Analytical Model for Prediction of Fatigue Life of Asphalt Concrete, Including Size Effect

Abstract

A local energy criterion is applied to the problem of a quasi-static extension of a subcritical crack embedded in a viscoelastic-plastic matrix. It extends the Griffith fracture criterion to include fatigue. The derived expression for the fatigue crack growth rate (FCGR) governs the subcritical crack growth to the point of gross instability. It utilizes only the material properties of the dense graded asphalt concrete mixes (DGAC), which are the dynamic modulus in bending, the flexural tensile strength, the fracture toughness and the normalized creep compliance function. The derived expression uses a new concept by Kharlab (1990) for the size effect by combining both the infinite and finite stresses at a crack tip in the mechanics of fracture. Published fatigue data for a large number of asphalt concrete mixes is used to validate the new analytical expression for the FCGR. The raw test data extracted from Majidzadeh et al. (1976) include dynamic modulus, indirect tensile strength, fracture toughness, creep and fatigue life of asphalt concrete beams consisting of 54 asphalt concrete mixtures, with three types of asphalt cement, numerous additives, five asphalt contents, and three filler asphalt ratios. The interaction of creep and fatigue is introduced through the viscoelastic correspondence principle. This facilitates the effects of accelerated testing on asphalt concrete mixes. The visual agreement between the model predictions of the fatigue lives of DGAC mixes and the published experiment data is good.

Keywords:

• Fatigue
• Analytical Model
• Asphalt Concrete
• Published Data
• Size Effect