PROCEDURE FOR PREDICTING OCCURRENCE AND SPACING OF THERMAL-SUSCEPTIBILITY CRACKING IN FLEXIBLE PAVEMENTS

The inability of previous models to accurately predict transverse cracking in pavements in the southwestern United States has led to the laboratory validation of the concept of thermal susceptibility of unstabilized base-course material. Thermal susceptibility is the volumetric contraction of a granular base-course materials when it is frozen. This contraction produces cracking in the base course that is highly dependent on the environment in the general area. This paper presents the results of a study that attempted to quantify this mechanism and to predict crack spacings and the rate of crack appearance. The procedure used involves the combination of linear viscoelasticity and linear visco-elastic fracture mechanics. Crack spacings in the base course are calculated by using the results of a finite-element study of the frozen propertions of the base course. The effect of these cracks (i.e., the rate at which they propagate refelction cracks through the asphalt surface layer) is determined by using a fracture mechanics approach. Intensity factors are calculated for the viscoelastic thermal stress in the asphalt caused by a temperature cycle and for the stress caused by the deformation of a crack in the base course caused by a freeze. The integration of these distributions in the Paris equation for crack growth gives the number of cycles to failure. These calculations were assembled into a computer model that uses daily climatic data and appropriate material properties to calculate the damage caused by daily temperature cycles. The behavior of asphalt and of sulfur asphalt are contrasted when placed over several base-course materials in two different environments, Abiliene and Amarillo, Texas, to illustrate the effects of materials-property variation and environmental influence. This model represents an initial theoretical approach to the problem of combining the effects on flexible pavements of environment and traffic to more accurately predict performance. Implications concerning reflection cracking can be drawn directly from the analysis of the effect of thermal susceptiblity of the base course on the rate of reflection crack appearance. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References;
  • Pagination: pp 39-46
  • Monograph Title: Analysis of pavement systems
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00193379
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 11 1979 12:00AM