Microdamage healing in asphalt and asphalt concrete, volume 3 : a micromechanics fracture and healing model for asphalt concrete.

2001Final; Feb. 1998.PDFTech ReportFHWA-RD-98-143;Research Report 7229DTFH6 1 -92-C-00 170AsphaltAsphalt concreteCracking of asphalt concrete pavementsViscoelasticityCrackingTensile strengthStrain (Mechanics)Viscoelastic fractureFatigue damageTensile fatiguePseudo-strainUnited StatesTurner-Fairbank Highway Research CenterLytton, R. L.Chen, C. W.Little, Dallas N.Texas Transportation InstituteUniversity of Wyoming Research Corporation. Western Research InstituteUnited States. Federal Highway AdministrationNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceNTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATIONFederal Highway AdministrationVolume 3 documents the development of a micromechanics fracture and healing model for asphaltconcrete. This model can be used to calculate the density and growth of microcracks during repeated directtensile controlled-strain loading. The model is based on a relationship among stiffness changes in the mixture asdamage occurs, the rate of change in dissipated pseudo strain energy as loading are applied to the samples andas damage occurs and mixture properties including crack length changes upon loading and mixture cohesivesurface energies. The report demonstrates that microcrack growth is the dominate mode of distress attemperatures below 25C and that microcrack healing is the dominate mode of recovery of dissipated pseudostrain energy at these test temperatures. However, at temperatures above about 25C, the predominate mode ofdistress is plastic damage. Cracking rates during fatigue damage are related to de-wetting cohesive surfaceenergy measurements of the bitumen whereas microcracking healing rates are related to wetting cohesive surfaceenergy measurements of the bitumen. Surface energies of five bitumens with widely different chemicalcompositions were found to correlate strongly with healing properties as defined by viscoelastic fracture andhealing theory