INVESTIGATION OF LABORATORY FATIGUE TESTING PROCEDURES FOR ASPHALT AGGREGATE MIXTURES

The primary purpose of this paper is to evaluate laboratory test procedures for measuring the fatigue response of asphalt paving mixtures. Available test methods are conveniently classified into the following categories: simple flexure, supported flexure, direct axial, diametral, triaxial, fracture mechanics, and wheel-track testing. Criteria used to evaluate each method for its potential use as a laboratory standard included: (1) Ability to simulate field conditions; (2) applicability of test results for use in modeling pavement performance; and (3) simplicity. The three most promising methods are considered to be simple flexure, diametral fatigue, and tests based on fracture mechanics principles. Although not a fatigue test in itself, direct tension testing offers considerable potential as a simple surrogate for more complex fatigue tests. Finally, in most prior work, the maximum principal tensile strain has been used as the cause or determinant of fatigue damage. Other damage determinants, such as work strain, as well as other cumulative failure laws, such as constancy of dissipated energy, offer promising alternatives.