MONITORING DISSIPATED ENERGY THROUGH THE FATIGUE PROCESS OF ASPHALT CONCRETE

Fatigue cracking is a serious distress associated with flexible pavements, itreduces the service life of the pavement. Fatigue damage of asphalt concreteis the amount of energy dissipated in the specimen during testing. Fatiguecould be minimized by controlling the dissipated energy; which can be usedto explain the decrease in mechanical properties, such as flexural stiffness.During dynamic-load repetition, amount of energy is carried into thematerial. Part of this energy is stored in the material and dissipated when theload is released. In this research, an investigation was made to monitor thechanges in dissipated energy through the fatigue resistance process ofasphalt pavement. Repeated four-point flexure bending beam test incontrolled strain mode has been implemented. Asphalt concrete mixtureswere prepared using different percentages of asphalt cement. Asphaltconcrete slab samples of (300x 400x 60) mm were prepared using rollercompaction, beam specimens of (400x 50x 60) mm were cut from the slabsamples. Beam specimens were divided into two groups, the first group wasdirectly tested for fatigue life using Nottingham four point bending beamdevice under the influence of three levels of micro strain (750, 400 and250), at 5, 20, and 30 °C , while the second group was subjected to moisturedamage impact before testing for fatigue life. During testing, dissipatedenergy per cycle was monitored through the changes in mix behavior anddamage accumulation. The impact of asphalt content, strain level, andtesting temperature on dissipated energy was discussed and compared.

Keywords:

Asphalt concrete , dissipated energy , moisture damage , fatigue