Opening-mode cracking in asphalt pavements : crack initiation and saturation.

49111-08-20This paper investigates the crack initiation and saturation for opening-mode cracking. Using elastic governing equationsand a weak form stress boundary condition, we derive an explicit solution of elastic fields in the surface course andobtain the energy release rate, so that opening-mode cracking initiation can be determined by fracture energy criterion.Interestingly, the longitudinal stress between such cracks along the surface undergoes a transition from tensile tocompressive with increasing applied tensile loading, which implies crack saturation. Opening-mode cracking in asphaltpavements is studied and a two-dimensional closed-form elastic solution of one section from the periodic crack patternis derived. Using the fracture energy criterion, the proposed model predicts the OMC initiation and saturation. For anintact asphalt pavement, there exists a threshold of mismatch deformation to induce the first OMC. The stiffer theinterface, the higher the threshold mismatch deformation. Once the first crack forms, the crack spacing rapidlydecreases to a certain value. Therefore, multiple OMCs may simultaneously form. The stiffer theinterface, the lower the crack spacing. When crack spacing approaches a certain value, the driven force to produce anew OMC will be significantly high. An asphalt pavement with a stiff interface has a narrow crack spacing range.Given asphalt material properties and loading condition, there exists a critical thickness for the asphalt overlay, belowwhich no OMC can initiate. Therefore, a thinner asphalt overlay may produce better performance for OMCs. Becauseasphalt materials exhibit viscoelastic behavior, the present elastic formulation may overly predict the OMC crackdensity. Future work to quantitatively evaluate the effect of the assumptions and release those assumptions is underway