image Analysis

摘要

One of the primary structural distress modes found in bituminous pavement layers is fatigue cracking, resulting from repeated application of traffic-induced stresses. The development of a four-point bending test arrangement to determine the dynamic mechanical properties of rectangular beam specimens (305 X 45 X 50 mm dimensions) of bituminous mixtures is discussed. This novel system allows the crack-damaged surfaces of beam specimens to be inspected and monitored digitally in situ during fatigue tests. The test fixture, which was integrated with a closed-loop servo hydraulic feedback system, incorporates a constant clamping mechanism and uses a combined displacement and loading mode of control. A series of four-point bending fatigue tests were performed on specimens of two standard Irish mixtures: a hot rolled asphalt and dense base course macadam. The digitally imaged information on fatigue cracking was used to measure the extent of damage and to characterize a linear elastic fracture mechanics model.