Study On The Initiation And Propagation Mechanism Of Reflection Crack In Asphalt Concrete Overlays

Many existing pavement,both rigid and flexible,have been rehabilitated with bituminous overlays.However,reflection crack occurs in these new overlays due to the movement of existing pavements under environmental or traffic loads,and/or a combination of both. This reflection crack is the main cause of early deterioration of bituminous concrete overlays, and therefore its prevention is an important consideration in the design of overlays.In this paper, linear fracture mechanics is employed to give a full analysis to the mechanism of reflection Crack propagation. After depicting the singularity of stress field at the top of crack,the finite element method to calculate stress intensity factor of plain fracture problems is established. The structural response of pavement suffering reflection crack is deeply analyzed in terms of traffic load and thermal load.The effects of the thickenss of overlay,its modular and base modular on the stress are found.The effects of the existing asphalt layer on the stresss in overlay have been analyzed in elastic three layer system too. This paper also studies the principle respectively how glass fiber grid prevents and controls reflection crack,and introduces corresponsive construction crafts in detail. The conclusion from analysis is that the reflection crack's propagateion is decided by the shear stress and thermal stresss at the top of the crack;The use of the GLASGRID is very effective to refrain the reflection crack in the new overlay.