Comparing Temperature Induced Fatigue Damage to Traffic Induced Fatigue Damage in Asphalt Concrete

Bottom-up fatigue cracking (i.e., alligator cracking) in Mechanistic-Empirical Pavement Design Guide (MEPDG) is predicted based on accumulated damage caused by repeated cycles of traffic loading. Since the number of thermal expansion and contraction is small compared to the number of traffic loads, MEPDG does not consider damage due to thermal expansion and contraction in fatigue cracking calculation of an asphalt pavement. However, thermal damage may be significant and possibly causes premature failure of asphalt pavement especially in zones where day-night and yearly temperature variations are relatively large. This study measures thermal fatigue damage at the bottom of an asphalt concrete and hence, the fatigue life of asphalt concrete using data from an instrumentation pavement section on Interstate 40 (I-40) at mile post 141 near Albuquerque in New Mexico. As a first step, fatigue models are developed for both vehicle and thermal loads based on laboratory beam fatigue test results. In the second step, using the field measured strain and modulus values, fatigue damages due to vehicle load and temperature fluctuations are determined. Finally, the fatigue damage is determined using MEPDG at level 3 analysis to evaluate the laboratory developed model. Results show that damages due to traffic load, daily and yearly temperature fluctuations are 47.7%, 0.6% and 51.7% of the total fatigue damage respectively. Therefore, this study suggests that pavement design should consider fatigue damage due to temperature load in addition to damage due to repeated traffic loading.