Mechanistic analysis procedures for pavement evaluation have been simplified with recent development in microcomputers. These procedures require pavement fatigue models to make them useful for evaluation of pavement life. Although numerous models exist, their applicability to cold climates requires further investigation. The purpose of this study was to determine the applicability of existing fatigue models in alaska, determine if different asphalt concrete mixes usedin alaska differed in performance, and determine whether laboratory-prepared samples perform differently than field-compacted samples. Testing consisted of three-point bending tests with temperatures ranging from 80 deg f to -15 deg f. A materials testing system modifiedfor the test procedure was used with computerized data acquisition systems. All tests were displacement controlled. None of the existing fatigue relationships were adequate. As a result, a new equation was developed that better fits ac-2.5 And ac-5 at temperatures below 45 deg f. This equation is much more sensitive to strain than the asphalt institute equations. Ac-2.5 And ac-5 performed similarly at temperatures below 20 deg f. At temperatures as low as -15 deg f, no difference in performance was noted. Laboratory-prepared samples and field samples showed equivalent performance. The data indicated a difference between the time at which the maximum load occurred and thetime at which the maximum strain occurred. This difference, or phase lag, was greatest at the beginning of the test and almost in phaseat the end of the test. This phenomenon should be explored further, because it may provide a method of determining remaining life. Thispaper appears in transportation research record no. 1269, Asphalt mix materials and mixtures 1990.
Abstract